Book Sle Admin

Administration Guide
SUSE Linux Enterprise Server 12 SP3

SUSE Linux Enterprise Server 12 SP3
Covers system administration tasks like maintaining, monitoring and customizing

an initially installed system.
Publication Date: February 09, 2018
SUSE LLC
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Suite 200
Cambridge MA 02141
USA
https://www.suse.com/documentation
Copyright © 2006– 2018 SUSE LLC and contributors. All rights reserved.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Docu-
mentation License, Version 1.2 or (at your option) version 1.3; with the Invariant Section being this copyright
notice and license. A copy of the license version 1.2 is included in the section entitled “GNU Free Documentation
License”.
For SUSE trademarks, see http://www.suse.com/company/legal/ . All other third-party trademarks are the prop-
erty of their respective owners. Trademark symbols (®, ™ etc.) denote trademarks of SUSE and its affiliates.
Asterisks (*) denote third-party trademarks.
All information found in this book has been compiled with utmost attention to detail. However, this does not
guarantee complete accuracy. Neither SUSE LLC, its affiliates, the authors nor the translators shall be held liable
for possible errors or the consequences thereof.
Contents
About This Guide xxi
I COMMON TASKS 1
1 Bash and Bash Scripts 2

1.1 What is “The Shell”? 2
Knowing the Bash Configuration Files 2 • The Directory Structure 4
1.2 Writing Shell Scripts 8
1.3 Redirecting Command Events 9
1.4 Using Aliases 10
1.5 Using Variables in Bash 10

Using Argument Variables 11 • Using Variable Substitution 12
1.6 Grouping and Combining Commands 13
1.7 Working with Common Flow Constructs 14

The if Control Command 14 • Creating Loops with the for Command 15
1.8 For More Information 15
2 sudo 16
2.1 Basic sudo Usage 16
Running a Single Command 16 • Starting a Shell 17 • Environment
Variables 18
2.2 Configuring sudo 18

Editing the Configuration Files 19 • Basic sudoers Configuration
Syntax 19 • Rules in sudoers 21
2.3 Common Use Cases 22

Using sudo without root Password 22 • Using sudo with X.Org
Applications 24
iii Administration Guide

2.4 More Information 24
3 YaST Online Update 25

3.1 The Online Update Dialog 26
3.2 Installing Patches 27
3.3 Automatic Online Update 28
4 YaST 30
4.1 Advanced Key Combinations 30
5 YaST in Text Mode 32

5.1 Navigation in Modules 33
5.2 Advanced Key Combinations 35
5.3 Restriction of Key Combinations 35
5.4 YaST Command Line Options 36

Starting the Individual Modules 36 • Installing Packages from the Command
Line 36 • Command Line Parameters of the YaST Modules 37
6 Managing Software with Command Line Tools 38

6.1 Using Zypper 38
General Usage 38 • Installing and Removing Software with
Zypper 40 • Updating Software with Zypper 44 • Identifying
Processes and Services Using Deleted Files 48 • Managing Repositories
with Zypper 49 • Querying Repositories and Packages with
Zypper 51 • Configuring Zypper 53 • Troubleshooting 53 • Zypper
Rollback Feature on Btrfs File System 54 • For More Information 54
6.2 RPM—the Package Manager 54

Verifying Package Authenticity 55 • Managing Packages: Install,
Update, and Uninstall 55 • Delta RPM Packages 57 • RPM
Queries 57 • Installing and Compiling Source Packages 60 • Compiling
RPM Packages with build 62 • Tools for RPM Archives and the RPM
Database 63
iv Administration Guide
7 System Recovery and Snapshot Management with
Snapper 64
7.1 Default Setup 64
Types of Snapshots 66 • Directories That Are Excluded from
Snapshots 66 • Customizing the Setup 68
7.2 Using Snapper to Undo Changes 71

Undoing YaST and Zypper Changes 72 • Using Snapper to Restore
Files 77
7.3 System Rollback by Booting from Snapshots 79

Snapshots after Rollback 81 • Accessing and Identifying Snapshot Boot
Entries 82 • Limitations 84
7.4 Creating and Modifying Snapper Configurations 85

Managing Existing Configurations 87
7.5 Manually Creating and Managing Snapshots 90

Snapshot Metadata 90 • Creating Snapshots 92 • Modifying Snapshot
Metadata 93 • Deleting Snapshots 94
7.6 Automatic Snapshot Clean-Up 95

Cleaning Up Numbered Snapshots 96 • Cleaning Up Timeline
Snapshots 97 • Cleaning Up Snapshot Pairs That Do Not
Differ 99 • Cleaning Up Manually Created Snapshots 99 • Adding Disk
Quota Support 100
7.7 Frequently Asked Questions 101
8 Remote Access with VNC 103

8.1 The vncviewer Client 103
Connecting Using the vncviewer CLI 103 • Connecting Using the vncviewer
GUI 104 • Notification of Unencrypted Connections 104
8.2 One-time VNC Sessions 104

Available Configurations 105 • Initiating a One-time VNC
Session 105 • Configuring One-time VNC Sessions 105
v Administration Guide
8.3 Persistent VNC Sessions 106
Connecting to a Persistent VNC Session 108 • Configuring Persistent VNC
Sessions 108
8.4 Encrypted VNC Communication 108
9 File Copying with RSync 111

9.1 Conceptual Overview 111
9.2 Basic Syntax 111
9.3 Copying Files and Directories Locally 112
9.4 Copying Files and Directories Remotely 113
9.5 Configuring and Using an Rsync Server 113
II BOOTING A LINUX SYSTEM 117
10 Introduction to the Booting Process 118

10.1 The Linux Boot Process 118
10.2 initramfs 120
10.3 Init on initramfs 121
11 UEFI (Unified Extensible Firmware Interface) 124

11.1 Secure Boot 124
Implementation on SUSE Linux Enterprise Server 125 • MOK (Machine
Owner Key) 127 • Booting a Custom Kernel 128 • Using Non-Inbox
Drivers 130 • Features and Limitations 131
12 The Boot Loader GRUB 2 133

12.1 Main Differences between GRUB Legacy and GRUB 2 133
vi Administration Guide
12.2 Configuration File Structure 133
The File /boot/grub2/grub.cfg 135 • The File /etc/default/
grub 135 • Scripts in /etc/grub.d 138 • Mapping between BIOS
Drives and Linux Devices 139 • Editing Menu Entries during the Boot
Procedure 140 • Setting a Boot Password 141
12.3 Configuring the Boot Loader with YaST 142

Boot Loader Location and Boot Code Options 144 • Adjusting the Disk
Order 145 • Configuring Advanced Options 146
12.4 Differences in Terminal Usage on z Systems 148

Limitations 148 • Key Combinations 149
12.5 Helpful GRUB 2 Commands 151
13 The systemd Daemon 153

13.1 The systemd Concept 153
What Is systemd 153 • Unit File 154
13.2 Basic Usage 155

Managing Services in a Running System 155 • Permanently Enabling/
Disabling Services 157
13.3 System Start and Target Management 159

Targets Compared to Runlevels 159 • Debugging System Start-
Up 162 • System V Compatibility 165
13.4 Managing Services with YaST 166
13.5 Customization of systemd 167

Customizing Service Files 168 • Creating “Drop-in” Files 168 • Creating
Custom Targets 168
13.6 Advanced Usage 169

Cleaning Temporary Directories 169 • System
Log 170 • Snapshots 170 • Loading Kernel Modules 171 • Performing
Actions before Loading a Service 171 • Kernel Control Groups
vii Administration Guide

(cgroups) 172 • Terminating Services (Sending Signals) 173 • Debugging
Services 174
III SYSTEM 176
14 32-Bit and 64-Bit Applications in a 64-Bit System

Environment 177
14.1 Runtime Support 177
14.2 Software Development 178
14.3 Software Compilation on Biarch Platforms 179
14.4 Kernel Specifications 180
15 journalctl: Query the systemd Journal 182

15.1 Making the Journal Persistent 182
15.2 journalctl Useful Switches 183
15.3 Filtering the Journal Output 184

Filtering Based on a Boot Number 184 • Filtering Based on Time
Interval 184 • Filtering Based on Fields 185
15.4 Investigating systemd Errors 186
15.5 Journald Configuration 187

Changing the Journal Size Limit 187 • Forwarding the Journal to /dev/
ttyX 187 • Forwarding the Journal to Syslog Facility 188
15.6 Using YaST to Filter the systemd Journal 188
16 Basic Networking 190

16.1 IP Addresses and Routing 193
IP Addresses 193 • Netmasks and Routing 193
16.2 IPv6—The Next Generation Internet 195

Advantages 196 • Address Types and Structure 197 • Coexistence of IPv4
and IPv6 201 • Configuring IPv6 203 • For More Information 203
viii Administration Guide

16.3 Name Resolution 204
16.4 Configuring a Network Connection with YaST 205

Configuring the Network Card with YaST 205 • IBM z Systems: Configuring
Network Devices 217
16.5 Configuring a Network Connection Manually 219

The wicked Network Configuration 219 • Configuration Files 227 • Testing
the Configuration 238 • Unit Files and Start-Up Scripts 241
16.6 Basic Router Setup 242
16.7 Setting Up Bonding Devices 244

Hotplugging of Bonding Slaves 246
16.8 Setting Up Team Devices for Network Teaming 247

Use Case: Loadbalancing with Network Teaming 251 • Use Case: Failover with
Network Teaming 252 • Use Case: VLAN over Team Device 253
16.9 Software-Defined Networking with Open vSwitch 255

Advantages of Open vSwitch 255 • Installing Open vSwitch 255 • Overview
of Open vSwitch Daemons and Utilities 256 • Creating a Bridge with Open
vSwitch 257 • Using Open vSwitch Directly with KVM 258 • Using Open
vSwitch with libvirt 260 • For More Information 261
17 Printer Operation 262

17.1 The CUPS Workflow 263
17.2 Methods and Protocols for Connecting Printers 264
17.3 Installing the Software 264
17.4 Network Printers 265
17.5 Configuring CUPS with Command Line Tools 266
17.6 Printing from the Command Line 268
17.7 Special Features in SUSE Linux Enterprise Server 268

CUPS and Firewall 268 • Browsing for Network Printers 269 • PPD Files in
Various Packages 269
ix Administration Guide
17.8 Troubleshooting 270
Printers without Standard Printer Language Support 270 • No
Suitable PPD File Available for a PostScript Printer 271 • Network
Printer Connections 271 • Defective Printouts without Error
Message 273 • Disabled Queues 274 • CUPS Browsing: Deleting Print
Jobs 274 • Defective Print Jobs and Data Transfer Errors 274 • Debugging
CUPS 275 • For More Information 275
18 The X Window System 276

18.1 Installing and Configuring Fonts 276
Showing Installed Fonts 278 • Viewing Fonts 278 • Querying
Fonts 278 • Installing Fonts 279 • Configuring the Appearance of
Fonts 280
19 Accessing File Systems with FUSE 290

19.1 Configuring FUSE 290
19.2 Mounting an NTFS Partition 290
20 Managing Kernel Modules 292

20.1 Listing Loaded Modules with lsmod and modinfo 292
20.2 Adding and Removing Kernel Modules 293

Loading Kernel Modules Automatically on Boot 293 • Blacklisting Kernel
Modules with modprobe 294
21 Dynamic Kernel Device Management with udev 296

21.1 The /dev Directory 296
21.2 Kernel uevents and udev 296
21.3 Drivers, Kernel Modules and Devices 297
21.4 Booting and Initial Device Setup 297
21.5 Monitoring the Running udev Daemon 298
x Administration Guide
21.6 Influencing Kernel Device Event Handling with udev Rules 299
Using Operators in udev Rules 301 • Using Substitutions in udev
Rules 302 • Using udev Match Keys 303 • Using udev Assign Keys 304
21.7 Persistent Device Naming 305
21.8 Files used by udev 306
22 Live Patching the Linux Kernel Using kGraft 308

22.1 Advantages of kGraft 308
22.2 Low-level Function of kGraft 309
22.3 Installing kGraft Patches 310

Activation of SLE Live Patching 310 • Updating System 310
22.4 Patch Lifecycle 311
22.5 Removing a kGraft Patch 312
22.6 Stuck Kernel Execution Threads 312
22.7 The kgr Tool 312
22.8 Scope of kGraft Technology 313
22.9 Scope of SLE Live Patching 313
22.10 Interaction with the Support Processes 313
23 Special System Features 315

23.1 Information about Special Software Packages 315
The bash Package and /etc/profile 315 • The cron
Package 316 • Stopping Cron Status Messages 317 • Log Files:
Package logrotate 317 • The locate Command 317 • The ulimit
Command 318 • The free Command 319 • Man Pages and Info
Pages 319 • Selecting Man Pages Using the man Command 319 • Settings
for GNU Emacs 320
23.2 Virtual Consoles 321
xi Administration Guide
23.3 Keyboard Mapping 321
23.4 Language and Country-Specific Settings 322

Some Examples 323 • Locale Settings in ~/.i18n 324 • Settings for
Language Support 324 • For More Information 325
IV SERVICES 326
24 Time Synchronization with NTP 327

24.1 Configuring an NTP Client with YaST 327
Basic Configuration 327 • Changing Basic Configuration 328
24.2 Manually Configuring NTP in the Network 331
24.3 Dynamic Time Synchronization at Runtime 331
24.4 Setting Up a Local Reference Clock 332
24.5 Clock Synchronization to an External Time Reference (ETR) 333
25 The Domain Name System 334

25.1 DNS Terminology 334
25.2 Installation 335
25.3 Configuration with YaST 335

Wizard Configuration 336 • Expert Configuration 338
25.4 Starting the BIND Name Server 346
25.5 The /etc/named.conf Configuration File 348

Important Configuration Options 349 • Logging 350 • Zone Entries 351
25.6 Zone Files 352
25.7 Dynamic Update of Zone Data 356
25.8 Secure Transactions 356
25.9 DNS Security 358
xii Administration Guide

26 DHCP 359
26.1 Configuring a DHCP Server with YaST 360
Initial Configuration (Wizard) 360 • DHCP Server Configuration (Expert) 365
26.2 DHCP Software Packages 370
26.3 The DHCP Server dhcpd 371

Clients with Fixed IP Addresses 373 • The SUSE Linux Enterprise Server
Version 374
27 Sharing File Systems with NFS 375

27.1 Terminology 375
27.2 Installing NFS Server 376
27.3 Configuring NFS Server 376

Exporting File Systems with YaST 377 • Exporting File Systems
Manually 378 • NFS with Kerberos 381
27.4 Configuring Clients 381

Importing File Systems with YaST 381 • Importing File Systems
Manually 382 • Parallel NFS (pNFS) 384
28 Samba 386
28.1 Terminology 386
28.2 Installing a Samba Server 387
28.3 Starting and Stopping Samba 388
28.4 Configuring a Samba Server 388

Configuring a Samba Server with YaST 388 • Configuring the Server
Manually 391
28.5 Configuring Clients 395

Configuring a Samba Client with YaST 395
xiii Administration Guide

28.6 Samba as Login Server 395
28.7 Samba Server in the Network with Active Directory 396
28.8 Advanced Topics 398

Transparent File Compression on Btrfs 398 • Snapshots 399
29 On-Demand Mounting with Autofs 408

29.1 Installation 408
29.2 Configuration 408

The Master Map File 408 • Map Files 410
29.3 Operation and Debugging 411

Controlling the autofs Service 411 • Debugging the Automounter
Problems 412
29.4 Auto-Mounting an NFS Share 413
29.5 Advanced Topics 414

/net Mount Point 414 • Using Wild Cards to Auto-Mount
Subdirectories 414 • Auto-Mounting CIFS File System 415
30 SLP 416
30.1 The SLP Front-End slptool 416
30.2 Providing Services via SLP 417

Setting up an SLP Installation Server 419
31 The Apache HTTP Server 420

31.1 Quick Start 420
Requirements 420 • Installation 421 • Start 421
31.2 Configuring Apache 422

Apache Configuration Files 422 • Configuring Apache
Manually 425 • Configuring Apache with YaST 430
xiv Administration Guide

31.3 Starting and Stopping Apache 436
31.4 Installing, Activating, and Configuring Modules 438

Module Installation 439 • Activation and Deactivation 439 • Base and
Extension Modules 439 • Multiprocessing Modules 442 • External
Modules 444 • Compilation 445
31.5 Enabling CGI Scripts 445

Apache Configuration 446 • Running an Example Script 446 • CGI
Troubleshooting 447
31.6 Setting Up a Secure Web Server with SSL 448

Creating an SSL Certificate 448 • Configuring Apache with SSL 452
31.7 Running Multiple Apache Instances on the Same Server 454
31.8 Avoiding Security Problems 457

Up-to-Date Software 457 • DocumentRoot Permissions 457 • File System
Access 458 • CGI Scripts 458 • User Directories 458

Apache 2.4 460 • Apache
Modules 460 • Development 461 • Miscellaneous Sources 461
32 Setting Up an FTP Server with YaST 462

32.1 Starting the FTP Server 463
32.2 FTP General Settings 463
32.3 FTP Performance Settings 464
32.4 Authentication 465
32.5 Expert Settings 465
xv Administration Guide
33 The Proxy Server Squid 466
33.1 Some Facts about Proxy Caches 466
Squid and Security 467 • Multiple Caches 467 • Caching Internet
Objects 468
33.2 System Requirements 468

RAM 469 • CPU 469 • Size of the Disk Cache 469 • Hard Disk/SSD
Architecture 470
33.3 Basic Usage of Squid 470

Starting Squid 470 • Checking Whether Squid Is Working 471 • Stopping,
Reloading, and Restarting Squid 473 • Removing Squid 473 • Local DNS
Server 474
33.4 The YaST Squid Module 475
33.5 The Squid Configuration File 475

General Configuration Options 476 • Options for Access Controls 479
33.6 Configuring a Transparent Proxy 482
33.7 Using the Squid Cache Manager CGI Interface (cachemgr.cgi) 485
33.8 squidGuard 487
33.9 Cache Report Generation with Calamaris 488
34 Web Based Enterprise Management Using SFCB 490

34.1 Introduction and Basic Concept 490
34.2 Setting Up SFCB 492

Installing Additional Providers 493 • Starting, Stopping and Checking Status
for SFCB 494 • Ensuring Secure Access 495
34.3 SFCB CIMOM Configuration 497

Environment Variables 497 • Command Line Options 498 • SFCB
Configuration File 500
xvi Administration Guide

34.4 Advanced SFCB Tasks 511
Installing CMPI Providers 511 • Testing SFCB 515 • Command Line CIM
Client: wbemcli 517
V MOBILE COMPUTERS 520
35 Mobile Computing with Linux 521

35.1 Laptops 521
Power Conservation 521 • Integration in Changing Operating
Environments 522 • Software Options 524 • Data Security 529
35.2 Mobile Hardware 530
35.3 Cellular Phones and PDAs 531
36 Using NetworkManager 532

36.1 Use Cases for NetworkManager 532
36.2 Enabling or Disabling NetworkManager 532
36.3 Configuring Network Connections 533

Managing Wired Network Connections 535 • Managing Wireless Network
Connections 535 • Configuring Your Wi-Fi/Bluetooth Card as an Access
Point 536 • NetworkManager and VPN 536
36.4 NetworkManager and Security 538

User and System Connections 538 • Storing Passwords and Credentials 538
36.5 Frequently Asked Questions 539
37 Power Management 542

37.1 Power Saving Functions 542
xvii Administration Guide

37.2 Advanced Configuration and Power Interface (ACPI) 543
Controlling the CPU Performance 544 • Troubleshooting 544
37.3 Rest for the Hard Disk 546

CPU Frequency Does Not Work 547
VI TROUBLESHOOTING 549
38 Help and Documentation 550

38.1 Documentation Directory 550
SUSE Manuals 551 • Package Documentation 551
38.2 Man Pages 552
38.3 Info Pages 553
38.4 Online Resources 554
39 Gathering System Information for Support 556

39.1 Displaying Current System Information 556
39.2 Collecting System Information with Supportconfig 557

Creating a Service Request Number 557 • Upload Targets 558 • Creating a
Supportconfig Archive with YaST 558 • Creating a Supportconfig Archive from
Command Line 560 • Common Supportconfig Options 561
39.3 Submitting Information to Global Technical Support 562
39.4 Analyzing System Information 564

SCA Command Line Tool 564 • SCA Appliance 566 • Developing Custom
Analysis Patterns 577
39.5 Gathering Information during the Installation 578
39.6 Support of Kernel Modules 578

Technical Background 579 • Working with Unsupported Modules 579
xviii Administration Guide

40 Common Problems and Their Solutions 582
40.1 Finding and Gathering Information 582
40.2 Installation Problems 585

Checking Media 585 • No Bootable DVD Drive Available 586 • Booting
from Installation Media Fails 587 • Fails to Boot 588 • Fails to Launch
Graphical Installer 590 • Only Minimalistic Boot Screen Started 592 • Log
Files 592
40.3 Boot Problems 593

The GRUB 2 Boot Loader Fails to Load 593 • No Graphical
Login 593 • Root Btrfs Partition Cannot Be Mounted 594 • Force Checking
Root Partitions 594
40.4 Login Problems 594

Valid User Name and Password Combinations Fail 595 • Valid User Name
and Password Not Accepted 596 • Login to Encrypted Home Partition
Fails 598 • Login Successful but GNOME Desktop Fails 599
40.5 Network Problems 599

NetworkManager Problems 603
40.6 Data Problems 604

Managing Partition Images 604 • Using the Rescue System 605
40.7 IBM z Systems: Using initrd as a Rescue System 612
A Documentation Updates 614

A.1 January 2018 (Maintenance Release of SUSE Linux Enterprise Server 12
SP3) 615
A.2 December 2017 (Maintenance Release of SUSE Linux Enterprise Server

12 SP3) 615
A.3 September 2017 (Initial Release of SUSE Linux Enterprise Server 12

SP3) 616
A.4 November 2016 (Initial Release of SUSE Linux Enterprise Server 12

SP2) 619
xix Administration Guide

A.5 March 2016 (Maintenance Release of SUSE Linux Enterprise Server 12
SP1) 621
A.6 December 2015 (Initial Release of SUSE Linux Enterprise Server 12

SP1) 622
A.7 February 2015 (Documentation Maintenance Update) 625
A.8 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) 626
B An Example Network 632
C GNU Licenses 633

C.1 GNU Free Documentation License 633
xx Administration Guide
About This Guide
This guide is intended for use by professional network and system administrators during the
operation of SUSE® Linux Enterprise. As such, it is solely concerned with ensuring that SUSE
Linux Enterprise is properly configured and that the required services on the network are avail-
able to allow it to function properly as initially installed. This guide does not cover the process
of ensuring that SUSE Linux Enterprise offers proper compatibility with your enterprise's appli-
cation software or that its core functionality meets those requirements. It assumes that a full
requirements audit has been done and the installation has been requested, or that a test instal-
lation for such an audit has been requested.
This guide contains the following:
Support and Common Tasks

SUSE Linux Enterprise offers a wide range of tools to customize various aspects of the
system. This part introduces a few of them. A breakdown of available device technologies,
high availability configurations, and advanced administration possibilities introduces the
system to the administrator.
System
Learn more about the underlying operating system by studying this part. SUSE Linux En-
terprise supports several hardware architectures and you can use this to adapt your own
applications to run on SUSE Linux Enterprise. The boot loader and boot procedure infor-
mation assists you in understanding how your Linux system works and how your own
custom scripts and applications may blend in with it.
Services
SUSE Linux Enterprise is designed to be a network operating system. It offers a wide range
of network services, such as DNS, DHCP, Web, proxy, and authentication services. It al-
so integrates well into heterogeneous environments, including MS Windows clients and
servers.
Mobile Computers
Laptops, and the communication between mobile devices like PDAs, or cellular phones
and SUSE Linux Enterprise need some special attention. Take care for power conservation
and for the integration of different devices into a changing network environment. Also get
in touch with the background technologies that provide the needed functionality.
xxi SLES 12 SP3

Troubleshooting
Provides an overview of finding help and additional documentation when you need more
information or want to perform specific tasks. There is also a list of the most frequent
problems with explanations how to x them.
1 Available Documentation
Note: Online Documentation and Latest Updates

Documentation for our products is available at http://www.suse.com/documentation/ ,
where you can also nd the latest updates, and browse or download the documentation
in various formats.
In addition, the product documentation is usually available in your installed system under /
usr/share/doc/manual .
The following documentation is available for this product:
Article “Installation Quick Start”

Lists the system requirements and guides you step-by-step through the installation of SUSE
Linux Enterprise Server from DVD, or from an ISO image.
Book “Deployment Guide”

Shows how to install single or multiple systems and how to exploit the product inher-
ent capabilities for a deployment infrastructure. Choose from various approaches, ranging
from a local installation or a network installation server to a mass deployment using a
remote-controlled, highly-customized, and automated installation technique.
Covers system administration tasks like maintaining, monitoring and customizing an ini-
tially installed system.
Book “Virtualization Guide”

Describes virtualization technology in general, and introduces libvirt—the unified inter-
face to virtualization—and detailed information on specific hypervisors.
xxii Available Documentation SLES 12 SP3

Book “Storage Administration Guide”
Provides information about how to manage storage devices on a SUSE Linux Enterprise
Server.
Book “AutoYaST”
AutoYaST is a system for unattended mass deployment SUSE Linux Enterprise Server sys-
tems using an AutoYaST profile containing installation and configuration data. The man-
ual guides you through the basic steps of auto-installation: preparation, installation, and
configuration.
Book “Security Guide”

Introduces basic concepts of system security, covering both local and network security
aspects. Shows how to use the product inherent security software like AppArmor or the
auditing system that reliably collects information about any security-relevant events.
Book “Security and Hardening Guide”

Deals with the particulars of installing and setting up a secure SUSE Linux Enterprise Serv-
er, and additional post-installation processes required to further secure and harden that
installation. Supports the administrator with security-related choices and decisions.
Book “System Analysis and Tuning Guide”

An administrator's guide for problem detection, resolution and optimization. Find how to
inspect and optimize your system by means of monitoring tools and how to efficiently
manage resources. Also contains an overview of common problems and solutions and of
additional help and documentation resources.
Book “Subscription Management Tool for SLES 12 SP3”

An administrator's guide to Subscription Management Tool—a proxy system for SUSE Cus-
tomer Center with repository and registration targets. Learn how to install and configure a
local SMT server, mirror and manage repositories, manage client machines, and configure
clients to use SMT.
Book “GNOME User Guide”

Introduces the GNOME desktop of SUSE Linux Enterprise Server. It guides you through
using and configuring the desktop and helps you perform key tasks. It is intended mainly
for end users who want to make efficient use of GNOME as their default desktop.
xxiii Available Documentation SLES 12 SP3

2 Feedback
Several feedback channels are available:
Bugs and Enhancement Requests

For services and support options available for your product, refer to http://www.suse.com/
support/ .
Help for openSUSE is provided by the community. Refer to https://en.opensuse.org/Por-
tal:Support for more information.
To report bugs for a product component, go to https://scc.suse.com/support/requests ,
log in, and click Create New.
User Comments
We want to hear your comments about and suggestions for this manual and the other doc-
umentation included with this product. Use the User Comments feature at the bottom of
each page in the online documentation or go to http://www.suse.com/documentation/feed-
back.html and enter your comments there.
Mail
For feedback on the documentation of this product, you can also send a mail to doc-
team@suse.com . Make sure to include the document title, the product version and the
publication date of the documentation. To report errors or suggest enhancements, provide
a concise description of the problem and refer to the respective section number and page
(or URL).
3 Documentation Conventions
The following notices and typographical conventions are used in this documentation:
/etc/passwd : directory names and le names
PLACEHOLDER : replace PLACEHOLDER with the actual value
PATH : the environment variable PATH
ls , --help : commands, options, and parameters
user : users or groups
xxiv Feedback SLES 12 SP3

package name : name of a package
Alt , Alt – F1 : a key to press or a key combination; keys are shown in uppercase as on
a keyboard
File, File Save As: menu items, buttons
x86_64 This paragraph is only relevant for the AMD64/Intel 64 architecture. The arrows
mark the beginning and the end of the text block.
System z, POWER This paragraph is only relevant for the architectures z Systems and
POWER . The arrows mark the beginning and the end of the text block.
Dancing Penguins (Chapter Penguins, ↑Another Manual): This is a reference to a chapter in

another manual.
Commands that must be run with root privileges. Often you can also prefix these com-
mands with the sudo command to run them as non-privileged user.
root # command
tux > sudo command
Commands that can be run by non-privileged users.
tux > command
Notices
Warning: Warning Notice

Vital information you must be aware of before proceeding. Warns you about security
issues, potential loss of data, damage to hardware, or physical hazards.
Important: Important Notice

Important information you should be aware of before proceeding.
Note: Note Notice

Additional information, for example about differences in software versions.
xxv Documentation Conventions SLES 12 SP3

Tip: Tip Notice
Helpful information, like a guideline or a piece of practical advice.
4 About the Making of This Documentation

This documentation is written in SUSEDoc, a subset of DocBook 5 (http://www.docbook.org) .
The XML source les were validated by jing (see https://code.google.com/p/jing-trang/ ),
processed by xsltproc , and converted into XSL-FO using a customized version of Norman
Walsh's stylesheets. The final PDF is formatted through FOP from Apache Software Foundation
(https://xmlgraphics.apache.org/fop) . The open source tools and the environment used to build
this documentation are provided by the DocBook Authoring and Publishing Suite (DAPS). The
project's home page can be found at https://github.com/openSUSE/daps .
The XML source code of this documentation can be found at https://github.com/SUSE/doc-sle .
xxvi About the Making of This Documentation SLES 12 SP3

I Common Tasks
1 Bash and Bash Scripts 2
2 sudo 16
3 YaST Online Update 25
4 YaST 30
5 YaST in Text Mode 32
6 Managing Software with Command Line Tools 38
7 System Recovery and Snapshot Management with Snapper 64
8 Remote Access with VNC 103
9 File Copying with RSync 111

1 Bash and Bash Scripts
Today, many people use computers with a graphical user interface (GUI) like
GNOME. Although they offer lots of features, their use is limited when it comes to
the execution of automated tasks. Shells are a good addition to GUIs and this chap-
ter gives you an overview of some aspects of shells, in this case Bash.
1.1 What is “The Shell”?

Traditionally, the shell is Bash (Bourne again Shell). When this chapter speaks about “the shell”
it means Bash. There are actually more available shells than Bash (ash, csh, ksh, zsh, …), each
employing different features and characteristics. If you need further information about other
shells, search for shell in YaST.
1.1.1 Knowing the Bash Configuration Files
A shell can be invoked as an:
1. Interactive login shell. This is used when logging in to a machine, invoking Bash with the
--login option or when logging in to a remote machine with SSH.
2. “Ordinary” interactive shell. This is normally the case when starting xterm, konsole,
gnome-terminal or similar tools.
3. Non-interactive shell. This is used when invoking a shell script at the command line.
Depending on which type of shell you use, different configuration les are being read. The
following tables show the login and non-login shell configuration les.
TABLE 1.1: BASH CONFIGURATION FILES FOR LOGIN SHELLS
File Description
/etc/profile Do not modify this le, otherwise your mod-

ifications can be destroyed during your next
update!
2 What is “The Shell”? SLES 12 SP3

File Description
/etc/profile.local Use this le if you extend /etc/profile
/etc/profile.d/ Contains system-wide configuration les for

specific programs
~/.profile Insert user specific configuration for login

shells here
Note that the login shell also sources the configuration les listed under Table 1.2, “Bash Config-
uration Files for Non-Login Shells”.
TABLE 1.2: BASH CONFIGURATION FILES FOR NON-LOGIN SHELLS
/etc/bash.bashrc Do not modify this le, otherwise your mod-

ifications can be destroyed during your next
update!
/etc/bash.bashrc.local Use this le to insert your system-wide modi-

fications for Bash only
~/.bashrc Insert user specific configuration here
Additionally, Bash uses some more les:
TABLE 1.3: SPECIAL FILES FOR BASH
File Description
~/.bash_history Contains a list of all commands you have

been typing
~/.bash_logout Executed when logging out
~/.alias User defined aliases of frequently used com-

mands. See man 1 alias for more details
about how to define aliases.
3 Knowing the Bash Configuration Files SLES 12 SP3

1.1.2 The Directory Structure
The following table provides a short overview of the most important higher-level directories that
you nd on a Linux system. Find more detailed information about the directories and important
subdirectories in the following list.
TABLE 1.4: OVERVIEW OF A STANDARD DIRECTORY TREE
Directory Contents
/ Root directory—the starting point of the directory tree.
/bin Essential binary les, such as commands that are needed by both
the system administrator and normal users. Usually also contains the
shells, such as Bash.
/boot Static les of the boot loader.
/dev Files needed to access host-specific devices.
/etc Host-specific system configuration les.
/home Holds the home directories of all users who have accounts on the
system. However, root 's home directory is not located in /home
but in /root .
/lib Essential shared libraries and kernel modules.
/media Mount points for removable media.
/mnt Mount point for temporarily mounting a le system.
/opt Add-on application software packages.
/root Home directory for the superuser root .
/sbin Essential system binaries.
/srv Data for services provided by the system.
/tmp Temporary les.
4 The Directory Structure SLES 12 SP3

Directory Contents
/usr Secondary hierarchy with read-only data.
/var Variable data such as log les.
/windows Only available if you have both Microsoft Windows* and Linux in-
stalled on your system. Contains the Windows data.
The following list provides more detailed information and gives some examples of which les
and subdirectories can be found in the directories:
/bin
Contains the basic shell commands that may be used both by root and by other users.
These commands include ls , mkdir , cp , mv , rm and rmdir . /bin also contains Bash,
the default shell in SUSE Linux Enterprise Server.
/boot
Contains data required for booting, such as the boot loader, the kernel, and other data that
is used before the kernel begins executing user-mode programs.
/dev
Holds device les that represent hardware components.
/etc
Contains local configuration les that control the operation of programs like the X Window
System. The /etc/init.d subdirectory contains LSB init scripts that can be executed
during the boot process.
/home/USERNAME
Holds the private data of every user who has an account on the system. The les located
here can only be modified by their owner or by the system administrator. By default, your
e-mail directory and personal desktop configuration are located here in the form of hidden
les and directories, such as .gconf/ and .config .
Note: Home Directory in a Network Environment

If you are working in a network environment, your home directory may be mapped
to a directory in the le system other than /home .

/lib
Contains the essential shared libraries needed to boot the system and to run the commands
in the root le system. The Windows equivalent for shared libraries are DLL les.
/media
Contains mount points for removable media, such as CD-ROMs, ash disks, and digital
cameras (if they use USB). /media generally holds any type of drive except the hard disk of
your system. When your removable medium has been inserted or connected to the system
and has been mounted, you can access it from here.
/mnt
This directory provides a mount point for a temporarily mounted le system. root may
mount le systems here.
/opt
Reserved for the installation of third-party software. Optional software and larger add-on
program packages can be found here.
/root
Home directory for the root user. The personal data of root is located here.
/run
A tmpfs directory used by systemd and various components. /var/run is a symbolic link
to /run .
/sbin
As the s indicates, this directory holds utilities for the superuser. /sbin contains the bi-
naries essential for booting, restoring and recovering the system in addition to the binaries
in /bin .
/srv
Holds data for services provided by the system, such as FTP and HTTP.
/tmp
This directory is used by programs that require temporary storage of les.
Important: Cleaning up /tmp at Boot Time

Data stored in /tmp is not guaranteed to survive a system reboot. It depends, for
example, on settings made in /etc/tmpfiles.d/tmp.conf .

/usr
/usr has nothing to do with users, but is the acronym for Unix system resources. The
data in /usr is static, read-only data that can be shared among various hosts compliant
with the Filesystem Hierarchy Standard (FHS). This directory contains all application
programs including the graphical desktops such as GNOME and establishes a secondary
hierarchy in the le system. /usr holds several subdirectories, such as /usr/bin , /usr/
sbin , /usr/local , and /usr/share/doc .
/usr/bin
Contains generally accessible programs.
/usr/sbin
Contains programs reserved for the system administrator, such as repair functions.
/usr/local
In this directory the system administrator can install local, distribution-independent ex-
tensions.
/usr/share/doc
Holds various documentation les and the release notes for your system. In the manual
subdirectory nd an online version of this manual. If more than one language is installed,
this directory may contain versions of the manuals for different languages.
Under packages nd the documentation included in the software packages installed on
your system. For every package, a subdirectory /usr/share/doc/packages/PACKAGE-
NAME is created that often holds README les for the package and sometimes examples,
configuration les or additional scripts.
If HOWTOs are installed on your system /usr/share/doc also holds the howto subdi-
rectory in which to nd additional documentation on many tasks related to the setup and
operation of Linux software.
/var
Whereas /usr holds static, read-only data, /var is for data which is written during system
operation and thus is variable data, such as log les or spooling data. For an overview of
the most important log les you can nd under /var/log/ , refer to Table 40.1, “Log Files”.

1.2 Writing Shell Scripts
Shell scripts provide a convenient way to perform a wide range of tasks: collecting data, search-
ing for a word or phrase in a text and other useful things. The following example shows a small
shell script that prints a text:
EXAMPLE 1.1: A SHELL SCRIPT PRINTING A TEXT
#!/bin/sh 1
# Output the following line: 2
echo "Hello World" 3
1 The rst line begins with the Shebang

characters ( #! ) which is an indicator that this le is a script. The script is executed with
the specified interpreter after the Shebang, in this case /bin/sh .
2 The second line is a comment beginning with the hash sign. It is recommended to comment
difficult lines to remember what they do.
3 The third line uses the built-in command echo to print the corresponding text.
Before you can run this script you need some prerequisites:
1. Every script should contain a Shebang line (as in the example above.) If the line is missing,
you need to call the interpreter manually.
2. You can save the script wherever you want. However, it is a good idea to save it in a
directory where the shell can nd it. The search path in a shell is determined by the
environment variable PATH . Usually a normal user does not have write access to /usr/
bin . Therefore it is recommended to save your scripts in the users' directory ~/bin/ . The
above example gets the name hello.sh .
3. The script needs executable permissions. Set the permissions with the following command:
chmod +x ~/bin/hello.sh
If you have fulfilled all of the above prerequisites, you can execute the script in the following
ways:
1. As Absolute Path. The script can be executed with an absolute path. In our case, it is ~/
bin/hello.sh .
2. Everywhere. If the PATH environment variable contains the directory where the script is
located, you can execute the script with hello.sh .
8 Writing Shell Scripts SLES 12 SP3

1.3 Redirecting Command Events
Each command can use three channels, either for input or output:
Standard Output. This is the default output channel. Whenever a command prints some-
thing, it uses the standard output channel.
Standard Input. If a command needs input from users or other commands, it uses this
channel.
Standard Error. Commands use this channel for error reporting.
To redirect these channels, there are the following possibilities:
Command > File

Saves the output of the command into a le, an existing le will be deleted. For example,
the ls command writes its output into the le listing.txt :
ls > listing.txt
Command >> File

Appends the output of the command to a le. For example, the ls command appends its
output to the le listing.txt :
ls >> listing.txt
Command < File

Reads the le as input for the given command. For example, the read command reads in
the content of the le into the variable:
read a < foo
Command1 | Command2
Redirects the output of the left command as input for the right command. For example,
the cat command outputs the content of the /proc/cpuinfo le. This output is used by
grep to filter only those lines which contain cpu :
cat /proc/cpuinfo | grep cpu
9 Redirecting Command Events SLES 12 SP3

Every channel has a le descriptor: 0 (zero) for standard input, 1 for standard output and 2 for
standard error. It is allowed to insert this le descriptor before a < or > character. For example,
the following line searches for a le starting with foo , but suppresses its errors by redirecting
it to /dev/null :
find / -name "foo*" 2>/dev/null
1.4 Using Aliases

An alias is a shortcut definition of one or more commands. The syntax for an alias is:
alias NAME=DEFINITION
For example, the following line defines an alias lt that outputs a long listing (option -l ), sorts
it by modification time ( -t ), and prints it in reverse sorted order ( -r ):
alias lt='ls -ltr'
To view all alias definitions, use alias . Remove your alias with unalias and the corresponding
alias name.
1.5 Using Variables in Bash

A shell variable can be global or local. Global variables, or environment variables, can be ac-
cessed in all shells. In contrast, local variables are visible in the current shell only.
To view all environment variables, use the printenv command. If you need to know the value
of a variable, insert the name of your variable as an argument:
printenv PATH
A variable, be it global or local, can also be viewed with echo :
echo $PATH
To set a local variable, use a variable name followed by the equal sign, followed by the value:
PROJECT="SLED"
10 Using Aliases SLES 12 SP3

Do not insert spaces around the equal sign, otherwise you get an error. To set an environment
variable, use export :
export NAME="tux"
To remove a variable, use unset :
unset NAME
The following table contains some common environment variables which can be used in you
shell scripts:
TABLE 1.5: USEFUL ENVIRONMENT VARIABLES
HOME the home directory of the current user
HOST the current host name
LANG when a tool is localized, it uses the language

from this environment variable. English can
also be set to C
PATH the search path of the shell, a list of directo-

ries separated by colon
PS1 specifies the normal prompt printed before

each command
PS2 specifies the secondary prompt printed when

you execute a multi-line command
PWD current working directory
USER the current user
1.5.1 Using Argument Variables

For example, if you have the script foo.sh you can execute it like this:
foo.sh "Tux Penguin" 2000
11 Using Argument Variables SLES 12 SP3

To access all the arguments which are passed to your script, you need positional parameters.
These are $1 for the rst argument, $2 for the second, and so on. You can have up to nine
parameters. To get the script name, use $0 .
The following script foo.sh prints all arguments from 1 to 4:
#!/bin/sh
echo \"$1\" \"$2\" \"$3\" \"$4\"
If you execute this script with the above arguments, you get:
"Tux Penguin" "2000" "" ""
1.5.2 Using Variable Substitution

Variable substitutions apply a pattern to the content of a variable either from the left or right
side. The following list contains the possible syntax forms:
${VAR#pattern}
removes the shortest possible match from the left:
file=/home/tux/book/book.tar.bz2
echo ${file#*/}
home/tux/book/book.tar.bz2
${VAR##pattern}
removes the longest possible match from the left:
echo ${file##*/}
book.tar.bz2
${VAR%pattern}
removes the shortest possible match from the right:
echo ${file%.*}
/home/tux/book/book.tar
${VAR%%pattern}
removes the longest possible match from the right:
echo ${file%%.*}
/home/tux/book/book
12 Using Variable Substitution SLES 12 SP3

${VAR/pattern_1/pattern_2}
substitutes the content of VAR from the PATTERN_1 with PATTERN_2 :
echo ${file/tux/wilber}
/home/wilber/book/book.tar.bz2
1.6 Grouping and Combining Commands

Shells allow you to concatenate and group commands for conditional execution. Each command
returns an exit code which determines the success or failure of its operation. If it is 0 (zero) the
command was successful, everything else marks an error which is specific to the command.
The following list shows, how commands can be grouped:
Command1 ; Command2
executes the commands in sequential order. The exit code is not checked. The following
line displays the content of the le with cat and then prints its le properties with ls
regardless of their exit codes:
cat filelist.txt ; ls -l filelist.txt
Command1 && Command2

runs the right command, if the left command was successful (logical AND). The following
line displays the content of the le and prints its le properties only, when the previous
command was successful (compare it with the previous entry in this list):
cat filelist.txt && ls -l filelist.txt
Command1 || Command2
runs the right command, when the left command has failed (logical OR). The following
line creates only a directory in /home/wilber/bar when the creation of the directory in
/home/tux/foo has failed:
mkdir /home/tux/foo || mkdir /home/wilber/bar
funcname(){ ... }
creates a shell function. You can use the positional parameters to access its arguments. The
following line defines the function hello to print a short message:
hello() { echo "Hello $1"; }
13 Grouping and Combining Commands SLES 12 SP3

You can call this function like this:
hello Tux
which prints:
Hello Tux
1.7 Working with Common Flow Constructs

To control the ow of your script, a shell has while , if , for and case constructs.
1.7.1 The if Control Command

The if command is used to check expressions. For example, the following code tests whether
the current user is Tux:
if test $USER = "tux"; then

echo "Hello Tux."
else
echo "You are not Tux."
fi
The test expression can be as complex or simple as possible. The following expression checks
if the le foo.txt exists:
if test -e /tmp/foo.txt ; then

echo "Found foo.txt"
fi
The test expression can also be abbreviated in angled brackets:
if [ -e /tmp/foo.txt ] ; then
echo "Found foo.txt"
fi
Find more useful expressions at http://www.cyberciti.biz/nixcraft/linux/docs/uniqlinuxfea-

tures/lsst/ch03sec02.html .
14 Working with Common Flow Constructs SLES 12 SP3

1.7.2 Creating Loops with the for Command
The for loop allows you to execute commands to a list of entries. For example, the following
code prints some information about PNG les in the current directory:
for i in *.png; do
ls -l $i
done
1.8 For More Information

Important information about Bash is provided in the man pages man bash . More about this
topic can be found in the following list:
http://tldp.org/LDP/Bash-Beginners-Guide/html/index.html —Bash Guide for Beginners
http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html —BASH Programming - Introduc-

tion HOW-TO
http://tldp.org/LDP/abs/html/index.html —Advanced Bash-Scripting Guide
http://www.grymoire.com/Unix/Sh.html —Sh - the Bourne Shell
15 Creating Loops with the for Command SLES 12 SP3

2 sudo
Many commands and system utilities need to be run as root to modify les and/or perform
tasks that only the super user is allowed to. For security reasons and to avoid accidentally
running dangerous commands, it is generally advisable not to log in directly as root . Instead,
it is recommended to work as a normal, unprivileged user and use the sudo command to run
commands with elevated privileges.
On SUSE Linux Enterprise Server, sudo is configured by default to work similarly to su. How-
ever, sudo offers the possibility to allow users to run commands with privileges of any other
user in a highly configurable manner. This can be used to assign roles with specific privileges to
certain users and groups. It is for example possible to allow members of the group users to run
a command with the privileges of wilber . Access to the command can be further restricted by,
for example, forbidding to specify any command options. While su always requires the root
password for authentication with PAM, sudo can be configured to authenticate with your own
credentials. This increases security by not having to share the root password. For example,
you can allow members of the group users to run a command frobnicate as wilber , with
the restriction that no arguments are specified. This can be used to assign roles with specific
abilities to certain users and groups.
2.1 Basic sudo Usage

sudo is simple to use, yet very powerful.
2.1.1 Running a Single Command

Logged in as normal user, you can run any command as root by adding sudo before it. It will
prompt for the root password and, if authenticated successfully, run the command as root :
tux > id -un 1
tux
tux > sudo id -un
root's password: 2
root
tux > id -un
tux 3
tux > sudo id -un

4
16 Basic sudo Usage SLES 12 SP3

root
1 The id -un command prints the login name of the current user.
2 The password is not shown during input, neither as clear text nor as bullets.
3 Only commands started with sudo are run with elevated privileges. If you run the same
command without the sudo prefix, it is run with the privileges of the current user again.
4 For a limited amount of time, you do not need to enter the root password again.
Tip: I/O Redirection

I/O redirection does not work as you would probably expect:
tux > sudo echo s > /proc/sysrq-trigger

bash: /proc/sysrq-trigger: Permission denied
tux > sudo cat < /proc/1/maps
bash: /proc/1/maps: Permission denied
Only the echo / cat binary is run with elevated privileges, while the redirection is per-
formed by the user's shell with user privileges. You can either start a shell like in Sec-
tion 2.1.2, “Starting a Shell” or use the dd utility instead:
echo s | sudo dd of=/proc/sysrq-trigger

sudo dd if=/proc/1/maps | cat
2.1.2 Starting a Shell

Having to add sudo before every command can be cumbersome. While you could specify a
shell as a command sudo bash , it is recommended to rather use one of the built-in mechanisms
to start a shell:
sudo -s (<command>)
Starts a shell specified by the SHELL environment variable or the target user's default shell.
If a command is given, it is passed to the shell (with the -c option), else the shell is run
in interactive mode.
tux:~ > sudo -i

root's password:
root:/home/tux # exit
17 Starting a Shell SLES 12 SP3

tux:~ >
sudo -i (<command>)
Like -s , but starts the shell as login shell. This means that the shell's start-up les ( .pro-
file etc.) are processed and the current working directory is set to the target user's home
directory.
tux:~ > sudo -i

root's password:
root:~ # exit
tux:~ >
2.1.3 Environment Variables

By default, sudo does not propagate environment variables:
tux > ENVVAR=test env | grep ENVVAR

ENVVAR=test
tux > ENVVAR=test sudo env | grep ENVVAR
root's password:
1
tux >
1 The empty output shows that the environment variable ENVVAR did not exist in the context
of the command run with sudo .
This behavior can be changed by the env_reset option, see Table 2.1, “Useful Flags and Options”.
2.2 Configuring sudo

sudo is a very flexible tool with extensive configuration.
Note: Locked yourself out of sudo

If you accidentally locked yourself out of sudo , use su - and the root password to get
a root shell. To x the error, run visudo .
18 Environment Variables SLES 12 SP3

2.2.1 Editing the Configuration Files
The main policy configuration le for sudo is /etc/sudoers . As it is possible to lock yourself
out of the system due to errors in this le, it is strongly recommended to use visudo for editing.
It will prevent simultaneous changes to the opened le and check for syntax errors before saving
the modifications.
Despite its name, you can also use editors other than vi by setting the EDITOR environment
variable, for example:
sudo EDITOR=/usr/bin/nano visudo
However, the /etc/sudoers le itself is supplied by the system packages and modifications
may break on updates. Therefore, it is recommended to put custom configuration into les in
the /etc/sudoers.d/ directory. Any le in there is automatically included. To create or edit
a le in that subdirectory, run:
sudo visudo -f /etc/sudoers.d/NAME
Alternatively with a different editor (for example nano ):
sudo EDITOR=/usr/bin/nano visudo -f /etc/sudoers.d/NAME
Note: Ignored Files in /etc/sudoers.d

The #includedir command in /etc/sudoers , used for /etc/sudoers.d , ignores les
that end in ~ (tilde) or contain a . (dot).
For more information on the visudo command, run man 8 visudo .
2.2.2 Basic sudoers Configuration Syntax

In the sudoers configuration les, there are two types of options: strings and ags. While strings
can contain any value, ags can be turned either ON or OFF. The most important syntax con-
structs for sudoers configuration les are:
# Everything on a line after a # gets ignored 1
Defaults !insults # Disable the insults flag 2
Defaults env_keep += "DISPLAY HOME" # Add DISPLAY and HOME to env_keep

tux ALL = NOPASSWD: /usr/bin/frobnicate, PASSWD: /usr/bin/journalctl 3
19 Editing the Configuration Files SLES 12 SP3

1 There are two exceptions: #include and #includedir are normal commands. Followed
by digits, it specifies a UID.
2 Remove the ! to set the specified ag to ON.
3 See Section 2.2.3, “Rules in sudoers”.
TABLE 2.1: USEFUL FLAGS AND OPTIONS
Option name Description Example
targetpw This ag controls whether Defaults targetpw # Turn

targetpw flag ON
the invoking user is required
to enter the password of the
target user (ON) (for example
root ) or the invoking user
(OFF).
rootpw If set, sudo will prompt for Defaults !rootpw # Turn

rootpw flag OFF
the root password instead
of the target user's or the in-
voker's. The default is OFF.
env_reset If set, sudo constructs a min- Defaults env_reset # Turn

env_reset flag ON
imal environment with only
TERM , PATH , HOME , MAIL ,
SHELL , LOGNAME , USER ,
USERNAME , and SUDO_* set.
Additionally, variables list-
ed in env_keep get import-
ed from the calling environ-
ment. The default is ON.
env_keep List of environment variables # Set env_keep to contain

EDITOR and PROMPT
to keep when the env_reset
Defaults env_keep = "EDITOR
ag is ON. PROMPT"
Defaults env_keep +=
"JRE_HOME" # Add JRE_HOME
Defaults env_keep -=
"JRE_HOME" # Remove
JRE_HOME
20 Basic sudoers Configuration Syntax SLES 12 SP3

Option name Description Example
env_delete List of environment variables # Set env_delete to contain

EDITOR and PROMPT
to remove when the env_re-
Defaults env_delete =
set ag is OFF. "EDITOR PROMPT"
Defaults env_delete +=
"JRE_HOME" # Add JRE_HOME
Defaults env_delete -
= "JRE_HOME" # Remove
JRE_HOME
The Defaults token can also be used to create aliases for a collection of users, hosts, and
commands. Furthermore, it is possible to apply an option only to a specific set of users.
For detailed information about the /etc/sudoers configuration le, consult man 5 sudoers .
2.2.3 Rules in sudoers

Rules in the sudoers configuration can be very complex, so this section will only cover the basics.
Each rule follows the basic scheme ( [] marks optional parts):
#Who Where As whom Tag What

User_List Host_List = [(User_List)] [NOPASSWD:|PASSWD:] Cmnd_List
SYNTAX FOR SUDOERS RULES
User_List
One or more (separated by , ) identifiers: Either a user name, a group in the format
%GROUPNAME or a user ID in the format #UID . Negation can be performed with a ! prefix.
Host_List
One or more (separated by , ) identifiers: Either a (fully qualified) host name or an IP ad-
dress. Negation can be performed with a ! prefix. ALL is the usual choice for Host_List .
NOPASSWD:|PASSWD:
The user will not be prompted for a password when running commands matching CMDSPEC
after NOPASSWD: .
PASSWD is the default, it only needs to be specified when both are on the same line:
tux ALL = PASSWD: /usr/bin/foo, NOPASSWD: /usr/bin/bar
21 Rules in sudoers SLES 12 SP3

Cmnd_List
One or more (separated by , ) specifiers: A path to an executable, followed by allowed
arguments or nothing.
/usr/bin/foo # Anything allowed

/usr/bin/foo bar # Only "/usr/bin/foo bar" allowed
/usr/bin/foo "" # No arguments allowed
ALL can be used as User_List , Host_List , and Cmnd_List .
A rule that allows tux to run all commands as root without entering a password:
tux ALL = NOPASSWD: ALL
A rule that allows tux to run systemctl restart apache2 :
tux ALL = /usr/bin/systemctl restart apache2
A rule that allows tux to run wall as admin with no arguments:
tux ALL = (admin) /usr/bin/wall ""
Warning: Dangerous constructs

Constructs of the kind
ALL ALL = ALL
must not be used without Defaults targetpw , otherwise anyone can run commands
as root .
2.3 Common Use Cases

Although the default configuration is often sufficient for simple setups and desktop environ-
ments, custom configurations can be very useful.
2.3.1 Using sudo without root Password

In cases with special restrictions (“user X can only run command Y as root ”) it is not possible.
In other cases, it is still favorable to have some kind of separation. By convention, members of
the group wheel can run all commands with sudo as root.
22 Common Use Cases SLES 12 SP3

1. Add yourself to the wheel group
If your user account is not already member of the wheel group, add it by running sudo
usermod -a -G wheel USERNAME and logging out and in again. Verify that the change
was successful by running groups USERNAME .
2. Make authentication with the invoking user's password the default.

Create the le /etc/sudoers.d/userpw with visudo (see Section 2.2.1, “Editing the Con-
figuration Files”) and add:
Defaults !targetpw
3. Select a new default rule.

Depending on whether you want users to re-enter their passwords, uncomment the specific
line in /etc/sudoers and comment out the default rule.
## Uncomment to allow members of group wheel to execute any command

# %wheel ALL=(ALL) ALL
## Same thing without a password

# %wheel ALL=(ALL) NOPASSWD: ALL
4. Make the default rule more restrictive

Comment out or remove the allow-everything rule in /etc/sudoers :
ALL ALL=(ALL) ALL # WARNING! Only use this together with 'Defaults targetpw'!
Warning: Dangerous rule in sudoers

Do not forget this step, otherwise any user can execute any command as root !
5. Test the configuration

Try to run sudo as member and non-member of wheel .
tux:~ > groups

users wheel
tux:~ > sudo id -un
tux's password:
root
wilber:~ > groups
users
wilber:~ > sudo id -un
wilber is not in the sudoers file. This incident will be reported.
23 Using sudo without root Password SLES 12 SP3

2.3.2 Using sudo with X.Org Applications
When starting graphical applications with sudo , you will encounter the following error:
tux > sudo xterm

xterm: Xt error: Can't open display: %s
xterm: DISPLAY is not set
YaST will pick the ncurses interface instead of the graphical one.
To use X.Org in applications started with sudo , the environment variables DISPLAY and XAU-
THORITY need to be propagated. To configure this, create the le /etc/sudoers.d/xorg , (see
Section 2.2.1, “Editing the Configuration Files”) and add the following line:
Defaults env_keep += "DISPLAY XAUTHORITY"
If not set already, set the XAUTHORITY variable as follows:
export XAUTHORITY=~/.Xauthority
Now X.Org applications can be run as usual:
sudo yast2
2.4 More Information

A quick overview about the available command line switches can be retrieved by sudo --help .
An explanation and other important information can be found in the man page: man 8 sudo ,
while the configuration is documented in man 5 sudoers .
24 Using sudo with X.Org Applications SLES 12 SP3

3 YaST Online Update
SUSE offers a continuous stream of software security updates for your product. By default, the
update applet is used to keep your system up-to-date. Refer to Book “Deployment Guide”, Chap-
ter 13 “Installing or Removing Software”, Section 13.4 “Keeping the System Up-to-date” for further in-
formation on the update applet. This chapter covers the alternative tool for updating software
packages: YaST Online Update.
The current patches for SUSE® Linux Enterprise Server are available from an update software
repository. If you have registered your product during the installation, an update repository
is already configured. If you have not registered SUSE Linux Enterprise Server, you can do so
by starting the Product Registration in YaST. Alternatively, you can manually add an update
repository from a source you trust. To add or remove repositories, start the Repository Manager
with Software Software Repositories in YaST. Learn more about the Repository Manager in Book
“Deployment Guide”, Chapter 13 “Installing or Removing Software”, Section 13.3 “Managing Software
Repositories and Services”.
Note: Error on Accessing the Update Catalog

If you are not able to access the update catalog, this might be because of an expired
subscription. Normally, SUSE Linux Enterprise Server comes with a one-year or three-
year subscription, during which you have access to the update catalog. This access will
be denied after the subscription ends.
If an access to the update catalog is denied, you will see a warning message prompting
you to visit the SUSE Customer Center and check your subscription. The SUSE Customer
Center is available at https://scc.suse.com// .
SUSE provides updates with different relevance levels:
Security Updates
Fix severe security hazards and should always be installed.
Recommended Updates
Fix issues that could compromise your computer.
Optional Updates
Fix non-security relevant issues or provide enhancements.
25 SLES 12 SP3
3.1 The Online Update Dialog
To open the YaST Online Update dialog, start YaST and select Software Online Update. Alterna-
tively, start it from the command line with yast2 online_update .
The Online Update window consists of four sections.
FIGURE 3.1: YAST ONLINE UPDATE
The Summary section on the left lists the available patches for SUSE Linux Enterprise Server.
The patches are sorted by security relevance: security , recommended , and optional . You
can change the view of the Summary section by selecting one of the following options from Show
Patch Category:
Needed Patches (default view)

Non-installed patches that apply to packages installed on your system.
Unneeded Patches
Patches that either apply to packages not installed on your system, or patches that have
requirements which have already have been fulfilled (because the relevant packages have
already been updated from another source).
All Patches
All patches available for SUSE Linux Enterprise Server.
26 The Online Update Dialog SLES 12 SP3

Each list entry in the Summary section consists of a symbol and the patch name. For an overview
of the possible symbols and their meaning, press Shift – F1 . Actions required by Security
and Recommended patches are automatically preset. These actions are Autoinstall, Autoupdate
and Autodelete.
If you install an up-to-date package from a repository other than the update repository, the
requirements of a patch for this package may be fulfilled with this installation. In this case a
check mark is displayed in front of the patch summary. The patch will be visible in the list until
you mark it for installation. This will in fact not install the patch (because the package already
is up-to-date), but mark the patch as having been installed.
Select an entry in the Summary section to view a short Patch Description at the bottom left corner
of the dialog. The upper right section lists the packages included in the selected patch (a patch
can consist of several packages). Click an entry in the upper right section to view details about
the respective package that is included in the patch.
3.2 Installing Patches

The YaST Online Update dialog allows you to either install all available patches at once or
manually select the desired patches. You may also revert patches that have been applied to the
system.
By default, all new patches (except optional ones) that are currently available for your system
are already marked for installation. They will be applied automatically once you click Accept or
Apply. If one or multiple patches require a system reboot, you will be notified about this before
the patch installation starts. You can then either decide to continue with the installation of the
selected patches, skip the installation of all patches that need rebooting and install the rest, or
go back to the manual patch selection.
PROCEDURE 3.1: APPLYING PATCHES WITH YAST ONLINE UPDATE
1. Start YaST and select Software Online Update.
2. To automatically apply all new patches (except optional ones) that are currently avail-
able for your system, press Apply or Accept.
3. First modify the selection of patches that you want to apply:
a. Use the respective filters and views that the interface provides. For details, refer to
Section 3.1, “The Online Update Dialog”.
27 Installing Patches SLES 12 SP3

b. Select or deselect patches according to your needs and wishes by right-clicking the
patch and choosing the respective action from the context menu.
Important: Always Apply Security Updates

Do not deselect any security -related patches without a very good reason.
These patches x severe security hazards and prevent your system from being
exploited.
c. Most patches include updates for several packages. If you want to change actions for
single packages, right-click a package in the package view and choose an action.
d. To confirm your selection and apply the selected patches, proceed with Apply or
Accept.
4. After the installation is complete, click Finish to leave the YaST Online Update. Your system
is now up-to-date.
3.3 Automatic Online Update

YaST also offers the possibility to set up an automatic update with daily, weekly or monthly
schedule. To use the respective module, you need to install the yast2-online-update-con-
figuration package rst.
By default, updates are downloaded as delta RPMs. Since rebuilding RPM packages from delta
RPMs is a memory- and processor-intensive task, certain setups or hardware configurations
might require you to disable the use of delta RPMs for the sake of performance.
Some patches, such as kernel updates or packages requiring license agreements, require user
interaction, which would cause the automatic update procedure to stop. You can configure to
skip patches that require user interaction.
PROCEDURE 3.2: CONFIGURING THE AUTOMATIC ONLINE UPDATE
1. After installation, start YaST and select Software Online Update Configuration.
Alternatively, start the module with yast2 online_update_configuration from the
command line.
2. Activate Automatic Online Update.
28 Automatic Online Update SLES 12 SP3

3. Choose the update interval: Daily, Weekly, or Monthly.
4. To automatically accept any license agreements, activate Agree with Licenses.
5. Select if you want to Skip Interactive Patches in case you want the update procedure to
proceed fully automatically.
Important: Skipping Patches

If you select to skip any packages that require interaction, run a manual Online Up-
date occasionally to install those patches, too. Otherwise you might miss important
patches.
6. To automatically install all packages recommended by updated packages, activate Include

Recommended Packages.
7. To disable the use of delta RPMs (for performance reasons), deactivate Use Delta RPMs.
8. To filter the patches by category (such as security or recommended), activate Filter by Cat-
egory and add the appropriate patch categories from the list. Only patches of the selected
categories will be installed. Others will be skipped.
9. Confirm your configuration with OK.
The automatic online update does not automatically restart the system afterward. If there are
package updates that require a system reboot, you need to do this manually.
29 Automatic Online Update SLES 12 SP3

4 YaST
YaST is the installation and configuration tool for SUSE Linux Enterprise Server. It has a graph-
ical interface and the capability to customize your system quickly during and after the installa-
tion. It can be used to set up hardware, configure the network, system services, and tune your
security settings.
4.1 Advanced Key Combinations

YaST has a set of advanced key combinations.
Print Screen
Take and save a screenshot. May not be available when YaST is running under some desk-
top environments.
Shift – F4
Enable/disable the color palette optimized for vision impaired users.
Shift – F7
Enable/disable logging of debug messages.
Shift – F8
Open a le dialog to save log les to a non-standard location.
Ctrl – Shift – Alt – D

Send a DebugEvent. YaST modules can react to this by executing special debugging actions.
The result depends on the specific YaST module.
Ctrl – Shift – Alt – M

Start/stop macro recorder.
Ctrl – Shift – Alt – P

Replay macro.
Ctrl – Shift – Alt – S

Show style sheet editor.
Ctrl – Shift – Alt – T

Dump widget tree to the log le.
30 Advanced Key Combinations SLES 12 SP3

Ctrl – Shift – Alt – X
Open a terminal window (xterm). Useful for installation process via VNC.
Ctrl – Shift – Alt – Y

Show widget tree browser.

5 YaST in Text Mode
This section is intended for system administrators and experts who do not run an X server on
their systems and depend on the text-based installation tool. It provides basic information about
starting and operating YaST in text mode.
YaST in text mode uses the ncurses library to provide an easy pseudo-graphical user interface.
The ncurses library is installed by default. The minimum supported size of the terminal emulator
in which to run YaST is 80x25 characters.
FIGURE 5.1: MAIN WINDOW OF YAST IN TEXT MODE
When you start YaST in text mode, the YaST control center appears (see Figure 5.1). The main
window consists of three areas. The left frame features the categories to which the various
modules belong. This frame is active when YaST is started and therefore it is marked by a
bold white border. The active category is selected. The right frame provides an overview of
the modules available in the active category. The bottom frame contains the buttons for Help
and Quit.
When you start the YaST control center, the category Software is selected automatically. Use
↓ and ↑ to change the category. To select a module from the category, activate the right
frame with → and then use ↓ and ↑ to select the module. Keep the arrow keys pressed to
scroll through the list of available modules. The selected module is selected. Press Enter to
start the active module.
32 SLES 12 SP3
Various buttons or selection elds in the module contain a highlighted letter (yellow by default).
Use Alt – highlighted_letter to select a button directly instead of navigating there with →| .
Exit the YaST control center by pressing Alt – Q or by selecting Quit and pressing Enter .
Tip: Refreshing YaST Dialogs

If a YaST dialog gets corrupted or distorted (for example, while resizing the window),
press Ctrl – L to refresh and restore its contents.
5.1 Navigation in Modules

The following description of the control elements in the YaST modules assumes that all function
keys and Alt key combinations work and are not assigned to different global functions. Read
Section 5.3, “Restriction of Key Combinations” for information about possible exceptions.
Navigation among Buttons and Selection Lists

Use →| to navigate among the buttons and frames containing selection lists. To navigate
in reverse order, use Alt – →| or Shift – →| combinations.
Navigation in Selection Lists

Use the arrow keys ( ↑ and ↓ ) to navigate among the individual elements in an active
frame containing a selection list. If individual entries within a frame exceed its width,
use Shift – → or Shift – ← to scroll horizontally to the right and left. Alternatively, use
Ctrl – E or Ctrl – A . This combination can also be used if using → or ← results in
changing the active frame or the current selection list, as in the control center.
Buttons, Radio Buttons, and Check Boxes

To select buttons with empty square brackets (check boxes) or empty parentheses (radio
buttons), press Space or Enter . Alternatively, radio buttons and check boxes can be
selected directly with Alt – highlighted_letter . In this case, you do not need to confirm
with Enter . If you navigate to an item with →| , press Enter to execute the selected
action or activate the respective menu item.
33 Navigation in Modules SLES 12 SP3

Function Keys
The function keys ( F1 ... F12 ) enable quick access to the various buttons. Available
function key combinations ( FX ) are shown in the bottom line of the YaST screen. Which
function keys are actually mapped to which buttons depend on the active YaST module,
because the different modules offer different buttons (Details, Info, Add, Delete, etc.). Use
F10 for Accept, OK, Next, and Finish. Press F1 to access the YaST help.
Using Navigation Tree in ncurses Mode

Some YaST modules use a navigation tree in the left part of the window to select config-
uration dialogs. Use the arrow keys ( ↑ and ↓ ) to navigate in the tree. Use Space to
open or close tree items. In ncurses mode, Enter must be pressed after a selection in the
navigation tree to show the selected dialog. This is an intentional behavior to save time
consuming redraws when browsing through the navigation tree.
Selecting Software in the Software Installation Module

Use the filters on the left side to limit the amount of displayed packages. Installed packages
are marked with the letter i . To change the status of a package, press Space or Enter .
Alternatively, use the Actions menu to select the needed status change (install, delete,
update, taboo or lock).
FIGURE 5.2: THE SOFTWARE INSTALLATION MODULE
34 Navigation in Modules SLES 12 SP3

5.2 Advanced Key Combinations
YaST in text mode has a set of advanced key combinations.
Shift – F1
Show a list of advanced hotkeys.
Shift – F4
Change color schema.
Ctrl –\
Quit the application.
Ctrl –L
Refresh screen.
Ctrl –D F1
Show a list of advanced hotkeys.
Ctrl –D Shift –D
Dump dialog to the log le as a screenshot.
Ctrl –D Shift –Y
Open YDialogSpy to see the widget hierarchy.
5.3 Restriction of Key Combinations

If your window manager uses global Alt combinations, the Alt combinations in YaST might
not work. Keys like Alt or Shift can also be occupied by the settings of the terminal.
Replacing Alt with Esc
Alt shortcuts can be executed with Esc instead of Alt . For example, Esc – H replaces
Alt – H . (First press Esc , then press H .)
Backward and Forward Navigation with Ctrl – F and Ctrl –B

If the Alt and Shift combinations are occupied by the window manager or the terminal,
use the combinations Ctrl – F (forward) and Ctrl – B (backward) instead.

Restriction of Function Keys
The function keys ( F1 ... F12 ) are also used for functions. Certain function keys might
be occupied by the terminal and may not be available for YaST. However, the Alt key
combinations and function keys should always be fully available on a pure text console.
5.4 YaST Command Line Options

Besides the text mode interface, YaST provides a pure command line interface. To get a list of
YaST command line options, enter:
yast -h
5.4.1 Starting the Individual Modules
To save time, the individual YaST modules can be started directly. To start a module, enter:
yast <module_name>
View a list of all module names available on your system with yast -l or yast --list . Start
the network module, for example, with yast lan .
5.4.2 Installing Packages from the Command Line

If you know a package name and the package is provided by any of your active installation
repositories, you can use the command line option -i to install the package:
yast -i <package_name>
or
yast --install <package_name>
PACKAGE_NAME can be a single short package name (for example gvim ) installed with depen-
dency checking, or the full path to an RPM package which is installed without dependency
checking.
36 YaST Command Line Options SLES 12 SP3

If you need a command line based software management utility with functionality beyond what
YaST provides, consider using Zypper. This utility uses the same software management library
that is also the foundation for the YaST package manager. The basic usage of Zypper is covered
in Section 6.1, “Using Zypper”.
5.4.3 Command Line Parameters of the YaST Modules

To use YaST functionality in scripts, YaST provides command line support for individual mod-
ules. Not all modules have command line support. To display the available options of a module,
enter:
yast <module_name> help
If a module does not provide command line support, the module is started in text mode and
the following message appears:
This YaST module does not support the command line interface.
37 Command Line Parameters of the YaST Modules SLES 12 SP3

6 Managing Software with Command Line Tools
This chapter describes Zypper and RPM, two command line tools for managing soft-
ware. For a definition of the terminology used in this context (for example, repos-
itory , patch , or update ) refer to Book “Deployment Guide”, Chapter 13 “Installing or
Removing Software”, Section 13.1 “Definition of Terms”.
6.1 Using Zypper

Zypper is a command line package manager for installing, updating and removing packages
a well as for managing repositories. It is especially useful for accomplishing remote software
management tasks or managing software from shell scripts.
6.1.1 General Usage

The general syntax of Zypper is:
zypper [--global-options] COMMAND [--command-options] [arguments]
The components enclosed in brackets are not required. See zypper help for a list of general
options and all commands. To get help for a specific command, type zypper help COMMAND .
Zypper Commands
The simplest way to execute Zypper is to type its name, followed by a command. For
example, to apply all needed patches to the system, use:
tux > sudo zypper patch
Global Options
Additionally, you can choose from one or more global options by typing them immediately
before the command:
tux > sudo zypper --non-interactive patch
In the above example, the option --non-interactive means that the command is run
without asking anything (automatically applying the default answers).
38 Using Zypper SLES 12 SP3

Command-Specific Options
To use options that are specific to a particular command, type them immediately after the
command:
tux > sudo zypper patch --auto-agree-with-licenses
In the above example, --auto-agree-with-licenses is used to apply all needed patch-

es to a system without you being asked to confirm any licenses. Instead, license will be
accepted automatically.
Arguments
Some commands require one or more arguments. For example, when using the command
install , you need to specify which package or which packages you want to install:
tux > sudo zypper install mplayer
Some options also require a single argument. The following command will list all known
patterns:
tux > zypper search -t pattern
You can combine all of the above. For example, the following command will install the as-
pell-de and aspell-fr packages from the factory repository while being verbose:
tux > sudo zypper -v install --from factory aspell-de aspell-fr
The --from option makes sure to keep all repositories enabled (for solving any dependencies)
while requesting the package from the specified repository.
Most Zypper commands have a dry-run option that does a simulation of the given command.
It can be used for test purposes.
tux > sudo zypper remove --dry-run MozillaFirefox
Zypper supports the global --userdata STRING option. You can specify a string with this
option, which gets written to Zypper's log les and plug-ins (such as the Btrfs plug-in). It can
be used to mark and identify transactions in log les.
tux > sudo zypper --userdata STRING patch
39 General Usage SLES 12 SP3

6.1.2 Installing and Removing Software with Zypper
To install or remove packages, use the following commands:
tux > sudo zypper install PACKAGE_NAME

sudo zypper remove PACKAGE_NAME
Warning: Do Not Remove Mandatory System Packages

Do not remove mandatory system packages like glibc , zypper , kernel . If they are
removed, the system can become unstable or stop working altogether.
6.1.2.1 Selecting Which Packages to Install or Remove
There are various ways to address packages with the commands zypper install and zypper
remove .
By Exact Package Name
tux > sudo zypper install MozillaFirefox
By Exact Package Name and Version Number
tux > sudo zypper install MozillaFirefox-52.2
By Repository Alias and Package Name
tux > sudo zypper install mozilla:MozillaFirefox
Where mozilla is the alias of the repository from which to install.
By Package Name Using Wild Cards

You can select all packages that have names starting or ending with a certain string. Use
wild cards with care, especially when removing packages. The following command will
install all packages starting with “Moz”:
tux > sudo zypper install 'Moz*'
40 Installing and Removing Software with Zypper SLES 12 SP3

Tip: Removing all -debuginfo Packages
When debugging a problem, you sometimes need to temporarily install a lot of -
debuginfo packages which give you more information about running processes.
After your debugging session finishes and you need to clean the environment, run
the following:
tux > sudo zypper remove '*-debuginfo'
By Capability
For example, if you want to install a Perl module without knowing the name of the package,
capabilities come in handy:
tux > sudo zypper install firefox
By Capability, Hardware Architecture, or Version

Together with a capability, you can specify a hardware architecture and a version:
The name of the desired hardware architecture is appended to the capability after a
full stop. For example, to specify the AMD64/Intel 64 architectures (which in Zypper
is named x86_64 ), use:
tux > sudo zypper install 'firefox.x86_64'
Versions must be appended to the end of the string and must be preceded by an
operator: < (lesser than), <= (lesser than or equal), = (equal), >= (greater than or
equal), > (greater than).
tux > sudo zypper install 'firefox>=52.2'
You can also combine a hardware architecture and version requirement:
tux > sudo zypper install 'firefox.x86_64>=52.2'
By Path to the RPM file

You can also specify a local or remote path to a package:
tux > sudo zypper install /tmp/install/MozillaFirefox.rpm

tux > sudo zypper install http://download.example.com/MozillaFirefox.rpm

6.1.2.2 Combining Installation and Removal of Packages
To install and remove packages simultaneously, use the +/- modifiers. To install emacs and
simultaneously remove vim , use:
tux > sudo zypper install emacs -vim
To remove emacs and simultaneously install vim , use:
tux > sudo zypper remove emacs +vim
To prevent the package name starting with the - being interpreted as a command option, always
use it as the second argument. If this is not possible, precede it with -- :
tux > sudo zypper install -emacs +vim # Wrong

tux > sudo zypper install vim -emacs # Correct
tux > sudo zypper install -- -emacs +vim # Correct
tux > sudo zypper remove emacs +vim # Correct
6.1.2.3 Cleaning Up Dependencies of Removed Packages

If (together with a certain package), you automatically want to remove any packages that be-
come unneeded after removing the specified package, use the --clean-deps option:
tux > sudo zypper rm PACKAGE_NAME --clean-deps
6.1.2.4 Using Zypper in Scripts

By default, Zypper asks for a confirmation before installing or removing a selected package, or
when a problem occurs. You can override this behavior using the --non-interactive option.
This option must be given before the actual command ( install , remove , and patch ), as can
be seen in the following:
tux > sudo zypper --non-interactive install PACKAGE_NAME
This option allows the use of Zypper in scripts and cron jobs.
6.1.2.5 Installing or Downloading Source Packages

To install the corresponding source package of a package, use:
tux > zypper source-install PACKAGE_NAME

When executed as root , the default location to install source packages is /usr/src/packages/
and ~/rpmbuild when run as user. These values can be changed in your local rpm configura-
tion.
This command will also install the build dependencies of the specified package. If you do not
want this, add the switch -D :
tux > sudo zypper source-install -D PACKAGE_NAME
To install only the build dependencies use -d .
tux > sudo zypper source-install -d PACKAGE_NAME
Of course, this will only work if you have the repository with the source packages enabled in your
repository list (it is added by default, but not enabled). See Section 6.1.5, “Managing Repositories
with Zypper” for details on repository management.
A list of all source packages available in your repositories can be obtained with:
tux > zypper search -t srcpackage
You can also download source packages for all installed packages to a local directory. To down-
load source packages, use:
tux > zypper source-download
The default download directory is /var/cache/zypper/source-download . You can change it

using the --directory option. To only show missing or extraneous packages without down-
loading or deleting anything, use the --status option. To delete extraneous source packages,
use the --delete option. To disable deleting, use the --no-delete option.
6.1.2.6 Installing Packages from Disabled Repositories

Normally you can only install or refresh packages from enabled repositories. The --plus-con-
tent TAG option helps you specify repositories to be refreshed, temporarily enabled during the
current Zypper session, and disabled after it completes.
For example, to enable repositories that may provide additional -debuginfo or -debugsource
packages, use --plus-content debug . You can specify this option multiple times.
To temporarily enable such 'debug' repositories to install a specific -debuginfo package, use
the option as follows:
tux > sudo zypper --plus-content debug \

install "debuginfo(build-id)=eb844a5c20c70a59fc693cd1061f851fb7d046f4"
The build-id string is reported by gdb for missing debuginfo packages.
6.1.2.7 Utilities
To verify whether all dependencies are still fulfilled and to repair missing dependencies, use:
tux > zypper verify
In addition to dependencies that must be fulfilled, some packages “recommend” other packages.
These recommended packages are only installed if actually available and installable. In case
recommended packages were made available after the recommending package has been installed
(by adding additional packages or hardware), use the following command:
tux > sudo zypper install-new-recommends
This command is very useful after plugging in a Web cam or Wi-Fi device. It will install drivers
for the device and related software, if available. Drivers and related software are only installable
if certain hardware dependencies are fulfilled.
6.1.3 Updating Software with Zypper

There are three different ways to update software using Zypper: by installing patches, by in-
stalling a new version of a package or by updating the entire distribution. The latter is achieved
with zypper dist-upgrade . Upgrading SUSE Linux Enterprise Server is discussed in Book “De-
ployment Guide”, Chapter 19 “Upgrading SUSE Linux Enterprise” .
6.1.3.1 Installing All Needed Patches

To install all officially released patches that apply to your system, run:
tux > sudo zypper patch
All patches available from repositories configured on your computer are checked for their rele-
vance to your installation. If they are relevant (and not classified as optional or feature ),
they are installed immediately. Note that the official update repository is only available after
registering your SUSE Linux Enterprise Server installation.
44 Updating Software with Zypper SLES 12 SP3

If a patch that is about to be installed includes changes that require a system reboot, you will
be warned before.
The plain zypper patch command does not apply patches from third party repositories. To
update also the third party repositories, use the with-update command option as follows:
tux > sudo zypper patch --with update
To install also optional patches, use:
tux > sudo zypper patch --with-optional
To install all patches relating to a specific Bugzilla issue, use:
tux > sudo zypper patch --bugzilla=NUMBER
To install all patches relating to a specific CVE database entry, use:
tux > sudo zypper patch --cve=NUMBER
For example, to install a security patch with the CVE number CVE-2010-2713 , execute:
tux > sudo zypper patch --cve=CVE-2010-2713
To install only patches which affect Zypper and the package management itself, use:
tux > sudo zypper patch --updatestack-only
Bear in mind that other command options that would also update other repositories will be
dropped if you use the updatestack-only command option.
6.1.3.2 Listing Patches

To nd out whether patches are available, Zypper allows viewing the following information:
Number of Needed Patches

To list the number of needed patches (patches that apply to your system but are not yet
installed), use patch-check :
tux > zypper patch-check

Loading repository data...
Reading installed packages...
5 patches needed (1 security patch)
This command can be combined with the --updatestack-only option to list only the
patches which affect Zypper and the package management itself.

List of Needed Patches
To list all needed patches (patches that apply to your system but are not yet installed),
use list-patches :
tux > zypper list-patches

Loading repository data...
Reading installed packages...
Repository | Name | Version | Category | Status | Summary

---------------+-------------+---------+----------+---------+---------
SLES12-Updates | SUSE-2014-8 | 1 | security | needed | openssl: Update for OpenSSL
List of All Patches

To list all patches available for SUSE Linux Enterprise Server, regardless of whether they
are already installed or apply to your installation, use zypper patches .
It is also possible to list and install patches relevant to specific issues. To list specific patches,
use the zypper list-patches command with the following options:
By Bugzilla Issues
To list all needed patches that relate to Bugzilla issues, use the option --bugzilla .
To list patches for a specific bug, you can also specify a bug number: --bugzilla=NUMBER .
To search for patches relating to multiple Bugzilla issues, add commas between the bug
numbers, for example:
tux > zypper list-patches --bugzilla=972197,956917
By CVE Number
To list all needed patches that relate to an entry in the CVE database (Common Vulnera-
bilities and Exposures), use the option --cve .
To list patches for a specific CVE database entry, you can also specify a CVE number: --
cve=NUMBER . To search for patches relating to multiple CVE database entries, add commas
between the CVE numbers, for example:
tux > zypper list-patches --bugzilla=CVE-2016-2315,CVE-2016-2324
To list all patches regardless of whether they are needed, use the option --all additionally.
For example, to list all patches with a CVE number assigned, use:
tux > zypper list-patches --all --cve

Issue | No. | Patch | Category | Severity | Status
------+---------------+-------------------+-------------+-----------+----------
cve | CVE-2015-0287 | SUSE-SLE-Module.. | recommended | moderate | needed

cve | CVE-2014-3566 | SUSE-SLE-SERVER.. | recommended | moderate | not needed
[...]
6.1.3.3 Installing New Package Versions

If a repository contains only new packages, but does not provide patches, zypper patch does
not show any effect. To update all installed packages with newer available versions (while main-
taining system integrity), use:
tux > sudo zypper update
To update individual packages, specify the package with either the update or install command:
tux > sudo zypper update PACKAGE_NAME

sudo zypper install PACKAGE_NAME
A list of all new installable packages can be obtained with the command:
tux > zypper list-updates
Note that this command only lists packages that match the following criteria:
has the same vendor like the already installed package,
is provided by repositories with at least the same priority than the already installed pack-
age,
is installable (all dependencies are satisfied).
A list of all new available packages (regardless whether installable or not) can be obtained with:
tux > sudo zypper list-updates --all
To nd out why a new package cannot be installed, use the zypper install or zypper update
command as described above.
6.1.3.4 Identifying Orphaned Packages

Whenever you remove a repository from Zypper or upgrade your system, some packages can
get in an “orphaned” state. These orphaned packages belong to no active repository anymore.
The following command gives you a list of these:
tux > sudo zypper packages --orphaned
With this list, you can decide if a package is still needed or can be removed safely.

6.1.4 Identifying Processes and Services Using Deleted Files
When patching, updating or removing packages, there may be running processes on the system
which continue to use les having been deleted by the update or removal. Use zypper ps to list
processes using deleted les. In case the process belongs to a known service, the service name
is listed, making it easy to restart the service. By default zypper ps shows a table:
tux > zypper ps

PID | PPID | UID | User | Command | Service | Files
------+------+-----+-------+--------------+--------------+-------------------
814 | 1 | 481 | avahi | avahi-daemon | avahi-daemon | /lib64/ld-2.19.s->
| | | | | | /lib64/libdl-2.1->
| | | | | | /lib64/libpthrea->
| | | | | | /lib64/libc-2.19->
[...]
PID: ID of the process

PPID: ID of the parent process
UID: ID of the user running the process
Login: Login name of the user running the process
Command: Command used to execute the process
Service: Service name (only if command is associated with a system service)
Files: The list of the deleted les
The output format of zypper ps can be controlled as follows:
zypper ps -s
Create a short table not showing the deleted les.
tux > zypper ps -s

PID | PPID | UID | User | Command | Service
------+------+------+---------+--------------+--------------
814 | 1 | 481 | avahi | avahi-daemon | avahi-daemon
817 | 1 | 0 | root | irqbalance | irqbalance
1567 | 1 | 0 | root | sshd | sshd
1761 | 1 | 0 | root | master | postfix
1764 | 1761 | 51 | postfix | pickup | postfix
1765 | 1761 | 51 | postfix | qmgr | postfix
2031 | 2027 | 1000 | tux | bash |
zypper ps -ss
Show only processes associated with a system service.
PID | PPID | UID | User | Command | Service
48 Identifying Processes and Services Using Deleted Files SLES 12 SP3

------+------+------+---------+--------------+--------------
814 | 1 | 481 | avahi | avahi-daemon | avahi-daemon
817 | 1 | 0 | root | irqbalance | irqbalance
1567 | 1 | 0 | root | sshd | sshd
1761 | 1 | 0 | root | master | postfix
1764 | 1761 | 51 | postfix | pickup | postfix
1765 | 1761 | 51 | postfix | qmgr | postfix
zypper ps -sss
Only show system services using deleted les.
avahi-daemon
irqbalance
postfix
sshd
zypper ps --print "systemctl status %s"

Show the commands to retrieve status information for services which might need a restart.
systemctl status avahi-daemon

systemctl status irqbalance
systemctl status postfix
systemctl status sshd
For more information about service handling refer to Chapter 13, The systemd Daemon.
6.1.5 Managing Repositories with Zypper

All installation or patch commands of Zypper rely on a list of known repositories. To list all
repositories known to the system, use the command:
tux > zypper repos
The result will look similar to the following output:
EXAMPLE 6.1: ZYPPER—LIST OF KNOWN REPOSITORIES
tux > zypper repos

# | Alias | Name | Enabled | Refresh
--+--------------+---------------+---------+--------
1 | SLEHA-12-GEO | SLEHA-12-GEO | Yes | No
2 | SLEHA-12 | SLEHA-12 | Yes | No
3 | SLES12 | SLES12 | Yes | No
49 Managing Repositories with Zypper SLES 12 SP3

When specifying repositories in various commands, an alias, URI or repository number from
the zypper repos command output can be used. A repository alias is a short version of the
repository name for use in repository handling commands. Note that the repository numbers
can change after modifying the list of repositories. The alias will never change by itself.
By default, details such as the URI or the priority of the repository are not displayed. Use the
following command to list all details:
tux > zypper repos -d
6.1.5.1 Adding Repositories

To add a repository, run
tux > sudo zypper addrepo URI ALIAS
URI can either be an Internet repository, a network resource, a directory or a CD or DVD

(see http://en.opensuse.org/openSUSE:Libzypp_URIs for details). The ALIAS is a shorthand and
unique identifier of the repository. You can freely choose it, with the only exception that it needs
to be unique. Zypper will issue a warning if you specify an alias that is already in use.
6.1.5.2 Refreshing Repositories

zypper enables you to fetch changes in packages from configured repositories. To fetch the
changes, run:
tux > sudo zypper refresh
Note: Default Behavior of zypper

By default, some commands perform refresh automatically, so you do not need to run
the command explicitly.
The refresh command enables you to view changes also in disabled repositories, by using the
--plus-content option:
tux > sudo zypper --plus-content refresh
This option fetches changes in repositories, but keeps the disabled repositories in the same state
—disabled.
50 Managing Repositories with Zypper SLES 12 SP3

6.1.5.3 Removing Repositories
To remove a repository from the list, use the command zypper removerepo together with the
alias or number of the repository you want to delete. For example, to remove the repository
SLEHA-12-GEO from Example 6.1, “Zypper—List of Known Repositories”, use one of the following
commands:
tux > sudo zypper removerepo 1

tux > sudo zypper removerepo "SLEHA-12-GEO"
6.1.5.4 Modifying Repositories

Enable or disable repositories with zypper modifyrepo . You can also alter the repository's
properties (such as refreshing behavior, name or priority) with this command. The following
command will enable the repository named updates , turn on auto-refresh and set its priority
to 20:
tux > sudo zypper modifyrepo -er -p 20 'updates'
Modifying repositories is not limited to a single repository—you can also operate on groups:
-a : all repositories
-l : local repositories
-t : remote repositories
-m TYPE : repositories of a certain type (where TYPE can be one of the following: http , https ,
ftp , cd , dvd , dir , file , cifs , smb , nfs , hd , iso )
To rename a repository alias, use the renamerepo command. The following example changes
the alias from Mozilla Firefox to firefox :
tux > sudo zypper renamerepo 'Mozilla Firefox' firefox
6.1.6 Querying Repositories and Packages with Zypper

Zypper offers various methods to query repositories or packages. To get lists of all products,
patterns, packages or patches available, use the following commands:
tux > zypper products

tux > zypper patterns
tux > zypper packages
51 Querying Repositories and Packages with Zypper SLES 12 SP3

tux > zypper patches
To query all repositories for certain packages, use search . To get information regarding par-
ticular packages, use the info command.
6.1.6.1 zypper search Usage

The zypper search command works on package names, or, optionally, on package summaries
and descriptions. String wrapped in / are interpreted as regular expressions. By default, the
search is not case-sensitive.
Simple search for a package name containing fire
tux > zypper search "fire"
Simple search for the exact package MozillaFirefox
tux > zypper search --match-exact "MozillaFirefox"
Also search in package descriptions and summaries
tux > zypper search -d fire
Only display packages not already installed
tux > zypper search -u fire
Display packages containing the string fir not followed be e
tux > zypper se "/fir[^e]/"
6.1.6.2 zypper what-provides Usage

To search for packages which provide a special capability, use the command what-provides .
For example, if you want to know which package provides the Perl module SVN::Core , use
the following command:
tux > zypper what-provides 'perl(SVN::Core)'
The what-provides PACKAGE_NAME is similar to rpm -q --whatprovides PACKAGE_NAME ,

but RPM is only able to query the RPM database (that is the database of all installed packages).
Zypper, on the other hand, will tell you about providers of the capability from any repository,
not only those that are installed.
52 Querying Repositories and Packages with Zypper SLES 12 SP3

6.1.6.3 zypper info Usage
To query single packages, use info with an exact package name as an argument. This displays
detailed information about a package. In case the package name does not match any package
name from repositories, the command outputs detailed information for non-package matches. If
you request a specific type (by using the -t option) and the type does not exist, the command
outputs other available matches but without detailed information.
If you specify a source package, the command displays binary packages built from the source
package. If you specify a binary package, the command outputs the source packages used to
build the binary package.
To also show what is required/recommended by the package, use the options --requires and
--recommends :
tux > zypper info --requires MozillaFirefox
6.1.7 Configuring Zypper

Zypper now comes with a configuration le, allowing you to permanently change Zypper's be-
havior (either system-wide or user-specific). For system-wide changes, edit /etc/zypp/zyp-
per.conf . For user-specific changes, edit ~/.zypper.conf . If ~/.zypper.conf does not yet
exist, you can use /etc/zypp/zypper.conf as a template: copy it to ~/.zypper.conf and
adjust it to your liking. Refer to the comments in the le for help about the available options.
6.1.8 Troubleshooting
If you have trouble accessing packages from configured repositories (for example, Zypper cannot
nd a certain package even though you know it exists in one the repositories), refreshing the
repositories may help:
tux > sudo zypper refresh
If that does not help, try
tux > sudo zypper refresh -fdb
This forces a complete refresh and rebuild of the database, including a forced download of raw
metadata.
53 Configuring Zypper SLES 12 SP3

6.1.9 Zypper Rollback Feature on Btrfs File System
If the Btrfs le system is used on the root partition and snapper is installed, Zypper automati-
cally calls snapper when committing changes to the le system to create appropriate le system
snapshots. These snapshots can be used to revert any changes made by Zypper. See Chapter 7,
System Recovery and Snapshot Management with Snapper for more information.
6.1.10 For More Information

For more information on managing software from the command line, enter zypper help , zyp-
per help COMMAND or refer to the zypper(8) man page. For a complete and detailed com-
mand reference, cheat sheets with the most important commands, and information on how
to use Zypper in scripts and applications, refer to http://en.opensuse.org/SDB:Zypper_usage .
A list of software changes for the latest SUSE Linux Enterprise Server version can be found at
http://en.opensuse.org/openSUSE:Zypper versions .
6.2 RPM—the Package Manager

RPM (RPM Package Manager) is used for managing software packages. Its main commands are
rpm and rpmbuild . The powerful RPM database can be queried by the users, system adminis-
trators and package builders for detailed information about the installed software.
Essentially, rpm has ve modes: installing, uninstalling (or updating) software packages, re-
building the RPM database, querying RPM bases or individual RPM archives, integrity checking
of packages and signing packages. rpmbuild can be used to build installable packages from
pristine sources.
54 Zypper Rollback Feature on Btrfs File System SLES 12 SP3

Installable RPM archives are packed in a special binary format. These archives consist of the
program les to install and certain meta information used during the installation by rpm to
configure the software package or stored in the RPM database for documentation purposes. RPM
archives normally have the extension .rpm .
Tip: Software Development Packages

For several packages, the components needed for software development (libraries, head-
ers, include les, etc.) have been put into separate packages. These development packages
are only needed if you want to compile software yourself (for example, the most recent
GNOME packages). They can be identified by the name extension -devel , such as the
packages alsa-devel and gimp-devel .
6.2.1 Verifying Package Authenticity
RPM packages have a GPG signature. To verify the signature of an RPM package, use the com-
mand rpm --checksig PACKAGE -1.2.3.rpm to determine whether the package originates from
SUSE or from another trustworthy facility. This is especially recommended for update packages
from the Internet.
While fixing issues in the operating system, you might need to install a Problem Temporary Fix
(PTF) into a production system. The packages provided by SUSE are signed against a special
PTF key. However, in contrast to SUSE Linux Enterprise 11, this key is not imported by default
on SUSE Linux Enterprise 12 systems. To manually import the key, use the following command:
tux > sudo rpm --import \

/usr/share/doc/packages/suse-build-key/suse_ptf_key.asc
After importing the key, you can install PTF packages on your system.
6.2.2 Managing Packages: Install, Update, and Uninstall
Normally, the installation of an RPM archive is quite simple: rpm -i PACKAGE .rpm. With this
command the package is installed, but only if its dependencies are fulfilled and if there are no
conflicts with other packages. With an error message, rpm requests those packages that need
to be installed to meet dependency requirements. In the background, the RPM database ensures
55 Verifying Package Authenticity SLES 12 SP3

that no conflicts arise—a specific le can only belong to one package. By choosing different
options, you can force rpm to ignore these defaults, but this is only for experts. Otherwise, you
risk compromising the integrity of the system and possibly jeopardize the ability to update the
system.
The options -U or --upgrade and -F or --freshen can be used to update a package (for ex-
ample, rpm -F PACKAGE .rpm). This command removes the les of the old version and immedi-
ately installs the new les. The difference between the two versions is that -U installs packages
that previously did not exist in the system, while -F merely updates previously installed pack-
ages. When updating, rpm updates configuration les carefully using the following strategy:
If a configuration le was not changed by the system administrator, rpm installs the new
version of the appropriate le. No action by the system administrator is required.
If a configuration le was changed by the system administrator before the update, rpm
saves the changed le with the extension .rpmorig or .rpmsave (backup le) and installs
the version from the new package. This is done only if the originally installed le and
the newer version are different. If this is the case, compare the backup le ( .rpmorig
or .rpmsave ) with the newly installed le and make your changes again in the new le.
Afterward, delete all .rpmorig and .rpmsave les to avoid problems with future updates.
.rpmnew les appear if the configuration le already exists and if the noreplace label
was specified in the .spec le.
Following an update, .rpmsave and .rpmnew les should be removed after comparing them,
so they do not obstruct future updates. The .rpmorig extension is assigned if the le has not
previously been recognized by the RPM database.
Otherwise, .rpmsave is used. In other words, .rpmorig results from updating from a foreign
format to RPM. .rpmsave results from updating from an older RPM to a newer RPM. .rpmnew
does not disclose any information to whether the system administrator has made any changes
to the configuration le. A list of these les is available in /var/adm/rpmconfigcheck . Some
configuration les (like /etc/httpd/httpd.conf ) are not overwritten to allow continued op-
eration.
The -U switch is not just an equivalent to uninstalling with the -e option and installing with
the -i option. Use -U whenever possible.
56 Managing Packages: Install, Update, and Uninstall SLES 12 SP3

To remove a package, enter rpm -e PACKAGE . This command only deletes the package if there
are no unresolved dependencies. It is theoretically impossible to delete Tcl/Tk, for example, as
long as another application requires it. Even in this case, RPM calls for assistance from the data-
base. If such a deletion is, for whatever reason, impossible (even if no additional dependencies
exist), it may be helpful to rebuild the RPM database using the option --rebuilddb .
6.2.3 Delta RPM Packages

Delta RPM packages contain the difference between an old and a new version of an RPM package.
Applying a delta RPM onto an old RPM results in a completely new RPM. It is not necessary
to have a copy of the old RPM because a delta RPM can also work with an installed RPM. The
delta RPM packages are even smaller in size than patch RPMs, which is an advantage when
transferring update packages over the Internet. The drawback is that update operations with
delta RPMs involved consume considerably more CPU cycles than plain or patch RPMs.
The makedeltarpm and applydelta binaries are part of the delta RPM suite (package
deltarpm ) and help you create and apply delta RPM packages. With the following commands,
you can create a delta RPM called new.delta.rpm . The following command assumes that
old.rpm and new.rpm are present:
tux > sudo makedeltarpm old.rpm new.rpm new.delta.rpm
Using applydeltarpm , you can reconstruct the new RPM from the le system if the old package
is already installed:
tux > sudo applydeltarpm new.delta.rpm new.rpm
To derive it from the old RPM without accessing the le system, use the -r option:
tux > sudo applydeltarpm -r old.rpm new.delta.rpm new.rpm
See /usr/share/doc/packages/deltarpm/README for technical details.
6.2.4 RPM Queries

With the -q option rpm initiates queries, making it possible to inspect an RPM archive (by
adding the option -p ) and to query the RPM database of installed packages. Several switches
are available to specify the type of information required. See Table 6.1, “The Most Important RPM
Query Options”.
57 Delta RPM Packages SLES 12 SP3

TABLE 6.1: THE MOST IMPORTANT RPM QUERY OPTIONS
-i Package information
-l File list
-f FILE Query the package that contains the le

FILE (the full path must be specified with
FILE )
-s File list with status information (implies -l )
-d List only documentation les (implies -l )
-c List only configuration les (implies -l )
--dump File list with complete details (to be used

with -l , -c , or -d )
--provides List features of the package that another

package can request with --requires
--requires , -R Capabilities the package requires
--scripts Installation scripts (preinstall, postinstall,

uninstall)
For example, the command rpm -q -i wget displays the information shown in Example 6.2,
“rpm -q -i wget”.
EXAMPLE 6.2: rpm -q -i wget
Name : wget
Version : 1.14
Release : 17.1
Architecture: x86_64
Install Date: Mon 30 Jan 2017 14:01:29 CET
Group : Productivity/Networking/Web/Utilities
Size : 2046483
License : GPL-3.0+
Signature : RSA/SHA256, Thu 08 Dec 2016 07:48:44 CET, Key ID 70af9e8139db7c82
Source RPM : wget-1.14-17.1.src.rpm
Build Date : Thu 08 Dec 2016 07:48:34 CET
Build Host : sheep09
Relocations : (not relocatable)
58 RPM Queries SLES 12 SP3

Packager : https://www.suse.com/
Vendor : SUSE LLC <https://www.suse.com/>
URL : http://www.gnu.org/software/wget/
Summary : A Tool for Mirroring FTP and HTTP Servers
Description :
Wget enables you to retrieve WWW documents or FTP files from a server.
This can be done in script files or via the command line.
Distribution: SUSE Linux Enterprise 12
The option -f only works if you specify the complete le name with its full path. Provide as
many le names as desired. For example:
tux > rpm -q -f /bin/rpm /usr/bin/wget

rpm-4.11.2-15.1.x86_64
wget-1.14-17.1.x86_64
If only part of the le name is known, use a shell script as shown in Example 6.3, “Script to Search
for Packages”. Pass the partial le name to the script shown as a parameter when running it.
EXAMPLE 6.3: SCRIPT TO SEARCH FOR PACKAGES
#! /bin/sh
for i in $(rpm -q -a -l | grep $1); do
echo "\"$i\" is in package:"
rpm -q -f $i
echo ""
done
The command rpm -q --changelog PACKAGE displays a detailed list of change information
about a specific package, sorted by date.
With the installed RPM database, verification checks can be made. Initiate these with -V , or
--verify . With this option, rpm shows all les in a package that have been changed since
installation. rpm uses eight character symbols to give some hints about the following changes:
TABLE 6.2: RPM VERIFY OPTIONS
5 MD5 check sum
S File size
L Symbolic link
T Modification time
D Major and minor device numbers
59 RPM Queries SLES 12 SP3

U Owner
G Group
M Mode (permissions and le type)
In the case of configuration les, the letter c is printed. For example, for changes to /etc/
wgetrc ( wget package):
tux > rpm -V wget

S.5....T c /etc/wgetrc
The les of the RPM database are placed in /var/lib/rpm . If the partition /usr has a size of
1 GB, this database can occupy nearly 30 MB, especially after a complete update. If the database
is much larger than expected, it is useful to rebuild the database with the option --rebuilddb .
Before doing this, make a backup of the old database. The cron script cron.daily makes
daily copies of the database (packed with gzip) and stores them in /var/adm/backup/rpmdb .
The number of copies is controlled by the variable MAX_RPMDB_BACKUPS (default: 5 ) in /etc/
sysconfig/backup . The size of a single backup is approximately 1 MB for 1 GB in /usr .
6.2.5 Installing and Compiling Source Packages

All source packages carry a .src.rpm extension (source RPM).
Note: Installed Source Packages

Source packages can be copied from the installation medium to the hard disk and un-
packed with YaST. They are not, however, marked as installed ( [i] ) in the package
manager. This is because the source packages are not entered in the RPM database. Only
installed operating system software is listed in the RPM database. When you “install” a
source package, only the source code is added to the system.
The following directories must be available for rpm and rpmbuild in /usr/src/packages
(unless you specified custom settings in a le like /etc/rpmrc ):
SOURCES
for the original sources ( .tar.bz2 or .tar.gz les, etc.) and for distribution-specific
adjustments (mostly .diff or .patch les)
60 Installing and Compiling Source Packages SLES 12 SP3

SPECS
for the .spec les, similar to a meta Makefile, which control the build process
BUILD
all the sources are unpacked, patched and compiled in this directory
RPMS
where the completed binary packages are stored
SRPMS
here are the source RPMs
When you install a source package with YaST, all the necessary components are installed in /
usr/src/packages : the sources and the adjustments in SOURCES and the relevant .spec le
in SPECS .
Warning: System Integrity

Do not experiment with system components ( glibc , rpm , etc.), because this endangers
the stability of your system.
The following example uses the wget.src.rpm package. After installing the source package,
you should have les similar to those in the following list:
/usr/src/packages/SOURCES/wget-1.11.4.tar.bz2
/usr/src/packages/SOURCES/wgetrc.patch
/usr/src/packages/SPECS/wget.spec
rpmbuild -bX /usr/src/packages/SPECS/wget.spec starts the compilation. X is a wild

card for various stages of the build process (see the output of --help or the RPM documentation
for details). The following is merely a brief explanation:
-bp
Prepare sources in /usr/src/packages/BUILD : unpack and patch.
-bc
Do the same as -bp , but with additional compilation.
-bi
Do the same as -bp , but with additional installation of the built software. Caution: if the
package does not support the BuildRoot feature, you might overwrite configuration les.
61 Installing and Compiling Source Packages SLES 12 SP3

-bb
Do the same as -bi , but with the additional creation of the binary package. If the compile
was successful, the binary should be in /usr/src/packages/RPMS .
-ba
Do the same as -bb , but with the additional creation of the source RPM. If the compilation
was successful, the binary should be in /usr/src/packages/SRPMS .
--short-circuit
Skip some steps.
The binary RPM created can now be installed with rpm -i or, preferably, with rpm -U . In-
stallation with rpm makes it appear in the RPM database.
Keep in mind, the BuildRoot directive in the spec le is deprecated since SUSE Linux Enterprise
Server 12. If you still need this feature, use the --buildroot option as a workaround.For a
more detailed background, see the support database at https://www.suse.com/support/kb/doc?
id=7017104 .
6.2.6 Compiling RPM Packages with build

The danger with many packages is that unwanted les are added to the running system during
the build process. To prevent this use build , which creates a defined environment in which
the package is built. To establish this chroot environment, the build script must be provided
with a complete package tree. This tree can be made available on the hard disk, via NFS, or
from DVD. Set the position with build --rpms DIRECTORY . Unlike rpm , the build command
looks for the .spec le in the source directory. To build wget (like in the above example) with
the DVD mounted in the system under /media/dvd , use the following commands as root :
root # cd /usr/src/packages/SOURCES/
root # mv ../SPECS/wget.spec .
root # build --rpms /media/dvd/suse/ wget.spec
Subsequently, a minimum environment is established at /var/tmp/build-root . The package

is built in this environment. Upon completion, the resulting packages are located in /var/tmp/
build-root/usr/src/packages/RPMS .
The build script offers several additional options. For example, cause the script to prefer your
own RPMs, omit the initialization of the build environment or limit the rpm command to one of
the above-mentioned stages. Access additional information with build --help and by reading
the build man page.
62 Compiling RPM Packages with build SLES 12 SP3

6.2.7 Tools for RPM Archives and the RPM Database
Midnight Commander ( mc ) can display the contents of RPM archives and copy parts of them.
It represents archives as virtual le systems, offering all usual menu options of Midnight Com-
mander. Display the HEADER with F3 . View the archive structure with the cursor keys and
Enter . Copy archive components with F5 .
A full-featured package manager is available as a YaST module. For details, see Book “Deployment
Guide”, Chapter 13 “Installing or Removing Software”.
63 Tools for RPM Archives and the RPM Database SLES 12 SP3
7 System Recovery and Snapshot Management with
Snapper
Being able to do le system snapshots providing the ability to do rollbacks on Linux
is a feature that was often requested in the past. Snapper, with the Btrfs le sys-
tem or thin-provisioned LVM volumes now lls that gap.
Btrfs , a new copy-on-write le system for Linux, supports le system snapshots (a
copy of the state of a subvolume at a certain point of time) of subvolumes (one or
more separately mountable le systems within each physical partition). Snapshots
are also supported on thin-provisioned LVM volumes formatted with XFS, Ext4 or
Ext3. Snapper lets you create and manage these snapshots. It comes with a com-
mand line and a YaST interface. Starting with SUSE Linux Enterprise Server 12 it is
also possible to boot from Btrfs snapshots—see Section 7.3, “System Rollback by Boot-
ing from Snapshots” for more information.
Using Snapper you can perform the following tasks:
Undo system changes made by zypper and YaST. See Section 7.2, “Using Snapper to Undo
Changes” for details.
Restore les from previous snapshots. See Section 7.2.2, “Using Snapper to Restore Files” for
details.
Do a system rollback by booting from a snapshot. See Section 7.3, “System Rollback by Booting
from Snapshots” for details.
Manually create snapshots on the y and manage existing snapshots. See Section 7.5, “Man-
ually Creating and Managing Snapshots” for details.
7.1 Default Setup

Snapper on SUSE Linux Enterprise Server is set up to serve as an “undo and recovery tool” for
system changes. By default, the root partition ( / ) of SUSE Linux Enterprise Server is formatted
with Btrfs . Taking snapshots is automatically enabled if the root partition ( / ) is big enough
(approximately more than 16 GB). Taking snapshots on partitions other than / is not enabled
by default.
64 Default Setup SLES 12 SP3

Tip: Enabling Snapper in the Installed System
If you disabled Snapper during the installation, you can enable it at any time later. To do
so, create a default Snapper configuration for the root le system by running
tux > sudo snapper -c root create-config /
Afterward enable the different snapshot types as described in Section 7.1.3.1, “Disabling/En-

abling Snapshots”.
Keep in mind that snapshots require a Btrfs root le system with subvolumes set up as
proposed by the installer and a partition size of at least 16 GB.
When a snapshot is created, both the snapshot and the original point to the same blocks in the
le system. So, initially a snapshot does not occupy additional disk space. If data in the original
le system is modified, changed data blocks are copied while the old data blocks are kept for
the snapshot. Therefore, a snapshot occupies the same amount of space as the data modified.
So, over time, the amount of space a snapshot allocates, constantly grows. As a consequence,
deleting les from a Btrfs le system containing snapshots may not free disk space!
Note: Snapshot Location

Snapshots always reside on the same partition or subvolume on which the snapshot has
been taken. It is not possible to store snapshots on a different partition or subvolume.
As a result, partitions containing snapshots need to be larger than “normal” partitions. The
exact amount strongly depends on the number of snapshots you keep and the amount of data
modifications. As a rule of thumb you should consider using twice the size than you normally
would. To prevent disks from running out of space, old snapshots are automatically cleaned up.
Refer to Section 7.1.3.4, “Controlling Snapshot Archiving” for details.
65 Default Setup SLES 12 SP3

7.1.1 Types of Snapshots
Although snapshots themselves do not differ in a technical sense, we distinguish between three
types of snapshots, based on the events that trigger them:
Timeline Snapshots
A single snapshot is created every hour. Old snapshots are automatically deleted. By de-
fault, the rst snapshot of the last ten days, months, and years are kept. Timeline snapshots
are disabled by default.
Installation Snapshots
Whenever one or more packages are installed with YaST or Zypper, a pair of snapshots
is created: one before the installation starts (“Pre”) and another one after the installation
has finished (“Post”). In case an important system component such as the kernel has been
installed, the snapshot pair is marked as important ( important=yes ). Old snapshots are
automatically deleted. By default the last ten important snapshots and the last ten “regular”
(including administration snapshots) snapshots are kept. Installation snapshots are enabled
by default.
Administration Snapshots
Whenever you administrate the system with YaST, a pair of snapshots is created: one when
a YaST module is started (“Pre”) and another when the module is closed (“Post”). Old
snapshots are automatically deleted. By default the last ten important snapshots and the
last ten “regular” snapshots (including installation snapshots) are kept. Administration
snapshots are enabled by default.
7.1.2 Directories That Are Excluded from Snapshots

Some directories need to be excluded from snapshots for different reasons. The following list
shows all directories that are excluded:
/boot/grub2/i386-pc , /boot/grub2/x86_64-efi , /boot/grub2/powerpc-ieee1275 , /

boot/grub2/s390x-emu
A rollback of the boot loader configuration is not supported. The directories listed above
are architecture-specific. The rst two directories are present on AMD64/Intel 64 ma-
chines, the latter two on IBM POWER and on IBM z Systems, respectively.
66 Types of Snapshots SLES 12 SP3

/home
If /home does not reside on a separate partition, it is excluded to avoid data loss on roll-
backs.
/opt , /var/opt
Third-party products usually get installed to /opt . It is excluded to avoid uninstalling
these applications on rollbacks.
/srv
Contains data for Web and FTP servers. It is excluded to avoid data loss on rollbacks.
/tmp , /var/tmp , /var/cache , /var/crash

All directories containing temporary les and caches are excluded from snapshots.
/usr/local
This directory is used when manually installing software. It is excluded to avoid unin-
stalling these installations on rollbacks.
/var/lib/libvirt/images
The default location for virtual machine images managed with libvirt. Excluded to ensure
virtual machine images are not replaced with older versions during a rollback. By default,
this subvolume is created with the option no copy on write .
/var/lib/mailman , /var/spool
Directories containing mails or mail queues are excluded to avoid a loss of mails after a
rollback.
/var/lib/named
Contains zone data for the DNS server. Excluded from snapshots to ensure a name server
can operate after a rollback.
/var/lib/mariadb , /var/lib/mysql , /var/lib/pgqsl

These directories contain database data. By default, these subvolumes are created with the
option no copy on write .
/var/log
Log le location. Excluded from snapshots to allow log le analysis after the rollback of
a broken system.
67 Directories That Are Excluded from Snapshots SLES 12 SP3

7.1.3 Customizing the Setup
SUSE Linux Enterprise Server comes with a reasonable default setup, which should be sufficient
for most use cases. However, all aspects of taking automatic snapshots and snapshot keeping
can be configured according to your needs.
7.1.3.1 Disabling/Enabling Snapshots

Each of the three snapshot types (timeline, installation, administration) can be enabled or dis-
abled independently.
Disabling/Enabling Timeline Snapshots

Enabling. snapper-c root set-config "TIMELINE_CREATE=yes"
Disabling. snapper -c root set-config "TIMELINE_CREATE=no"

Timeline snapshots are enabled by default, except for the root partition.
Disabling/Enabling Installation Snapshots

Enabling: Install the package snapper-zypp-plugin
Disabling: Uninstall the package snapper-zypp-plugin

Installation snapshots are enabled by default.
Disabling/Enabling Administration Snapshots

Enabling: Set USE_SNAPPER to yes in /etc/sysconfig/yast2 .
Disabling: Set USE_SNAPPER to no in /etc/sysconfig/yast2 .

Administration snapshots are enabled by default.
7.1.3.2 Controlling Installation Snapshots

Taking snapshot pairs upon installing packages with YaST or Zypper is handled by the snap-
per-zypp-plugin . An XML configuration le, /etc/snapper/zypp-plugin.conf defines,
when to make snapshots. By default the le looks like the following:
1 <?xml version="1.0" encoding="utf-8"?>

2 <snapper-zypp-plugin-conf>
3 <solvables>
4 <solvable match="w" 1 important="true" 2 >kernel-* 3 </solvable>
5 <solvable match="w" important="true">dracut</solvable>
68 Customizing the Setup SLES 12 SP3

6 <solvable match="w" important="true">glibc</solvable>
7 <solvable match="w" important="true">systemd*</solvable>
8 <solvable match="w" important="true">udev</solvable>
9 <solvable match="w">*</solvable> 4
10 </solvables>
11 </snapper-zypp-plugin-conf>
1 The match attribute defines whether the pattern is a Unix shell-style wild card ( w ) or a
Python regular expression ( re ).
2 If the given pattern matches and the corresponding package is marked as important (for
example kernel packages), the snapshot will also be marked as important.
3 Pattern to match a package name. Based on the setting of the match attribute, special
characters are either interpreted as shell wild cards or regular expressions. This pattern
matches all package names starting with kernel- .
4 This line unconditionally matches all packages.
With this configuration snapshot, pairs are made whenever a package is installed (line 9). When
the kernel, dracut, glibc, systemd, or udev packages marked as important are installed, the
snapshot pair will also be marked as important (lines 4 to 8). All rules are evaluated.
To disable a rule, either delete it or deactivate it using XML comments. To prevent the system
from making snapshot pairs for every package installation for example, comment line 9:
1 <?xml version="1.0" encoding="utf-8"?>

2 <snapper-zypp-plugin-conf>
3 <solvables>
4 <solvable match="w" important="true">kernel-*</solvable>
5 <solvable match="w" important="true">dracut</solvable>
6 <solvable match="w" important="true">glibc</solvable>
7 <solvable match="w" important="true">systemd*</solvable>
8 <solvable match="w" important="true">udev</solvable>
9 
10 </solvables>
11 </snapper-zypp-plugin-conf>
7.1.3.3 Creating and Mounting New Subvolumes
Creating a new subvolume underneath the / hierarchy and permanently mounting it is sup-
ported. Such a subvolume will be excluded from snapshots. You need to make sure not to create
it inside an existing snapshot, since you would not be able to delete snapshots anymore after
a rollback.

SUSE Linux Enterprise Server is configured with the /@/ subvolume which serves as an inde-
pendent root for permanent subvolumes such as /opt , /srv , /home and others. Any new sub-
volumes you create and permanently mount need to be created in this initial root le system.
To do so, run the following commands. In this example, a new subvolume /usr/important
is created from /dev/sda2 .
tux > sudo mount /dev/sda2 -o subvol=@ /mnt

tux > sudo btrfs subvolume create /mnt/usr/important
tux > sudo umount /mnt
The corresponding entry in /etc/fstab needs to look like the following:
/dev/sda2 /usr/important btrfs subvol=@/usr/important 0 0
Tip: Disable Copy-On-Write (cow)

A subvolume may contain les that constantly change, such as virtualized disk images,
database les, or log les. If so, consider disabling the copy-on-write feature for this
volume, to avoid duplication of disk blocks. Use the nodatacow mount option in /etc/
fstab to do so:
/dev/sda2 /usr/important btrfs nodatacow,subvol=@/usr/important 0 0
To alternatively disable copy-on-write for single les or directories, use the command
chattr +C PATH .
7.1.3.4 Controlling Snapshot Archiving
Snapshots occupy disk space. To prevent disks from running out of space and thus causing system
outages, old snapshots are automatically deleted. By default, up to ten important installation
and administration snapshots and up to ten regular installation and administration snapshots are
kept. If these snapshots occupy more than 50% of the root le system size, additional snapshots
will be deleted. A minimum of four important and two regular snapshots are always kept.
Refer to Section 7.4.1, “Managing Existing Configurations” for instructions on how to change these
values.

7.1.3.5 Using Snapper on Thin-Provisioned LVM Volumes
Apart from snapshots on Btrfs le systems, Snapper also supports taking snapshots on thin-
provisioned LVM volumes (snapshots on regular LVM volumes are not supported) formatted
with XFS, Ext4 or Ext3. For more information and setup instructions on LVM volumes, refer to
Book “Deployment Guide”, Chapter 12 “Advanced Disk Setup”, Section 12.2 “LVM Configuration”.
To use Snapper on a thin-provisioned LVM volume you need to create a Snapper configuration
for it. On LVM it is required to specify the le system with --fstype=lvm(FILESYSTEM) . ext3 ,
etx4 or xfs are valid values for FILESYSTEM . Example:
tux > sudo snapper -c lvm create-config --fstype="lvm(xfs)" /thin_lvm
You can adjust this configuration according to your needs as described in Section 7.4.1, “Managing
Existing Configurations”.
7.2 Using Snapper to Undo Changes

Snapper on SUSE Linux Enterprise Server is preconfigured to serve as a tool that lets you undo
changes made by zypper and YaST. For this purpose, Snapper is configured to create a pair of
snapshots before and after each run of zypper and YaST. Snapper also lets you restore system
les that have been accidentally deleted or modified. Timeline snapshots for the root partition
need to be enabled for this purpose—see Section 7.1.3.1, “Disabling/Enabling Snapshots” for details.
By default, automatic snapshots as described above are configured for the root partition and its
subvolumes. To make snapshots available for other partitions such as /home for example, you
can create custom configurations.
Important: Undoing Changes Compared to Rollback

When working with snapshots to restore data, it is important to know that there are two
fundamentally different scenarios Snapper can handle:
Undoing Changes
When undoing changes as described in the following, two snapshots are being com-
pared and the changes between these two snapshots are made undone. Using this
method also allows to explicitly select the les that should be restored.
71 Using Snapper to Undo Changes SLES 12 SP3

Rollback
When doing rollbacks as described in Section 7.3, “System Rollback by Booting from
Snapshots”, the system is reset to the state at which the snapshot was taken.
When undoing changes, it is also possible to compare a snapshot against the current
system. When restoring all les from such a comparison, this will have the same result
as doing a rollback. However, using the method described in Section 7.3, “System Rollback
by Booting from Snapshots” for rollbacks should be preferred, since it is faster and allows
you to review the system before doing the rollback.
Warning: Data Consistency

There is no mechanism to ensure data consistency when creating a snapshot. Whenever a
le (for example, a database) is written at the same time as the snapshot is being created,
it will result in a corrupted or partly written le. Restoring such a le will cause problems.
Furthermore, some system les such as /etc/mtab must never be restored. Therefore it
is strongly recommended to always closely review the list of changed les and their dis.
Only restore les that really belong to the action you want to revert.
7.2.1 Undoing YaST and Zypper Changes

If you set up the root partition with Btrfs during the installation, Snapper—preconfigured for
doing rollbacks of YaST or Zypper changes—will automatically be installed. Every time you start
a YaST module or a Zypper transaction, two snapshots are created: a “pre-snapshot” capturing
the state of the le system before the start of the module and a “post-snapshot” after the module
has been finished.
Using the YaST Snapper module or the snapper command line tool, you can undo the changes
made by YaST/Zypper by restoring les from the “pre-snapshot”. Comparing two snapshots the
tools also allow you to see which les have been changed. You can also display the differences
between two versions of a le (di).
PROCEDURE 7.1: UNDOING CHANGES USING THE YAST SNAPPER MODULE
1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2
snapper .
72 Undoing YaST and Zypper Changes SLES 12 SP3

2. Make sure Current Configuration is set to root. This is always the case unless you have
manually added own Snapper configurations.
3. Choose a pair of pre- and post-snapshots from the list. Both, YaST and Zypper snapshot
pairs are of the type Pre & Post. YaST snapshots are labeled as zypp(y2base) in the
Description column; Zypper snapshots are labeled zypp(zypper) .
4. Click Show Changes to open the list of les that differ between the two snapshots.

5. Review the list of les. To display a “di” between the pre- and post-version of a le,
select it from the list.
6. To restore one or more les, select the relevant les or directories by activating the re-
spective check box. Click Restore Selected and confirm the action by clicking Yes.

To restore a single le, activate its di view by clicking its name. Click Restore From First
and confirm your choice with Yes.
PROCEDURE 7.2: UNDOING CHANGES USING THE snapper COMMAND
1. Get a list of YaST and Zypper snapshots by running snapper list -t pre-post . YaST
snapshots are labeled as yast MODULE_NAME in the Description column; Zypper snapshots
are labeled zypp(zypper) .
tux > sudo snapper list -t pre-post

Pre # | Post # | Pre Date | Post Date | Description
------+--------+-------------------------------+-------------------------------+--------------
311 | 312 | Tue 06 May 2014 14:05:46 CEST | Tue 06 May 2014 14:05:52 CEST | zypp(y2base)
340 | 341 | Wed 07 May 2014 16:15:10 CEST | Wed 07 May 2014 16:15:16 CEST | zypp(zypper)
342 | 343 | Wed 07 May 2014 16:20:38 CEST | Wed 07 May 2014 16:20:42 CEST | zypp(y2base)
344 | 345 | Wed 07 May 2014 16:21:23 CEST | Wed 07 May 2014 16:21:24 CEST | zypp(zypper)
2. Get a list of changed les for a snapshot pair with snapper status PRE .. POST . Files
with content changes are marked with c, les that have been added are marked with +
and deleted les are marked with -.
tux > sudo snapper status 350..351

+..... /usr/share/doc/packages/mikachan-fonts

+..... /usr/share/doc/packages/mikachan-fonts/COPYING
+..... /usr/share/doc/packages/mikachan-fonts/dl.html
c..... /usr/share/fonts/truetype/fonts.dir
c..... /usr/share/fonts/truetype/fonts.scale
+..... /usr/share/fonts/truetype/#####-p.ttf
+..... /usr/share/fonts/truetype/#####-pb.ttf
+..... /usr/share/fonts/truetype/#####-ps.ttf
+..... /usr/share/fonts/truetype/#####.ttf
c..... /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4
c..... /var/lib/rpm/Basenames
c..... /var/lib/rpm/Dirnames
c..... /var/lib/rpm/Group
c..... /var/lib/rpm/Installtid
c..... /var/lib/rpm/Name
c..... /var/lib/rpm/Packages
c..... /var/lib/rpm/Providename
c..... /var/lib/rpm/Requirename
c..... /var/lib/rpm/Sha1header
c..... /var/lib/rpm/Sigmd5
3. To display the di for a certain le, run snapper diff PRE .. POST FILENAME . If you do
not specify FILENAME , a di for all les will be displayed.
tux > sudo snapper diff 350..351 /usr/share/fonts/truetype/fonts.scale

--- /.snapshots/350/snapshot/usr/share/fonts/truetype/fonts.scale 2014-04-23
15:58:57.000000000 +0200
+++ /.snapshots/351/snapshot/usr/share/fonts/truetype/fonts.scale 2014-05-07
16:46:31.000000000 +0200
@@ -1,4 +1,4 @@
-1174
+1486
ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso10646-1
ds=y:ai=0.2:luximr.ttf -b&h-luxi mono-bold-i-normal--0-0-0-0-c-0-iso8859-1
[...]
4. To restore one or more les run snapper -v undochange PRE .. POST FILENAMES . If you
do not specify a FILENAMES , all changed les will be restored.
tux > sudo snapper -v undochange 350..351

create:0 modify:13 delete:7
undoing change...
deleting /usr/share/doc/packages/mikachan-fonts
deleting /usr/share/doc/packages/mikachan-fonts/COPYING
deleting /usr/share/doc/packages/mikachan-fonts/dl.html
deleting /usr/share/fonts/truetype/#####-p.ttf
deleting /usr/share/fonts/truetype/#####-pb.ttf

deleting /usr/share/fonts/truetype/#####-ps.ttf
deleting /usr/share/fonts/truetype/#####.ttf
modifying /usr/share/fonts/truetype/fonts.dir
modifying /usr/share/fonts/truetype/fonts.scale
modifying /var/cache/fontconfig/7ef2298fde41cc6eeb7af42e48b7d293-x86_64.cache-4
modifying /var/lib/rpm/Basenames
modifying /var/lib/rpm/Dirnames
modifying /var/lib/rpm/Group
modifying /var/lib/rpm/Installtid
modifying /var/lib/rpm/Name
modifying /var/lib/rpm/Packages
modifying /var/lib/rpm/Providename
modifying /var/lib/rpm/Requirename
modifying /var/lib/rpm/Sha1header
modifying /var/lib/rpm/Sigmd5
undoing change done
Warning: Reverting User Additions

Reverting user additions via undoing changes with Snapper is not recommended. Since
certain directories are excluded from snapshots, les belonging to these users will remain
in the le system. If a user with the same user ID as a deleted user is created, this user will
inherit the les. Therefore it is strongly recommended to use the YaST User and Group
Management tool to remove users.
7.2.2 Using Snapper to Restore Files

Apart from the installation and administration snapshots, Snapper creates timeline snapshots.
You can use these backup snapshots to restore les that have accidentally been deleted or to
restore a previous version of a le. By using Snapper's di feature you can also nd out which
modifications have been made at a certain point of time.
Being able to restore les is especially interesting for data, which may reside on subvolumes or
partitions for which snapshots are not taken by default. To be able to restore les from home
directories, for example, create a separate Snapper configuration for /home doing automatic
timeline snapshots. See Section 7.4, “Creating and Modifying Snapper Configurations” for instructions.
77 Using Snapper to Restore Files SLES 12 SP3

Warning: Restoring Files Compared to Rollback
Snapshots taken from the root le system (defined by Snapper's root configuration), can
be used to do a system rollback. The recommended way to do such a rollback is to boot
from the snapshot and then perform the rollback. See Section 7.3, “System Rollback by Booting
from Snapshots” for details.
Performing a rollback would also be possible by restoring all les from a root le system
snapshot as described below. However, this is not recommended. You may restore single
les, for example a configuration le from the /etc directory, but not the complete list
of les from the snapshot.
This restriction only affects snapshots taken from the root le system!
PROCEDURE 7.3: RESTORING FILES USING THE YAST SNAPPER MODULE
1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2
snapper .
2. Choose the Current Configuration from which to choose a snapshot.
3. Select a timeline snapshot from which to restore a le and choose Show Changes. Timeline
snapshots are of the type Single with a description value of timeline.
4. Select a le from the text box by clicking the le name. The difference between the snap-
shot version and the current system is shown. Activate the check box to select the le for
restore. Do so for all les you want to restore.
5. Click Restore Selected and confirm the action by clicking Yes.
PROCEDURE 7.4: RESTORING FILES USING THE snapper COMMAND
1. Get a list of timeline snapshots for a specific configuration by running the following com-
mand:
tux > sudo snapper -c CONFIG list -t single | grep timeline
CONFIG needs to be replaced by an existing Snapper configuration. Use snapper list-

configs to display a list.
2. Get a list of changed les for a given snapshot by running the following command:
tux > sudo snapper -c CONFIG status SNAPSHOT_ID..0
78 Using Snapper to Restore Files SLES 12 SP3

Replace SNAPSHOT_ID by the ID for the snapshot from which you want to restore the
le(s).
3. Optionally list the differences between the current le version and the one from the snap-
shot by running
tux > sudo snapper -c CONFIG diff SNAPSHOT_ID..0 FILE NAME
If you do not specify <FILE NAME> , the difference for all les are shown.
4. To restore one or more les, run
tux > sudo snapper -c CONFIG -v undochange SNAPSHOT_ID..0 FILENAME1 FILENAME2
If you do not specify le names, all changed les will be restored.
7.3 System Rollback by Booting from Snapshots

The GRUB 2 version included on SUSE Linux Enterprise Server can boot from Btrfs snapshots.
Together with Snapper's rollback feature, this allows to recover a misconfigured system. Only
snapshots created for the default Snapper configuration ( root ) are bootable.
Important: Supported Configuration

As of SUSE Linux Enterprise Server 12 SP3 system rollbacks are only supported if the
default subvolume configuration of the root partition has not been changed.
When booting a snapshot, the parts of the le system included in the snapshot are mounted
read-only; all other le systems and parts that are excluded from snapshots are mounted read-
write and can be modified.
79 System Rollback by Booting from Snapshots SLES 12 SP3

Important: Undoing Changes Compared to Rollback
When working with snapshots to restore data, it is important to know that there are two
fundamentally different scenarios Snapper can handle:
Undoing Changes
When undoing changes as described in Section 7.2, “Using Snapper to Undo Changes”,
two snapshots are compared and the changes between these two snapshots are re-
verted. Using this method also allows to explicitly exclude selected les from being
restored.
Rollback
When doing rollbacks as described in the following, the system is reset to the state
at which the snapshot was taken.
To do a rollback from a bootable snapshot, the following requirements must be met. When doing
a default installation, the system is set up accordingly.
REQUIREMENTS FOR A ROLLBACK FROM A BOOTABLE SNAPSHOT
The root le system needs to be Btrfs. Booting from LVM volume snapshots is not support-
ed.
The root le system needs to be on a single device, a single partition and a single subvol-
ume. Directories that are excluded from snapshots such as /srv (see Section 7.1.2, “Direc-
tories That Are Excluded from Snapshots” for a full list) may reside on separate partitions.
The system needs to be bootable via the installed boot loader.
To perform a rollback from a bootable snapshot, do as follows:
1. Boot the system. In the boot menu choose Bootable snapshots and select the snapshot you
want to boot. The list of snapshots is listed by date—the most recent snapshot is listed rst.
2. Log in to the system. Carefully check whether everything works as expected. Note that
you cannot write to any directory that is part of the snapshot. Data you write to other
directories will not get lost, regardless of what you do next.
80 System Rollback by Booting from Snapshots SLES 12 SP3

3. Depending on whether you want to perform the rollback or not, choose your next step:
a. If the system is in a state where you do not want to do a rollback, reboot to boot
into the current system state. You can then choose a different snapshot, or start the
rescue system.
b. To perform the rollback, run
tux > sudo snapper rollback
and reboot afterward. On the boot screen, choose the default boot entry to reboot
into the reinstated system. A snapshot of the le system status before the rollback
is created. The default subvolume for root will be replaced with a fresh read-write
snapshot. For details, see Section 7.3.1, “Snapshots after Rollback”.
It is useful to add a description for the snapshot with the -d option. For example:
New file system root since rollback on DATE TIME
Tip: Rolling Back to a Specific Installation State

If snapshots are not disabled during installation, an initial bootable snapshot is created
at the end of the initial system installation. You can go back to that state at any time
by booting this snapshot. The snapshot can be identified by the description after in-
stallation .
A bootable snapshot is also created when starting a system upgrade to a service pack or
a new major release (provided snapshots are not disabled).
7.3.1 Snapshots after Rollback

Before a rollback is performed, a snapshot of the running le system is created. The description
references the ID of the snapshot that was restored in the rollback.
Snapshots created by rollbacks receive the value number for the Cleanup attribute. The rollback
snapshots are therefore automatically deleted when the set number of snapshots is reached.
Refer to Section 7.6, “Automatic Snapshot Clean-Up” for details. If the snapshot contains important
data, extract the data from the snapshot before it is removed.
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7.3.1.1 Example of Rollback Snapshot
For example, after a fresh installation the following snapshots are available on the system:
root # snapper --iso list

Type | # | | Cleanup | Description | Userdata
-------+---+ ... +---------+-----------------------+--------------
single | 0 | | | current |
single | 1 | | | first root filesystem |
single | 2 | | number | after installation | important=yes
After running sudo snapper rollback snapshot 3 is created and contains the state of the
system before the rollback was executed. Snapshot 4 is the new default Btrfs subvolume and
thus the system after a reboot.
root # snapper --iso list

Type | # | | Cleanup | Description | Userdata
-------+---+ ... +---------+-----------------------+--------------
single | 0 | | | current |
single | 1 | | number | first root filesystem |
single | 2 | | number | after installation | important=yes
single | 3 | | number | rollback backup of #1 | important=yes
single | 4 | | | |
7.3.2 Accessing and Identifying Snapshot Boot Entries

To boot from a snapshot, reboot your machine and choose Start Bootloader from a read-only
snapshot. A screen listing all bootable snapshots opens. The most recent snapshot is listed rst,
the oldest last. Use the keys ↓ and ↑ to navigate and press Enter to activate the selected
snapshot. Activating a snapshot from the boot menu does not reboot the machine immediately,
but rather opens the boot loader of the selected snapshot.
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FIGURE 7.1: BOOT LOADER: SNAPSHOTS
Each snapshot entry in the boot loader follows a naming scheme which makes it possible to
identify it easily:
[*] 1 OS 2 (KERNEL 3 ,DATE 4 TTIME 5 ,DESCRIPTION 6 )
1 If the snapshot was marked important , the entry is marked with a * .

2 Operating system label.
4 Date in the format YYYY-MM-DD .
5 Time in the format HH:MM .
6 This eld contains a description of the snapshot. In case of a manually created snapshot
this is the string created with the option --description or a custom string (see Tip: Setting
a Custom Description for Boot Loader Snapshot Entries). In case of an automatically created
snapshot, it is the tool that was called, for example zypp(zypper) or yast_sw_single .
Long descriptions may be truncated, depending on the size of the boot screen.
83 Accessing and Identifying Snapshot Boot Entries SLES 12 SP3

Tip: Setting a Custom Description for Boot Loader Snapshot
Entries
It is possible to replace the default string in the description eld of a snapshot with a
custom string. This is for example useful if an automatically created description is not
sufficient, or a user-provided description is too long. To set a custom string STRING for
snapshot NUMBER , use the following command:
tux > sudo snapper modify --userdata "bootloader=STRING" NUMBER
The description should be no longer than 25 characters—everything that exceeds this size
will not be readable on the boot screen.
7.3.3 Limitations
A complete system rollback, restoring the complete system to the identical state as it was in when
a snapshot was taken, is not possible.
7.3.3.1 Directories Excluded from Snapshots
Root le system snapshots do not contain all directories. See Section 7.1.2, “Directories That Are
Excluded from Snapshots” for details and reasons. As a general consequence, data from these di-
rectories is not restored, resulting in the following limitations.
Add-ons and Third Party Software may be Unusable after a Rollback

Applications and add-ons installing data in subvolumes excluded from the snapshot, such
as /opt , may not work after a rollback, if others parts of the application data are also
installed on subvolumes included in the snapshot. Re-install the application or the add-
on to solve this problem.
File Access Problems

If an application had changed le permissions and/or ownership in between snapshot and
current system, the application may not be able to access these les. Reset permissions
and/or ownership for the affected les after the rollback.
84 Limitations SLES 12 SP3

Incompatible Data Formats
If a service or an application has established a new data format in between snapshot and
current system, the application may not be able to read the affected data les after a
rollback.
Subvolumes with a Mixture of Code and Data

Subvolumes like /srv may contain a mixture of code and data. A rollback may result in
non-functional code. A downgrade of the PHP version, for example, may result in broken
PHP scripts for the Web server.
User Data
If a rollback removes users from the system, data that is owned by these users in directories
excluded from the snapshot, is not removed. If a user with the same user ID is created, this
user will inherit the les. Use a tool like find to locate and remove orphaned les.
7.3.3.2 No Rollback of Boot Loader Data
A rollback of the boot loader is not possible, since all “stages” of the boot loader must t together.
This cannot be guaranteed when doing rollbacks of /boot .
7.4 Creating and Modifying Snapper Configurations

The way Snapper behaves is defined in a configuration le that is specific for each partition or
Btrfs subvolume. These configuration les reside under /etc/snapper/configs/ .
In case the root le system is big enough (approximately 12 GB), snapshots are automatically
enabled for the root le system / upon installation. The corresponding default configuration is
named root . It creates and manages the YaST and Zypper snapshot. See Section 7.4.1.1, “Config-
uration Data” for a list of the default values.
Note: Minimum Root File System Size for Enabling Snapshots

As explained in Section 7.1, “Default Setup”, enabling snapshots requires additional free
space in the root le system. The amount depends on the amount of packages installed and
the amount of changes made to the volume that is included in snapshots. The snapshot
frequency and the number of snapshots that get archived also matter.
85 Creating and Modifying Snapper Configurations SLES 12 SP3

There is a minimum root le system size that is required in order to automatically enable
snapshots during the installation. As of SUSE Linux Enterprise Server 12 SP3 this size is
approximately 12 GB. This value may change in the future, depending on architecture
and the size of the base system. It depends on the values for the following tags in the le
/control.xml from the installation media:
<root_base_size>
<btrfs_increase_percentage>
It is calculated with the following formula: ROOT_BASE_SIZE * (1 + BTRFS_IN-

CREASE_PERCENTAGE /100)
Keep in mind that this value is a minimum size. Consider using more space for the root
le system. As a rule of thumb, double the size you would use when not having enabled
snapshots.
You may create your own configurations for other partitions formatted with Btrfs or existing
subvolumes on a Btrfs partition. In the following example we will set up a Snapper configu-
ration for backing up the Web server data residing on a separate, Btrfs -formatted partition
mounted at /srv/www .
After a configuration has been created, you can either use snapper itself or the YaST Snapper
module to restore les from these snapshots. In YaST you need to select your Current Configura-
tion, while you need to specify your configuration for snapper with the global switch -c (for
example, snapper -c myconfig list ).
To create a new Snapper configuration, run snapper create-config :
tux > sudo snapper -c www-data 1 create-config /srv/www 2
1 Name of configuration le.

2 Mount point of the partition or Btrfs subvolume on which to take snapshots.
This command will create a new configuration le /etc/snapper/configs/www-data with
reasonable default values (taken from /etc/snapper/config-templates/default ). Refer to
Section 7.4.1, “Managing Existing Configurations” for instructions on how to adjust these defaults.
86 Creating and Modifying Snapper Configurations SLES 12 SP3

Tip: Configuration Defaults
Default values for a new configuration are taken from /etc/snapper/config-tem-
plates/default . To use your own set of defaults, create a copy of this le in the same
directory and adjust it to your needs. To use it, specify the -t option with the create-con-
fig command:
tux > sudo snapper -c www-data create-config -t MY_DEFAULTS /srv/www
7.4.1 Managing Existing Configurations

The snapper offers several subcommands for managing existing configurations. You can list,
show, delete and modify them:
List Configurations
Use the command snapper list-configs to get all existing configurations:
tux > sudo snapper list-configs

Config | Subvolume
-------+----------
root | /
usr | /usr
local | /local
Show a Configuration
Use the subcommand snapper -c CONFIG get-config to display the specified configu-
ration. Config needs to be replaced by a configuration name shown by snapper list-
configs . See Section 7.4.1.1, “Configuration Data” for more information on the configuration
options.
To display the default configuration run
tux > sudo snapper -c root get-config
Modify a Configuration
Use the subcommand snapper -c CONFIG set-config OPTION=VALUE to modify an
option in the specified configuration. Config needs to be replaced by a configuration
name shown by snapper list-configs . Possible values for OPTION and VALUE are listed
in Section 7.4.1.1, “Configuration Data”.
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Delete a Configuration
Use the subcommand snapper -c CONFIG delete-config to delete a configuration.
Config needs to be replaced by a configuration name shown by snapper list-configs .
7.4.1.1 Configuration Data
Each configuration contains a list of options that can be modified from the command line. The
following list provides details for each option. To change a value, run snapper -c CONFIG
set-config "KEY=VALUE" .
ALLOW_GROUPS , ALLOW_USERS
Granting permissions to use snapshots to regular users. See Section 7.4.1.2, “Using Snapper
as Regular User” for more information.
The default value is "" .
BACKGROUND_COMPARISON
Defines whether pre and post snapshots should be compared in the background after cre-
ation.
The default value is "yes" .
EMPTY_*
Defines the clean-up algorithm for snapshots pairs with identical pre and post snapshots.
See Section 7.6.3, “Cleaning Up Snapshot Pairs That Do Not Differ” for details.
FSTYPE
File system type of the partition. Do not change.
The default value is "btrfs" .
NUMBER_*
Defines the clean-up algorithm for installation and admin snapshots. See Section 7.6.1,
“Cleaning Up Numbered Snapshots” for details.
QGROUP / SPACE_LIMIT
Adds quota support to the clean-up algorithms. See Section 7.6.5, “Adding Disk Quota Support”
for details.
SUBVOLUME
Mount point of the partition or subvolume to snapshot. Do not change.
The default value is "/" .

SYNC_ACL
If Snapper is used by regular users (see Section 7.4.1.2, “Using Snapper as Regular User”), the
users must be able to access the .snapshot directories and to read les within them.
If SYNC_ACL is set to yes , Snapper automatically makes them accessible using ACLs for
users and groups from the ALLOW_USERS or ALLOW_GROUPS entries.
The default value is "no" .
TIMELINE_CREATE
If set to yes , hourly snapshots are created. Valid values: yes , no .
The default value is "no" .
TIMELINE_CLEANUP / TIMELINE_LIMIT_*
Defines the clean-up algorithm for timeline snapshots. See Section 7.6.2, “Cleaning Up Timeline
Snapshots” for details.
7.4.1.2 Using Snapper as Regular User

By default Snapper can only be used by root . However, there are cases in which certain groups
or users need to be able to create snapshots or undo changes by reverting to a snapshot:
Web site administrators who want to take snapshots of /srv/www
Users who want to take a snapshot of their home directory
For these purposes Snapper configurations that grant permissions to users or/and groups can be
created. The corresponding .snapshots directory needs to be readable and accessible by the
specified users. The easiest way to achieve this is to set the SYNC_ACL option to yes .
PROCEDURE 7.5: ENABLING REGULAR USERS TO USE SNAPPER
Note that all steps in this procedure need to be run by root .
1. If not existing, create a Snapper configuration for the partition or subvolume on which
the user should be able to use Snapper. Refer to Section 7.4, “Creating and Modifying Snapper
Configurations” for instructions. Example:
tux > sudo snapper --config web_data create /srv/www
2. The configuration le is created under /etc/snapper/configs/CONFIG , where CONFIG

is the value you specified with -c/--config in the previous step (for example /etc/
snapper/configs/web_data ). Adjust it according to your needs; see Section 7.4.1, “Man-
aging Existing Configurations” for details.

3. Set values for ALLOW_USERS and/or ALLOW_GROUPS to grant permissions to users and/or
groups, respectively. Multiple entries need to be separated by Space . To grant permissions
to the user www_admin for example, run:
tux > sudo snapper -c web_data set-config "ALLOW_USERS=www_admin" SYNC_ACL="yes"
4. The given Snapper configuration can now be used by the specified user(s) and/or group(s).
You can test it with the list command, for example:
www_admin:~ > snapper -c web_data list
7.5 Manually Creating and Managing Snapshots

Snapper is not restricted to creating and managing snapshots automatically by configuration;
you can also create snapshot pairs (“before and after”) or single snapshots manually using either
the command-line tool or the YaST module.
All Snapper operations are carried out for an existing configuration (see Section 7.4, “Creating
and Modifying Snapper Configurations” for details). You can only take snapshots of partitions or
volumes for which a configuration exists. By default the system configuration ( root ) is used. If
you want to create or manage snapshots for your own configuration you need to explicitly choose
it. Use the Current Configuration drop-down box in YaST or specify the -c on the command line
( snapper -c MYCONFIG COMMAND ).
7.5.1 Snapshot Metadata

Each snapshot consists of the snapshot itself and some metadata. When creating a snapshot you
also need to specify the metadata. Modifying a snapshot means changing its metadata—you
cannot modify its content. Use snapper list to show existing snapshots and their metadata:
snapper --config home list

Lists snapshots for the configuration home . To list snapshots for the default configuration
(root), use snapper -c root list or snapper list .
snapper list -a
Lists snapshots for all existing configurations.
snapper list -t pre-post

Lists all pre and post snapshot pairs for the default ( root ) configuration.
90 Manually Creating and Managing Snapshots SLES 12 SP3

snapper list -t single
Lists all snapshots of the type single for the default ( root ) configuration.
The following metadata is available for each snapshot:
Type: Snapshot type, see Section 7.5.1.1, “Snapshot Types” for details. This data cannot be
changed.
Number: Unique number of the snapshot. This data cannot be changed.
Pre Number: Specifies the number of the corresponding pre snapshot. For snapshots of
type post only. This data cannot be changed.
Description: A description of the snapshot.
Userdata: An extended description where you can specify custom data in the form of a
comma-separated key=value list: reason=testing, project=foo . This eld is also used
to mark a snapshot as important ( important=yes ) and to list the user that created the
snapshot (user=tux).
Cleanup-Algorithm: Cleanup-algorithm for the snapshot, see Section 7.6, “Automatic Snap-

shot Clean-Up” for details.
7.5.1.1 Snapshot Types
Snapper knows three different types of snapshots: pre, post, and single. Physically they do not
differ, but Snapper handles them differently.
pre
Snapshot of a le system before a modification. Each pre snapshot has got a corresponding
post snapshot. Used for the automatic YaST/Zypper snapshots, for example.
post
Snapshot of a le system after a modification. Each post snapshot has got a corresponding
pre snapshot. Used for the automatic YaST/Zypper snapshots, for example.
single
Stand-alone snapshot. Used for the automatic hourly snapshots, for example. This is the
default type when creating snapshots.
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7.5.1.2 Cleanup-algorithms
Snapper provides three algorithms to clean up old snapshots. The algorithms are executed in a
daily cron job. It is possible to define the number of different types of snapshots to keep in the
Snapper configuration (see Section 7.4.1, “Managing Existing Configurations” for details).
number
Deletes old snapshots when a certain snapshot count is reached.
timeline
Deletes old snapshots having passed a certain age, but keeps several hourly, daily, monthly,
and yearly snapshots.
empty-pre-post
Deletes pre/post snapshot pairs with empty dis.
7.5.2 Creating Snapshots

Creating a snapshot is done by running snapper create or by clicking Create in the YaST
module Snapper. The following examples explain how to create snapshots from the command
line. It should be easy to adopt them when using the YaST interface.
Tip: Snapshot Description

You should always specify a meaningful description to later be able to identify its purpose.
Even more information can be specified via the user data option.
snapper create --description "Snapshot for week 2 2014"

Creates a stand-alone snapshot (type single) for the default ( root ) configuration with a
description. Because no cleanup-algorithm is specified, the snapshot will never be deleted
automatically.
snapper --config home create --description "Cleanup in ~tux"

Creates a stand-alone snapshot (type single) for a custom configuration named home with
a description. Because no cleanup-algorithm is specified, the snapshot will never be deleted
automatically.
92 Creating Snapshots SLES 12 SP3

snapper --config home create --description "Daily data backup" --cleanup-algo-
rithm timeline >
Creates a stand-alone snapshot (type single) for a custom configuration named home with
a description. The le will automatically be deleted when it meets the criteria specified
for the timeline cleanup-algorithm in the configuration.
snapper create --type pre --print-number --description "Before the Apache config
cleanup" --userdata "important=yes"
Creates a snapshot of the type pre and prints the snapshot number. First command needed
to create a pair of snapshots used to save a “before” and “after” state. The snapshot is
marked as important.
snapper create --type post --pre-number 30 --description "After the Apache

config cleanup" --userdata "important=yes"
Creates a snapshot of the type post paired with the pre snapshot number 30 . Second
command needed to create a pair of snapshots used to save a “before” and “after” state.
The snapshot is marked as important.
snapper create --command COMMAND --description "Before and after COMMAND"

Automatically creates a snapshot pair before and after running COMMAND . This option is
only available when using snapper on the command line.
7.5.3 Modifying Snapshot Metadata

Snapper allows you to modify the description, the cleanup algorithm, and the user data of a
snapshot. All other metadata cannot be changed. The following examples explain how to mod-
ify snapshots from the command line. It should be easy to adopt them when using the YaST
interface.
To modify a snapshot on the command line, you need to know its number. Use snapper list
to display all snapshots and their numbers.
The YaST Snapper module already lists all snapshots. Choose one from the list and click Modify.
snapper modify --cleanup-algorithm "timeline" 10

Modifies the metadata of snapshot 10 for the default ( root ) configuration. The cleanup
algorithm is set to timeline .
93 Modifying Snapshot Metadata SLES 12 SP3

snapper --config home modify --description "daily backup" -cleanup-algorithm
"timeline" 120
Modifies the metadata of snapshot 120 for a custom configuration named home . A new
description is set and the cleanup algorithm is unset.
7.5.4 Deleting Snapshots

To delete a snapshot with the YaST Snapper module, choose a snapshot from the list and click
Delete.
To delete a snapshot with the command line tool, you need to know its number. Get it by running
snapper list . To delete a snapshot, run snapper delete NUMBER .
Deleting the current default subvolume snapshot is not allowed.

When deleting snapshots with Snapper, the freed space will be claimed by a Btrfs process running
in the background. Thus the visibility and the availability of free space is delayed. In case you
need space freed by deleting a snapshot to be available immediately, use the option --sync
with the delete command.
Tip: Deleting Snapshot Pairs

When deleting a pre snapshot, you should always delete its corresponding post snap-
shot (and vice versa).
snapper delete 65
Deletes snapshot 65 for the default ( root ) configuration.
snapper -c home delete 89 90

Deletes snapshots 89 and 90 for a custom configuration named home .
snapper delete --sync 23

Deletes snapshot 23 for the default ( root ) configuration and makes the freed space avail-
able immediately.
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Tip: Delete Unreferenced Snapshots
Sometimes the Btrfs snapshot is present but the XML le containing the metadata for
Snapper is missing. In this case the snapshot is not visible for Snapper and needs to be
deleted manually:
btrfs subvolume delete /.snapshots/SNAPSHOTNUMBER/snapshot

rm -rf /.snapshots/SNAPSHOTNUMBER
Tip: Old Snapshots Occupy More Disk Space

If you delete snapshots to free space on your hard disk, make sure to delete old snapshots
rst. The older a snapshot is, the more disk space it occupies.
Snapshots are also automatically deleted by a daily cron job. Refer to Section 7.5.1.2, “Cleanup-
algorithms” for details.
7.6 Automatic Snapshot Clean-Up

Snapshots occupy disk space and over time the amount of disk space occupied by the snapshots
may become large. To prevent disks from running out of space, Snapper offers algorithms to
automatically delete old snapshots. These algorithms differentiate between timeline snapshots
and numbered snapshots (administration plus installation snapshot pairs). You can specify the
number of snapshots to keep for each type.
In addition to that, you can optionally specify a disk space quota, defining the maximum amount
of disk space the snapshots may occupy. It is also possible to automatically delete pre and post
snapshots pairs that do not differ.
A clean-up algorithm is always bound to a single Snapper configuration, so you need to config-
ure algorithms for each configuration. To prevent certain snapshots from being automatically
deleted, refer to Q:.
The default setup ( root ) is configured to do clean-up for numbered snapshots and empty pre
and post snapshot pairs. Quota support is enabled—snapshots may not occupy more than 50%
of the available disk space of the root partition. Timeline snapshots are disabled by default,
therefore the timeline clean-up algorithm is also disabled.
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7.6.1 Cleaning Up Numbered Snapshots
Cleaning up numbered snapshots—administration plus installation snapshot pairs—is controlled
by the following parameters of a Snapper configuration.
NUMBER_CLEANUP
Enables or disables clean-up of installation and admin snapshot pairs. If enabled, snap-
shot pairs are deleted when the total snapshot count exceeds a number specified
with NUMBER_LIMIT and/or NUMBER_LIMIT_IMPORTANT and an age specified with NUM-
BER_MIN_AGE . Valid values: yes (enable), no (disable).
Example command to change or set:
tux > sudo snapper -c CONFIG set-config "NUMBER_CLEANUP=no"
NUMBER_LIMIT / NUMBER_LIMIT_IMPORTANT
Defines how many regular and/or important installation and administration snapshot pairs
to keep. Only the youngest snapshots will be kept. Ignored if NUMBER_CLEANUP is set to
"no" .
The default value is "2-10" for NUMBER_LIMIT and "4-10" for NUMBER_LIMIT_IMPOR-
TANT .
tux > sudo snapper -c CONFIG set-config "NUMBER_LIMIT=10"
Important: Ranged Compared to Constant Values

In case quota support is enabled (see Section 7.6.5, “Adding Disk Quota Support”) the
limit needs to be specified as a minimum-maximum range, for example 2-10 . If
quota support is disabled, a constant value, for example 10 , needs to be provided,
otherwise cleaning-up will fail with an error.
NUMBER_MIN_AGE
Defines the minimum age in seconds a snapshot must have before it can automatically be
deleted. Snapshots younger than the value specified here will not be deleted, regardless
of how many exist.
The default value is "1800" .
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tux > sudo snapper -c CONFIG set-config "NUMBER_MIN_AGE=864000"
Note: Limit and Age

NUMBER_LIMIT , NUMBER_LIMIT_IMPORTANT and NUMBER_MIN_AGE are always evaluated.
Snapshots are only deleted when all conditions are met.
If you always want to keep the number of snapshots defined with NUMBER_LIMIT* re-
gardless of their age, set NUMBER_MIN_AGE to 0 .
The following example shows a configuration to keep the last 10 important and regular
snapshots regardless of age:
NUMBER_CLEANUP=yes
NUMBER_LIMIT_IMPORTANT=10
NUMBER_LIMIT=10
NUMBER_MIN_AGE=0
On the other hand, if you do not want to keep snapshots beyond a certain age, set NUM-
BER_LIMIT* to 0 and provide the age with NUMBER_MIN_AGE .
The following example shows a configuration to only keep snapshots younger than ten
days:
NUMBER_CLEANUP=yes
NUMBER_LIMIT_IMPORTANT=0
NUMBER_LIMIT=0
NUMBER_MIN_AGE=864000
7.6.2 Cleaning Up Timeline Snapshots

Cleaning up timeline snapshots is controlled by the following parameters of a Snapper config-
uration.
TIMELINE_CLEANUP
Enables or disables clean-up of timeline snapshots. If enabled, snapshots are deleted when
the total snapshot count exceeds a number specified with TIMELINE_LIMIT_* and an age
specified with TIMELINE_MIN_AGE . Valid values: yes , no .
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tux > sudo snapper -c CONFIG set-config "TIMELINE_CLEANUP=yes"
TIMELINE_LIMIT_DAILY , TIMELINE_LIMIT_HOURLY , TIMELINE_LIMIT_MONTHLY ,

TIMELINE_LIMIT_WEEKLY , TIMELINE_LIMIT_YEARLY
Number of snapshots to keep for hour, day, month, week, and year.
The default value for each entry is "10" , except for TIMELINE_LIMIT_WEEKLY , which is
set to "0" by default.
TIMELINE_MIN_AGE
Defines the minimum age in seconds a snapshot must have before it can automatically
be deleted.
EXAMPLE 7.1: EXAMPLE TIMELINE CONFIGURATION
TIMELINE_CLEANUP="yes"
TIMELINE_CREATE="yes"
TIMELINE_LIMIT_DAILY="7"
TIMELINE_LIMIT_HOURLY="24"
TIMELINE_LIMIT_MONTHLY="12"
TIMELINE_LIMIT_WEEKLY="4"
TIMELINE_LIMIT_YEARLY="2"
TIMELINE_MIN_AGE="1800"
This example configuration enables hourly snapshots which are automatically cleaned up.
TIMELINE_MIN_AGE and TIMELINE_LIMIT_* are always both evaluated. In this example,
the minimum age of a snapshot before it can be deleted is set to 30 minutes (1800 seconds).
Since we create hourly snapshots, this ensures that only the latest snapshots are kept. If
TIMELINE_LIMIT_DAILY is set to not zero, this means that the rst snapshot of the day
is kept, too.
SNAPSHOTS TO BE KEPT
Hourly: The last 24 snapshots that have been made.
Daily: The rst daily snapshot that has been made is kept from the last seven days.
Monthly: The rst snapshot made on the last day of the month is kept for the last
twelve months.
98 Cleaning Up Timeline Snapshots SLES 12 SP3

Weekly: The rst snapshot made on the last day of the week is kept from the last
four weeks.
Yearly: The rst snapshot made on the last day of the year is kept for the last two
years.
7.6.3 Cleaning Up Snapshot Pairs That Do Not Differ

As explained in Section 7.1.1, “Types of Snapshots”, whenever you run a YaST module or execute
Zypper, a pre snapshot is created on start-up and a post snapshot is created when exiting. In
case you have not made any changes there will be no difference between the pre and post
snapshots. Such “empty” snapshot pairs can be automatically be deleted by setting the following
parameters in a Snapper configuration:
EMPTY_PRE_POST_CLEANUP
If set to yes , pre and post snapshot pairs that do not differ will be deleted.
EMPTY_PRE_POST_MIN_AGE
Defines the minimum age in seconds a pre and post snapshot pair that does not differ must
have before it can automatically be deleted.
7.6.4 Cleaning Up Manually Created Snapshots

Snapper does not offer custom clean-up algorithms for manually created snapshots. However,
you can assign the number or timeline clean-up algorithm to a manually created snapshot. If
you do so, the snapshot will join the “clean-up queue” for the algorithm you specified. You can
specify a clean-up algorithm when creating a snapshot, or by modifying an existing snapshot:
snapper create --description "Test" --cleanup-algorithm number

Creates a stand-alone snapshot (type single) for the default (root) configuration and assigns
the number clean-up algorithm.
snapper modify --cleanup-algorithm "timeline" 25

Modifies the snapshot with the number 25 and assigns the clean-up algorithm timeline .
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7.6.5 Adding Disk Quota Support
In addition to the number and/or timeline clean-up algorithms described above, Snapper sup-
ports quotas. You can define what percentage of the available space snapshots are allowed to
occupy. This percentage value always applies to the Btrfs subvolume defined in the respective
Snapper configuration.
If Snapper was enabled during the installation, quota support is automatically enabled. In case
you manually enable Snapper at a later point in time, you can enable quota support by running
snapper setup-quota . This requires a valid configuration (see Section 7.4, “Creating and Modi-
fying Snapper Configurations” for more information).
Quota support is controlled by the following parameters of a Snapper configuration.
QGROUP
The Btrfs quota group used by Snapper. If not set, run snapper setup-quota . If already
set, only change if you are familiar with man 8 btrfs-qgroup . This value is set with
snapper setup-quota and should not be changed.
SPACE_LIMIT
Limit of space snapshots are allowed to use in fractions of 1 (100%). Valid values range
from 0 to 1 (0.1 = 10%, 0.2 = 20%, ...).
The following limitations and guidelines apply:
Quotas are only activated in addition to an existing number and/or timeline clean-up al-
gorithm. If no clean-up algorithm is active, quota restrictions are not applied.
With quota support enabled, Snapper will perform two clean-up runs if required. The rst
run will apply the rules specified for number and timeline snapshots. Only if the quota is
exceeded after this run, the quota-specific rules will be applied in a second run.
Even if quota support is enabled, Snapper will always keep the number of snapshots
specified with the NUMBER_LIMIT* and TIMELINE_LIMIT* values, even if the quota will
be exceeded. It is therefore recommended to specify ranged values ( MIN-MAX ) for NUM-
BER_LIMIT* and TIMELINE_LIMIT* to ensure the quota can be applied.
If, for example, NUMBER_LIMIT=5-20 is set, Snapper will perform a rst clean-up run and
reduce the number of regular numbered snapshots to 20. In case these 20 snapshots exceed
the quota, Snapper will delete the oldest ones in a second run until the quota is met. A
minimum of ve snapshots will always be kept, regardless of the amount of space they
occupy.
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7.7 Frequently Asked Questions
Q: Why does Snapper Never Show Changes in /var/log , /tmp and Other Directories?
A: For some directories we decided to exclude them from snapshots. See Section 7.1.2, “Direc-
tories That Are Excluded from Snapshots” for a list and reasons. To exclude a path from snap-
shots we create a subvolume for that path.
Q: How much disk space is used by snapshots? How to free disk space?
A: Displaying the amount of disk space a snapshot allocates is currently not supported by the
Btrfs tools. However, if you have quota enabled, it is possible to determine how much
space would be freed if all snapshots would be deleted:
1. Get the quota group ID ( 1/0 in the following example):
tux > sudo snapper -c root get-config | grep QGROUP

QGROUP | 1/0
2. Rescan the subvolume quotas:
tux > sudo btrfs quota rescan -w /
3. Show the data of the quota group ( 1/0 in the following example):
tux > sudo btrfs qgroup show / | grep "1/0"

1/0 4.80GiB 108.82MiB
The third column shows the amount of space that would be freed when deleting all
snapshots ( 108.82MiB ).
To free space on a Btrfs partition containing snapshots you need to delete unneeded
snapshots rather than les. Older snapshots occupy more space than recent ones. See Sec-
tion 7.1.3.4, “Controlling Snapshot Archiving” for details.
Doing an upgrade from one service pack to another results in snapshots occupying a lot of
disk space on the system subvolumes, because a lot of data gets changed (package updates).
Manually deleting these snapshots after they are no longer needed is recommended. See
Section 7.5.4, “Deleting Snapshots” for details.
Q: Can I Boot a Snapshot from the Boot Loader?

A: Yes—refer to Section 7.3, “System Rollback by Booting from Snapshots” for details.
101 Frequently Asked Questions SLES 12 SP3

Q: How to make a snapshot permanent?
A: Currently Snapper does not offer means to prevent a snapshot from being deleted manual-
ly. However, you can prevent snapshots from being automatically deleted by clean-up al-
gorithms. Manually created snapshots (see Section 7.5.2, “Creating Snapshots”) have no clean-
up algorithm assigned unless you specify one with --cleanup-algorithm . Automatically
created snapshots always either have the number or timeline algorithm assigned. To
remove such an assignment from one or more snapshots, proceed as follows:
1. List all available snapshots:
tux > sudo snapper list -a
2. Memorize the number of the snapshot(s) you want to prevent from being deleted.
3. Run the following command and replace the number placeholders with the num-
ber(s) you memorized:
tux > sudo snapper modify --cleanup-algorithm "" #1 #2 #n
4. Check the result by running snapper list -a again. The entry in the column
Cleanup should now be empty for the snapshots you modified.
Q: Where can I get more information on Snapper?

A: See the Snapper home page at http://snapper.io/ .

8 Remote Access with VNC
Virtual Network Computing (VNC) enables you to control a remote computer via a
graphical desktop (as opposed to a remote shell access). VNC is platform-indepen-
dent and lets you access the remote machine from any operating system.
SUSE Linux Enterprise Server supports two different kinds of VNC sessions: One-
time sessions that “live” as long as the VNC connection from the client is kept up,
and persistent sessions that “live” until they are explicitly terminated.
Note: Session Types

A machine can offer both kinds of sessions simultaneously on different ports, but an open
session cannot be converted from one type to the other.
8.1 The vncviewer Client

To connect to a VNC service provided by a server, a client is needed. The default in SUSE Linux
Enterprise Server is vncviewer , provided by the tigervnc package.
8.1.1 Connecting Using the vncviewer CLI

To start your VNC viewer and initiate a session with the server, use the command:
vncviewer jupiter.example.com:1
Instead of the VNC display number you can also specify the port number with two colons:
vncviewer jupiter.example.com::5901
Note: Display and Port Number

The actual display or port number you specify in the VNC client must be the same as the
display or port number picked by the vncserver command on the target machine. See
Section 8.3, “Persistent VNC Sessions” for further info.
103 The vncviewer Client SLES 12 SP3

8.1.2 Connecting Using the vncviewer GUI
By running vncviewer without specifying --listen or a host to connect to, it will show a
window to ask for connection details. Enter the host into the VNC server eld like in Section 8.1.1,
“Connecting Using the vncviewer CLI” and click Connect.
FIGURE 8.1: VNCVIEWER
8.1.3 Notification of Unencrypted Connections

The VNC protocol supports different kinds of encrypted connections, not to be confused with
password authentication. If a connection does not use TLS, the text “(Connection not encrypt-
ed!)” can be seen in the window title of the VNC viewer.
8.2 One-time VNC Sessions

A one-time session is initiated by the remote client. It starts a graphical login screen on the
server. This way you can choose the user which starts the session and, if supported by the
login manager, the desktop environment. When you terminate the client connection to such a
VNC session, all applications started within that session will be terminated, too. One-time VNC
sessions cannot be shared, but it is possible to have multiple sessions on a single host at the
same time.
PROCEDURE 8.1: ENABLING ONE-TIME VNC SESSIONS
1. Start YaST Network Services Remote Administration (VNC).
104 Connecting Using the vncviewer GUI SLES 12 SP3

2. Check Allow Remote Administration.
3. If necessary, also check Open Port in Firewall (for example, when your network interface
is configured to be in the External Zone). If you have more than one network interface,
restrict opening the firewall ports to a specific interface via Firewall Details.
4. Confirm your settings with Finish.
5. In case not all needed packages are available yet, you need to approve the installation
of missing packages.
8.2.1 Available Configurations

The default configuration on SUSE Linux Enterprise Server serves sessions with a resolution of
1024x768 pixels at a color depth of 16-bit. The sessions are available on ports 5901 for “regular”
VNC viewers (equivalent to VNC display 1 ) and on port 5801 for Web browsers.
Other configurations can be made available on different ports, see Section 8.2.3, “Configuring One-
time VNC Sessions”.
VNC display numbers and X display numbers are independent in one-time sessions. A VNC dis-
play number is manually assigned to every configuration that the server supports (:1 in the ex-
ample above). Whenever a VNC session is initiated with one of the configurations, it automat-
ically gets a free X display number.
By default, both the VNC client and server try to communicate securely via a self-signed SSL
certificate, which is generated after installation. You can either use the default one, or replace it
with your own. When using the self-signed certificate, you need to confirm its signature before
the rst connection.
8.2.2 Initiating a One-time VNC Session

To connect to a persistent VNC session, a VNC viewer must be installed, see also Section 8.1,
“The vncviewer Client”.
8.2.3 Configuring One-time VNC Sessions

You can skip this section, if you do not need or want to modify the default configuration.
105 Available Configurations SLES 12 SP3

One-time VNC sessions are started via the xinetd daemon. A configuration le is located at /
etc/xinetd.d/vnc . By default it offers six configuration blocks: three for VNC viewers ( vnc1
to vnc3 ), and three serving a Java applet ( vnchttpd1 to vnchttpd3 ). By default only vnc1
and vnchttpd1 are active.
To activate a configuration, comment the line disable = yes with a # character in the rst
column, or remove that line completely. To deactivate a configuration uncomment or add that
line.
The Xvnc server can be configured via the server_args option—see Xnvc --help for a list
of options.
When adding custom configurations, make sure they are not using ports that are already in use
by other configurations, other services, or existing persistent VNC sessions on the same host.
Activate configuration changes by entering the following command:
sudo systemctl reload xinetd
Important: Firewall and VNC Ports

When activating Remote Administration as described in Procedure 8.1, “Enabling One-time
VNC Sessions”, the ports 5801 and 5901 are opened in the firewall. If the network in-
terface serving the VNC sessions is protected by a firewall, you need to manually open
the respective ports when activating additional ports for VNC sessions. See Book “Security
Guide”, Chapter 15 “Masquerading and Firewalls” for instructions.
8.3 Persistent VNC Sessions

A persistent VNC session is initiated on the server. The session and all applications started in
this session run regardless of client connections until the session is terminated.
A persistent session can be accessed from multiple clients simultaneously. This is ideal for
demonstration purposes where one client has full access and all other clients have view-only
access. Another use case are trainings where the trainer might need access to the trainee's desk-
top. However, most of the times you probably do not want to share your VNC session.
In contrast to one-time sessions that start a display manager, a persistent session starts a ready-
to-operate desktop that runs as the user that started the VNC session. Access to persistent sessions
is protected by a password.
106 Persistent VNC Sessions SLES 12 SP3

Access to persistent sessions is protected by two possible types of passwords:
a regular password that grants full access or
an optional view-only password that grants a non-interactive (view-only) access.
A session can have multiple client connections of both kinds at once.
PROCEDURE 8.2: STARTING A PERSISTENT VNC SESSION
1. Open a shell and make sure you are logged in as the user that should own the VNC session.
2. If the network interface serving the VNC sessions is protected by a firewall, you need to
manually open the port used by your session in the firewall. If starting multiple sessions
you may alternatively open a range of ports. See Book “Security Guide”, Chapter 15 “Mas-
querading and Firewalls” for details on how to configure the firewall.
vncserver uses the ports 5901 for display :1 , 5902 for display :2 , and so on. For
persistent sessions, the VNC display and the X display usually have the same number.
3. To start a session with a resolution of 1024x769 pixel and with a color depth of 16-bit,
enter the following command:
vncserver -geometry 1024x768 -depth 16
The vncserver command picks an unused display number when none is given and prints
its choice. See man 1 vncserver for more options.
When running vncserver for the rst time, it asks for a password for full access to the session.
If needed, you can also provide a password for view-only access to the session.
The password(s) you are providing here are also used for future sessions started by the same
user. They can be changed with the vncpasswd command.
Important: Security Considerations

Make sure to use strong passwords of significant length (eight or more characters). Do
not share these passwords.
To terminate the session shut down the desktop environment that runs inside the VNC session
from the VNC viewer as you would shut it down if it was a regular local X session.
107 Persistent VNC Sessions SLES 12 SP3

If you prefer to manually terminate a session, open a shell on the VNC server and make sure you
are logged in as the user that owns the VNC session you want to terminate. Run the following
command to terminate the session that runs on display :1 : vncserver -kill :1
8.3.1 Connecting to a Persistent VNC Session

To connect to a persistent VNC session, a VNC viewer must be installed, see also Section 8.1,
“The vncviewer Client”.
8.3.2 Configuring Persistent VNC Sessions

Persistent VNC sessions can be configured by editing $HOME/.vnc/xstartup . By default this
shell script starts the same GUI/window manager it was started from. In SUSE Linux Enterprise
Server this will either be GNOME or IceWM. If you want to start your session with a window
manager of your choice, set the variable WINDOWMANAGER :
WINDOWMANAGER=gnome vncserver -geometry 1024x768

WINDOWMANAGER=icewm vncserver -geometry 1024x768
Note: One Configuration for Each User

Persistent VNC sessions are configured in a single per-user configuration. Multiple ses-
sions started by the same user will all use the same start-up and password les.
8.4 Encrypted VNC Communication

If the VNC server is set up properly, all communication between the VNC server and the client is
encrypted. The authentication happens at the beginning of the session, the actual data transfer
only begins afterward.
108 Connecting to a Persistent VNC Session SLES 12 SP3

Whether for a one-time or a persistent VNC session, security options are configured via the -
securitytypes parameter of the /usr/bin/Xvnc command located on the server_args line.
The -securitytypes parameter selects both authentication method and encryption. It has the
following options:
AUTHENTICATIONS
None, TLSNone, X509None

No authentication.
VncAuth, TLSVnc, X509Vnc

Authentication using custom password.
Plain, TLSPlain, X509Plain

Authentication using PAM to verify user's password.
ENCRYPTIONS
None, VncAuth, Plain

No encryption.
TLSNone, TLSVnc, TLSPlain

Anonymous TLS encryption. Everything is encrypted, but there is no verification of the
remote host. So you are protected against passive attackers, but not against man-in-the-
middle attackers.
X509None, X509Vnc, X509Plain

TLS encryption with certificate. If you use a self-signed certificate, you will be asked to
verify it on the rst connection. On subsequent connections you will be warned only if
the certificate changed. So you are protected against everything except man-in-the-middle
on the rst connection (similar to typical SSH usage). If you use a certificate signed by
a certificate authority matching the machine name, then you get full security (similar to
typical HTTPS usage).
Tip: Path to Certificate and Key

With X509 based encryption, you need to specify the path to the X509 certificate
and the key with -X509Cert and -X509Key options.
109 Encrypted VNC Communication SLES 12 SP3

If you select multiple security types separated by comma, the rst one supported and allowed
by both client and server will be used. That way you can configure opportunistic encryption on
the server. This is useful if you need to support VNC clients that do not support encryption.
On the client, you can also specify the allowed security types to prevent a downgrade attack if
you are connecting to a server which you know has encryption enabled (although our vncviewer
will warn you with the "Connection not encrypted!" message in that case).
110 Encrypted VNC Communication SLES 12 SP3

9 File Copying with RSync
Today, a typical user has several computers: home and workplace machines, a lap-
top, a smartphone or a tablet. This makes the task of keeping les and documents in
sync across multiple devices all more important.
Warning: Risk of Data Loss

Before you start using a synchronization tool, you should familiarize yourself with its
features and functionality. Make sure to back up your important les.
9.1 Conceptual Overview

For synchronizing a large amount of data over a slow network connection, Rsync offers a reliable
method of transmitting only changes within les. This applies not only to text les but also
binary les. To detect the differences between les, Rsync subdivides the les into blocks and
computes check sums over them.
Detecting changes requires some computing power. So make sure that machines on both ends
have enough resources, including RAM.
Rsync can be particularly useful when large amounts of data containing only minor changes
need to be transmitted regularly. This is often the case when working with backups. Rsync can
also be useful for mirroring staging servers that store complete directory trees of Web servers
to a Web server in a DMZ.
Despite its name, Rsync is not a synchronization tool. Rsync is a tool that copies data only in
one direction at a time. It does not and cannot do the reverse. If you need a bidirectional tool
which is able to synchronize both source and destination, use Csync.
9.2 Basic Syntax

Rsync is a command-line tool that has the following basic syntax:
rsync [OPTION] SOURCE [SOURCE]... DEST
111 Conceptual Overview SLES 12 SP3

You can use Rsync on any local or remote machine, provided you have access and write per-
missions. It is possible to have multiple SOURCE entries. The SOURCE and DEST placeholders
can be paths, URLs, or both.
Below are the most common Rsync options:
-v
Outputs more verbose text
-a
Archive mode; copies les recursively and preserves timestamps, user/group ownership,
le permissions, and symbolic links
-z
Compresses the transmitted data
Note: Trailing Slashes Count

When working with Rsync, you should pay particular attention to trailing slashes. A trail-
ing slash after the directory denotes the content of the directory. No trailing slash denotes
the directory itself.
9.3 Copying Files and Directories Locally

The following description assumes that the current user has write permissions to the directory
/var/backup . To copy a single le from one directory on your machine to another path, use
tux > rsync -avz backup.tar.xz /var/backup/
The le backup.tar.xz is copied to /var/backup/ ; the absolute path will be /var/back-
up/backup.tar.xz .
Do not forget to add the trailing slash after the /var/backup/ directory! If you do not insert
the slash, the le backup.tar.xz is copied to /var/backup (le) not inside the directory /
var/backup/ !
Copying a directory is similar to copying a single le. The following example copies the directory
tux/ and its content into the directory /var/backup/ :
tux > rsync -avz tux /var/backup/
112 Copying Files and Directories Locally SLES 12 SP3

Find the copy in the absolute path /var/backup/tux/ .
9.4 Copying Files and Directories Remotely

The Rsync tool is required on both machines. To copy les from or to remote directories requires
an IP address or a domain name. A user name is optional if your current user names on the local
and remote machine are the same.
To copy the le file.tar.xz from your local host to the remote host 192.168.1.1 with same
users (being local and remote), use the following command:
tux > rsync -avz file.tar.xz tux@192.168.1.1:
Depending on what you prefer, these commands are also possible and equivalent:
tux > rsync -avz file.tar.xz 192.168.1.1:~

tux > rsync -avz file.tar.xz 192.168.1.1:/home/tux
In all cases with standard configuration, you will be prompted to enter your passphrase of the
remote user. This command will copy file.tar.xz to the home directory of user tux (usually
/home/tux ).
Copying a directory remotely is similar to copying a directory locally. The following example
copies the directory tux/ and its content into the remote directory /var/backup/ on the
192.168.1.1 host:
tux > rsync -avz tux 192.168.1.1:/var/backup/
Assuming you have write permissions on the host 192.168.1.1 , you will nd the copy in the
absolute path /var/backup/tux .
9.5 Configuring and Using an Rsync Server

Rsync can run as a daemon ( rsyncd ) listing on default port 873 for incoming connections. This
daemon can receive “copying targets”.
113 Copying Files and Directories Remotely SLES 12 SP3

The following description explains how to create an Rsync server on jupiter with a backup
target. This target can be used to store your backups. To create an Rsync server, do the following:
PROCEDURE 9.1: SETTING UP AN RSYNC SERVER
1. On jupiter, create a directory to store all your backup les. In this example, we use /
var/backup :
root # mkdir /var/backup
2. Specify ownership. In this case, the directory is owned by user tux in group users :
root # chown tux.users /var/backup
3. Configure the rsyncd daemon.

We will separate the configuration le into a main le and some “modules” which hold
your backup target. This makes it easier to add additional targets later. Global values
can be stored in /etc/rsyncd.d/*.inc les, whereas your modules are placed in /etc/
rsyncd.d/*.conf les:
a. Create a directory /etc/rsyncd.d/ :
root # mkdir /etc/rsyncd.d/
b. In the main configuration le /etc/rsyncd.conf , add the following lines:
# rsyncd.conf main configuration file

log file = /var/log/rsync.log
pid file = /var/lock/rsync.lock
&merge /etc/rsyncd.d 1
&include /etc/rsyncd.d 2
1 Merges global values from /etc/rsyncd.d/*.inc les into the main configu-
ration le.
2 Loads any modules (or targets) from /etc/rsyncd.d/*.conf les. These les
should not contain any references to global values.
c. Create your module (your backup target) in the le /etc/rsyncd.d/backup.conf

with the following lines:
# backup.conf: backup module

[backup] 1
114 Configuring and Using an Rsync Server SLES 12 SP3

uid = tux 2
gid = users 2
path = /var/backup 3
auth users = tux 4
secrets file = /etc/rsyncd.secrets 5
comment = Our backup target
1 The backup target. You can use any name you like. However, it is a good idea to
name a target according to its purpose and use the same name in your *.conf
le.
2 Specifies the user name or group name that is used when the le transfer takes
place.
3 Defines the path to store your backups (from Step 1).
4 Specifies a comma-separated list of allowed users. In its simplest form, it con-
tains the user names that are allowed to connect to this module. In our case,
only user tux is allowed.
5 Specifies the path of a le that contains lines with user names and plain pass-
words.
d. Create the /etc/rsyncd.secrets le with the following content and replace
PASSPHRASE :
# user:passwd
tux:PASSPHRASE
e. Make sure the le is only readable by root :
root # chmod 0600 /etc/rsyncd.secrets
4. Start and enable the rsyncd daemon with:
root # systemctl enable rsyncd

root # systemctl start rsyncd
5. Test the access to your Rsync server:
tux > rsync jupiter::
You should see a response that looks like this:
backup Our backup target
115 Configuring and Using an Rsync Server SLES 12 SP3

Otherwise, check your configuration le, firewall and network settings.
The above steps create an Rsync server that can now be used to store backups. The example
also creates a log le listing all connections. This le is stored in /var/log/rsyncd.log . This
is useful if you want to debug your transfers.
To list the content of your backup target, use the following command:
rsync -avz jupiter::backup
This command lists all les present in the directory /var/backup on the server. This request is
also logged in the log le /var/log/rsyncd.log . To start an actual transfer, provide a source
directory. Use . for the current directory. For example, the following command copies the
current directory to your Rsync backup server:
rsync -avz . jupiter::backup
By default, Rsync does not delete les and directories when it runs. To enable deletion, the
additional option --delete must be stated. To ensure that no newer les are deleted, the option
--update can be used instead. Any conflicts that arise must be resolved manually.

CSync
Bidirectional le synchronizer, see https://www.csync.org/ .
RSnapshot
Creates incremental backups, see http://rsnapshot.org .
Unison
A le synchronizer similar to CSync but with a graphical interface, see http://www.seas.u-
penn.edu/~bcpierce/unison/ .
Rear
A disaster recovery framework, see the Administration Guide of the SUSE Linux Enterprise
High Availability Extension https://www.suse.com/documentation/sle-ha-12/ .
116 For More Information SLES 12 SP3

II Booting a Linux System
10 Introduction to the Booting Process 118
11 UEFI (Unified Extensible Firmware Interface) 124
12 The Boot Loader GRUB 2 133
13 The systemd Daemon 153

10 Introduction to the Booting Process
Booting a Linux system involves different components and tasks. The hardware it-
self is initialized by the BIOS or the UEFI, which starts the kernel by means of a
boot loader. After this point, the boot process is completely controlled by the op-
erating system and handled by systemd . systemd provides a set of “targets” that
boot setups for everyday usage, maintenance or emergencies.
10.1 The Linux Boot Process

The Linux boot process consists of several stages, each represented by a different component.
The following list briey summarizes the boot process and features all the major components
involved:
1. BIOS/UEFI. After turning on the computer, the BIOS or the UEFI initializes the screen and
keyboard, and tests the main memory. Up to this stage, the machine does not access any
mass storage media. Subsequently, the information about the current date, time, and the
most important peripherals are loaded from the CMOS values. When the rst hard disk and
its geometry are recognized, the system control passes from the BIOS to the boot loader.
If the BIOS supports network booting, it is also possible to configure a boot server that
provides the boot loader. On AMD64/Intel 64 systems, PXE boot is needed. Other archi-
tectures commonly use the BOOTP protocol to get the boot loader. For more information
on UEFI, refer to Chapter 11, UEFI (Unified Extensible Firmware Interface).
2. Boot Loader. The rst physical 512-byte data sector of the rst hard disk is loaded into
the main memory and the boot loader that resides at the beginning of this sector takes
over. The commands executed by the boot loader determine the remaining part of the boot
process. Therefore, the rst 512 bytes on the rst hard disk are called the Master Boot
Record (MBR). The boot loader then passes control to the actual operating system, in this
case, the Linux kernel. More information about GRUB 2, the Linux boot loader, can be
found in Chapter 12, The Boot Loader GRUB 2. For a network boot, the BIOS acts as the boot
loader. It gets the boot image from the boot server and starts the system. This is completely
independent of local hard disks.
If the root le system fails to mount from within the boot environment, it must be checked
and repaired before the boot can continue. The le system checker will be automatically
started for Ext3 and Ext4 le systems. The repair process is not automated for XFS and
118 The Linux Boot Process SLES 12 SP3

Btrfs le systems, and the user is be presented with information describing the options
available to repair the le system. When the le system has been successfully repaired,
exiting the boot environment will cause the system to retry mounting the root le system.
If successful, the boot will continue normally.
3. Kernel and initramfs . To pass system control, the boot loader loads both the kernel
and an initial RAM-based le system ( initramfs ) into memory. The contents of the
initramfs can be used by the kernel directly. initramfs contains a small executable
called init that handles the mounting of the real root le system. If special hardware
drivers are needed before the mass storage can be accessed, they must be in initramfs .
For more information about initramfs , refer to Section 10.2, “initramfs”. If the system
does not have a local hard disk, the initramfs must provide the root le system for the
kernel. This can be done using a network block device like iSCSI or SAN, but it is also
possible to use NFS as the root device.
Note: The init Process Naming

Two different programs are commonly named “init”:
a. the initramfs process mounting the root le system
b. the operating system process setting up the system
In this chapter we will therefore refer to them as “ init on initramfs ” and “ sys-
temd ”, respectively.
4. init on initramfs . This program performs all actions needed to mount the proper root
le system. It provides kernel functionality for the needed le system and device drivers
for mass storage controllers with udev . After the root le system has been found, it is
checked for errors and mounted. If this is successful, the initramfs is cleaned and the
systemd daemon on the root le system is executed. For more information about init on
initramfs , refer to Section 10.3, “Init on initramfs”. Find more information about udev
in Chapter 21, Dynamic Kernel Device Management with udev.
5. systemd . By starting services and mounting le systems, systemd handles the actual
booting of the system. systemd is described in Chapter 13, The systemd Daemon.
119 The Linux Boot Process SLES 12 SP3

10.2 initramfs
initramfs is a small cpio archive that the kernel can load into a RAM disk. It provides a
minimal Linux environment that enables the execution of programs before the actual root le
system is mounted. This minimal Linux environment is loaded into memory by BIOS or UEFI
routines and does not have specific hardware requirements other than sufficient memory. The
initramfs archive must always provide an executable named init that executes the systemd
daemon on the root le system for the boot process to proceed.
Before the root le system can be mounted and the operating system can be started, the kernel
needs the corresponding drivers to access the device on which the root le system is located.
These drivers may include special drivers for certain kinds of hard disks or even network drivers
to access a network le system. The needed modules for the root le system may be loaded by
init on initramfs . After the modules are loaded, udev provides the initramfs with the
needed devices. Later in the boot process, after changing the root le system, it is necessary to
regenerate the devices. This is done by the systemd unit udev.service with the command
udevtrigger .
If you need to change hardware (for example, hard disks), and this hardware requires different
drivers to be in the kernel at boot time, you must update the initramfs le. This is done by
calling dracut -f (the option -f overwrites the existing initramfs le). To add a driver for
the new hardware, edit /etc/dracut.conf.d/01-dist.conf and add the following line. If the
le does not exist, create it.
force_drivers+="DRIVER1"
Replace DRIVER1 with the module name of the driver. If you need to add more than one driver,
list them space-separated ( DRIVER1 DRIVER2 ).
Important: Updating initramfs or init

The boot loader loads initramfs or init in the same way as the kernel. It is not neces-
sary to re-install GRUB 2 after updating initramfs or init , because GRUB 2 searches
the directory for the right le when booting.
120 initramfs SLES 12 SP3

Tip: Changing Kernel Variables
If you change the values of kernel variables via the sysctl interface by editing related
les ( /etc/sysctl.conf or /etc/sysctl.d/*.conf ), the change will be lost on the
next system reboot. Even if you load the values with sysctl --system at runtime, the
changes are not saved into the initramfs le. You need to update it by calling dracut -
f (the option -f overwrites the existing initramfs le).
10.3 Init on initramfs

The main purpose of init on initramfs is to prepare the mounting of and access to the real
root le system. Depending on your system configuration, init on initramfs is responsible
for the following tasks.
Loading Kernel Modules

Depending on your hardware configuration, special drivers may be needed to access the
hardware components of your computer (the most important component being your hard
disk). To access the final root le system, the kernel needs to load the proper le system
drivers.
Providing Block Special Files

For each loaded module, the kernel generates device events. udev handles these events
and generates the required special block les on a RAM le system in /dev . Without those
special les, the le system and other devices would not be accessible.
Managing RAID and LVM Setups

If you configured your system to hold the root le system under RAID or LVM, init on
initramfs sets up LVM or RAID to enable access to the root le system later.
To change your /usr or swap partitions directly without the help of YaST, further actions
are needed. If you forget these steps, your system will start in emergency mode. To avoid
starting in emergency mode, perform the following steps:
PROCEDURE 10.1: UPDATING INIT RAM DISK WHEN SWITCHING TO LOGICAL VOLUMES
1. Edit the corresponding entry in /etc/fstab and replace your previous partitions
with the logical volume.
121 Init on initramfs SLES 12 SP3

2. Execute the following commands:
root # mount -a
root # swapon -a
3. Regenerate your initial RAM disk (initramfs) with mkinitrd or dracut .
4. For z Systems, additionally run grub2-install .
Find more information about RAID and LVM in Book “Deployment Guide”, Chapter 12 “Ad-
vanced Disk Setup”.
Managing Network Configuration

If you configured your system to use a network-mounted root le system (mounted via
NFS), init on initramfs must make sure that the proper network drivers are loaded
and that they are set up to allow access to the root le system.
If the le system resides on a network block device like iSCSI or SAN, the connection to
the storage server is also set up by init on initramfs . SUSE Linux Enterprise Server
supports booting from a secondary iSCSI target if the primary target is not available. For
more details regarding configuration of the booting iSCSI target refer to Book “Storage
Administration Guide”, Chapter 14 “Mass Storage over IP Networks: iSCSI”, Section 14.3.1 “Using
YaST for the iSCSI Initiator Configuration”.
When init on initramfs is called during the initial boot as part of the installation process,
its tasks differ from those mentioned above:
Finding the Installation Medium

When starting the installation process, your machine loads an installation kernel and a
special init containing the YaST installer. The YaST installer is running in a RAM le
system and needs to have information about the location of the installation medium to
access it for installing the operating system.
Initiating Hardware Recognition and Loading Appropriate Kernel Modules

As mentioned in Section 10.2, “initramfs”, the boot process starts with a minimum set of
drivers that can be used with most hardware configurations. init starts an initial hard-
ware scanning process that determines the set of drivers suitable for your hardware con-
figuration. These drivers are used to generate a custom initramfs that is needed to boot
the system. If the modules are not needed for boot but for coldplug, the modules can be
loaded with systemd ; for more information, see Section 13.6.4, “Loading Kernel Modules”.

Loading the Installation System
When the hardware is properly recognized, the appropriate drivers are loaded. The udev
program creates the special device les and init starts the installation system with the
YaST installer.
Starting YaST
Finally, init starts YaST, which starts package installation and system configuration.

11 UEFI (Unified Extensible Firmware Interface)
UEFI (Unified Extensible Firmware Interface) is the interface between the rmware that comes
with the system hardware, all the hardware components of the system, and the operating system.
UEFI is becoming more and more available on PC systems and thus is replacing the traditional
PC-BIOS. UEFI, for example, properly supports 64-bit systems and offers secure booting (“Secure
Boot”, rmware version 2.3.1c or better required), which is one of its most important features.
Lastly, with UEFI a standard rmware will become available on all x86 platforms.
UEFI additionally offers the following advantages:
Booting from large disks (over 2 TiB) with a GUID Partition Table (GPT).
CPU-independent architecture and drivers.
Flexible pre-OS environment with network capabilities.
CSM (Compatibility Support Module) to support booting legacy operating systems via a
PC-BIOS-like emulation.
For more information, see http://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface .

The following sections are not meant as a general UEFI overview; these are only hints about
how some features are implemented in SUSE Linux Enterprise Server.
11.1 Secure Boot

In the world of UEFI, securing the bootstrapping process means establishing a chain of trust. The
“platform” is the root of this chain of trust; in the context of SUSE Linux Enterprise Server, the
mainboard and the on-board rmware could be considered the “platform”. In other words, it is
the hardware vendor, and the chain of trust ows from that hardware vendor to the component
manufacturers, the OS vendors, etc.
The trust is expressed via public key cryptography. The hardware vendor puts a so-called Plat-
form Key (PK) into the rmware, representing the root of trust. The trust relationship with op-
erating system vendors and others is documented by signing their keys with the Platform Key.
Finally, security is established by requiring that no code will be executed by the rmware unless
it has been signed by one of these “trusted” keys—be it an OS boot loader, some driver located in
the ash memory of some PCI Express card or on disk, or be it an update of the rmware itself.
124 Secure Boot SLES 12 SP3

To use Secure Boot, you need to have your OS loader signed with a key trusted by the rmware,
and you need the OS loader to verify that the kernel it loads can be trusted.
Key Exchange Keys (KEK) can be added to the UEFI key database. This way, you can use other
certificates, as long as they are signed with the private part of the PK.
11.1.1 Implementation on SUSE Linux Enterprise Server

Microsoft’s Key Exchange Key (KEK) is installed by default.
Note: GUID Partitioning Table (GPT) Required

The Secure Boot feature is enabled by default on UEFI/x86_64 installations. You can nd
the Enable Secure Boot Support option in the Boot Code Options tab of the Boot Loader
Settings dialog. It supports booting when the secure boot is activated in the rmware,
while making it possible to boot when it is deactivated.
FIGURE 11.1: SECURE BOOT SUPPORT
The Secure Boot feature requires that a GUID Partitioning Table (GPT) replaces the old
partitioning with a Master Boot Record (MBR). If YaST detects EFI mode during the in-
stallation, it will try to create a GPT partition. UEFI expects to nd the EFI programs on
a FAT-formatted EFI System Partition (ESP).
125 Implementation on SUSE Linux Enterprise Server SLES 12 SP3

Supporting UEFI Secure Boot essentially requires having a boot loader with a digital signature
that the rmware recognizes as a trusted key. That key is trusted by the rmware a priori,
without requiring any manual intervention.
There are two ways of getting there. One is to work with hardware vendors to have them en-
dorse a SUSE key, which SUSE then signs the boot loader with. The other way is to go through
Microsoft’s Windows Logo Certification program to have the boot loader certified and have Mi-
crosoft recognize the SUSE signing key (that is, have it signed with their KEK). By now, SUSE
got the loader signed by UEFI Signing Service (that is Microsoft in this case).
FIGURE 11.2: UEFI: SECURE BOOT PROCESS
At the implementation layer, SUSE uses the shim loader which is installed by default. It is a
smart solution that avoids legal issues, and simplifies the certification and signing step consid-
erably. The shim loader’s job is to load a boot loader such as GRUB 2 and verify it; this boot
loader in turn will load kernels signed by a SUSE key only. SUSE provides this functionality
since SLE11 SP3 on fresh installations with UEFI Secure Boot enabled.
There are two types of trusted users:
First, those who hold the keys. The Platform Key (PK) allows almost everything. The Key
Exchange Key (KEK) allows all a PK can except changing the PK.
Second, anyone with physical access to the machine. A user with physical access can reboot
the machine, and configure UEFI.
126 Implementation on SUSE Linux Enterprise Server SLES 12 SP3

UEFI offers two types of variables to fulfill the needs of those users:
The rst is the so-called “Authenticated Variables”, which can be updated from both within
the boot process (the so-called Boot Services Environment) and the running OS. This can
be done only when the new value of the variable is signed with the same key that the old
value of the variable was signed with. And they can only be appended to or changed to
a value with a higher serial number.
The second is the so-called “Boot Services Only Variables”. These variables are accessible
to any code that runs during the boot process. After the boot process ends and before the
OS starts, the boot loader must call the ExitBootServices call. After that, these variables
are no longer accessible, and the OS cannot touch them.
The various UEFI key lists are of the rst type, as this allows online updating, adding, and
blacklisting of keys, drivers, and rmware fingerprints. It is the second type of variable, the
“Boot Services Only Variable”, that helps to implement Secure Boot in a secure and open source-
friendly manner, and thus compatible with GPLv3.
SUSE starts with shim —a small and simple EFI boot loader signed by SUSE and Microsoft.
This allows shim to load and execute.
shim then goes on to verify that the boot loader it wants to load is trusted. In a default situation
shim will use an independent SUSE certificate embedded in its body. In addition, shim will
allow to “enroll” additional keys, overriding the default SUSE key. In the following, we call
them “Machine Owner Keys” or MOKs for short.
Next the boot loader will verify and then boot the kernel, and the kernel will do the same on
the modules.
11.1.2 MOK (Machine Owner Key)

If the user (“machine owner”) wants to replace any components of the boot process, Machine
Owner Keys (MOKs) are to be used. The mokutils tool will help with signing components and
managing MOKs.
The enrollment process begins with rebooting the machine and interrupting the boot process (for
example, pressing a key) when shim loads. shim will then go into enrollment mode, allowing
the user to replace the default SUSE key with keys from a le on the boot partition. If the user
127 MOK (Machine Owner Key) SLES 12 SP3

chooses to do so, shim will then calculate a hash of that le and put the result in a “Boot
Services Only” variable. This allows shim to detect any change of the le made outside of Boot
Services and thus avoid tampering with the list of user-approved MOKs.
All of this happens during boot time—only verified code is executing now. Therefore, only a
user present at the console can use the machine owner's set of keys. It cannot be malware or a
hacker with remote access to the OS because hackers or malware can only change the le, but
not the hash stored in the “Boot Services Only” variable.
The boot loader, after having been loaded and verified by shim , will call back to shim when
it wants to verify the kernel—to avoid duplication of the verification code. Shim will use the
same list of MOKs for this and tell the boot loader whether it can load the kernel.
This way, you can install your own kernel or boot loader. It is only necessary to install a new set
of keys and authorize them by being physically present during the rst reboot. Because MOKs
are a list and not not a single MOK, you can make shim trust keys from several vendors, allowing
dual- and multi-boot from the boot loader.
11.1.3 Booting a Custom Kernel

The following is based on http://en.opensuse.org/openSUSE:UEFI#Booting_a_custom_kernel .
Secure Boot does not prevent you from using a self-compiled kernel. You must sign it with your
own certificate and make that certificate known to the rmware or MOK.
1. Create a custom X.509 key and certificate used for signing:
openssl req -new -x509 -newkey rsa:2048 -keyout key.asc \

-out cert.pem -nodes -days 666 -subj "/CN=$USER/"
For more information about creating certificates, see http://en.opensuse.org/openSUSE:UE-

FI_Image_File_Sign_Tools#Create_Your_Own_Certificate .
2. Package the key and the certificate as a PKCS#12 structure:
openssl pkcs12 -export -inkey key.asc -in cert.pem \

-name kernel_cert -out cert.p12
3. Generate an NSS database for use with pesign :
certutil -d . -N
128 Booting a Custom Kernel SLES 12 SP3

4. Import the key and the certificate contained in PKCS#12 into the NSS database:
pk12util -d . -i cert.p12
5. “Bless” the kernel with the new signature using pesign :
pesign -n . -c kernel_cert -i arch/x86/boot/bzImage \

-o vmlinuz.signed -s
6. List the signatures on the kernel image:
pesign -n . -S -i vmlinuz.signed
At that point, you can install the kernel in /boot as usual. Because the kernel now has
a custom signature the certificate used for signing needs to be imported into the UEFI
rmware or MOK.
7. Convert the certificate to the DER format for import into the rmware or MOK:
openssl x509 -in cert.pem -outform der -out cert.der
8. Copy the certificate to the ESP for easier access:
sudo cp cert.der /boot/efi/
9. Use mokutil to launch the MOK list automatically.
• a. Import the certificate to MOK:
mokutil --root-pw --import cert.der
The --root-pw option enables usage of the root user directly.
b. Check the list of certificates that are prepared to be enrolled:
mokutil --list-new
c. Reboot the system; shim should launch MokManager. You need to enter the
root password to confirm the import of the certificate to the MOK list.
d. Check if the newly imported key was enrolled:
mokutil --list-enrolled
129 Booting a Custom Kernel SLES 12 SP3

• a. Alternatively, this is the procedure if you want to launch MOK manually:
Reboot
b. In the GRUB 2 menu press the ' c ' key.
c. Type:
chainloader $efibootdir/MokManager.efi
boot
d. Select Enroll key from disk.
e. Navigate to the cert.der le and press Enter .
f. Follow the instructions to enroll the key. Normally this should be pressing ' 0 '
and then ' y ' to confirm.
Alternatively, the rmware menu may provide ways to add a new key to the
Signature Database.
11.1.4 Using Non-Inbox Drivers

There is no support for adding non-inbox drivers (that is, drivers that do not come with SUSE
Linux Enterprise Server) during installation with Secure Boot enabled. The signing key used for
SolidDriver/PLDP is not trusted by default.
It is possible to install third party drivers during installation with Secure Boot enabled in two
different ways. In both cases:
Add the needed keys to the rmware database via rmware/system management tools
before the installation. This option depends on the specific hardware you are using. Consult
your hardware vendor for more information.
Use a bootable driver ISO from https://drivers.suse.com/ or your hardware vendor to

enroll the needed keys in the MOK list at rst boot.
To use the bootable driver ISO to enroll the driver keys to the MOK list, follow these steps:
1. Burn the ISO image above to an empty CD/DVD medium.
2. Start the installation using the new CD/DVD medium, having the standard installation
media at hand or a URL to a network installation server.
130 Using Non-Inbox Drivers SLES 12 SP3

If doing a network installation, enter the URL of the network installation source on the
boot command line using the install= option.
If doing installation from optical media, the installer will rst boot from the driver kit and
then ask to insert the rst installation disk of the product.
3. An initrd containing updated drivers will be used for installation.
For more information, see https://drivers.suse.com/doc/Usage/Secure_Boot_Certificate.html .
11.1.5 Features and Limitations

When booting in Secure Boot mode, the following features apply:
Installation to UEFI default boot loader location, a mechanism to keep or restore the EFI
boot entry.
Reboot via UEFI.
Xen hypervisor will boot with UEFI when there is no legacy BIOS to fall back to.
UEFI IPv6 PXE boot support.
UEFI videomode support, the kernel can retrieve video mode from UEFI to configure KMS
mode with the same parameters.
UEFI booting from USB devices is supported.
When booting in Secure Boot mode, the following limitations apply:
To ensure that Secure Boot cannot be easily circumvented, some kernel features are dis-
abled when running under Secure Boot.
Boot loader, kernel, and kernel modules must be signed.
Kexec and Kdump are disabled.
Hibernation (suspend on disk) is disabled.
Access to /dev/kmem and /dev/mem is not possible, not even as root user.
Access to the I/O port is not possible, not even as root user. All X11 graphical drivers must
use a kernel driver.
PCI BAR access through sysfs is not possible.
131 Features and Limitations SLES 12 SP3

custom_method in ACPI is not available.
debugfs for asus-wmi module is not available.
the acpi_rsdp parameter does not have any effect on the kernel.

http://www.uefi.org —UEFI home page where you can nd the current UEFI specifica-
tions.
Blog posts by Olaf Kirch and Vojtěch Pavlík (the chapter above is heavily based on these
posts):
http://www.suse.com/blogs/uefi-secure-boot-plan/
http://www.suse.com/blogs/uefi-secure-boot-overview/
http://www.suse.com/blogs/uefi-secure-boot-details/
http://en.opensuse.org/openSUSE:UEFI —UEFI with openSUSE.

12 The Boot Loader GRUB 2
This chapter describes how to configure GRUB 2, the boot loader used in SUSE®
Linux Enterprise Server. It is the successor to the traditional GRUB boot loader—
now called “GRUB Legacy”. GRUB 2 has been the default boot loader in SUSE®
Linux Enterprise Server since version 12. A YaST module is available for configur-
ing the most important settings. The boot procedure as a whole is outlined in Chap-
ter 10, Introduction to the Booting Process. For details on Secure Boot support for UEFI
machines, see Chapter 11, UEFI (Unified Extensible Firmware Interface).
12.1 Main Differences between GRUB Legacy and

GRUB 2
The configuration is stored in different les.
More le systems are supported (for example, Btrfs).
Can directly read les stored on LVM or RAID devices.
The user interface can be translated and altered with themes.
Includes a mechanism for loading modules to support additional features, such as le
systems, etc.
Automatically searches for and generates boot entries for other kernels and operating sys-
tems, such as Windows.
Includes a minimal Bash-like console.
12.2 Configuration File Structure

The configuration of GRUB 2 is based on the following les:
/boot/grub2/grub.cfg
This le contains the configuration of the GRUB 2 menu items. It replaces menu.lst used
in GRUB Legacy. grub.cfg is automatically generated by the grub2-mkconfig com-
mand, and should not be edited.
133 Main Differences between GRUB Legacy and GRUB 2 SLES 12 SP3
/boot/grub2/custom.cfg
This optional le is directly sourced by grub.cfg at boot time and can be used to add
custom items to the boot menu. Starting with SUSE Linux Enterprise Server these entries
will also be parsed when using grub-once .
/etc/default/grub
This le controls the user settings of GRUB 2 and usually includes additional environmental
settings such as backgrounds and themes.
Scripts under /etc/grub.d/

The scripts in this directory are read during execution of the grub2-mkconfig command.
Their instructions are integrated into the main configuration le /boot/grub/grub.cfg .
/etc/sysconfig/bootloader
This configuration le is used when configuring the boot loader with YaST and every time
a new kernel is installed. It is evaluated by the perl-bootloader which modifies the boot
loader configuration le (for example /boot/grub2/grub.cfg for GRUB 2) accordingly.
/etc/sysconfig/bootloader is not a GRUB 2-specific configuration le—the values are
applied to any boot loader installed on SUSE Linux Enterprise Server.
/boot/grub2/x86_64-efi , /boot/grub2/power-ieee1275 , /boot/grub2/s390x

These configuration les contain architecture-specific options.
GRUB 2 can be controlled in various ways. Boot entries from an existing configuration can be se-
lected from the graphical menu (splash screen). The configuration is loaded from the le /boot/
grub2/grub.cfg which is compiled from other configuration les (see below). All GRUB 2
configuration les are considered system les, and you need root privileges to edit them.
Note: Activating Configuration Changes

After having manually edited GRUB 2 configuration les, you need to run grub2-mkcon-
fig to activate the changes. However, this is not necessary when changing the configu-
ration with YaST, since it will automatically run grub2-mkconfig .
134 Configuration File Structure SLES 12 SP3

12.2.1 The File /boot/grub2/grub.cfg
The graphical splash screen with the boot menu is based on the GRUB 2 configuration le /
boot/grub2/grub.cfg , which contains information about all partitions or operating systems
that can be booted by the menu.
Every time the system is booted, GRUB 2 loads the menu le directly from the le system. For
this reason, GRUB 2 does not need to be re-installed after changes to the configuration le.
grub.cfg is automatically rebuilt with kernel installations or removals.
grub.cfg is compiled by the grub2-mkconfig from the le /etc/default/grub and scripts
found in the /etc/grub.d/ directory. Therefore you should never edit the le manually. In-
stead, edit the related source les or use the YaST Boot Loader module to modify the configura-
tion as described in Section 12.3, “Configuring the Boot Loader with YaST”.
12.2.2 The File /etc/default/grub
More general options of GRUB 2 belong here, such as the time the menu is displayed, or the
default OS to boot. To list all available options, see the output of the following command:
grep "export GRUB_DEFAULT" -A50 /usr/sbin/grub2-mkconfig | grep GRUB_
In addition to already defined variables, the user may introduce their own variables, and use
them later in the scripts found in the /etc/grub.d directory.
After having edited /etc/default/grub , run grub2-mkconfig to update the main configu-
ration le.
Note: Scope
All options set in this le are general options that affect all boot entries. Specific options
for Xen kernels or the Xen hypervisor can be set via the GRUB_*_XEN_* configuration
options. See below for details.
GRUB_DEFAULT
Sets the boot menu entry that is booted by default. Its value can be a numeric value, the
complete name of a menu entry, or “saved”.
GRUB_DEFAULT=2 boots the third (counted from zero) boot menu entry.
GRUB_DEFAULT="2>0" boots the rst submenu entry of the third top-level menu entry.
135 The File /boot/grub2/grub.cfg SLES 12 SP3

GRUB_DEFAULT="Example boot menu entry" boots the menu entry with the title “Ex-
ample boot menu entry”.
GRUB_DEFAULT=saved boots the entry specified by the grub2-once or grub2-set-de-
fault commands. While grub2-reboot sets the default boot entry for the next reboot on-
ly, grub2-set-default sets the default boot entry until changed. grub2-editenv list
lists next boot entry.
GRUB_HIDDEN_TIMEOUT
Waits the specified number of seconds for the user to press a key. During the period no
menu is shown unless the user presses a key. If no key is pressed during the time specified,
the control is passed to GRUB_TIMEOUT . GRUB_HIDDEN_TIMEOUT=0 rst checks whether
Shift is pressed and shows the boot menu if yes, otherwise immediately boots the default
menu entry. This is the default when only one bootable OS is identified by GRUB 2.
GRUB_HIDDEN_TIMEOUT_QUIET
If false is specified, a countdown timer is displayed on a blank screen when the
GRUB_HIDDEN_TIMEOUT feature is active.
GRUB_TIMEOUT
Time period in seconds the boot menu is displayed before automatically booting the default
boot entry. If you press a key, the timeout is cancelled and GRUB 2 waits for you to make
the selection manually. GRUB_TIMEOUT=-1 will cause the menu to be displayed until you
select the boot entry manually.
GRUB_CMDLINE_LINUX
Entries on this line are added at the end of the boot entries for normal and recovery mode.
Use it to add kernel parameters to the boot entry.
GRUB_CMDLINE_LINUX_DEFAULT
Same as GRUB_CMDLINE_LINUX but the entries are appended in the normal mode only.
GRUB_CMDLINE_LINUX_RECOVERY
Same as GRUB_CMDLINE_LINUX but the entries are appended in the recovery mode only.
GRUB_CMDLINE_LINUX_XEN_REPLACE
This entry will completely replace the GRUB_CMDLINE_LINUX parameters for all Xen boot
entries.
GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT
Same as GRUB_CMDLINE_LINUX_XEN_REPLACE but it will only replace parameters
of GRUB_CMDLINE_LINUX_DEFAULT .
136 The File /etc/default/grub SLES 12 SP3

GRUB_CMDLINE_XEN
This entry specifies the kernel parameters for the Xen guest kernel only—the operation
principle is the same as for GRUB_CMDLINE_LINUX .
GRUB_CMDLINE_XEN_DEFAULT
Same as GRUB_CMDLINE_XEN —the operation principle is the same as for
GRUB_CMDLINE_LINUX_DEFAULT .
GRUB_TERMINAL
Enables and specifies an input/output terminal device. Can be console (PC BIOS and EFI
consoles), serial (serial terminal), ofconsole (Open Firmware console), or the default
gfxterm (graphics-mode output). It is also possible to enable more than one device by
quoting the required options, for example GRUB_TERMINAL="console serial" .
GRUB_GFXMODE
The resolution used for the gfxterm graphical terminal. Note that you can only use modes
supported by your graphics card (VBE). The default is ‘auto’, which tries to select a pre-
ferred resolution. You can display the screen resolutions available to GRUB 2 by typing
videoinfo in the GRUB 2 command line. The command line is accessed by typing C
when the GRUB 2 boot menu screen is displayed.

You can also specify a color depth by appending it to the resolution setting, for example
GRUB_GFXMODE=1280x1024x24 .
GRUB_BACKGROUND
Set a background image for the gfxterm graphical terminal. The image must be a le
readable by GRUB 2 at boot time, and it must end with the .png , .tga , .jpg , or .jpeg
suffix. If necessary, the image will be scaled to t the screen.
GRUB_DISABLE_OS_PROBER
If this option is set to true , automatic searching for other operating systems is disabled.
Only the kernel images in /boot/ and the options from your own scripts in /etc/grub.d/
are detected.
SUSE_BTRFS_SNAPSHOT_BOOTING
If this option is set to true , GRUB 2 can boot directly into Snapper snapshots. For more
information, see Section 7.3, “System Rollback by Booting from Snapshots”.
For a complete list of options, see the GNU GRUB manual (http://www.gnu.org/software/grub/
manual/grub.html#Simple-configuration) . For a complete list of possible parameters, see http://
en.opensuse.org/Linuxrc .
137 The File /etc/default/grub SLES 12 SP3

12.2.3 Scripts in /etc/grub.d
The scripts in this directory are read during execution of the grub2-mkconfig command, and
their instructions are incorporated into /boot/grub2/grub.cfg . The order of menu items in
grub.cfg is determined by the order in which the les in this directory are run. Files with a
leading numeral are executed rst, beginning with the lowest number. 00_header is run be-
fore 10_linux , which would run before 40_custom . If les with alphabetic names are present,
they are executed after the numerically-named les. Only executable les generate output to
grub.cfg during execution of grub2-mkconfig . By default all les in the /etc/grub.d di-
rectory are executable.
Tip: Persistent Custom Content in grub.cfg

Because /boot/grub2/grub.cfg is recompiled each time grub2-mkconfig is run, any
custom content is lost. If you want to insert your lines directly into /boot/grub2/
grub.cfg without losing them after grub2-mkconfig is run, insert it between
### BEGIN /etc/grub.d/90_persistent ###
and
### END /etc/grub.d/90_persistent ###
lines. The 90_persistent script ensures that such content will be preserved.
A list of the most important scripts follows:
00_header
Sets environmental variables such as system le locations, display settings, themes, and
previously saved entries. It also imports preferences stored in the /etc/default/grub .
Normally you do not need to make changes to this le.
10_linux
Identifies Linux kernels on the root device and creates relevant menu entries. This includes
the associated recovery mode option if enabled. Only the latest kernel is displayed on the
main menu page, with additional kernels included in a submenu.
138 Scripts in /etc/grub.d SLES 12 SP3

30_os-prober
This script uses OS-prober to search for Linux and other operating systems and places
the results in the GRUB 2 menu. There are sections to identify specific other operating
systems, such as Windows or macOS.
40_custom
This le provides a simple way to include custom boot entries into grub.cfg . Make sure
that you do not change the exec tail -n +3 $0 part at the beginning.
The processing sequence is set by the preceding numbers with the lowest number being executed
rst. If scripts are preceded by the same number the alphabetical order of the complete name
decides the order.
Tip: /boot/grub2/custom.cfg
If you create /boot/grub2/custom.cfg and ll it with a custom content, it will be au-
tomatically included into /boot/grub2/grub.cfg at boot time.
12.2.4 Mapping between BIOS Drives and Linux Devices
In GRUB Legacy, the device.map configuration le was used to derive Linux device names
from BIOS drive numbers. The mapping between BIOS drives and Linux devices cannot always
be guessed correctly. For example, GRUB Legacy would get a wrong order if the boot sequence
of IDE and SCSI drives is exchanged in the BIOS configuration.
GRUB 2 avoids this problem by using device ID strings (UUIDs) or le system labels when
generating grub.cfg . GRUB 2 utilities create a temporary device map on the y, which is
usually sufficient, particularly in the case of single-disk systems.
However, if you need to override the GRUB 2's automatic device mapping mechanism, create
your custom mapping le /boot/grub2/device.map . The following example changes the map-
ping to make DISK 3 the boot disk. Note that GRUB 2 partition numbers start with 1 and not
with 0 as in GRUB Legacy.
(hd1) /dev/disk-by-id/DISK3 ID
139 Mapping between BIOS Drives and Linux Devices SLES 12 SP3
12.2.5 Editing Menu Entries during the Boot Procedure
Being able to directly edit menu entries is useful when the system does not boot anymore because
of a faulty configuration. It can also be used to test new settings without altering the system
configuration.
1. In the graphical boot menu, select the entry you want to edit with the arrow keys.
2. Press E to open the text-based editor.
3. Use the arrow keys to move to the line you want to edit.
FIGURE 12.1: GRUB 2 BOOT EDITOR
Now you have two options:
a. Add space-separated parameters to the end of the line starting with linux or lin-
uxefi to edit the kernel parameters. A complete list of parameters is available at
http://en.opensuse.org/Linuxrc .
b. Or edit the general options to change for example the kernel version. The →| key
suggests all possible completions.
4. Press F10 to boot the system with the changes you made or press Esc to discard your
edits and return to the GRUB 2 menu.
140 Editing Menu Entries during the Boot Procedure SLES 12 SP3
Changes made this way only apply to the current boot process and are not saved permanently.
Important: Keyboard Layout During the Boot Procedure

The US keyboard layout is the only one available when booting. See Figure 40.2, “US Key-
board Layout”.
Note: Boot Loader on the Installation Media

The Boot Loader of the installation media on systems with a traditional BIOS is still GRUB
Legacy. To add boot options, select an entry and start typing. Additions you make to the
installation boot entry will be permanently saved in the installed system.
Note: Editing GRUB 2 Menu Entries on z Systems

Cursor movement and editing commands on IBM z Systems differ—see Section 12.4, “Dif-
ferences in Terminal Usage on z Systems” for details.
12.2.6 Setting a Boot Password
Even before the operating system is booted, GRUB 2 enables access to le systems. Users without
root permissions can access les in your Linux system to which they have no access after the
system is booted. To block this kind of access or to prevent users from booting certain menu
entries, set a boot password.
Important: Booting Requires Password

If set, the boot password is required on every boot, which means the system does not
boot automatically.
Proceed as follows to set a boot password. Alternatively use YaST (Protect Boot Loader with Pass-
word ).
1. Encrypt the password using grub2-mkpasswd-pbkdf2:
tux > sudo grub2-mkpasswd-pbkdf2
141 Setting a Boot Password SLES 12 SP3

Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...
2. Paste the resulting string into the le /etc/grub.d/40_custom together with the set
superusers command.
set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...
3. Run grub2-mkconfig to import the changes into the main configuration le.
After you reboot, you will be prompted for a user name and a password when trying to boot
a menu entry. Enter root and the password you typed during the grub2-mkpasswd-pbkdf2
command. If the credentials are correct, the system will boot the selected boot entry.
For more information, see https://www.gnu.org/software/grub/manual/grub.html#Security .
12.3 Configuring the Boot Loader with YaST

The easiest way to configure general options of the boot loader in your SUSE Linux Enterprise
Server system is to use the YaST module. In the YaST Control Center, select System Boot Loader.
The module shows the current boot loader configuration of your system and allows you to make
changes.
Use the Boot Code Options tab to view and change settings related to type, location and advanced
loader settings. You can choose whether to use GRUB 2 in standard or EFI mode.
142 Configuring the Boot Loader with YaST SLES 12 SP3

FIGURE 12.2: BOOT CODE OPTIONS
Important: EFI Systems require GRUB2-EFI

If you have an EFI system you can only install GRUB2-EFI, otherwise your system is no
longer bootable.
Important: Reinstalling the Boot Loader

To reinstall the boot loader, make sure to change a setting in YaST and then change
it back. For example, to reinstall GRUB2-EFI, select GRUB2 rst and then immediately
switch back to GRUB2-EFI.
Otherwise, the boot loader may only be partially reinstalled.
Note: Custom Boot Loader

To use a boot loader other than the ones listed, select Do Not Install Any Boot Loader. Read
the documentation of your boot loader carefully before choosing this option.
143 Configuring the Boot Loader with YaST SLES 12 SP3

12.3.1 Boot Loader Location and Boot Code Options
The default location of the boot loader depends on the partition setup and is either the Master
Boot Record (MBR) or the boot sector of the / partition. To modify the location of the boot
loader, follow these steps:
PROCEDURE 12.1: CHANGING THE BOOT LOADER LOCATION
1. Select the Boot Code Options tab and then choose one of the following options for Boot
Loader Location:
Boot from Master Boot Record

This installs the boot loader in the MBR of the disk containing the directory /boot .
Usually this will be the disk mounted to / , but if /boot is mounted to a separate
partition on a different disk, the MBR of that disk will be used.
Boot from Root Partition

This installs the boot loader in the boot sector of the / partition.
Custom Boot Partition

Use this option to specify the location of the boot loader manually.
2. Click OK to apply your changes.
FIGURE 12.3: CODE OPTIONS
144 Boot Loader Location and Boot Code Options SLES 12 SP3
The Boot Code Options tab includes the following additional options:
Set Active Flag in Partition Table for Boot Partition

Activates the partition that contains the /boot directorythe PReP partition. Use this option
on systems with old BIOS and/or legacy operating systems because they may fail to boot
from a non-active partition. It is safe to leave this option active.
Write Generic Boot Code to MBR

If MBR contains a custom 'non-GRUB' code, this option replaces it with a generic, operat-
ing system independent code. If you deactivate this option, the system may become un-
bootable.
Enable Trusted Boot Support

Starts TrustedGRUB2 which supports trusted computing functionality (Trusted Plat-
form Module (TPM)). For more information refer to https://github.com/Sirrix-AG/Trusted-
GRUB2 .
12.3.2 Adjusting the Disk Order

If your computer has more than one hard disk, you can specify the boot sequence of the disks.
The rst disk in the list is where GRUB 2 will be installed in the case of booting from MBR. It is
the disk where SUSE Linux Enterprise Server is installed by default. The rest of the list is a hint
for GRUB 2's device mapper (see Section 12.2.4, “Mapping between BIOS Drives and Linux Devices”).
Warning: Unbootable System

The default value is usually valid for almost all deployments. If you change the boot order
of disks wrongly, the system may become unbootable on the next reboot. For example,
if the rst disk in the list is not part of BIOS boot order, and the other disk in the list
have empty MBRs.
PROCEDURE 12.2: SETTING THE DISK ORDER
1. Open the Boot Code Options tab.
2. Click Edit Disk Boot Order.
3. If more than one disk is listed, select a disk and click Up or Down to reorder the displayed
disks.
145 Adjusting the Disk Order SLES 12 SP3

4. Click OK two times to save the changes.
12.3.3 Configuring Advanced Options
Advanced boot options can be configured via the Boot Loader Options tab.
12.3.3.1 Boot Loader Options Tab
FIGURE 12.4: BOOT LOADER OPTIONS
Boot Loader Time-Out

Change the value of Time-Out in Seconds by typing in a new value and clicking the appro-
priate arrow key with your mouse.
Probe Foreign OS
When selected, the boot loader searches for other systems like Windows or other Linux
installations.
Hide Menu on Boot

Hides the boot menu and boots the default entry.
146 Configuring Advanced Options SLES 12 SP3

Adjusting the Default Boot Entry
Select the desired entry from the “Default Boot Section” list. Note that the “>” sign in the
boot entry name delimits the boot section and its subsection.
Protect Boot Loader with Password

Protects the boot loader and the system with an additional password. For more informa-
tion, see Section 12.2.6, “Setting a Boot Password”.
12.3.3.2 Kernel Parameters Tab
FIGURE 12.5: KERNEL PARAMETERS
Console resolution
The Console resolution option specifies the default screen resolution during the boot process.
Kernel Command Line Parameter

The optional kernel parameters are added at the end of the default parameters. For a list
of all possible parameters, see http://en.opensuse.org/Linuxrc .
Use graphical console

When checked, the boot menu appears on a graphical splash screen rather than in a text
mode. The resolution of the boot screen can be then set from the Console resolution list,
and graphical theme definition le can be specified with the Console theme le-chooser.
147 Configuring Advanced Options SLES 12 SP3

Use Serial Console
If your machine is controlled via a serial console, activate this option and specify which
COM port to use at which speed. See info grub or http://www.gnu.org/software/grub/
manual/grub.html#Serial-terminal
12.4 Differences in Terminal Usage on z Systems

On 3215 and 3270 terminals there are some differences and limitations on how to move the
cursor and how to issue editing commands within GRUB 2.
12.4.1 Limitations
Interactivity
Interactivity is strongly limited. Typing often does not result in visual feedback. To see
where the cursor is, type an underscore ( _ ).
Note: 3270 Compared to 3215

The 3270 terminal is much better at displaying and refreshing screens than the 3215
terminal.
Cursor Movement
“Traditional” cursor movement is not possible. Alt , Meta , Ctrl and the cursor keys
do not work. To move the cursor, use the key combinations listed in Section 12.4.2, “Key
Combinations”.
Caret
The caret ( ^ ) is used as a control character. To type a literal ^ followed by a letter,
type ^ , ^ , LETTER .
Enter
The Enter key does not work, use ^ – J instead.
148 Differences in Terminal Usage on z Systems SLES 12 SP3

12.4.2 Key Combinations
Common Substitutes: ^ –J engage (“Enter”)
^ –L abort, return to previous

“state”
^ –I tab completion (in edit and

shell mode)
Keys Available in Menu ^ –A rst entry

Mode:
^ –E last entry
^ –P previous entry
^ –N next entry
^ –G previous page
^ –C next page
^ –F boot selected entry or enter

submenu (same as ^ –J )
E edit selected entry
C enter GRUB-Shell
Keys Available in Edit Mode: ^ –P previous line
^ –N next line
^ –B backward char
^ –F forward char
^ –A beginning of line
^ –E end of line
149 Key Combinations SLES 12 SP3

^ –H backspace
^ –D delete
^ –K kill line
^ –Y yank
^ –O open line
^ –L refresh screen
^ –X boot entry
^ –C enter GRUB-Shell
Keys Available in Command ^ –P previous command

Line Mode:
^ –N next command from history
^ –A beginning of line
^ –E end of line
^ –B backward char
^ –F forward char
^ –H backspace
^ –D delete
^ –K kill line
^ –U discard line
^ –Y yank
150 Key Combinations SLES 12 SP3

12.5 Helpful GRUB 2 Commands
grub2-mkconfig
Generates a new /boot/grub2/grub.cfg based on /etc/default/grub and the scripts
from /etc/grub.d/ .
EXAMPLE 12.1: USAGE OF GRUB2-MKCONFIG
grub2-mkconfig -o /boot/grub2/grub.cfg
Tip: Syntax Check

Running grub2-mkconfig without any parameters prints the configuration to STD-
OUT where it can be reviewed. Use grub2-script-check after /boot/grub2/
grub.cfg has been written to check its syntax.
Important: grub2-mkconfig Cannot Repair UEFI Secure Boot

Tables
If you are using UEFI Secure Boot and your system is not reaching GRUB 2 correctly
anymore, you may need to additionally reinstall Shim and regenerate the UEFI boot
table. To do so, use:
root # shim-install --config-file=/boot/grub2/grub.cfg
grub2-mkrescue
Creates a bootable rescue image of your installed GRUB 2 configuration.
EXAMPLE 12.2: USAGE OF GRUB2-MKRESCUE
grub2-mkrescue -o save_path/name.iso iso
grub2-script-check
Checks the given le for syntax errors.
EXAMPLE 12.3: USAGE OF GRUB2-SCRIPT-CHECK
grub2-script-check /boot/grub2/grub.cfg
151 Helpful GRUB 2 Commands SLES 12 SP3

grub2-once
Set the default boot entry for the next boot only. To get the list of available boot entries
use the --list option.
EXAMPLE 12.4: USAGE OF GRUB2-ONCE
grub2-once number_of_the_boot_entry
Tip: grub2-once Help

Call the program without any option to get a full list of all possible options.

Extensive information about GRUB 2 is available at http://www.gnu.org/software/grub/ . Also
refer to the grub info page. You can also search for the keyword “GRUB 2” in the Technical
Information Search at http://www.suse.com/support to get information about special issues.
152 More Information SLES 12 SP3

13 The systemd Daemon
The program systemd is the process with process ID 1. It is responsible for initializing the
system in the required way. systemd is started directly by the kernel and resists signal 9, which
normally terminates processes. All other programs are either started directly by systemd or by
one of its child processes.
Starting with SUSE Linux Enterprise Server 12 systemd is a replacement for the popular System
V init daemon. systemd is fully compatible with System V init (by supporting init scripts). One
of the main advantages of systemd is that it considerably speeds up boot time by aggressively
paralleling service starts. Furthermore, systemd only starts a service when it is really needed.
Daemons are not started unconditionally at boot time, but rather when being required for the
rst time. systemd also supports Kernel Control Groups (cgroups), snapshotting and restoring
the system state and more. See http://www.freedesktop.org/wiki/Software/systemd/ for details.
13.1 The systemd Concept

This section will go into detail about the concept behind systemd.
13.1.1 What Is systemd

systemd is a system and session manager for Linux, compatible with System V and LSB init
scripts. The main features are:
provides aggressive parallelization capabilities
uses socket and D-Bus activation for starting services
offers on-demand starting of daemons
keeps track of processes using Linux cgroups
supports snapshotting and restoring of the system state
maintains mount and automount points
implements an elaborate transactional dependency-based service control logic
153 The systemd Concept SLES 12 SP3

13.1.2 Unit File
A unit configuration le contains information about a service, a socket, a device, a mount point,
an automount point, a swap le or partition, a start-up target, a watched le system path,
a timer controlled and supervised by systemd, a temporary system state snapshot, a resource
management slice or a group of externally created processes. “Unit le” is a generic term used
by systemd for the following:
Service. Information about a process (for example running a daemon); le ends with .ser-
vice
Targets. Used for grouping units and as synchronization points during start-up; le ends
with .target
Sockets. Information about an IPC or network socket or a le system FIFO, for sock-
et-based activation (like inetd ); le ends with .socket
Path. Used to trigger other units (for example running a service when les change); le
ends with .path
Timer. Information about a timer controlled, for timer-based activation; le ends
with .timer
Mount point. Usually auto-generated by the fstab generator; le ends with .mount
Automount point. Information about a le system automount point; le ends with .auto-
mount
Swap. Information about a swap device or le for memory paging; le ends with .swap
Device. Information about a device unit as exposed in the sysfs/udev(7) device tree; le
ends with .device
Scope / Slice. A concept for hierarchically managing resources of a group of processes;

le ends with .scope/.slice
For more information about systemd.unit see http://www.freedesktop.org/software/sys-

temd/man/systemd.unit.html
154 Unit File SLES 12 SP3

13.2 Basic Usage
The System V init system uses several commands to handle services—the init scripts, insserv ,
telinit and others. systemd makes it easier to manage services, since there is only one com-
mand to memorize for the majority of service-handling tasks: systemctl . It uses the “command
plus subcommand” notation like git or zypper :
systemctl GENERAL OPTIONS SUBCOMMAND SUBCOMMAND OPTIONS
See man 1 systemctl for a complete manual.
Tip: Terminal Output and Bash Completion

If the output goes to a terminal (and not to a pipe or a le, for example) systemd com-
mands send long output to a pager by default. Use the --no-pager option to turn o
paging mode.
systemd also supports bash-completion, allowing you to enter the rst letters of a sub-
command and then press →| to automatically complete it. This feature is only available
in the bash shell and requires the installation of the package bash-completion .
13.2.1 Managing Services in a Running System

Subcommands for managing services are the same as for managing a service with System V init
( start , stop , ...). The general syntax for service management commands is as follows:
systemd
systemctl reload|restart|start|status|stop|... MY_SERVICE(S)
System V init
rcMY_SERVICE(S) reload|restart|start|status|stop|...
systemd allows you to manage several services in one go. Instead of executing init scripts one
after the other as with System V init, execute a command like the following:
systemctl start MY_1ST_SERVICE MY_2ND_SERVICE
155 Basic Usage SLES 12 SP3

To list all services available on the system:
systemctl list-unit-files --type=service
The following table lists the most important service management commands for systemd and
System V init:
TABLE 13.1: SERVICE MANAGEMENT COMMANDS
Task systemd Command System V init

Command
Starting. start start
Stopping. stop stop
Restarting. Shuts down services and starts restart restart

them afterward. If a service is not yet run-
ning it will be started.
Restarting conditionally. Restarts services if try-restart try-restart

they are currently running. Does nothing for
services that are not running.
Reloading. Tells services to reload their con- reload reload

figuration les without interrupting opera-
tion. Use case: Tell Apache to reload a mod-
ified httpd.conf configuration le. Note
that not all services support reloading.
Reloading or restarting. Reloads services reload-or-restart n/a

if reloading is supported, otherwise restarts
them. If a service is not yet running it will be
started.
Reloading or restarting conditionally. Re- reload-or-try-restart n/a

loads services if reloading is supported, oth-
erwise restarts them if currently running.
Does nothing for services that are not run-
ning.
156 Managing Services in a Running System SLES 12 SP3

Task systemd Command System V init
Command
Getting detailed status information. Lists in- status status

formation about the status of services. The
systemd command shows details such as
description, executable, status, cgroup, and
messages last issued by a service (see Sec-
tion 13.6.8, “Debugging Services”). The level of
details displayed with the System V init dif-
fers from service to service.
Getting short status information. Shows is-active status

whether services are active or not.
13.2.2 Permanently Enabling/Disabling Services

The service management commands mentioned in the previous section let you manipulate ser-
vices for the current session. systemd also lets you permanently enable or disable services, so
they are automatically started when requested or are always unavailable. You can either do this
by using YaST, or on the command line.
13.2.2.1 Enabling/Disabling Services on the Command Line
The following table lists enabling and disabling commands for systemd and System V init:
Important: Service Start

When enabling a service on the command line, it is not started automatically. It is sched-
uled to be started with the next system start-up or runlevel/target change. To immediate-
ly start a service after having enabled it, explicitly run systemctl start MY_SERVICE
or rc MY_SERVICE start .
157 Permanently Enabling/Disabling Services SLES 12 SP3

TABLE 13.2: COMMANDS FOR ENABLING AND DISABLING SERVICES
Task systemd Command System V init Com-

mand
Enabling. systemctl enable insserv

MY_SERVICE(S) MY_SERVICE(S) ,
chkconfig -a
MY_SERVICE(S)
Disabling. systemctl disable insserv -r

MY_SERVICE(S).service MY_SERVICE(S) ,
chkconfig -d
MY_SERVICE(S)
Checking. Shows whether a systemctl is-enabled chkconfig

service is enabled or not. MY_SERVICE MY_SERVICE
Re-enabling. Similar to systemctl reenable n/a

restarting a service, this MY_SERVICE
command rst disables and
then enables a service. Use-
ful to re-enable a service
with its defaults.
Masking. After “disabling” systemctl mask MY_SERVICE n/a

a service, it can still be
started manually. To com-
pletely disable a service,
you need to mask it. Use
with care.
Unmasking. A service that systemctl unmask MY_SERVICE n/a

has been masked can only
be used again after it has
been unmasked.
158 Permanently Enabling/Disabling Services SLES 12 SP3

13.3 System Start and Target Management
The entire process of starting the system and shutting it down is maintained by systemd. From
this point of view, the kernel can be considered a background process to maintain all other
processes and adjust CPU time and hardware access according to requests from other programs.
13.3.1 Targets Compared to Runlevels

With System V init the system was booted into a so-called “Runlevel”. A runlevel defines how the
system is started and what services are available in the running system. Runlevels are numbered;
the most commonly known ones are 0 (shutting down the system), 3 (multiuser with network)
and 5 (multiuser with network and display manager).
systemd introduces a new concept by using so-called “target units”. However, it remains fully
compatible with the runlevel concept. Target units are named rather than numbered and serve
specific purposes. For example, the targets local-fs.target and swap.target mount local
le systems and swap spaces.
The target graphical.target provides a multiuser system with network and display manager
capabilities and is equivalent to runlevel 5. Complex targets, such as graphical.target act
as “meta” targets by combining a subset of other targets. Since systemd makes it easy to create
custom targets by combining existing targets, it offers great flexibility.
The following list shows the most important systemd target units. For a full list refer to man
7 systemd.special .
SELECTED SYSTEMD TARGET UNITS
default.target
The target that is booted by default. Not a “real” target, but rather a symbolic link to an-
other target like graphic.target . Can be permanently changed via YaST (see Section 13.4,
“Managing Services with YaST”). To change it for a session, use the kernel parameter sys-
temd.unit=MY_TARGET.target at the boot prompt.
emergency.target
Starts an emergency shell on the console. Only use it at the boot prompt as systemd.u-
nit=emergency.target .
graphical.target
Starts a system with network, multiuser support and a display manager.
159 System Start and Target Management SLES 12 SP3

halt.target
Shuts down the system.
mail-transfer-agent.target
Starts all services necessary for sending and receiving mails.
multi-user.target
Starts a multiuser system with network.
reboot.target
Reboots the system.
rescue.target
Starts a single-user system without network.
To remain compatible with the System V init runlevel system, systemd provides special targets
named runlevelX.target mapping the corresponding runlevels numbered X .
If you want to know the current target, use the command: systemctl get-default
TABLE 13.3: SYSTEM V RUNLEVELS AND systemd TARGET UNITS
System V run- systemd target Purpose

level
0 runlevel0.target , halt.tar- System shutdown

get , poweroff.target
1, S runlevel1.target , rescue.tar- Single-user mode

get ,
2 runlevel2.target , mul- Local multiuser without remote

ti-user.target , network
3 runlevel3.target , mul- Full multiuser with network

ti-user.target ,
4 runlevel4.target Unused/User-defined
5 runlevel5.target , graphi- Full multiuser with network and

cal.target , display manager
160 Targets Compared to Runlevels SLES 12 SP3

System V run- systemd target Purpose
level
6 runlevel6.target , reboot.tar- System reboot

get ,
Important: systemd Ignores /etc/inittab

The runlevels in a System V init system are configured in /etc/inittab . systemd does
not use this configuration. Refer to Section 13.5.3, “Creating Custom Targets” for instructions
on how to create your own bootable target.
13.3.1.1 Commands to Change Targets
Use the following commands to operate with target units:
Task systemd Command System V init Command
Change the cur- systemctl isolate MY_TARGET .target telinit X

rent target/run-
level
Change to the systemctl default n/a

default tar-
get/runlevel
Get the current systemctl list-units --type=target who -r

target/runlevel With systemd there is usually more than one or
active target. The command lists all currently runlevel
active targets.
persistently Use the Services Manager or run the follow- Use the Services Manager
change the de- ing command: or change the line
fault runlevel ln -sf /usr/lib/systemd/system/ id: X :initdefault:
MY_TARGET .target /etc/systemd/system/de- in /etc/inittab
fault.target
161 Targets Compared to Runlevels SLES 12 SP3

Task systemd Command System V init Command
Change the de- Enter the following option at the boot Enter the desired run-
fault runlevel for prompt level number at the boot
the current boot systemd.unit= MY_TARGET .target prompt.
process
Show a tar- systemctl show -p "Requires" MY_TAR- n/a

get's/runlevel's GET .target
dependencies systemctl show -p "Wants" MY_TAR-
GET .target
“Requires” lists the hard dependencies

(the ones that must be resolved), whereas
“Wants” lists the soft dependencies (the ones
that get resolved if possible).
13.3.2 Debugging System Start-Up

systemd offers the means to analyze the system start-up process. You can review the list of all
services and their status (rather than having to parse /varlog/ ). systemd also allows you to
scan the start-up procedure to nd out how much time each service start-up consumes.
13.3.2.1 Review Start-Up of Services
To review the complete list of services that have been started since booting the system, enter
the command systemctl . It lists all active services like shown below (shortened). To get more
information on a specific service, use systemctl status MY_SERVICE .
EXAMPLE 13.1: LIST ACTIVE SERVICES
root # systemctl
UNIT LOAD ACTIVE SUB JOB DESCRIPTION
[...]
iscsi.service loaded active exited Login and scanning of iSC+
kmod-static-nodes.service loaded active exited Create list of required s+
libvirtd.service loaded active running Virtualization daemon
nscd.service loaded active running Name Service Cache Daemon
162 Debugging System Start-Up SLES 12 SP3

ntpd.service loaded active running NTP Server Daemon
polkit.service loaded active running Authorization Manager
postfix.service loaded active running Postfix Mail Transport Ag+
rc-local.service loaded active exited /etc/init.d/boot.local Co+
rsyslog.service loaded active running System Logging Service
[...]
LOAD = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB = The low-level unit activation state, values depend on unit type.
161 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.
To restrict the output to services that failed to start, use the --failed option:
EXAMPLE 13.2: LIST FAILED SERVICES
root # systemctl --failed

UNIT LOAD ACTIVE SUB JOB DESCRIPTION
apache2.service loaded failed failed apache
NetworkManager.service loaded failed failed Network Manager
plymouth-start.service loaded failed failed Show Plymouth Boot Screen
[...]
13.3.2.2 Debug Start-Up Time
To debug system start-up time, systemd offers the systemd-analyze command. It shows the
total start-up time, a list of services ordered by start-up time and can also generate an SVG
graphic showing the time services took to start in relation to the other services.
Listing the System Start-Up Time
root # systemd-analyze
Startup finished in 2666ms (kernel) + 21961ms (userspace) = 24628ms
Listing the Services Start-Up Time
root # systemd-analyze blame

6472ms systemd-modules-load.service
5833ms remount-rootfs.service
4597ms network.service

4254ms systemd-vconsole-setup.service
4096ms postfix.service
2998ms xdm.service
2483ms localnet.service
2470ms SuSEfirewall2_init.service
2189ms avahi-daemon.service
2120ms systemd-logind.service
1210ms xinetd.service
1080ms ntp.service
[...]
75ms fbset.service
72ms purge-kernels.service
47ms dev-vda1.swap
38ms bluez-coldplug.service
35ms splash_early.service
Services Start-Up Time Graphics
root # systemd-analyze plot > jupiter.example.com-startup.svg

13.3.2.3 Review the Complete Start-Up Process
The above-mentioned commands let you review the services that started and the time it took
to start them. If you need to know more details, you can tell systemd to verbosely log the
complete start-up procedure by entering the following parameters at the boot prompt:
systemd.log_level=debug systemd.log_target=kmsg
Now systemd writes its log messages into the kernel ring buer. View that buer with dmesg :
dmesg -T | less
13.3.3 System V Compatibility

systemd is compatible with System V, allowing you to still use existing System V init scripts.
However, there is at least one known issue where a System V init script does not work with
systemd out of the box: starting a service as a different user via su or sudo in init scripts will
result in a failure of the script, producing an “Access denied” error.
When changing the user with su or sudo , a PAM session is started. This session will be termi-
nated after the init script is finished. As a consequence, the service that has been started by the
init script will also be terminated. To work around this error, proceed as follows:
1. Create a service le wrapper with the same name as the init script plus the le name
extension .service :
[Unit]
Description=DESCRIPTION
After=network.target
[Service]
User=USER
Type=forking 1
PIDFile=PATH TO PID FILE 1
ExecStart=PATH TO INIT SCRIPT start

ExecStop=PATH TO INIT SCRIPT stop
ExecStopPost=/usr/bin/rm -f PATH TO PID FILE 1
[Install]
WantedBy=multi-user.target 2
Replace all values written in UPPERCASE LETTERS with appropriate values.
165 System V Compatibility SLES 12 SP3

1 Optional—only use if the init script starts a daemon.
2 multi-user.target also starts the init script when booting into graphical.tar-
get . If it should only be started when booting into the display manager, user graph-
ical.target here.
2. Start the daemon with systemctl start APPLICATION .
13.4 Managing Services with YaST

Basic service management can also be done with the YaST Services Manager module. It supports
starting, stopping, enabling and disabling services. It also lets you show a service's status and
change the default target. Start the YaST module with YaST System Services Manager.
FIGURE 13.1: SERVICES MANAGER
Changing the Default System Target

To change the target the system boots into, choose a target from the Default System Target
drop-down box. The most often used targets are Graphical Interface (starting a graphical
login screen) and Multi-User (starting the system in command line mode).
166 Managing Services with YaST SLES 12 SP3

Starting or Stopping a Service
Select a service from the table. The Active column shows whether it is currently running
(Active) or not (Inactive). Toggle its status by choosing Start/Stop.
Starting or stopping a service changes its status for the currently running session. To change
its status throughout a reboot, you need to enable or disable it.
Enabling or Disabling a Service

Select a service from the table. The Enabled column shows whether it is currently Enabled
or Disabled. Toggle its status by choosing Enable/Disable.
By enabling or disabling a service you configure whether it is started during booting (En-
abled) or not (Disabled). This setting will not affect the current session. To change its status
in the current session, you need to start or stop it.
View a Status Messages

To view the status message of a service, select it from the list and choose Show Details.
The output you will see is identical to the one generated by the command systemctl -
l status MY_SERVICE .
Warning: Faulty Runlevel Settings May Damage Your System

Faulty runlevel settings may make your system unusable. Before applying your changes,
make absolutely sure that you know their consequences.
13.5 Customization of systemd

The following sections contain some examples for systemd customization.
Warning: Avoiding Overwritten Customization

Always do systemd customization in /etc/systemd/ , never in /usr/lib/systemd/ .
Otherwise your changes will be overwritten by the next update of systemd.
167 Customization of systemd SLES 12 SP3

13.5.1 Customizing Service Files
The systemd service les are located in /usr/lib/systemd/system . If you want to customize
them, proceed as follows:
1. Copy the les you want to modify from /usr/lib/systemd/system to /etc/sys-

temd/system . Keep the le names identical to the original ones.
2. Modify the copies in /etc/systemd/system according to your needs.
3. For an overview of your configuration changes, use the systemd-delta command. It

can compare and identify configuration les that override other configuration les. For
details, refer to the systemd-delta man page.
The modified les in /etc/systemd will take precedence over the original les in /usr/lib/
systemd/system , provided that their le name is the same.
13.5.2 Creating “Drop-in” Files

If you only want to add a few lines to a configuration le or modify a small part of it, you can
use so-called “drop-in” les. Drop-in les let you extend the configuration of unit les without
having to edit or override the unit les themselves.
For example, to change one value for the FOOBAR service located in /usr/lib/systemd/sys-
tem/FOOBAR.SERVICE , proceed as follows:
1. Create a directory called /etc/systemd/system/MY_SERVICE.service.d/ .

Note the .d suffix. The directory must otherwise be named like the service that you want
to patch with the drop-in le.
2. In that directory, create a le WHATEVERMODIFICATION.conf .

Make sure it only contains the line with the value that you want to modify.
3. Save your changes to the le. It will be used as an extension of the original le.
13.5.3 Creating Custom Targets

On System V init SUSE systems, runlevel 4 is unused to allow administrators to create their
own runlevel configuration. systemd allows you to create any number of custom targets. It is
suggested to start by adapting an existing target such as graphical.target .
168 Customizing Service Files SLES 12 SP3

1. Copy the configuration le /usr/lib/systemd/system/graphical.target to /etc/
systemd/system/MY_TARGET.target and adjust it according to your needs.
2. The configuration le copied in the previous step already covers the required (“hard”)
dependencies for the target. To also cover the wanted (“soft”) dependencies, create a
directory /etc/systemd/system/MY_TARGET.target.wants .
3. For each wanted service, create a symbolic link from /usr/lib/systemd/system into /
etc/systemd/system/MY_TARGET.target.wants .
4. Once you have finished setting up the target, reload the systemd configuration to make
the new target available:
systemctl daemon-reload
13.6 Advanced Usage

The following sections cover advanced topics for system administrators. For even more advanced
systemd documentation, refer to Lennart Pöttering's series about systemd for administrators at
http://0pointer.de/blog/projects .
13.6.1 Cleaning Temporary Directories

systemd supports cleaning temporary directories regularly. The configuration from the previ-
ous system version is automatically migrated and active. tmpfiles.d —which is responsible
for managing temporary les—reads its configuration from /etc/tmpfiles.d/*.conf , /run/
tmpfiles.d/*.conf , and /usr/lib/tmpfiles.d/*.conf les. Configuration placed in /etc/
tmpfiles.d/*.conf overrides related configurations from the other two directories ( /usr/
lib/tmpfiles.d/*.conf is where packages store their configuration les).
The configuration format is one line per path containing action and path, and optionally mode,
ownership, age and argument elds, depending on the action. The following example unlinks
the X11 lock les:
Type Path Mode UID GID Age Argument

r /tmp/.X[0-9]*-lock
To get the status the tmpfile timer:
systemctl status systemd-tmpfiles-clean.timer
169 Advanced Usage SLES 12 SP3

systemd-tmpfiles-clean.timer - Daily Cleanup of Temporary Directories
Loaded: loaded (/usr/lib/systemd/system/systemd-tmpfiles-clean.timer; static)
Active: active (waiting) since Tue 2014-09-09 15:30:36 CEST; 1 weeks 6 days ago
Docs: man:tmpfiles.d(5)
man:systemd-tmpfiles(8)
Sep 09 15:30:36 jupiter systemd[1]: Starting Daily Cleanup of Temporary Directories.

Sep 09 15:30:36 jupiter systemd[1]: Started Daily Cleanup of Temporary Directories.
For more information on temporary les handling, see man 5 tmpfiles.d .
13.6.2 System Log

Section 13.6.8, “Debugging Services” explains how to view log messages for a given service. How-
ever, displaying log messages is not restricted to service logs. You can also access and query the
complete log messages written by systemd —the so-called “Journal”. Use the command sys-
temd-journalctl to display the complete log messages starting with the oldest entries. Refer to
man 1 systemd-journalctl for options such as applying filters or changing the output format.
13.6.3 Snapshots
You can save the current state of systemd to a named snapshot and later revert to it with the
isolate subcommand. This is useful when testing services or custom targets, because it allows
you to return to a defined state at any time. A snapshot is only available in the current session
and will automatically be deleted on reboot. A snapshot name must end in .snapshot .
Create a Snapshot
systemctl snapshot MY_SNAPSHOT.snapshot
Delete a Snapshot
systemctl delete MY_SNAPSHOT.snapshot
View a Snapshot
systemctl show MY_SNAPSHOT.snapshot
Activate a Snapshot
systemctl isolate MY_SNAPSHOT.snapshot
170 System Log SLES 12 SP3

13.6.4 Loading Kernel Modules
With systemd , kernel modules can automatically be loaded at boot time via a configuration
le in /etc/modules-load.d . The le should be named MODULE .conf and have the following
content:
# load module MODULE at boot time

MODULE
In case a package installs a configuration le for loading a kernel module, the le gets installed
to /usr/lib/modules-load.d . If two configuration les with the same name exist, the one in
/etc/modules-load.d tales precedence.
For more information, see the modules-load.d(5) man page.
13.6.5 Performing Actions before Loading a Service

With System V init actions that need to be performed before loading a service, needed to be
specified in /etc/init.d/before.local . This procedure is no longer supported with systemd.
If you need to do actions before starting services, do the following:
Loading Kernel Modules

Create a drop-in le in /etc/modules-load.d directory (see man modules-load.d for
the syntax)
Creating Files or Directories, Cleaning-up Directories, Changing Ownership

Create a drop-in le in /etc/tmpfiles.d (see man tmpfiles.d for the syntax)
Other Tasks
Create a system service le, for example /etc/systemd/system/before.service , from
the following template:
[Unit]
Before=NAME OF THE SERVICE YOU WANT THIS SERVICE TO BE STARTED BEFORE
[Service]
Type=oneshot
RemainAfterExit=true
ExecStart=YOUR_COMMAND
# beware, executable is run directly, not through a shell, check the man pages
# systemd.service and systemd.unit for full syntax
[Install]
# target in which to start the service
171 Loading Kernel Modules SLES 12 SP3

WantedBy=multi-user.target
#WantedBy=graphical.target
When the service le is created, you should run the following commands (as root ):
systemctl enable before
Every time you modify the service le, you need to run:
13.6.6 Kernel Control Groups (cgroups)

On a traditional System V init system it is not always possible to clearly assign a process to the
service that spawned it. Some services, such as Apache, spawn a lot of third-party processes (for
example CGI or Java processes), which themselves spawn more processes. This makes a clear
assignment difficult or even impossible. Additionally, a service may not terminate correctly,
leaving some children alive.
systemd solves this problem by placing each service into its own cgroup. cgroups are a ker-
nel feature that allows aggregating processes and all their children into hierarchical organized
groups. systemd names each cgroup after its service. Since a non-privileged process is not al-
lowed to “leave” its cgroup, this provides an effective way to label all processes spawned by a
service with the name of the service.
To list all processes belonging to a service, use the command systemd-cgls . The result will
look like the following (shortened) example:
EXAMPLE 13.3: LIST ALL PROCESSES BELONGING TO A SERVICE
root # systemd-cgls --no-pager

├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 20
├─user.slice
│ └─user-1000.slice
│ ├─session-102.scope
│ │ ├─12426 gdm-session-worker [pam/gdm-password]
│ │ ├─15858 /usr/lib/gnome-terminal-server
[...]
172 Kernel Control Groups (cgroups) SLES 12 SP3

└─system.slice
├─systemd-hostnamed.service
│ └─17616 /usr/lib/systemd/systemd-hostnamed
├─cron.service
│ └─1689 /usr/sbin/cron -n
├─ntpd.service
│ └─1328 /usr/sbin/ntpd -p /var/run/ntp/ntpd.pid -g -u ntp:ntp -c /etc/ntp.conf
├─postfix.service
│ ├─ 1676 /usr/lib/postfix/master -w
│ ├─ 1679 qmgr -l -t fifo -u
│ └─15590 pickup -l -t fifo -u
├─sshd.service
│ └─1436 /usr/sbin/sshd -D
[...]
See Book “System Analysis and Tuning Guide”, Chapter 9 “Kernel Control Groups” for more information
about cgroups.
13.6.7 Terminating Services (Sending Signals)

As explained in Section 13.6.6, “Kernel Control Groups (cgroups)”, it is not always possible to assign a
process to its parent service process in a System V init system. This makes it difficult to terminate
a service and all of its children. Child processes that have not been terminated will remain as
zombie processes.
systemd's concept of confining each service into a cgroup makes it possible to clearly identify all
child processes of a service and therefore allows you to send a signal to each of these processes.
Use systemctl kill to send signals to services. For a list of available signals refer to man
7 signals .
Sending SIGTERM to a Service

SIGTERM is the default signal that is sent.
systemctl kill MY_SERVICE
Sending SIGNAL to a Service

Use the -s option to specify the signal that should be sent.
systemctl kill -s SIGNAL MY_SERVICE
173 Terminating Services (Sending Signals) SLES 12 SP3

Selecting Processes
By default the kill command sends the signal to all processes of the specified cgroup.
You can restrict it to the control or the main process. The latter is for example useful to
force a service to reload its configuration by sending SIGHUP :
systemctl kill -s SIGHUP --kill-who=main MY_SERVICE
Warning: Terminating or Restarting the D-Bus Service is Not

Supported
The D-Bus service is the message bus for communication between systemd clients and the
systemd manager that is running as pid 1. Even though dbus is a stand-alone daemon,
it is an integral part of the init infrastructure.
Terminating dbus or restarting it in the running system is similar to an attempt to termi-
nate or restart pid 1. It will break systemd client/server communication and make most
systemd functions unusable.
Therefore, terminating or restarting dbus is neither recommended nor supported.
13.6.8 Debugging Services

By default, systemd is not overly verbose. If a service was started successfully, no output will
be produced. In case of a failure, a short error message will be displayed. However, systemctl
status provides means to debug start-up and operation of a service.
systemd comes with its own logging mechanism (“The Journal”) that logs system messages. This
allows you to display the service messages together with status messages. The status command
works similar to tail and can also display the log messages in different formats, making it a
powerful debugging tool.
Show Service Start-Up Failure

Whenever a service fails to start, use systemctl status MY_SERVICE to get a detailed
error message:
root # systemctl start apache2

Job failed. See system journal and 'systemctl status' for details.
root # systemctl status apache2
Loaded: loaded (/usr/lib/systemd/system/apache2.service; disabled)
Active: failed (Result: exit-code) since Mon, 04 Jun 2012 16:52:26 +0200; 29s ago
174 Debugging Services SLES 12 SP3

Process: 3088 ExecStart=/usr/sbin/start_apache2 -D SYSTEMD -k start (code=exited,
status=1/FAILURE)
CGroup: name=systemd:/system/apache2.service
Jun 04 16:52:26 g144 start_apache2[3088]: httpd2-prefork: Syntax error on line

205 of /etc/apache2/httpd.conf: Syntax error on li...alHost>
Show Last N Service Messages

The default behavior of the status subcommand is to display the last ten messages a
service issued. To change the number of messages to show, use the --lines=N parameter:
systemctl status ntp

systemctl --lines=20 status ntp
Show Service Messages in Append Mode

To display a “live stream” of service messages, use the --follow option, which works
like tail -f :
systemctl --follow status ntp
Messages Output Format

The --output=MODE parameter allows you to change the output format of service mes-
sages. The most important modes available are:
short
The default format. Shows the log messages with a human readable time stamp.
verbose
Full output with all elds.
cat
Terse output without time stamps.

For more information on systemd refer to the following online resources:
Homepage
http://www.freedesktop.org/wiki/Software/systemd
systemd for Administrators

Lennart Pöttering, one of the systemd authors, has written a series of blog entries (13 at
the time of writing this chapter). Find them at http://0pointer.de/blog/projects .
175 More Information SLES 12 SP3

III System
14 32-Bit and 64-Bit Applications in a 64-Bit System Environment 177
15 journalctl: Query the systemd Journal 182
16 Basic Networking 190
17 Printer Operation 262
18 The X Window System 276
19 Accessing File Systems with FUSE 290
20 Managing Kernel Modules 292
21 Dynamic Kernel Device Management with udev 296
22 Live Patching the Linux Kernel Using kGraft 308
23 Special System Features 315

14 32-Bit and 64-Bit Applications in a 64-Bit System
Environment
SUSE® Linux Enterprise Server is available for several 64-bit platforms. This does not necessar-
ily mean that all the applications included have already been ported to 64-bit platforms. SUSE
Linux Enterprise Server supports the use of 32-bit applications in a 64-bit system environment.
This chapter offers a brief overview of how this support is implemented on 64-bit SUSE Linux
Enterprise Server platforms. It explains how 32-bit applications are executed and how 32-bit
applications should be compiled to enable them to run both in 32-bit and 64-bit system envi-
ronments. Additionally, nd information about the kernel API and an explanation of how 32-
bit applications can run under a 64-bit kernel.
SUSE Linux Enterprise Server for the 64-bit platforms POWER, z Systems and AMD64/Intel 64
is designed so that existing 32-bit applications run in the 64-bit environment “out-of-the-box.”
The corresponding 32-bit platforms are ppc for POWER, and x86 for AMD64/Intel 64. This
support means that you can continue to use your preferred 32-bit applications without waiting
for a corresponding 64-bit port to become available. The current POWER system runs most
applications in 32-bit mode, but you can run 64-bit applications.
14.1 Runtime Support
Important: Conflicts Between Application Versions

If an application is available both for 32-bit and 64-bit environments, parallel installation
of both versions is bound to lead to problems. In such cases, decide on one of the two
versions and install and use this.
An exception to this rule is PAM (pluggable authentication modules). SUSE Linux Enter-
prise Server uses PAM in the authentication process as a layer that mediates between
user and application. On a 64-bit operating system that also runs 32-bit applications it is
necessary to always install both versions of a PAM module.
To be executed correctly, every application requires a range of libraries. Unfortunately, the

names for the 32-bit and 64-bit versions of these libraries are identical. They must be differen-
tiated from each other in another way.
177 Runtime Support SLES 12 SP3

To retain compatibility with the 32-bit version, the libraries are stored at the same place in the
system as in the 32-bit environment. The 32-bit version of libc.so.6 is located under /lib/
libc.so.6 in both the 32-bit and 64-bit environments.
All 64-bit libraries and object les are located in directories called lib64 . The 64-bit object
les that you would normally expect to nd under /lib and /usr/lib are now found under
/lib64 and /usr/lib64 . This means that there is space for the 32-bit libraries under /lib
and /usr/lib , so the le name for both versions can remain unchanged.
Subdirectories of 32-bit /lib directories which contain data content that does not depend on
the word size are not moved. This scheme conforms to LSB (Linux Standards Base) and FHS
(File System Hierarchy Standard).
14.2 Software Development

All 64-bit architectures support the development of 64-bit objects. The level of support for 32-
bit compiling depends on the architecture. These are the various implementation options for
the toolchain from GCC (GNU Compiler Collection) and binutils, which include the assembler
as and the linker ld :
Both 32-bit and 64-bit objects can be generated with a biarch development toolchain. A biarch
development toolchain allows generation of 32-bit and 64-bit objects. The compilation of 64-bit
objects is the default on almost all platforms. 32-bit objects can be generated if special ags are
used. This special ag is -m32 for GCC. The ags for the binutils are architecture-dependent,
but GCC transfers the correct ags to linkers and assemblers. A biarch development toolchain
currently exists for amd64 (supports development for x86 and amd64 instructions), for z Systems
and for POWER. 32-bit objects are normally created on the POWER platform. The -m64 ag
must be used to generate 64-bit objects.
All header les must be written in an architecture-independent form. The installed 32-bit and
64-bit libraries must have an API (application programming interface) that matches the installed
header les. The normal SUSE Linux Enterprise Server environment is designed according to
this principle. In the case of manually updated libraries, resolve these issues yourself.
178 Software Development SLES 12 SP3

14.3 Software Compilation on Biarch Platforms
To develop binaries for the other architecture on a biarch architecture, the respective li-
braries for the second architecture must additionally be installed. These packages are called
rpmname-32bit or rpmname-x86 if the second architecture is a 32-bit architecture or rpm-
name-64bit if the second architecture is a 64-bit architecture. You also need the respective
headers and libraries from the rpmname-devel packages and the development libraries for the
second architecture from rpmname-devel-32bit or rpmname-devel-64bit .
For example, to compile a program that uses libaio on a system with a 32-bit second archi-
tecture (x86_64 or z Systems), you need the following RPMs:
libaio-32bit
32-bit runtime package
libaio-devel-32bit
Headers and libraries for 32-bit development
libaio
64-bit runtime package
libaio-devel
64-bit development headers and libraries
Most open source programs use an autoconf -based program configuration. To use autoconf
for configuring a program for the second architecture, overwrite the normal compiler and linker
settings of autoconf by running the configure script with additional environment variables.
The following example refers to an x86_64 system with x86 as the second architecture. Examples
for POWER with ppc as the second architecture would be similar.
1. Use the 32-bit compiler:
CC="gcc -m32"
2. Instruct the linker to process 32-bit objects (always use gcc as the linker front-end):
LD="gcc -m32"
3. Set the assembler to generate 32-bit objects:
AS="gcc -c -m32"
179 Software Compilation on Biarch Platforms SLES 12 SP3

4. Specify linker ags, such as the location of 32-bit libraries, for example:
LDFLAGS="-L/usr/lib"
5. Specify the location for the 32-bit object code libraries:
--libdir=/usr/lib
6. Specify the location for the 32-bit X libraries:
--x-libraries=/usr/lib
Not all of these variables are needed for every program. Adapt them to the respective program.
An example configure call to compile a native 32-bit application on x86_64, POWER or z Sys-
tems could appear as follows:
CC="gcc -m32"
LDFLAGS="-L/usr/lib;"
./configure --prefix=/usr --libdir=/usr/lib --x-libraries=/usr/lib
make
make install
14.4 Kernel Specifications

The 64-bit kernels for AMD64/Intel 64, POWER and z Systems offer both a 64-bit and a 32-
bit kernel ABI (application binary interface). The latter is identical with the ABI for the corre-
sponding 32-bit kernel. This means that the 32-bit application can communicate with the 64-
bit kernel in the same way as with the 32-bit kernel.
The 32-bit emulation of system calls for a 64-bit kernel does not support all the APIs used by
system programs. This depends on the platform. For this reason, few applications, like lspci ,
must be compiled on non-POWER platforms as 64-bit programs to function properly. On IBM
z Systems, not all ioctls are available in the 32-bit kernel ABI.
A 64-bit kernel can only load 64-bit kernel modules that have been specially compiled for this
kernel. It is not possible to use 32-bit kernel modules.
180 Kernel Specifications SLES 12 SP3

Tip: Kernel-loadable Modules
Some applications require separate kernel-loadable modules. If you intend to use such a
32-bit application in a 64-bit system environment, contact the provider of this application
and SUSE to make sure that the 64-bit version of the kernel-loadable module and the 32-
bit compiled version of the kernel API are available for this module.
181 Kernel Specifications SLES 12 SP3

15 journalctl: Query the systemd Journal
When systemd replaced traditional init scripts in SUSE Linux Enterprise 12 (see Chapter 13, The
systemd Daemon), it introduced its own logging system called journal. There is no need to run
a syslog based service anymore, as all system events are written in the journal.
The journal itself is a system service managed by systemd . Its full name is systemd-jour-
nald.service . It collects and stores logging data by maintaining structured indexed journals
based on logging information received from the kernel, user processes, standard input, and sys-
tem service errors. The systemd-journald service is on by default:
# systemctl status systemd-journald

systemd-journald.service - Journal Service
Loaded: loaded (/usr/lib/systemd/system/systemd-journald.service; static)
Active: active (running) since Mon 2014-05-26 08:36:59 EDT; 3 days ago
Docs: man:systemd-journald.service(8)
man:journald.conf(5)
Main PID: 413 (systemd-journal)
Status: "Processing requests..."
CGroup: /system.slice/systemd-journald.service
└─413 /usr/lib/systemd/systemd-journald
[...]
15.1 Making the Journal Persistent

The journal stores log data in /run/log/journal/ by default. Because the /run/ directory is
volatile by nature, log data is lost at reboot. To make the log data persistent, the directory /var/
log/journal/ with correct ownership and permissions must exist, where the systemd-journald
service can store its data. systemd will create the directory for you—and switch to persistent
logging—if you do the following:
1. As root , open /etc/systemd/journald.conf for editing.
# vi /etc/systemd/journald.conf
2. Uncomment the line containing Storage= and change it to
[...]
[Journal]
Storage=persistent
#Compress=yes
182 Making the Journal Persistent SLES 12 SP3

[...]
3. Save the le and restart systemd-journald:
systemctl restart systemd-journald
15.2 journalctl Useful Switches

This section introduces several common useful options to enhance the default journalctl
behavior. All switches are described in the journalctl manual page, man 1 journalctl .
Tip: Messages Related to a Specific Executable

To show all journal messages related to a specific executable, specify the full path to the
executable:
journalctl /usr/lib/systemd/systemd
-f
Shows only the most recent journal messages, and prints new log entries as they are added
to the journal.
-e
Prints the messages and jumps to the end of the journal, so that the latest entries are visible
within the pager.
-r
Prints the messages of the journal in reverse order, so that the latest entries are listed rst.
-k
Shows only kernel messages. This is equivalent to the eld match _TRANSPORT=kernel
(see Section 15.3.3, “Filtering Based on Fields”).
-u
Shows only messages for the specified systemd unit. This is equivalent to the eld match
_SYSTEMD_UNIT=UNIT (see Section 15.3.3, “Filtering Based on Fields”).
# journalctl -u apache2
[...]
Jun 03 10:07:11 pinkiepie systemd[1]: Starting The Apache Webserver...
183 journalctl Useful Switches SLES 12 SP3

Jun 03 10:07:12 pinkiepie systemd[1]: Started The Apache Webserver.
15.3 Filtering the Journal Output

When called without switches, journalctl shows the full content of the journal, the oldest
entries listed rst. The output can be filtered by specific switches and elds.
15.3.1 Filtering Based on a Boot Number

journalctl can filter messages based on a specific system boot. To list all available boots, run
# journalctl --list-boots
-1 097ed2cd99124a2391d2cffab1b566f0 Mon 2014-05-26 08:36:56 EDT—Fri 2014-05-30 05:33:44
EDT
0 156019a44a774a0bb0148a92df4af81b Fri 2014-05-30 05:34:09 EDT—Fri 2014-05-30 06:15:01
EDT
The rst column lists the boot offset: 0 for the current boot, -1 for the previous one, -2 for
the one prior to that, etc. The second column contains the boot ID followed by the limiting time
stamps of the specific boot.
Show all messages from the current boot:
# journalctl -b
If you need to see journal messages from the previous boot, add an offset parameter. The fol-
lowing example outputs the previous boot messages:
# journalctl -b -1
Another way is to list boot messages based on the boot ID. For this purpose, use the _BOOT_ID
eld:
# journalctl _BOOT_ID=156019a44a774a0bb0148a92df4af81b
15.3.2 Filtering Based on Time Interval

You can filter the output of journalctl by specifying the starting and/or ending date. The date
specification should be of the format "2014-06-30 9:17:16". If the time part is omitted, midnight
is assumed. If seconds are omitted, ":00" is assumed. If the date part is omitted, the current day
is assumed. Instead of numeric expression, you can specify the keywords "yesterday", "today",
184 Filtering the Journal Output SLES 12 SP3

or "tomorrow". They refer to midnight of the day before the current day, of the current day, or
of the day after the current day. If you specify "now", it refers to the current time. You can also
specify relative times prefixed with - or + , referring to times before or after the current time.
Show only new messages since now, and update the output continuously:
# journalctl --since "now" -f
Show all messages since last midnight till 3:20am:
# journalctl --since "today" --until "3:20"
15.3.3 Filtering Based on Fields

You can filter the output of the journal by specific elds. The syntax of a eld to be matched is
FIELD_NAME=MATCHED_VALUE , such as _SYSTEMD_UNIT=httpd.service . You can specify mul-
tiple matches in a single query to filter the output messages even more. See man 7 sys-
temd.journal-fields for a list of default elds.
Show messages produced by a specific process ID:
# journalctl _PID=1039
Show messages belonging to a specific user ID:
# journalctl _UID=1000
Show messages from the kernel ring buer (the same as dmesg produces):
# journalctl _TRANSPORT=kernel
Show messages from the service's standard or error output:
# journalctl _TRANSPORT=stdout
Show messages produced by a specified service only:
# journalctl _SYSTEMD_UNIT=avahi-daemon.service
If two different elds are specified, only entries that match both expressions at the same time
are shown:
# journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=1488
If two matches refer to the same eld, all entries matching either expression are shown:
# journalctl _SYSTEMD_UNIT=avahi-daemon.service _SYSTEMD_UNIT=dbus.service
185 Filtering Based on Fields SLES 12 SP3

You can use the '+' separator to combine two expressions in a logical 'OR'. The following example
shows all messages from the Avahi service process with the process ID 1480 together with all
messages from the D-Bus service:
# journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=1480 + _SYSTEMD_UNIT=dbus.service
15.4 Investigating systemd Errors

This section introduces a simple example to illustrate how to nd and x the error reported by
systemd during apache2 start-up.
1. Try to start the apache2 service:
# systemctl start apache2

Job for apache2.service failed. See 'systemctl status apache2' and 'journalctl -xn'
for details.
2. Let us see what the service's status says:
# systemctl status apache2

apache2.service - The Apache Webserver
Active: failed (Result: exit-code) since Tue 2014-06-03 11:08:13 CEST; 7min ago
Process: 11026 ExecStop=/usr/sbin/start_apache2 -D SYSTEMD -DFOREGROUND \
-k graceful-stop (code=exited, status=1/FAILURE)
The ID of the process causing the failure is 11026.
3. Show the verbose version of messages related to process ID 11026:
# journalctl -o verbose _PID=11026

[...]
MESSAGE=AH00526: Syntax error on line 6 of /etc/apache2/default-server.conf:
[...]
MESSAGE=Invalid command 'DocumenttRoot', perhaps misspelled or defined by a module
[...]
4. Fix the typo inside /etc/apache2/default-server.conf , start the apache2 service, and
print its status:
# systemctl start apache2 && systemctl status apache2

apache2.service - The Apache Webserver
186 Investigating systemd Errors SLES 12 SP3

Active: active (running) since Tue 2014-06-03 11:26:24 CEST; 4ms ago
Process: 11026 ExecStop=/usr/sbin/start_apache2 -D SYSTEMD -DFOREGROUND
-k graceful-stop (code=exited, status=1/FAILURE)
Main PID: 11263 (httpd2-prefork)
Status: "Processing requests..."
CGroup: /system.slice/apache2.service
├─11263 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...]
└─11285 /usr/sbin/httpd2-prefork -f /etc/apache2/httpd.conf -D [...]
15.5 Journald Configuration

The behavior of the systemd-journald service can be adjusted by modifying /etc/sys-
temd/journald.conf . This section introduces only basic option settings. For a complete le
description, see man 5 journald.conf . Note that you need to restart the journal for the changes
to take effect with
# systemctl restart systemd-journald
15.5.1 Changing the Journal Size Limit

If the journal log data is saved to a persistent location (see Section 15.1, “Making the Journal Persis-
tent”), it uses up to 10% of the le system the /var/log/journal resides on. For example, if /
var/log/journal is located on a 30 GB /var partition, the journal may use up to 3 GB of the
disk space. To change this limit, change (and uncomment) the SystemMaxUse option:
SystemMaxUse=50M
15.5.2 Forwarding the Journal to /dev/ttyX

You can forward the journal to a terminal device to inform you about system messages on a
preferred terminal screen, for example /dev/tty12 . Change the following journald options to
ForwardToConsole=yes
TTYPath=/dev/tty12
187 Journald Configuration SLES 12 SP3

15.5.3 Forwarding the Journal to Syslog Facility
Journald is backward compatible with traditional syslog implementations such as rsyslog .
Make sure the following is valid:
rsyslog is installed.
# rpm -q rsyslog
rsyslog-7.4.8-2.16.x86_64
rsyslog service is enabled.
# systemctl is-enabled rsyslog

enabled
Forwarding to syslog is enabled in /etc/systemd/journald.conf .
ForwardToSyslog=yes
15.6 Using YaST to Filter the systemd Journal

For an easy way of filtering the systemd journal (without having to deal with the journalctl
syntax), you can use the YaST journal module. After installing it with sudo zypper in yast2-
journal , start it from YaST by selecting System Systemd Journal. Alternatively, start it from
command line by entering sudo yast2 journal .
FIGURE 15.1: YAST SYSTEMD JOURNAL
188 Forwarding the Journal to Syslog Facility SLES 12 SP3

The module displays the log entries in a table. The search box on top allows you to search for
entries that contain certain characters, similar to using grep . To filter the entries by date and
time, unit, le, or priority, click Change filters and set the respective options.
189 Using YaST to Filter the systemd Journal SLES 12 SP3

16 Basic Networking
Linux offers the necessary networking tools and features for integration into all
types of network structures. Network access using a network card can be configured
with YaST. Manual configuration is also possible. In this chapter only the funda-
mental mechanisms and the relevant network configuration les are covered.
Linux and other Unix operating systems use the TCP/IP protocol. It is not a single network
protocol, but a family of network protocols that offer various services. The protocols listed
in Several Protocols in the TCP/IP Protocol Family, are provided for exchanging data between two
machines via TCP/IP. Networks combined by TCP/IP, comprising a worldwide network, are also
called “the Internet.”
RFC stands for Request for Comments. RFCs are documents that describe various Internet pro-
tocols and implementation procedures for the operating system and its applications. The RFC
documents describe the setup of Internet protocols. For more information about RFCs, see http://
www.ietf.org/rfc.html .
SEVERAL PROTOCOLS IN THE TCP/IP PROTOCOL FAMILY
TCP
Transmission Control Protocol: a connection-oriented secure protocol. The data to transmit
is rst sent by the application as a stream of data and converted into the appropriate format
by the operating system. The data arrives at the respective application on the destination
host in the original data stream format it was initially sent. TCP determines whether any
data has been lost or jumbled during the transmission. TCP is implemented wherever the
data sequence matters.
UDP
User Datagram Protocol: a connectionless, insecure protocol. The data to transmit is sent
in the form of packets generated by the application. The order in which the data arrives at
the recipient is not guaranteed and data loss is possible. UDP is suitable for record-oriented
applications. It features a smaller latency period than TCP.
ICMP
Internet Control Message Protocol: This is not a protocol for the end user, but a special
control protocol that issues error reports and can control the behavior of machines partic-
ipating in TCP/IP data transfer. In addition, it provides a special echo mode that can be
viewed using the program ping.
190 SLES 12 SP3

IGMP
Internet Group Management Protocol: This protocol controls machine behavior when im-
plementing IP multicast.
As shown in Figure 16.1, “Simplified Layer Model for TCP/IP”, data exchange takes place in different
layers. The actual network layer is the insecure data transfer via IP (Internet protocol). On top
of IP, TCP (transmission control protocol) guarantees, to a certain extent, security of the data
transfer. The IP layer is supported by the underlying hardware-dependent protocol, such as
Ethernet.
TCP/IP Model OSI Model
Application Layer
Application Layer Presentation Layer
Session Layer
Transport Layer Transport Layer
Internet Layer Network Layer
Data Link Layer

Network Access Layer
Physical Layer
FIGURE 16.1: SIMPLIFIED LAYER MODEL FOR TCP/IP
191 SLES 12 SP3

The diagram provides one or two examples for each layer. The layers are ordered according to
abstraction levels. The lowest layer is very close to the hardware. The uppermost layer, however,
is almost a complete abstraction from the hardware. Every layer has its own special function.
The special functions of each layer are mostly implicit in their description. The data link and
physical layers represent the physical network used, such as Ethernet.
Almost all hardware protocols work on a packet-oriented basis. The data to transmit is collected
into packets (it cannot be sent all at once). The maximum size of a TCP/IP packet is approximately
64 KB. Packets are normally quite smaller, as the network hardware can be a limiting factor.
The maximum size of a data packet on an Ethernet is about fifteen hundred bytes. The size of a
TCP/IP packet is limited to this amount when the data is sent over an Ethernet. If more data is
transferred, more data packets need to be sent by the operating system.
For the layers to serve their designated functions, additional information regarding each layer
must be saved in the data packet. This takes place in the header of the packet. Every layer
attaches a small block of data, called the protocol header, to the front of each emerging packet.
A sample TCP/IP data packet traveling over an Ethernet cable is illustrated in Figure 16.2, “TCP/
IP Ethernet Packet”. The proof sum is located at the end of the packet, not at the beginning. This
simplifies things for the network hardware.
FIGURE 16.2: TCP/IP ETHERNET PACKET
When an application sends data over the network, the data passes through each layer, all im-
plemented in the Linux kernel except the physical layer. Each layer is responsible for preparing
the data so it can be passed to the next layer. The lowest layer is ultimately responsible for
sending the data. The entire procedure is reversed when data is received. Like the layers of an
onion, in each layer the protocol headers are removed from the transported data. Finally, the
transport layer is responsible for making the data available for use by the applications at the
destination. In this manner, one layer only communicates with the layer directly above or below
it. For applications, it is irrelevant whether data is transmitted via a 100 Mbit/s FDDI network
or via a 56-Kbit/s modem line. Likewise, it is irrelevant for the data line which kind of data is
transmitted, as long as packets are in the correct format.
192 SLES 12 SP3

16.1 IP Addresses and Routing
The discussion in this section is limited to IPv4 networks. For information about IPv6 protocol,
the successor to IPv4, refer to Section 16.2, “IPv6—The Next Generation Internet”.
16.1.1 IP Addresses
Every computer on the Internet has a unique 32-bit address. These 32 bits (or 4 bytes) are
normally written as illustrated in the second row in Example 16.1, “Writing IP Addresses”.
EXAMPLE 16.1: WRITING IP ADDRESSES
IP Address (binary): 11000000 10101000 00000000 00010100

IP Address (decimal): 192. 168. 0. 20
In decimal form, the four bytes are written in the decimal number system, separated by periods.
The IP address is assigned to a host or a network interface. It can be used only once throughout
the world. There are exceptions to this rule, but these are not relevant to the following passages.
The points in IP addresses indicate the hierarchical system. Until the 1990s, IP addresses were
strictly categorized in classes. However, this system proved too inflexible and was discontinued.
Now, classless routing (CIDR, classless interdomain routing) is used.
16.1.2 Netmasks and Routing

Netmasks are used to define the address range of a subnet. If two hosts are in the same subnet,
they can reach each other directly. If they are not in the same subnet, they need the address
of a gateway that handles all the traffic for the subnet. To check if two IP addresses are in the
same subnet, simply “AND” both addresses with the netmask. If the result is identical, both IP
addresses are in the same local network. If there are differences, the remote IP address, and thus
the remote interface, can only be reached over a gateway.
To understand how the netmask works, look at Example 16.2, “Linking IP Addresses to the Netmask”.
The netmask consists of 32 bits that identify how much of an IP address belongs to the network.
All those bits that are 1 mark the corresponding bit in the IP address as belonging to the network.
All bits that are 0 mark bits inside the subnet. This means that the more bits are 1 , the smaller
the subnet is. Because the netmask always consists of several successive 1 bits, it is also possible
to count the number of bits in the netmask. In Example 16.2, “Linking IP Addresses to the Netmask”
the rst net with 24 bits could also be written as 192.168.0.0/24 .
193 IP Addresses and Routing SLES 12 SP3

EXAMPLE 16.2: LINKING IP ADDRESSES TO THE NETMASK
IP address (192.168.0.20): 11000000 10101000 00000000 00010100

Netmask (255.255.255.0): 11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link: 11000000 10101000 00000000 00000000
In the decimal system: 192. 168. 0. 0
IP address (213.95.15.200): 11010101 10111111 00001111 11001000

Netmask (255.255.255.0): 11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link: 11010101 10111111 00001111 00000000
In the decimal system: 213. 95. 15. 0
To give another example: all machines connected with the same Ethernet cable are usually lo-
cated in the same subnet and are directly accessible. Even when the subnet is physically divided
by switches or bridges, these hosts can still be reached directly.
IP addresses outside the local subnet can only be reached if a gateway is configured for the
target network. In the most common case, there is only one gateway that handles all traffic that
is external. However, it is also possible to configure several gateways for different subnets.
If a gateway has been configured, all external IP packets are sent to the appropriate gateway.
This gateway then attempts to forward the packets in the same manner—from host to host—
until it reaches the destination host or the packet's TTL (time to live) expires.
SPECIFIC ADDRESSES
Base Network Address

This is the netmask AND any address in the network, as shown in Example 16.2, “Linking IP
Addresses to the Netmask” under Result . This address cannot be assigned to any hosts.
Broadcast Address
This could be paraphrased as: “Access all hosts in this subnet.” To generate this, the net-
mask is inverted in binary form and linked to the base network address with a logical OR.
The above example therefore results in 192.168.0.255. This address cannot be assigned
to any hosts.
Local Host
The address 127.0.0.1 is assigned to the “loopback device” on each host. A connection
can be set up to your own machine with this address and with all addresses from the
complete 127.0.0.0/8 loopback network as defined with IPv4. With IPv6 there is only
one loopback address ( ::1 ).
194 Netmasks and Routing SLES 12 SP3

Because IP addresses must be unique all over the world, you cannot select random addresses.
There are three address domains to use if you want to set up a private IP-based network. These
cannot get any connection from the rest of the Internet, because they cannot be transmitted over
the Internet. These address domains are specified in RFC 1597 and listed in Table 16.1, “Private
IP Address Domains”.
TABLE 16.1: PRIVATE IP ADDRESS DOMAINS
Network/Netmask Domain
10.0.0.0 / 255.0.0.0 10.x.x.x
172.16.0.0 / 255.240.0.0 172.16.x.x – 172.31.x.x
192.168.0.0 / 255.255.0.0 192.168.x.x
16.2 IPv6—The Next Generation Internet
Important: IBM z Systems: IPv6 Support

IPv6 is not supported by the CTC and IUCV network connections of the IBM z Systems
hardware.
Due to the emergence of the World Wide Web (WWW), the Internet has experienced explosive
growth, with an increasing number of computers communicating via TCP/IP in the past fifteen
years. Since Tim Berners-Lee at CERN (http://public.web.cern.ch ) invented the WWW in 1990,
the number of Internet hosts has grown from a few thousand to about a hundred million.
As mentioned, an IPv4 address consists of only 32 bits. Also, quite a few IP addresses are lost
—they cannot be used because of the way in which networks are organized. The number of
addresses available in your subnet is two to the power of the number of bits, minus two. A
subnet has, for example, 2, 6, or 14 addresses available. To connect 128 hosts to the Internet,
for example, you need a subnet with 256 IP addresses, from which only 254 are usable, because
two IP addresses are needed for the structure of the subnet itself: the broadcast and the base
network address.
Under the current IPv4 protocol, DHCP or NAT (network address translation) are the typical
mechanisms used to circumvent the potential address shortage. Combined with the convention
to keep private and public address spaces separate, these methods can certainly mitigate the
195 IPv6—The Next Generation Internet SLES 12 SP3

shortage. The problem with them lies in their configuration, which is a chore to set up and a
burden to maintain. To set up a host in an IPv4 network, you need several address items, such
as the host's own IP address, the subnetmask, the gateway address and maybe a name server
address. All these items need to be known and cannot be derived from somewhere else.
With IPv6, both the address shortage and the complicated configuration should be a thing of
the past. The following sections tell more about the improvements and benefits brought by IPv6
and about the transition from the old protocol to the new one.
16.2.1 Advantages
The most important and most visible improvement brought by the new protocol is the enormous
expansion of the available address space. An IPv6 address is made up of 128 bit values instead
of the traditional 32 bits. This provides for as many as several quadrillion IP addresses.
However, IPv6 addresses are not only different from their predecessors with regard to their
length. They also have a different internal structure that may contain more specific information
about the systems and the networks to which they belong. More details about this are found in
Section 16.2.2, “Address Types and Structure”.
The following is a list of other advantages of the new protocol:
Autoconfiguration
IPv6 makes the network “plug and play” capable, which means that a newly set up system
integrates into the (local) network without any manual configuration. The new host uses its
automatic configuration mechanism to derive its own address from the information made
available by the neighboring routers, relying on a protocol called the neighbor discovery
(ND) protocol. This method does not require any intervention on the administrator's part
and there is no need to maintain a central server for address allocation—an additional
advantage over IPv4, where automatic address allocation requires a DHCP server.
Nevertheless if a router is connected to a switch, the router should send periodic advertise-
ments with ags telling the hosts of a network how they should interact with each other.
For more information, see RFC 2462 and the radvd.conf(5) man page, and RFC 3315.
Mobility
IPv6 makes it possible to assign several addresses to one network interface at the same time.
This allows users to access several networks easily, something that could be compared with
the international roaming services offered by mobile phone companies. When you take
196 Advantages SLES 12 SP3

your mobile phone abroad, the phone automatically logs in to a foreign service when it
enters the corresponding area, so you can be reached under the same number everywhere
and can place an outgoing call, as you would in your home area.
Secure Communication
With IPv4, network security is an add-on function. IPv6 includes IPsec as one of its core
features, allowing systems to communicate over a secure tunnel to avoid eavesdropping
by outsiders on the Internet.
Backward Compatibility
Realistically, it would be impossible to switch the entire Internet from IPv4 to IPv6 at one
time. Therefore, it is crucial that both protocols can coexist not only on the Internet, but
also on one system. This is ensured by compatible addresses (IPv4 addresses can easily be
translated into IPv6 addresses) and by using several tunnels. See Section 16.2.3, “Coexistence
of IPv4 and IPv6”. Also, systems can rely on a dual stack IP technique to support both protocols
at the same time, meaning that they have two network stacks that are completely separate,
such that there is no interference between the two protocol versions.
Custom Tailored Services through Multicasting

With IPv4, some services, such as SMB, need to broadcast their packets to all hosts in
the local network. IPv6 allows a much more ne-grained approach by enabling servers to
address hosts through multicasting, that is by addressing several hosts as parts of a group.
This is different from addressing all hosts through broadcasting or each host individually
through unicasting). Which hosts are addressed as a group may depend on the concrete
application. There are some predefined groups to address all name servers (the all name
servers multicast group), for example, or all routers (the all routers multicast group).
16.2.2 Address Types and Structure

As mentioned, the current IP protocol has two major limitations: there is an increasing shortage
of IP addresses, and configuring the network and maintaining the routing tables is becoming
a more complex and burdensome task. IPv6 solves the rst problem by expanding the address
space to 128 bits. The second one is mitigated by introducing a hierarchical address structure
combined with sophisticated techniques to allocate network addresses, and multihoming (the
ability to assign several addresses to one device, giving access to several networks).
197 Address Types and Structure SLES 12 SP3

When dealing with IPv6, it is useful to know about three different types of addresses:
Unicast
Addresses of this type are associated with exactly one network interface. Packets with such
an address are delivered to only one destination. Accordingly, unicast addresses are used
to transfer packets to individual hosts on the local network or the Internet.
Multicast
Addresses of this type relate to a group of network interfaces. Packets with such an address
are delivered to all destinations that belong to the group. Multicast addresses are mainly
used by certain network services to communicate with certain groups of hosts in a well-
directed manner.
Anycast
Addresses of this type are related to a group of interfaces. Packets with such an address
are delivered to the member of the group that is closest to the sender, according to the
principles of the underlying routing protocol. Anycast addresses are used to make it easier
for hosts to nd out about servers offering certain services in the given network area. All
servers of the same type have the same anycast address. Whenever a host requests a service,
it receives a reply from the server with the closest location, as determined by the routing
protocol. If this server should fail for some reason, the protocol automatically selects the
second closest server, then the third one, and so forth.
An IPv6 address is made up of eight four-digit elds, each representing 16 bits, written in hexa-
decimal notation. They are separated by colons ( : ). Any leading zero bytes within a given eld
may be dropped, but zeros within the eld or at its end may not. Another convention is that
more than four consecutive zero bytes may be collapsed into a double colon. However, only
one such :: is allowed per address. This kind of shorthand notation is shown in Example 16.3,
“Sample IPv6 Address”, where all three lines represent the same address.
EXAMPLE 16.3: SAMPLE IPV6 ADDRESS
fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4

fe80 : 0 : 0 : 0 : 0 : 10 : 1000 : 1a4
fe80 : : 10 : 1000 : 1a4
Each part of an IPv6 address has a defined function. The rst bytes form the prefix and specify
the type of address. The center part is the network portion of the address, but it may be unused.
The end of the address forms the host part. With IPv6, the netmask is defined by indicating the
length of the prefix after a slash at the end of the address. An address, as shown in Example 16.4,

“IPv6 Address Specifying the Prefix Length”, contains the information that the rst 64 bits form the
network part of the address and the last 64 form its host part. In other words, the 64 means that
the netmask is lled with 64 1-bit values from the left. As with IPv4, the IP address is combined
with AND with the values from the netmask to determine whether the host is located in the
same subnet or in another one.
EXAMPLE 16.4: IPV6 ADDRESS SPECIFYING THE PREFIX LENGTH
fe80::10:1000:1a4/64
IPv6 knows about several predefined types of prefixes. Some are shown in Various IPv6 Prefixes.
VARIOUS IPV6 PREFIXES
00
IPv4 addresses and IPv4 over IPv6 compatibility addresses. These are used to maintain
compatibility with IPv4. Their use still requires a router able to translate IPv6 packets into
IPv4 packets. Several special addresses, such as the one for the loopback device, have this
prefix as well.
2 or 3 as the first digit

Aggregatable global unicast addresses. As is the case with IPv4, an interface can be as-
signed to form part of a certain subnet. Currently, there are the following address spaces:
2001::/16 (production quality address space) and 2002::/16 (6to4 address space).
fe80::/10
Link-local addresses. Addresses with this prefix should not be routed and should therefore
only be reachable from within the same subnet.
fec0::/10
Site-local addresses. These may be routed, but only within the network of the organization
to which they belong. In effect, they are the IPv6 equivalent of the current private network
address space, such as 10.x.x.x .
ff
These are multicast addresses.
A unicast address consists of three basic components:
Public Topology
The rst part (which also contains one of the prefixes mentioned above) is used to route
packets through the public Internet. It includes information about the company or institu-
tion that provides the Internet access.

Site Topology
The second part contains routing information about the subnet to which to deliver the
packet.
Interface ID
The third part identifies the interface to which to deliver the packet. This also allows for the
MAC to form part of the address. Given that the MAC is a globally unique, xed identifier
coded into the device by the hardware maker, the configuration procedure is substantially
simplified. In fact, the rst 64 address bits are consolidated to form the EUI-64 token,
with the last 48 bits taken from the MAC, and the remaining 24 bits containing special
information about the token type. This also makes it possible to assign an EUI-64 token
to interfaces that do not have a MAC, such as those based on PPP.
On top of this basic structure, IPv6 distinguishes between ve different types of unicast address-
es:
:: (unspecified)
This address is used by the host as its source address when the interface is initialized for
the rst time (at which point, the address cannot yet be determined by other means).
::1 (loopback)
The address of the loopback device.
IPv4 Compatible Addresses

The IPv6 address is formed by the IPv4 address and a prefix consisting of 96 zero bits.
This type of compatibility address is used for tunneling (see Section 16.2.3, “Coexistence of
IPv4 and IPv6”) to allow IPv4 and IPv6 hosts to communicate with others operating in a
pure IPv4 environment.
IPv4 Addresses Mapped to IPv6

This type of address specifies a pure IPv4 address in IPv6 notation.
Local Addresses
There are two address types for local use:
link-local
This type of address can only be used in the local subnet. Packets with a source or
target address of this type should not be routed to the Internet or other subnets. These
addresses contain a special prefix ( fe80::/10 ) and the interface ID of the network

card, with the middle part consisting of zero bytes. Addresses of this type are used
during automatic configuration to communicate with other hosts belonging to the
same subnet.
site-local
Packets with this type of address may be routed to other subnets, but not to the wider
Internet—they must remain inside the organization's own network. Such addresses
are used for intranets and are an equivalent of the private address space defined by
IPv4. They contain a special prefix ( fec0::/10 ), the interface ID, and a 16 bit eld
specifying the subnet ID. Again, the rest is lled with zero bytes.
As a completely new feature introduced with IPv6, each network interface normally gets several
IP addresses, with the advantage that several networks can be accessed through the same inter-
face. One of these networks can be configured completely automatically using the MAC and a
known prefix with the result that all hosts on the local network can be reached when IPv6 is en-
abled (using the link-local address). With the MAC forming part of it, any IP address used in the
world is unique. The only variable parts of the address are those specifying the site topology and
the public topology, depending on the actual network in which the host is currently operating.
For a host to go back and forth between different networks, it needs at least two addresses. One
of them, the home address, not only contains the interface ID but also an identifier of the home
network to which it normally belongs (and the corresponding prefix). The home address is a
static address and, as such, it does not normally change. Still, all packets destined to the mobile
host can be delivered to it, regardless of whether it operates in the home network or somewhere
outside. This is made possible by the completely new features introduced with IPv6, such as
stateless autoconfiguration and neighbor discovery. In addition to its home address, a mobile host
gets one or more additional addresses that belong to the foreign networks where it is roaming.
These are called care-of addresses. The home network has a facility that forwards any packets
destined to the host when it is roaming outside. In an IPv6 environment, this task is performed
by the home agent, which takes all packets destined to the home address and relays them through
a tunnel. On the other hand, those packets destined to the care-of address are directly transferred
to the mobile host without any special detours.
16.2.3 Coexistence of IPv4 and IPv6

The migration of all hosts connected to the Internet from IPv4 to IPv6 is a gradual process.
Both protocols will coexist for some time to come. The coexistence on one system is guaranteed
where there is a dual stack implementation of both protocols. That still leaves the question of
201 Coexistence of IPv4 and IPv6 SLES 12 SP3

how an IPv6 enabled host should communicate with an IPv4 host and how IPv6 packets should
be transported by the current networks, which are predominantly IPv4-based. The best solutions
offer tunneling and compatibility addresses (see Section 16.2.2, “Address Types and Structure”).
IPv6 hosts that are more or less isolated in the (worldwide) IPv4 network can communicate
through tunnels: IPv6 packets are encapsulated as IPv4 packets to move them across an IPv4
network. Such a connection between two IPv4 hosts is called a tunnel. To achieve this, packets
must include the IPv6 destination address (or the corresponding prefix) and the IPv4 address of
the remote host at the receiving end of the tunnel. A basic tunnel can be configured manually
according to an agreement between the hosts' administrators. This is also called static tunneling.
However, the configuration and maintenance of static tunnels is often too labor-intensive to use
them for daily communication needs. Therefore, IPv6 provides for three different methods of
dynamic tunneling:
6over4
IPv6 packets are automatically encapsulated as IPv4 packets and sent over an IPv4 network
capable of multicasting. IPv6 is tricked into seeing the whole network (Internet) as a huge
local area network (LAN). This makes it possible to determine the receiving end of the IPv4
tunnel automatically. However, this method does not scale very well and is also hampered
because IP multicasting is far from widespread on the Internet. Therefore, it only provides a
solution for smaller corporate or institutional networks where multicasting can be enabled.
The specifications for this method are laid down in RFC 2529.
6to4
With this method, IPv4 addresses are automatically generated from IPv6 addresses, en-
abling isolated IPv6 hosts to communicate over an IPv4 network. However, several prob-
lems have been reported regarding the communication between those isolated IPv6 hosts
and the Internet. The method is described in RFC 3056.
IPv6 Tunnel Broker

This method relies on special servers that provide dedicated tunnels for IPv6 hosts. It is
described in RFC 3053.
202 Coexistence of IPv4 and IPv6 SLES 12 SP3

16.2.4 Configuring IPv6
To configure IPv6, you normally do not need to make any changes on the individual worksta-
tions. IPv6 is enabled by default. To disable or enable IPv6 on an installed system, use the YaST
Network Settings module. On the Global Options tab, check or uncheck the Enable IPv6 option as
necessary. To enable it temporarily until the next reboot, enter modprobe -i ipv6 as root .
It is impossible to unload the IPv6 module after it has been loaded.
Because of the autoconfiguration concept of IPv6, the network card is assigned an address in
the link-local network. Normally, no routing table management takes place on a workstation.
The network routers can be queried by the workstation, using the router advertisement protocol,
for what prefix and gateways should be implemented. The radvd program can be used to set
up an IPv6 router. This program informs the workstations which prefix to use for the IPv6
addresses and which routers. Alternatively, use zebra/quagga for automatic configuration of
both addresses and routing.
For information about how to set up various types of tunnels using the /etc/sysconfig/net-
work les, see the man page of ifcfg-tunnel ( man ifcfg-tunnel ).

The above overview does not cover the topic of IPv6 comprehensively. For a more in-depth look
at the new protocol, refer to the following online documentation and books:
http://www.ipv6.org/
The starting point for everything about IPv6.
http://www.ipv6day.org
All information needed to start your own IPv6 network.
http://www.ipv6-to-standard.org/
The list of IPv6-enabled products.
http://www.bieringer.de/linux/IPv6/
Here, nd the Linux IPv6-HOWTO and many links related to the topic.
RFC 2460
The fundamental RFC about IPv6.
203 Configuring IPv6 SLES 12 SP3

IPv6 Essentials
A book describing all the important aspects of the topic is IPv6 Essentials by Silvia Hagen
(ISBN 0-596-00125-8).
16.3 Name Resolution

DNS assists in assigning an IP address to one or more names and assigning a name to an IP
address. In Linux, this conversion is usually carried out by a special type of software known as
bind. The machine that takes care of this conversion is called a name server. The names make
up a hierarchical system in which each name component is separated by a period. The name
hierarchy is, however, independent of the IP address hierarchy described above.
Consider a complete name, such as jupiter.example.com , written in the format host-
name.domain . A full name, called a fully qualified domain name (FQDN), consists of a host name
and a domain name ( example.com ). The latter also includes the top level domain or TLD ( com ).
TLD assignment has become quite confusing for historical reasons. Traditionally, three-letter
domain names are used in the USA. In the rest of the world, the two-letter ISO national codes
are the standard. In addition to that, longer TLDs were introduced in 2000 that represent certain
spheres of activity (for example, .info , .name , .museum ).
In the early days of the Internet (before 1990), the le /etc/hosts was used to store the names
of all the machines represented over the Internet. This quickly proved to be impractical in the
face of the rapidly growing number of computers connected to the Internet. For this reason, a
decentralized database was developed to store the host names in a widely distributed manner.
This database, similar to the name server, does not have the data pertaining to all hosts in the
Internet readily available, but can dispatch requests to other name servers.
The top of the hierarchy is occupied by root name servers. These root name servers manage the
top level domains and are run by the Network Information Center (NIC). Each root name server
knows about the name servers responsible for a given top level domain. Information about top
level domain NICs is available at http://www.internic.net .
DNS can do more than resolve host names. The name server also knows which host is receiving
e-mails for an entire domain—the mail exchanger (MX).
For your machine to resolve an IP address, it must know about at least one name server and
its IP address. Easily specify such a name server using YaST. The configuration of name server
access with SUSE® Linux Enterprise Server is described in Section 16.4.1.4, “Configuring Host Name
and DNS”. Setting up your own name server is described in Chapter 25, The Domain Name System.
204 Name Resolution SLES 12 SP3

The protocol whois is closely related to DNS. With this program, quickly nd out who is re-
sponsible for a given domain.
Note: MDNS and .local Domain Names

The .local top level domain is treated as link-local domain by the resolver. DNS requests
are send as multicast DNS requests instead of normal DNS requests. If you already use
the .local domain in your name server configuration, you must switch this option o
in /etc/host.conf . For more information, see the host.conf manual page.
If you want to switch o MDNS during installation, use nomdns=1 as a boot parameter.
For more information on multicast DNS, see http://www.multicastdns.org .
16.4 Configuring a Network Connection with YaST

There are many supported networking types on Linux. Most of them use different device names
and the configuration les are spread over several locations in the le system. For a detailed
overview of the aspects of manual network configuration, see Section 16.5, “Configuring a Network
Connection Manually”.
All network interfaces with link up (with a network cable connected) are automatically config-
ured. Additional hardware can be configured any time on the installed system. The following
sections describe the network configuration for all types of network connections supported by
SUSE Linux Enterprise Server.
Tip: IBM z Systems: Hotpluggable Network Cards

On IBM z Systems platforms, hotpluggable network cards are supported, but not their
automatic network integration via DHCP (as is the case on the PC). After detection, man-
ually configure the interface.
16.4.1 Configuring the Network Card with YaST

To configure your Ethernet or Wi-Fi/Bluetooth card in YaST, select System Network Settings.
After starting the module, YaST displays the Network Settings dialog with four tabs: Global Op-
tions, Overview, Hostname/DNS and Routing.
205 Configuring a Network Connection with YaST SLES 12 SP3

The Global Options tab allows you to set general networking options such as the network setup
method, IPv6, and general DHCP options. For more information, see Section 16.4.1.1, “Configuring
Global Networking Options”.
The Overview tab contains information about installed network interfaces and configurations.
Any properly detected network card is listed with its name. You can manually configure new
cards, remove or change their configuration in this dialog. To manually configure a card that was
not automatically detected, see Section 16.4.1.3, “Configuring an Undetected Network Card”. If you
want to change the configuration of an already configured card, see Section 16.4.1.2, “Changing
the Configuration of a Network Card”.
The Hostname/DNS tab allows to set the host name of the machine and name the servers to be
used. For more information, see Section 16.4.1.4, “Configuring Host Name and DNS”.
The Routing tab is used for the configuration of routing. See Section 16.4.1.5, “Configuring Routing”
for more information.
FIGURE 16.3: CONFIGURING NETWORK SETTINGS
206 Configuring the Network Card with YaST SLES 12 SP3

16.4.1.1 Configuring Global Networking Options
The Global Options tab of the YaST Network Settings module allows you to set important global
networking options, such as the use of NetworkManager, IPv6 and DHCP client options. These
settings are applicable for all network interfaces.
Note: NetworkManager Provided by Workstation Extension

NetworkManager is now provided by the Workstation Extension. To install Network-
Manager, activate the Workstation Extension repository, and select the NetworkManager
packages.
In the Network Setup Method choose the way network connections are managed. If you want a
NetworkManager desktop applet to manage connections for all interfaces, choose NetworkMan-
ager Service. NetworkManager is well suited for switching between multiple wired and wireless
networks. If you do not run a desktop environment, or if your computer is a Xen server, virtual
system, or provides network services such as DHCP or DNS in your network, use the Wicked
Service method. If NetworkManager is used, nm-applet should be used to configure network
options and the Overview, Hostname/DNS and Routing tabs of the Network Settings module are
disabled. For more information on NetworkManager, see the SUSE Linux Enterprise Desktop
documentation.
In the IPv6 Protocol Settings choose whether to use the IPv6 protocol. It is possible to use IPv6
together with IPv4. By default, IPv6 is enabled. However, in networks not using IPv6 protocol,
response times can be faster with IPv6 protocol disabled. To disable IPv6, deactivate Enable
IPv6. If IPv6 is disabled, the kernel no longer loads the IPv6 module automatically. This setting
will be applied after reboot.
In the DHCP Client Options configure options for the DHCP client. The DHCP Client Identifier must
be different for each DHCP client on a single network. If left empty, it defaults to the hardware
address of the network interface. However, if you are running several virtual machines using
the same network interface and, therefore, the same hardware address, specify a unique free-
form identifier here.
The Hostname to Send specifies a string used for the host name option eld when the DHCP client
sends messages to DHCP server. Some DHCP servers update name server zones (forward and
reverse records) according to this host name (Dynamic DNS). Also, some DHCP servers require

the Hostname to Send option eld to contain a specific string in the DHCP messages from clients.
Leave AUTO to send the current host name (that is the one defined in /etc/HOSTNAME ). Make
the option eld empty for not sending any host name.
If you do not want to change the default route according to the information from DHCP, deac-
tivate Change Default Route via DHCP.
16.4.1.2 Changing the Configuration of a Network Card
To change the configuration of a network card, select a card from the list of the detected cards
in Network Settings Overview in YaST and click Edit. The Network Card Setup dialog appears in
which to adjust the card configuration using the General, Address and Hardware tabs.
16.4.1.2.1 Configuring IP Addresses
You can set the IP address of the network card or the way its IP address is determined in the
Address tab of the Network Card Setup dialog. Both IPv4 and IPv6 addresses are supported. The
network card can have No IP Address (which is useful for bonding devices), a Statically Assigned
IP Address (IPv4 or IPv6) or a Dynamic Address assigned via DHCP or Zeroconf or both.
If using Dynamic Address, select whether to use DHCP Version 4 Only (for IPv4), DHCP Version
6 Only (for IPv6) or DHCP Both Version 4 and 6.
If possible, the rst network card with link that is available during the installation is automati-
cally configured to use automatic address setup via DHCP.
Note: IBM z Systems and DHCP

On IBM z Systems platforms, DHCP-based address configuration is only supported with
network cards that have a MAC address. This is only the case with OSA and OSA Express
cards.
DHCP should also be used if you are using a DSL line but with no static IP assigned by the
ISP (Internet Service Provider). If you decide to use DHCP, configure the details in DHCP Client
Options in the Global Options tab of the Network Settings dialog of the YaST network card config-
uration module. If you have a virtual host setup where different hosts communicate through the
same interface, an DHCP Client Identifier is necessary to distinguish them.

DHCP is a good choice for client configuration but it is not ideal for server configuration. To
set a static IP address, proceed as follows:
1. Select a card from the list of detected cards in the Overview tab of the YaST network card
configuration module and click Edit.
2. In the Address tab, choose Statically Assigned IP Address.
3. Enter the IP Address. Both IPv4 and IPv6 addresses can be used. Enter the network mask in
Subnet Mask. If the IPv6 address is used, use Subnet Mask for prefix length in format /64 .
Optionally, you can enter a fully qualified Hostname for this address, which will be written
to the /etc/hosts configuration le.
4. Click Next.
5. To activate the configuration, click OK.
Note: Interface Activation and Link Detection

During activation of a network interface, wicked checks for a carrier and only applies
the IP configuration when a link has been detected. If you need to apply the configuration
regardless of the link status (for example, when you want to test a service listening to a
certain address), you can skip link detection by adding the variable LINK_REQUIRED=no
to the configuration le of the interface in /etc/sysconfig/network/ifcfg .
Additionally, you can use the variable LINK_READY_WAIT=5 to specify the timeout for
waiting for a link in seconds.
For more information about the ifcfg-* configuration les, refer to Section 16.5.2.5, “/
etc/sysconfig/network/ifcfg-*” and man 5 ifcfg .
If you use the static address, the name servers and default gateway are not configured automat-
ically. To configure name servers, proceed as described in Section 16.4.1.4, “Configuring Host Name
and DNS”. To configure a gateway, proceed as described in Section 16.4.1.5, “Configuring Routing”.
16.4.1.2.2 Configuring Multiple Addresses
One network device can have multiple IP addresses.

Note: Aliases Are a Compatibility Feature
These so-called aliases or labels, respectively, work with IPv4 only. With IPv6 they will
be ignored. Using iproute2 network interfaces can have one or more addresses.
Using YaST to set additional addresses for your network card, proceed as follows:
1. Select a card from the list of detected cards in the Overview tab of the YaST Network Settings
dialog and click Edit.
2. In the Address Additional Addresses tab, click Add.
3. Enter IPv4 Address Label, IP Address, and Netmask. Do not include the interface name in
the alias name.
4. To activate the configuration, confirm the settings.
16.4.1.2.3 Changing the Device Name and Udev Rules
It is possible to change the device name of the network card when it is used. It is also possible
to determine whether the network card should be identified by udev via its hardware (MAC)
address or via the bus ID. The later option is preferable in large servers to simplify hotplugging
of cards. To set these options with YaST, proceed as follows:
1. Select a card from the list of detected cards in the Overview tab of the YaST Network Settings
dialog and click Edit.
2. Go to the Hardware tab. The current device name is shown in Udev Rules. Click Change.
3. Select whether udev should identify the card by its MAC Address or Bus ID. The current
MAC address and bus ID of the card are shown in the dialog.
4. To change the device name, check the Change Device Name option and edit the name.

16.4.1.2.4 Changing Network Card Kernel Driver
For some network cards, several kernel drivers may be available. If the card is already config-
ured, YaST allows you to select a kernel driver to be used from a list of available suitable dri-
vers. It is also possible to specify options for the kernel driver. To set these options with YaST,
proceed as follows:
1. Select a card from the list of detected cards in the Overview tab of the YaST Network
Settings module and click Edit.
2. Go to the Hardware tab.
3. Select the kernel driver to be used in Module Name. Enter any options for the selected
driver in Options in the form = = VALUE . If more options are used, they should be space-
separated.
16.4.1.2.5 Activating the Network Device
If you use the method with wicked , you can configure your device to either start during boot,
on cable connection, on card detection, manually, or never. To change device start-up, proceed
as follows:
1. In YaST select a card from the list of detected cards in System Network Settings and click
Edit.
2. In the General tab, select the desired entry from Device Activation.
Choose At Boot Time to start the device during the system boot. With On Cable Connection,
the interface is watched for any existing physical connection. With On Hotplug, the inter-
face is set when available. It is similar to the At Boot Time option, and only differs in that
no error occurs if the interface is not present at boot time. Choose Manually to control the
interface manually with ifup . Choose Never to not start the device. The On NFSroot is
similar to At Boot Time, but the interface does not shut down with the systemctl stop
network command; the network service also cares about the wicked service if wicked
is active. Use this if you use an NFS or iSCSI root le system.

Tip: NFS as a Root File System
On (diskless) systems where the root partition is mounted via network as an NFS share,
you need to be careful when configuring the network device with which the NFS share
is accessible.
When shutting down or rebooting the system, the default processing order is to turn o
network connections, then unmount the root partition. With NFS root, this order causes
problems as the root partition cannot be cleanly unmounted as the network connection
to the NFS share is already not activated. To prevent the system from deactivating the
relevant network device, open the network device configuration tab as described in Sec-
tion 16.4.1.2.5, “Activating the Network Device” and choose On NFSroot in the Device Activation
pane.
16.4.1.2.6 Setting Up Maximum Transfer Unit Size
You can set a maximum transmission unit (MTU) for the interface. MTU refers to the largest
allowed packet size in bytes. A higher MTU brings higher bandwidth efficiency. However, large
packets can block up a slow interface for some time, increasing the lag for further packets.
1. In YaST select a card from the list of detected cards in System Network Settings and click
Edit.
2. In the General tab, select the desired entry from the Set MTU list.
16.4.1.2.7 PCIe Multifunction Devices
Multifunction devices that support LAN, iSCSI, and FCoE are supported. YaST FCoE client
( yast2 fcoe-client ) shows the private ags in additional columns to allow the user to select
the device meant for FCoE. YaST network module ( yast2 lan ) excludes “storage only devices”
for network configuration.
For more information about FCoE, see Book “Storage Administration Guide”, Chapter 15 “Fibre Chan-
nel Storage over Ethernet Networks: FCoE”, Section 15.3 “Managing FCoE Services with YaST”.

16.4.1.2.8 Infiniband Configuration for IP-over-InfiniBand (IPoIB)
1. In YaST select the InfiniBand device in System Network Settings and click Edit.
2. In the General tab, select one of the IP-over-InfiniBand (IPoIB) modes: connected (default)
or datagram.
For more information about InfiniBand, see /usr/src/linux/Documentation/infini-

band/ipoib.txt .
16.4.1.2.9 Configuring the Firewall
Without having to enter the detailed firewall setup as described in Book “Security Guide”, Chap-
ter 15 “Masquerading and Firewalls”, Section 15.4.1 “Configuring the Firewall with YaST”, you can deter-
mine the basic firewall configuration for your device as part of the device setup. Proceed as
follows:
1. Open the YaST System Network Settings module. In the Overview tab, select a card from
the list of detected cards and click Edit.
2. Enter the General tab of the Network Settings dialog.
3. Determine the Firewall Zone to which your interface should be assigned. The following
options are available:
Firewall Disabled
This option is available only if the firewall is disabled and the firewall does not run.
Only use this option if your machine is part of a greater network that is protected
by an outer firewall.
Automatically Assign Zone

This option is available only if the firewall is enabled. The firewall is running and
the interface is automatically assigned to a firewall zone. The zone which contains
the keyword any or the external zone will be used for such an interface.

Internal Zone (Unprotected)
The firewall is running, but does not enforce any rules to protect this interface. Use
this option if your machine is part of a greater network that is protected by an outer
firewall. It is also useful for the interfaces connected to the internal network, when
the machine has more network interfaces.
Demilitarized Zone
A demilitarized zone is an additional line of defense in front of an internal network
and the (hostile) Internet. Hosts assigned to this zone can be reached from the inter-
nal network and from the Internet, but cannot access the internal network.
External Zone
The firewall is running on this interface and fully protects it against other—presum-
ably hostile—network traffic. This is the default option.
16.4.1.3 Configuring an Undetected Network Card
If a network card is not detected correctly, the card is not included in the list of detected cards.
If you are sure that your system includes a driver for your card, you can configure it manually.
You can also configure special network device types, such as bridge, bond, TUN or TAP. To
configure an undetected network card (or a special device) proceed as follows:
1. In the System Network Settings Overview dialog in YaST click Add.
2. In the Hardware dialog, set the Device Type of the interface from the available options and
Configuration Name. If the network card is a PCMCIA or USB device, activate the respective
check box and exit this dialog with Next. Otherwise, you can define the kernel Module
Name to be used for the card and its Options, if necessary.
In Ethtool Options, you can set ethtool options used by ifup for the interface. For infor-
mation about available options, see the ethtool manual page.
If the option string starts with a - (for example, -K INTERFACE_NAME rx on ), the second
word in the string is replaced with the current interface name. Otherwise (for example,
autoneg off speed 10 ) ifup adds -s INTERFACE_NAME to the beginning.
3. Click Next.

4. Configure any needed options, such as the IP address, device activation or firewall zone
for the interface in the General, Address, and Hardware tabs. For more information about
the configuration options, see Section 16.4.1.2, “Changing the Configuration of a Network Card”.
5. If you selected Wireless as the device type of the interface, configure the wireless connec-
tion in the next dialog.
6. To activate the new network configuration, confirm the settings.
16.4.1.4 Configuring Host Name and DNS
If you did not change the network configuration during installation and the Ethernet card was
already available, a host name was automatically generated for your computer and DHCP was
activated. The same applies to the name service information your host needs to integrate into
a network environment. If DHCP is used for network address setup, the list of domain name
servers is automatically lled with the appropriate data. If a static setup is preferred, set these
values manually.
To change the name of your computer and adjust the name server search list, proceed as follows:
1. Go to the Network Settings Hostname/DNS tab in the System module in YaST.
2. Enter the Hostname and, if needed, the Domain Name. The domain is especially important
if the machine is a mail server. Note that the host name is global and applies to all set
network interfaces.
If you are using DHCP to get an IP address, the host name of your computer will be
automatically set by the DHCP. You should disable this behavior if you connect to different
networks, because they may assign different host names and changing the host name at
runtime may confuse the graphical desktop. To disable using DHCP to get an IP address
deactivate Change Hostname via DHCP.
Assign Hostname to Loopback IP associates your host name with 127.0.0.2 (loopback)
IP address in /etc/hosts . This is a useful option if you want to have the host name
resolvable at all times, even without active network.
3. In Modify DNS Configuration, select the way the DNS configuration (name servers, search
list, the content of the /etc/resolv.conf le) is modified.

If the Use Default Policy option is selected, the configuration is handled by the netconfig
script which merges the data defined statically (with YaST or in the configuration les)
with data obtained dynamically (from the DHCP client or NetworkManager). This default
policy is usually sufficient.
If the Only Manually option is selected, netconfig is not allowed to modify the /etc/
resolv.conf le. However, this le can be edited manually.
If the Custom Policy option is selected, a Custom Policy Rule string defining the merge policy
should be specified. The string consists of a comma-separated list of interface names to be
considered a valid source of settings. Except for complete interface names, basic wild cards
to match multiple interfaces are allowed, as well. For example, eth* ppp? will rst target
all eth and then all ppp0-ppp9 interfaces. There are two special policy values that indicate
how to apply the static settings defined in the /etc/sysconfig/network/config le:
STATIC
The static settings need to be merged together with the dynamic settings.
STATIC_FALLBACK
The static settings are used only when no dynamic configuration is available.
For more information, see the man page of netconfig (8) ( man 8 netconfig ).
4. Enter the Name Servers and ll in the Domain Search list. Name servers must be specified
by IP addresses, such as 192.168.1.116, not by host names. Names specified in the Domain
Search tab are domain names used for resolving host names without a specified domain.
If more than one Domain Search is used, separate domains with commas or white space.
It is also possible to edit the host name using YaST from the command line. The changes made
by YaST take effect immediately (which is not the case when editing the /etc/HOSTNAME le
manually). To change the host name, use the following command:
yast dns edit hostname=HOSTNAME
To change the name servers, use the following commands:
yast dns edit nameserver1=192.168.1.116


16.4.1.5 Configuring Routing
To make your machine communicate with other machines and other networks, routing infor-
mation must be given to make network traffic take the correct path. If DHCP is used, this infor-
mation is automatically provided. If a static setup is used, this data must be added manually.
1. In YaST go to Network Settings Routing.
2. Enter the IP address of the Default Gateway (IPv4 and IPv6 if necessary). The default
gateway matches every possible destination, but if a routing table entry exists that matches
the required address, this will be used instead of the default route via the Default Gateway.
3. More entries can be entered in the Routing Table. Enter the Destination network IP address,
Gateway IP address and the Netmask. Select the Device through which the traffic to the
defined network will be routed (the minus sign stands for any device). To omit any of
these values, use the minus sign - . To enter a default gateway into the table, use default
in the Destination eld.
Note: Route Prioritization

If more default routes are used, it is possible to specify the metric option to de-
termine which route has a higher priority. To specify the metric option, enter -
metric NUMBER in Options. The route with the highest metric is used as default.
If the network device is disconnected, its route will be removed and the next one
will be used. However, the current kernel does not use metric in static routing, only
routing daemons like multipathd do.
4. If the system is a router, enable IPv4 Forwarding and IPv6 Forwarding in the Network Settings
as needed.
16.4.2 IBM z Systems: Configuring Network Devices

SUSE Linux Enterprise Server for IBM z Systems supports several types of network interfaces.
YaST can be used to configure all of them.
217 IBM z Systems: Configuring Network Devices SLES 12 SP3

16.4.2.1 The qeth-hsi Device
To add a qeth-hsi (Hipersockets) interface to the installed system, start the System Network
Settings module in YaST. Select one of the devices marked Hipersocket to use as the READ device
address and click Edit. Enter the device numbers for the read, write and control channels (ex-
ample device number format: 0.0.0800 ). Then click next. In the Network Address Setup dialog,
specify the IP address and netmask for the new interface and leave the network configuration
by clicking Next and OK.
16.4.2.2 The qeth-ethernet Device
To add a qeth-ethernet (IBM OSA Express Ethernet Card) interface to the installed system,
start the System Network Settings module in YaST. Select one of the devices marked IBM OSA
Express Ethernet Card to use as the READ device address and click Edit. Enter a device number
for the read, write and control channels (example device number format: 0.0.0700 ). Enter
the needed port name, port number (if applicable) and some additional options (see the Linux
for IBM z Systems: Device Drivers, Features, and Commands manual for reference, http://www.ib-
m.com/developerworks/linux/linux390/documentation_suse.html ), your IP address, and an ap-
propriate netmask. Leave the network configuration with Next and OK.
16.4.2.3 The ctc Device
To add a ctc (IBM parallel CTC Adapter) interface to the installed system, start the System Net-
work Settings module in YaST. Select one of the devices marked IBM Parallel CTC Adapter to
use as your read channel and click Configure. Choose the Device Settings that t your devices
(usually this would be Compatibility Mode). Specify both your IP address and the IP address of
the remote partner. If needed, adjust the MTU size with Advanced Detailed Settings. Leave the
network configuration with Next and OK.
Warning: CTC is no Longer Supported

The use of this interface is deprecated. This interface will not be supported in future
versions of SUSE Linux Enterprise Server.
218 IBM z Systems: Configuring Network Devices SLES 12 SP3

16.4.2.4 The lcs Device
To add an lcs (IBM OSA-2 Adapter) interface to the installed system, start the System Network
Settings module in YaST. Select one of the devices marked IBM OSA-2 Adapter and click Configure.
Enter the needed port number, some additional options (see the Linux for IBM z Systems: Device
Drivers, Features, and Commands manual for reference, http://www.ibm.com/developerworks/lin-
ux/linux390/documentation_suse.html ), your IP address and an appropriate netmask. Leave
the network configuration with Next and OK.
16.4.2.5 The IUCV Device
To add an iucv (IUCV) interface to the installed system, start the System Network Settings
module in YaST. Select a device marked IUCV and click Edit. YaST prompts you for the name of
your IUCV partner (Peer). Enter the name (this entry is case-sensitive) and select Next. Specify
both the IP Address and the Remote IP Address of your partner. If needed, Set MTU size on General
tab. Leave the network configuration with Next and OK.
Warning: IUCV is no Longer Supported

The use of this interface is deprecated. This interface will not be supported in future
versions of SUSE Linux Enterprise Server.
16.5 Configuring a Network Connection Manually

Manual configuration of the network software should be the last alternative. Using YaST is
recommended. However, this background information about the network configuration can also
assist your work with YaST.
16.5.1 The wicked Network Configuration

The tool and library called wicked provides a new framework for network configuration.
One of the challenges with traditional network interface management is that different layers
of network management get jumbled together into one single script, or at most two different
scripts. These scripts interact with each other in a way that is not well-defined. This leads to un-
219 Configuring a Network Connection Manually SLES 12 SP3

predictable issues, obscure constraints and conventions, etc. Several layers of special hacks for a
variety of different scenarios increase the maintenance burden. Address configuration protocols
are being used that are implemented via daemons like dhcpcd, which interact rather poorly with
the rest of the infrastructure. Funky interface naming schemes that require heavy udev support
are introduced to achieve persistent identification of interfaces.
The idea of wicked is to decompose the problem in several ways. None of them is entirely novel,
but trying to put ideas from different projects together is hopefully going to create a better
solution overall.
One approach is to use a client/server model. This allows wicked to define standardized facilities
for things like address configuration that are well integrated with the overall framework. For
example, using a specific address configuration, the administrator may request that an interface
should be configured via DHCP or IPv4 zeroconf. In this case, the address configuration service
simply obtains the lease from its server and passes it on to the wicked server process that installs
the requested addresses and routes.
The other approach to decomposing the problem is to enforce the layering aspect. For any type
of network interface, it is possible to define a dbus service that configures the network interface's
device layer—a VLAN, a bridge, a bonding, or a paravirtualized device. Common functionality,
such as address configuration, is implemented by joint services that are layered on top of these
device specific services without having to implement them specifically.
The wicked framework implements these two aspects by using a variety of dbus services, which
get attached to a network interface depending on its type. Here is a rough overview of the
current object hierarchy in wicked.
Each network interface is represented via a child object of /org/opensuse/Network/Inter-
faces . The name of the child object is given by its ifindex. For example, the loopback interface,
which usually gets ifindex 1, is /org/opensuse/Network/Interfaces/1 , the rst Ethernet in-
terface registered is /org/opensuse/Network/Interfaces/2 .
Each network interface has a “class” associated with it, which is used to select the dbus interfaces
it supports. By default, each network interface is of class netif , and wickedd will automatically
attach all interfaces compatible with this class. In the current implementation, this includes the
following interfaces:
org.opensuse.Network.Interface
Generic network interface functions, such as taking the link up or down, assigning an MTU,
etc.
220 The wicked Network Configuration SLES 12 SP3

org.opensuse.Network.Addrconf.ipv4.dhcp,
org.opensuse.Network.Addrconf.ipv6.dhcp,
org.opensuse.Network.Addrconf.ipv4.auto
Address configuration services for DHCP, IPv4 zeroconf, etc.
Beyond this, network interfaces may require or offer special configuration mechanisms. For an
Ethernet device, for example, you should be able to control the link speed, offloading of check-
summing, etc. To achieve this, Ethernet devices have a class of their own, called netif-ether-
net , which is a subclass of netif . As a consequence, the dbus interfaces assigned to an Ether-
net interface include all the services listed above, plus the org.opensuse.Network.Ethernet
service available only to objects belonging to the netif-ethernet class.
Similarly, there exist classes for interface types like bridges, VLANs, bonds, or infinibands.
How do you interact with an interface like VLAN (which is really a virtual network interface that
sits on top of an Ethernet device) that needs to be created rst? For this, wicked defines factory
interfaces, such as org.opensuse.Network.VLAN.Factory . Such a factory interface offers a
single function that lets you create an interface of the requested type. These factory interfaces
are attached to the /org/opensuse/Network/Interfaces list node.
16.5.1.1 wicked Architecture and Features
The wicked service comprises several parts as depicted in Figure 16.4, “wicked architecture”.
FIGURE 16.4: wicked ARCHITECTURE

wicked currently supports the following:
Configuration le back-ends to parse SUSE style /etc/sysconfig/network les.
An internal configuration back-end to represent network interface configuration in XML.
Bring up and shutdown of “normal” network interfaces such as Ethernet or InfiniBand,

VLAN, bridge, bonds, tun, tap, dummy, macvlan, macvtap, hsi, qeth, iucv, and wireless
(currently limited to one wpa-psk/eap network) devices.
A built-in DHCPv4 client and a built-in DHCPv6 client.
The nanny daemon (enabled by default) helps to automatically bring up configured inter-
faces when the device is available (interface hotplugging) and set up the IP configuration
when a link (carrier) is detected. See Section 16.5.1.3, “Nanny” for more information.
wicked was implemented as a group of DBus services that are integrated with systemd.
So the usual systemctl commands will apply to wicked .
16.5.1.2 Using wicked
On SUSE Linux Enterprise, wicked is running by default. If you want to check what is currently
enabled and whether it is running, call:
On openSUSE Leap wicked is running by default on desktop or server hardware. On mobile
hardware NetworkManager is running by default. If you want to check what is currently enabled
and whether it is running, call:
systemctl status network
If wicked is enabled, you will see something along these lines:
wicked.service - wicked managed network interfaces

Loaded: loaded (/usr/lib/systemd/system/wicked.service; enabled)
...
In case something different is running (for example, NetworkManager) and you want to switch
to wicked , rst stop what is running and then enable wicked :
systemctl is-active network && \

systemctl stop network
systemctl enable --force wicked

This enables the wicked services, creates the network.service to wicked.service alias link,
and starts the network at the next boot.
Starting the server process:
systemctl start wickedd
This starts wickedd (the main server) and associated supplicants:
/usr/lib/wicked/bin/wickedd-auto4 --systemd --foreground

/usr/lib/wicked/bin/wickedd-dhcp4 --systemd --foreground
/usr/lib/wicked/bin/wickedd-dhcp6 --systemd --foreground
/usr/sbin/wickedd --systemd --foreground
/usr/sbin/wickedd-nanny --systemd --foreground
Then bringing up the network:
systemctl start wicked
Alternatively use the network.service alias:
systemctl start network
These commands are using the default or system configuration sources as defined in /etc/
wicked/client.xml .
To enable debugging, set WICKED_DEBUG in /etc/sysconfig/network/config , for example:
WICKED_DEBUG="all"
Or, to omit some:
WICKED_DEBUG="all,-dbus,-objectmodel,-xpath,-xml"
Use the client utility to display interface information for all interfaces or the interface specified
with IFNAME :
wicked show all

wicked show IFNAME
In XML output:
wicked show-xml all

wicked show-xml IFNAME
Bringing up one interface:
wicked ifup eth0

wicked ifup wlan0
...
Because there is no configuration source specified, the wicked client checks its default sources
of configuration defined in /etc/wicked/client.xml :
1. firmware: iSCSI Boot Firmware Table (iBFT)
2. compat: ifcfg les—implemented for compatibility
Whatever wicked gets from those sources for a given interface is applied. The intended order
of importance is firmware , then compat —this may be changed in the future.
For more information, see the wicked man page.
16.5.1.3 Nanny
Nanny is an event and policy driven daemon that is responsible for asynchronous or unsolicited
scenarios such as hotplugging devices. Thus the nanny daemon helps with starting or restarting
delayed or temporarily gone devices. Nanny monitors device and link changes, and integrates
new devices defined by the current policy set. Nanny continues to set up even if ifup already
exited because of specified timeout constraints.
By default, the nanny daemon is active on the system. It is enabled in the /etc/wicked/com-
mon.xml configuration le:
<config>
...
<use-nanny>true</use-nanny>
</config>
This setting causes ifup and ifreload to apply a policy with the effective configuration to the
nanny daemon; then, nanny configures wickedd and thus ensures hotplug support. It waits in
the background for events or changes (such as new devices or carrier on).
16.5.1.4 Bringing Up Multiple Interfaces

For bonds and bridges, it may make sense to define the entire device topology in one le (ifcfg-
bondX), and bring it up in one go. wicked then can bring up the whole configuration if you
specify the top level interface names (of the bridge or bond):
wicked ifup br0

This command automatically sets up the bridge and its dependencies in the appropriate order
without the need to list the dependencies (ports, etc.) separately.
To bring up multiple interfaces in one command:
wicked ifup bond0 br0 br1 br2
Or also all interfaces:
wicked ifup all
16.5.1.5 Using Tunnels with Wicked

When you need to use tunnels with Wicked, the TUNNEL_DEVICE is used for this. It permits to
specify an optional device name to bind the tunnel to the device. The tunneled packets will only
be routed via this device.
For more information, refer to man 5 ifcfg-tunnel .
16.5.1.6 Handling Incremental Changes

With wicked , there is no need to actually take down an interface to reconfigure it (unless
it is required by the kernel). For example, to add another IP address or route to a statically
configured network interface, add the IP address to the interface definition, and do another
“ifup” operation. The server will try hard to update only those settings that have changed. This
applies to link-level options such as the device MTU or the MAC address, and network-level
settings, such as addresses, routes, or even the address configuration mode (for example, when
moving from a static configuration to DHCP).
Things get tricky of course with virtual interfaces combining several real devices such as bridges
or bonds. For bonded devices, it is not possible to change certain parameters while the device
is up. Doing that will result in an error.
However, what should still work, is the act of adding or removing the child devices of a bond
or bridge, or choosing a bond's primary interface.
16.5.1.7 Wicked Extensions: Address Configuration

wicked is designed to be extensible with shell scripts. These extensions can be defined in the
config.xml le.

Currently, several classes of extensions are supported:
link configuration: these are scripts responsible for setting up a device's link layer according
to the configuration provided by the client, and for tearing it down again.
address configuration: these are scripts responsible for managing a device's address con-
figuration. Usually address configuration and DHCP are managed by wicked itself, but
can be implemented by means of extensions.
firewall extension: these scripts can apply firewall rules.
Typically, extensions have a start and a stop command, an optional “pid le”, and a set of
environment variables that get passed to the script.
To illustrate how this is supposed to work, look at a firewall extension defined in etc/serv-
er.xml :
<dbus-service interface="org.opensuse.Network.Firewall">
<action name="firewallUp" command="/etc/wicked/extensions/firewall up"/>
<action name="firewallDown" command="/etc/wicked/extensions/firewall down"/>

<putenv name="WICKED_OBJECT_PATH" value="$object-path"/>
<putenv name="WICKED_INTERFACE_NAME" value="$property:name"/>
<putenv name="WICKED_INTERFACE_INDEX" value="$property:index"/>
</dbus-service>
The extension is attached to the <dbus-service> tag and defines commands to execute for the
actions of this interface. Further, the declaration can define and initialize environment variables
passed to the actions.
16.5.1.8 Wicked Extensions: Configuration Files
You can extend the handling of configuration les with scripts as well. For example, DNS up-
dates from leases are ultimately handled by the extensions/resolver script, with behavior
configured in server.xml :
<system-updater name="resolver">
<action name="backup" command="/etc/wicked/extensions/resolver backup"/>
<action name="restore" command="/etc/wicked/extensions/resolver restore"/>
<action name="install" command="/etc/wicked/extensions/resolver install"/>
<action name="remove" command="/etc/wicked/extensions/resolver remove"/>

</system-updater>
When an update arrives in wickedd , the system updater routines parse the lease and call the
appropriate commands ( backup , install , etc.) in the resolver script. This in turn configures
the DNS settings using /sbin/netconfig , or by manually writing /etc/resolv.conf as a
fallback.
16.5.2 Configuration Files

This section provides an overview of the network configuration les and explains their purpose
and the format used.
16.5.2.1 /etc/wicked/common.xml
The /etc/wicked/common.xml le contains common definitions that should be used by all
applications. It is sourced/included by the other configuration les in this directory. Although
you can use this le to enable debugging across all wicked components, we recommend to
use the le /etc/wicked/local.xml for this purpose. After applying maintenance updates you
might lose your changes as the /etc/wicked/common.xml might be overwritten. The /etc/
wicked/common.xml le includes the /etc/wicked/local.xml in the default installation, thus
you typically do not need to modify the /etc/wicked/common.xml .
In case you want to disable nanny by setting the <use-nanny> to false , restart the wicked-
d.service and then run the following command to apply all configurations and policies:
wicked ifup all
Note: Configuration Files

The wickedd , wicked , or nanny programs try to read /etc/wicked/common.xml if
their own configuration les do not exist.
16.5.2.2 /etc/wicked/server.xml
The le /etc/wicked/server.xml is read by the wickedd server process at start-up. The le
stores extensions to the /etc/wicked/common.xml . On top of that this le configures handling
of a resolver and receiving information from addrconf supplicants, for example DHCP.
227 Configuration Files SLES 12 SP3

We recommend to add changes required to this le into a separate le /etc/wicked/serv-
er-local.xml , that gets included by /etc/wicked/server.xml . By using a separate le you
avoid overwriting of your changes during maintenance updates.
16.5.2.3 /etc/wicked/client.xml
The /etc/wicked/client.xml is used by the wicked command. The le specifies the location
of a script used when discovering devices managed by ibft and configures locations of network
interface configurations.
We recommend to add changes required to this le into a separate le /etc/wicked/client-
local.xml , that gets included by /etc/wicked/server.xml . By using a separate le you avoid
overwriting of your changes during maintenance updates.
16.5.2.4 /etc/wicked/nanny.xml
The /etc/wicked/nanny.xml configures types of link layers. We recommend to add specific

configuration into a separate le: /etc/wicked/nanny-local.xml to avoid losing the changes
during maintenance updates.
16.5.2.5 /etc/sysconfig/network/ifcfg-*
These les contain the traditional configurations for network interfaces. In SUSE Linux Enter-
prise 11, this was the only supported format besides iBFT rmware.
Note: wicked and the ifcfg-* Files

wicked reads these les if you specify the compat: prefix. According to the SUSE Lin-
ux Enterprise Server default configuration in /etc/wicked/client.xml , wicked tries
these les before the XML configuration les in /etc/wicked/ifconfig .
The --ifconfig switch is provided mostly for testing only. If specified, default config-
uration sources defined in /etc/wicked/ifconfig are not applied.

The ifcfg-* les include information such as the start mode and the IP address. Possible
parameters are described in the manual page of ifup . Additionally, most variables from the
dhcp and wireless les can be used in the ifcfg-* les if a general setting should be used
for only one interface. However, most of the /etc/sysconfig/network/config variables are
global and cannot be overridden in ifcfg-les. For example, NETCONFIG_* variables are global.
For configuring macvlan and macvtab interfaces, see the ifcfg-macvlan and ifcfg-macv-
tap man pages. For example, for a macvlan interface provide a ifcfg-macvlan0 with settings
as follows:
STARTMODE='auto'
MACVLAN_DEVICE='eth0'
#MACVLAN_MODE='vepa'
#LLADDR=02:03:04:05:06:aa
For ifcfg.template , see Section 16.5.2.6, “/etc/sysconfig/network/config, /etc/syscon-

fig/network/dhcp, and /etc/sysconfig/network/wireless”.
System z IBM z Systems does not support USB. The names of the interface les and network
aliases contain z Systems-specific elements like qeth .
16.5.2.6 /etc/sysconfig/network/config, /etc/sysconfig/network/

dhcp, and /etc/sysconfig/network/wireless
The le config contains general settings for the behavior of ifup , ifdown and ifstatus .
dhcp contains settings for DHCP and wireless for wireless LAN cards. The variables in all three
configuration les are commented. Some variables from /etc/sysconfig/network/config
can also be used in ifcfg-* les, where they are given a higher priority. The /etc/syscon-
fig/network/ifcfg.template le lists variables that can be specified in a per interface scope.
However, most of the /etc/sysconfig/network/config variables are global and cannot be
overridden in ifcfg-les. For example, NETWORKMANAGER or NETCONFIG_* variables are global.
Note: Using DHCPv6

In SUSE Linux Enterprise 11, DHCPv6 used to work even on networks where IPv6 Router
Advertisements (RAs) were not configured properly. Starting with SUSE Linux Enter-
prise 12, DHCPv6 will correctly require that at least one of the routers on the network
sends out RAs that indicate that this network is managed by DHCPv6.

For networks where the router cannot be configured correctly, the ifcfg option allows
the user to override this behavior by specifying DHCLIENT6_MODE='managed' in the
ifcfg le. You can also activate this workaround with a boot parameter in the instal-
lation system:
ifcfg=eth0=dhcp6,DHCLIENT6_MODE=managed
16.5.2.7 /etc/sysconfig/network/routes and /etc/sysconfig/

network/ifroute-*
The static routing of TCP/IP packets is determined by the /etc/sysconfig/network/routes

and /etc/sysconfig/network/ifroute-* les. All the static routes required by the various
system tasks can be specified in /etc/sysconfig/network/routes : routes to a host, routes
to a host via a gateway and routes to a network. For each interface that needs individual rout-
ing, define an additional configuration le: /etc/sysconfig/network/ifroute-* . Replace
the wild card ( * ) with the name of the interface. The entries in the routing configuration les
look like this:
# Destination Gateway Netmask Interface Options
The route's destination is in the rst column. This column may contain the IP address of a
network or host or, in the case of reachable name servers, the fully qualified network or host
name. The network should be written in CIDR notation (address with the associated routing
prefix-length) such as 10.10.0.0/16 for IPv4 or fc00::/7 for IPv6 routes. The keyword default
indicates that the route is the default gateway in the same address family as the gateway. For
devices without a gateway use explicit 0.0.0.0/0 or ::/0 destinations.
The second column contains the default gateway or a gateway through which a host or network
can be accessed.
The third column is deprecated; it used to contain the IPv4 netmask of the destination. For IPv6
routes, the default route, or when using a prefix-length (CIDR notation) in the rst column,
enter a dash ( - ) here.
The fourth column contains the name of the interface. If you leave it empty using a dash ( - ), it
can cause unintended behavior in /etc/sysconfig/network/routes . For more information,
see the routes man page.

An (optional) fth column can be used to specify special options. For details, see the routes
man page.
EXAMPLE 16.5: COMMON NETWORK INTERFACES AND SOME STATIC ROUTES
# --- IPv4 routes in CIDR prefix notation:

# Destination [Gateway] - Interface
127.0.0.0/8 - - lo
204.127.235.0/24 - - eth0
default 204.127.235.41 - eth0
207.68.156.51/32 207.68.145.45 - eth1
192.168.0.0/16 207.68.156.51 - eth1
# --- IPv4 routes in deprecated netmask notation"

# Destination [Dummy/Gateway] Netmask Interface
#
127.0.0.0 0.0.0.0 255.255.255.0 lo
204.127.235.0 0.0.0.0 255.255.255.0 eth0
default 204.127.235.41 0.0.0.0 eth0
207.68.156.51 207.68.145.45 255.255.255.255 eth1
192.168.0.0 207.68.156.51 255.255.0.0 eth1
# --- IPv6 routes are always using CIDR notation:

# Destination [Gateway] - Interface
2001:DB8:100::/64 - - eth0
2001:DB8:100::/32 fe80::216:3eff:fe6d:c042 - eth0
16.5.2.8 /etc/resolv.conf
The domain to which the host belongs is specified in /etc/resolv.conf (keyword search ).
Up to six domains with a total of 256 characters can be specified with the search option. When
resolving a name that is not fully qualified, an attempt is made to generate one by attaching the
individual search entries. Up to 3 name servers can be specified with the nameserver option,
each on a line of its own. Comments are preceded by hash mark or semicolon signs ( # or ; ).
As an example, see Example 16.6, “/etc/resolv.conf”.
However, the /etc/resolv.conf should not be edited by hand. Instead, it is generated by the
netconfig script. To define static DNS configuration without using YaST, edit the appropriate
variables manually in the /etc/sysconfig/network/config le:
NETCONFIG_DNS_STATIC_SEARCHLIST
list of DNS domain names used for host name lookup

NETCONFIG_DNS_STATIC_SERVERS
list of name server IP addresses to use for host name lookup
NETCONFIG_DNS_FORWARDER
the name of the DNS forwarder that needs to be configured, for example bind or re-
solver
NETCONFIG_DNS_RESOLVER_OPTIONS
arbitrary options that will be written to /etc/resolv.conf , for example:
debug attempts:1 timeout:10
For more information, see the resolv.conf man page.
NETCONFIG_DNS_RESOLVER_SORTLIST
list of up to 10 items, for example:
130.155.160.0/255.255.240.0 130.155.0.0
For more information, see the resolv.conf man page.
To disable DNS configuration using netconfig, set NETCONFIG_DNS_POLICY='' . For more infor-
mation about netconfig , see the netconfig(8) man page ( man 8 netconfig ).
EXAMPLE 16.6: /etc/resolv.conf
# Our domain
search example.com
#
# We use dns.example.com (192.168.1.116) as nameserver
nameserver 192.168.1.116
16.5.2.9 /sbin/netconfig
netconfig is a modular tool to manage additional network configuration settings. It merges

statically defined settings with settings provided by autoconfiguration mechanisms as DHCP or
PPP according to a predefined policy. The required changes are applied to the system by calling
the netconfig modules that are responsible for modifying a configuration le and restarting a
service or a similar action.

netconfig recognizes three main actions. The netconfig modify and netconfig remove
commands are used by daemons such as DHCP or PPP to provide or remove settings to netconfig.
Only the netconfig update command is available for the user:
modify
The netconfig modify command modifies the current interface and service specific dy-
namic settings and updates the network configuration. Netconfig reads settings from stan-
dard input or from a le specified with the --lease-file FILENAME option and inter-
nally stores them until a system reboot (or the next modify or remove action). Already
existing settings for the same interface and service combination are overwritten. The in-
terface is specified by the -i INTERFACE_NAME parameter. The service is specified by the
-s SERVICE_NAME parameter.
remove
The netconfig remove command removes the dynamic settings provided by a modifica-
tory action for the specified interface and service combination and updates the network
configuration. The interface is specified by the -i INTERFACE_NAME parameter. The ser-
vice is specified by the -s SERVICE_NAME parameter.
update
The netconfig update command updates the network configuration using current set-
tings. This is useful when the policy or the static configuration has changed. Use the -
m MODULE_TYPE parameter, if you want to update a specified service only ( dns , nis ,
or ntp ).
The netconfig policy and the static configuration settings are defined either manually or using
YaST in the /etc/sysconfig/network/config le. The dynamic configuration settings pro-
vided by autoconfiguration tools such as DHCP or PPP are delivered directly by these tools with
the netconfig modify and netconfig remove actions. When NetworkManager is enabled,
netconfig (in policy mode auto ) uses only NetworkManager settings, ignoring settings from
any other interfaces configured using the traditional ifup method. If NetworkManager does not
provide any setting, static settings are used as a fallback. A mixed usage of NetworkManager
and the wicked method is not supported.
For more information about netconfig , see man 8 netconfig .

16.5.2.10 /etc/hosts
In this le, shown in Example 16.7, “/etc/hosts”, IP addresses are assigned to host names. If no
name server is implemented, all hosts to which an IP connection will be set up must be listed
here. For each host, enter a line consisting of the IP address, the fully qualified host name, and
the host name into the le. The IP address must be at the beginning of the line and the entries
separated by blanks and tabs. Comments are always preceded by the # sign.
EXAMPLE 16.7: /etc/hosts
127.0.0.1 localhost
192.168.2.100 jupiter.example.com jupiter
192.168.2.101 venus.example.com venus
16.5.2.11 /etc/networks
Here, network names are converted to network addresses. The format is similar to that of the
hosts le, except the network names precede the addresses. See Example 16.8, “/etc/networks”.
EXAMPLE 16.8: /etc/networks
loopback 127.0.0.0
localnet 192.168.0.0
16.5.2.12 /etc/host.conf
Name resolution—the translation of host and network names via the resolver library—is con-
trolled by this le. This le is only used for programs linked to libc4 or libc5. For current glibc
programs, refer to the settings in /etc/nsswitch.conf . Each parameter must always be en-
tered on a separate line. Comments are preceded by a # sign. Table 16.2, “Parameters for /etc/
host.conf” shows the parameters available. A sample /etc/host.conf is shown in Example 16.9,
“/etc/host.conf”.
TABLE 16.2: PARAMETERS FOR /ETC/HOST.CONF
order hosts, bind Specifies in which order the services are ac-
cessed for the name resolution. Available ar-
guments are (separated by blank spaces or
commas):
hosts: searches the /etc/hosts le

bind: accesses a name server
nis: uses NIS
multi on/o Defines if a host entered in /etc/hosts can

have multiple IP addresses.
nospoof on spoofalert on/o These parameters influence the name serv-

er spoofing but do not exert any influence on
the network configuration.
trim domainname The specified domain name is separated from

the host name after host name resolution
(as long as the host name includes the do-
main name). This option is useful only if
names from the local domain are in the /
etc/hosts le, but should still be recog-
nized with the attached domain names.
EXAMPLE 16.9: /etc/host.conf
# We have named running

order hosts bind
# Allow multiple address
multi on
16.5.2.13 /etc/nsswitch.conf
The introduction of the GNU C Library 2.0 was accompanied by the introduction of the Name
Service Switch (NSS). Refer to the nsswitch.conf(5) man page and The GNU C Library Reference
Manual for details.
The order for queries is defined in the le /etc/nsswitch.conf . A sample nsswitch.conf
is shown in Example 16.10, “/etc/nsswitch.conf”. Comments are preceded by # signs. In this
example, the entry under the hosts database means that a request is sent to /etc/hosts
( files ) via DNS (see Chapter 25, The Domain Name System).
EXAMPLE 16.10: /etc/nsswitch.conf
passwd: compat

group: compat
hosts: files dns

networks: files dns
services: db files
protocols: db files
rpc: files
ethers: files
netmasks: files
netgroup: files nis
publickey: files
bootparams: files
automount: files nis
aliases: files nis
shadow: compat
The “databases” available over NSS are listed in Table 16.3, “Databases Available via /etc/nss-
witch.conf”.
The configuration options for NSS databases are listed in Table 16.4, “Configuration Options for NSS
“Databases””.
TABLE 16.3: DATABASES AVAILABLE VIA /ETC/NSSWITCH.CONF
aliases Mail aliases implemented by sendmail ; see

man 5 aliases .
ethers Ethernet addresses.
netmasks List of networks and their subnet masks. On-

ly needed, if you use subnetting.
group User groups used by getgrent . See also the

man page for group .
hosts Host names and IP addresses, used by geth-

ostbyname and similar functions.
netgroup Valid host and user lists in the network for

controlling access permissions; see the net-
group(5) man page.

networks Network names and addresses, used by get-
netent .
publickey Public and secret keys for Secure_RPC used

by NFS and NIS+.
passwd User passwords, used by getpwent ; see the

passwd(5) man page.
protocols Network protocols, used by getprotoent ;

see the protocols(5) man page.
rpc Remote procedure call names and address-

es, used by getrpcbyname and similar func-
tions.
services Network services, used by getservent .
shadow Shadow passwords of users, used by getsp-

nam ; see the shadow(5) man page.
TABLE 16.4: CONFIGURATION OPTIONS FOR NSS “DATABASES”
files directly access les, for example, /etc/

aliases
db access via a database
nis , nisplus NIS, see also Book “Security Guide”, Chapter 3

“Using NIS”
dns can only be used as an extension for hosts

and networks
compat can only be used as an extension for pass-

wd , shadow and group

16.5.2.14 /etc/nscd.conf
This le is used to configure nscd (name service cache daemon). See the nscd(8) and
nscd.conf(5) man pages. By default, the system entries of passwd , groups and hosts are
cached by nscd. This is important for the performance of directory services, like NIS and LDAP,
because otherwise the network connection needs to be used for every access to names, groups
or hosts.
If the caching for passwd is activated, it usually takes about fifteen seconds until a newly added
local user is recognized. Reduce this waiting time by restarting nscd with:
systemctl restart nscd
16.5.2.15 /etc/HOSTNAME
/etc/HOSTNAME contains the fully qualified host name (FQHN). The fully qualified host name
is the host name with the domain name attached. This le must contain only one line (in which
the host name is set). It is read while the machine is booting.
16.5.3 Testing the Configuration

Before you write your configuration to the configuration les, you can test it. To set up a test
configuration, use the ip command. To test the connection, use the ping command.
The command ip changes the network configuration directly without saving it in the configu-
ration le. Unless you enter your configuration in the correct configuration les, the changed
network configuration is lost on reboot.
Note: ifconfig and route Are Obsolete

The ifconfig and route tools are obsolete. Use ip instead. ifconfig , for example,
limits interface names to 9 characters.
16.5.3.1 Configuring a Network Interface with ip
ip is a tool to show and configure network devices, routing, policy routing, and tunnels.
238 Testing the Configuration SLES 12 SP3

ip is a very complex tool. Its common syntax is ip OPTIONS OBJECT COMMAND . You can work
with the following objects:
link
This object represents a network device.
address
This object represents the IP address of device.
neighbor
This object represents an ARP or NDISC cache entry.
route
This object represents the routing table entry.
rule
This object represents a rule in the routing policy database.
maddress
This object represents a multicast address.
mroute
This object represents a multicast routing cache entry.
tunnel
This object represents a tunnel over IP.
If no command is given, the default command is used (usually list ).

Change the state of a device with the command ip link set DEVICE_NAME . For example,
to deactivate device eth0, enter ip link set eth0 down . To activate it again, use ip link
set eth0 up .
After activating a device, you can configure it. To set the IP address, use ip addr
add IP_ADDRESS + dev DEVICE_NAME . For example, to set the address of the interface
eth0 to 192.168.12.154/30 with standard broadcast (option brd ), enter ip addr add
192.168.12.154/30 brd + dev eth0 .
To have a working connection, you must also configure the default gateway. To set a gateway
for your system, enter ip route add gateway_ip_address . To translate one IP address to
another, use nat : ip route add nat ip_address via other_ip_address .

To display all devices, use ip link ls . To display the running interfaces only, use ip link
ls up . To print interface statistics for a device, enter ip -s link ls device_name . To view
addresses of your devices, enter ip addr . In the output of the ip addr , also nd information
about MAC addresses of your devices. To show all routes, use ip route show .
For more information about using ip , enter ip help or see the ip(8) man page. The help
option is also available for all ip subcommands. If, for example, you need help for ip addr ,
enter ip addr help . Find the ip manual in /usr/share/doc/packages/iproute2/ip-cre-
f.pdf .
16.5.3.2 Testing a Connection with ping
The ping command is the standard tool for testing whether a TCP/IP connection works. It uses
the ICMP protocol to send a small data packet, ECHO_REQUEST datagram, to the destination
host, requesting an immediate reply. If this works, ping displays a message to that effect. This
indicates that the network link is functioning.
ping does more than only test the function of the connection between two computers: it also
provides some basic information about the quality of the connection. In Example 16.11, “Output
of the Command ping”, you can see an example of the ping output. The second-to-last line con-
tains information about the number of transmitted packets, packet loss, and total time of ping
running.
As the destination, you can use a host name or IP address, for example, ping example.com or
ping 192.168.3.100 . The program sends packets until you press Ctrl –C .
If you only need to check the functionality of the connection, you can limit the number of
the packets with the -c option. For example to limit ping to three packets, enter ping -c 3
example.com .
EXAMPLE 16.11: OUTPUT OF THE COMMAND PING
ping -c 3 example.com
PING example.com (192.168.3.100) 56(84) bytes of data.
64 bytes from example.com (192.168.3.100): icmp_seq=1 ttl=49 time=188 ms
--- example.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2007ms
rtt min/avg/max/mdev = 183.417/185.447/188.259/2.052 ms

The default interval between two packets is one second. To change the interval, ping provides
the option -i . For example, to increase the ping interval to ten seconds, enter ping -i 10
example.com .
In a system with multiple network devices, it is sometimes useful to send the ping through a
specific interface address. To do so, use the -I option with the name of the selected device, for
example, ping -I wlan1 example.com .
For more options and information about using ping, enter ping -h or see the ping (8) man
page.
Tip: Pinging IPv6 Addresses

For IPv6 addresses use the ping6 command. Note, to ping link-local addresses, you must
specify the interface with -I . The following command works, if the address is reachable
via eth1 :
ping6 -I eth1 fe80::117:21ff:feda:a425
16.5.4 Unit Files and Start-Up Scripts

Apart from the configuration les described above, there are also systemd unit les and various
scripts that load the network services while the machine is booting. These are started when the
system is switched to the multi-user.target target. Some of these unit les and scripts are
described in Some Unit Files and Start-Up Scripts for Network Programs. For more information about
systemd , see Chapter 13, The systemd Daemon and for more information about the systemd
targets, see the man page of systemd.special ( man systemd.special ).
SOME UNIT FILES AND START-UP SCRIPTS FOR NETWORK PROGRAMS
network.target
network.target is the systemd target for networking, but its mean depends on the set-
tings provided by the system administrator.
For more information, see http://www.freedesktop.org/wiki/Software/systemd/NetworkTar-
get/ .
multi-user.target
multi-user.target is the systemd target for a multiuser system with all required net-
work services.
241 Unit Files and Start-Up Scripts SLES 12 SP3

xinetd
Starts xinetd. xinetd can be used to make server services available on the system. For
example, it can start vsftpd whenever an FTP connection is initiated.
rpcbind
Starts the rpcbind utility that converts RPC program numbers to universal addresses. It is
needed for RPC services, such as an NFS server.
ypserv
Starts the NIS server.
ypbind
Starts the NIS client.
/etc/init.d/nfsserver
Starts the NFS server.
/etc/init.d/postfix
Controls the postfix process.
16.6 Basic Router Setup

A router is a networking device that delivers and receives data (network packets) to or from
more than one network back and forth. You often use a router to connect your local network to
the remote network (Internet) or to connect local network segments. With SUSE Linux Enterprise
Server you can build a router with features such as NAT (Network Address Translation) or
advanced firewalling.
The following are basic steps to turn SUSE Linux Enterprise Server into a router.
1. Enable forwarding, for example in /etc/sysctl.d/50-router.conf
net.ipv4.conf.all.forwarding = 1
net.ipv6.conf.all.forwarding = 1
Then provide a static IPv4 and IPv6 IP setup for the interfaces. Enabling forwarding dis-
ables several mechanisms, for example IPv6 does not accept an IPv6 RA (router advertise-
ment) anymore, which also prevents the creation of a default route.
242 Basic Router Setup SLES 12 SP3

2. In many situations (for example, when you can reach the same network via more than one
interface, or when VPN usually is used and already on “normal multi-home hosts”), you
must disable the IPv4 reverse path filter (this feature does not currently exist for IPv6):
net.ipv4.conf.all.rp_filter = 0
You can also filter with firewall settings instead.
3. To accept an IPv6 RA (from the router on an external, uplink, or ISP interface) and create
a default (or also a more specific) IPv6 route again, set:
net.ipv6.conf.${ifname}.accept_ra = 2
net.ipv6.conf.${ifname}.autoconf = 0
(Note: “ eth0.42 ” needs to be written as eth0/42 in a dot-separated sysfs path.)
More router behavior and forwarding dependencies are described in https://www.kernel.org/doc/

Documentation/networking/ip-sysctl.txt .
To provide IPv6 on your internal (DMZ) interfaces, and announce yourself as an IPv6 router
and “autoconf networks” to the clients, install and configure radvd in /etc/radvd.conf , for
example:
interface eth0
{
IgnoreIfMissing on; # do not fail if interface missed
AdvSendAdvert on; # enable sending RAs

AdvManagedFlag on; # IPv6 addresses managed via DHCPv6
AdvOtherConfigFlag on; # DNS, NTP... only via DHCPv6
AdvDefaultLifetime 3600; # client default route lifetime of 1 hour
prefix 2001:db8:0:1::/64 # (/64 is default and required for autoconf)

{
AdvAutonomous off; # Disable address autoconf (DHCPv6 only)
AdvValidLifetime 3600; # prefix (autoconf addr) is valid 1 h

AdvPreferredLifetime 1800; # prefix (autoconf addr) is prefered 1/2 h
}
}
243 Basic Router Setup SLES 12 SP3

Lastly configure the firewall. In SuSEfirewall2, you need to set FW_ROUTE="yes" (otherwise it
will also reset forwarding sysctl again) and define the interfaces in the FW_DEV_INT , FW_DE-
V_EXT (and FW_DEV_DMZ ) zone variables as needed, perhaps also FW_MASQUERADE="yes" and
FW_MASQ_DEV .
16.7 Setting Up Bonding Devices

For some systems, there is a desire to implement network connections that comply to more than
the standard data security or availability requirements of a typical Ethernet device. In these
cases, several Ethernet devices can be aggregated to a single bonding device.
The configuration of the bonding device is done by means of bonding module options. The
behavior is mainly affected by the mode of the bonding device. By default, this is mode=ac-
tive-backup which means that a different slave device will become active if the active slave
fails.
Tip: Bonding and Xen

Using bonding devices is only of interest for machines where you have multiple real net-
work cards available. In most configurations, this means that you should use the bonding
configuration only in Dom0. Only if you have multiple network cards assigned to a VM
Guest system it may also be useful to set up the bond in a VM Guest.
To configure a bonding device, use the following procedure:
1. Run YaST System Network Settings.
2. Use Add and change the Device Type to Bond. Proceed with Next.
244 Setting Up Bonding Devices SLES 12 SP3

3. Select how to assign the IP address to the bonding device. Three methods are at your
disposal:
No IP Address
Dynamic Address (with DHCP or Zeroconf)
Statically assigned IP Address
Use the method that is appropriate for your environment.
4. In the Bond Slaves tab, select the Ethernet devices that should be included into the bond
by activating the related check box.
5. Edit the Bond Driver Options. The modes that are available for configuration are the fol-
lowing:
balance-rr
active-backup
balance-xor
broadcast
802.3ad
802.3ad is the standardized LACP “IEEE 802.3ad Dynamic link aggregation” mode.
245 Setting Up Bonding Devices SLES 12 SP3

balance-tlb
balance-alb
6. Make sure that the parameter miimon=100 is added to the Bond Driver Options. Without
this parameter, the data integrity is not checked regularly.
7. Click Next and leave YaST with OK to create the device.
All modes, and many more options are explained in detail in the Linux Ethernet Bonding Dri-
ver HOWTO found at /usr/src/linux/Documentation/networking/bonding.txt after in-
stalling the package kernel-source .
16.7.1 Hotplugging of Bonding Slaves

In specific network environments (such as High Availability), there are cases when you need
to replace a bonding slave interface with another one. The reason may be a constantly failing
network device. The solution is to set up hotplugging of bonding slaves.
The bond is configured as usual (according to man 5 ifcfg-bonding ), for example:
ifcfg-bond0
STARTMODE='auto' # or 'onboot'
BOOTPROTO='static'
IPADDR='192.168.0.1/24'
BONDING_MASTER='yes'
BONDING_SLAVE_0='eth0'
BONDING_SLAVE_1='eth1'
BONDING_MODULE_OPTS='mode=active-backup miimon=100'
The slaves are specified with STARTMODE=hotplug and BOOTPROTO=none :
ifcfg-eth0
STARTMODE='hotplug'
BOOTPROTO='none'
ifcfg-eth1
STARTMODE='hotplug'
BOOTPROTO='none'
BOOTPROTO=none uses the ethtool options (when provided), but does not set the link up on
ifup eth0 . The reason is that the slave interface is controlled by the bond master.
246 Hotplugging of Bonding Slaves SLES 12 SP3

STARTMODE=hotplug causes the slave interface to join the bond automatically when it is avail-
able.
The udev rules in /etc/udev/rules.d/70-persistent-net.rules need to be changed to
match the device by bus ID (udev KERNELS keyword equal to "SysFS BusID" as visible in hwin-
fo --netcard ) instead of by MAC address. This allows replacement of defective hardware (a
network card in the same slot but with a different MAC) and prevents confusion when the bond
changes the MAC address of all its slaves.
For example:
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*",

KERNELS=="0000:00:19.0", ATTR{dev_id}=="0x0", ATTR{type}=="1",
KERNEL=="eth*", NAME="eth0"
At boot time, the systemd network.service does not wait for the hotplug slaves, but for the
bond to become ready, which requires at least one available slave. When one of the slave in-
terfaces gets removed (unbind from NIC driver, rmmod of the NIC driver or true PCI hotplug
remove) from the system, the kernel removes it from the bond automatically. When a new card
is added to the system (replacement of the hardware in the slot), udev renames it using the
bus-based persistent name rule to the name of the slave, and calls ifup for it. The ifup call
automatically joins it into the bond.
16.8 Setting Up Team Devices for Network Teaming

The term “link aggregation” is the general term which describes combining (or aggregating) a
network connection to provide a logical layer. Sometimes you nd the terms “channel teaming”,
“Ethernet bonding”, “port truncating”, etc. which are synonyms and refer to the same concept.
This concept is widely known as “bonding” and was originally integrated into the Linux kernel
(see Section 16.7, “Setting Up Bonding Devices” for the original implementation). The term Network
Teaming is used to refer to the new implementation of this concept.
The main difference between bonding and Network Teaming is that teaming supplies a set of
small kernel modules responsible for providing an interface for teamd instances. Everything
else is handled in user space. This is different from the original bonding implementation which
contains all of its functionality exclusively in the kernel. For a comparison refer to Table 16.5,
“Feature Comparison between Bonding and Team”.
247 Setting Up Team Devices for Network Teaming SLES 12 SP3

TABLE 16.5: FEATURE COMPARISON BETWEEN BONDING AND TEAM
Feature Bonding Team
broadcast, round-robin TX yes yes

policy
active-backup TX policy yes yes
LACP (802.3ad) support yes yes
hash-based TX policy yes yes
user can set hash function no yes
TX load-balancing support yes yes

(TLB)
TX load-balancing support no yes

for LACP
Ethtool link monitoring yes yes
ARP link monitoring yes yes
NS/NA (IPV6) link monitor- no yes

ing
RCU locking on TX/RX paths no yes
port prio and stickiness no yes
separate per-port link moni- no yes

toring setup
multiple link monitoring set- limited yes

up
VLAN support yes yes
multiple device stacking yes yes
Source: http://libteam.org/files/teamdev.pp.pdf
Both implementations, bonding and Network Teaming, can be used in parallel. Network Team-
ing is an alternative to the existing bonding implementation. It does not replace bonding.

Network Teaming can be used for different use cases. The two most important use cases are
explained later and involve:
Load balancing between different network devices.
Failover from one network device to another in case one of the devices should fail.
Currently, there is no YaST module to support creating a teaming device. You need to configure
Network Teaming manually. The general procedure is shown below which can be applied for
all your Network Teaming configurations:
PROCEDURE 16.1: GENERAL PROCEDURE
1. Make sure you have all the necessary packages installed. Install the packages libteam-
tools , libteamdctl0 , and python-libteam .
2. Create a configuration le under /etc/sysconfig/network/ . Usually it will be ifcfg-

team0 . If you need more than one Network Teaming device, give them ascending numbers.
This configuration le contains several variables which are explained in the man pages
(see man ifcfg and man ifcfg-team ). An example configuration can be found in your
system in the le /etc/sysconfig/network/ifcfg.template .
3. Remove the configuration les of the interfaces which will be used for the teaming device
(usually ifcfg-eth0 and ifcfg-eth1 ).
It is recommended to make a backup and remove both les. Wicked will re-create the
configuration les with the necessary parameters for teaming.
4. Optionally, check if everything is included in Wicked's configuration le:
wicked show-config
5. Start the Network Teaming device team0 :
wicked ifup all team0
In case you need additional debug information, use the option --debug all after the
all subcommand.

6. Check the status of the Network Teaming device. This can be done by the following com-
mands:
Get the state of the teamd instance from Wicked:
wicked ifstatus --verbose team0
Get the state of the entire instance:
teamdctl team0 state
Get the systemd state of the teamd instance:
systemctl status teamd@team0
Each of them shows a slightly different view depending on your needs.
7. In case you need to change something in the ifcfg-team0 le afterward, reload its con-
figuration with:
wicked ifreload team0
Do not use systemctl for starting or stopping the teaming device! Instead, use the wicked
command as shown above.
To completely remove the team device, use this procedure:
PROCEDURE 16.2: REMOVING A TEAM DEVICE
1. Stop the Network Teaming device team0 :
wicked ifdown team0
2. Rename the le /etc/sysconfig/network/ifcfg-team0 to /etc/sysconfig/net-

work/.ifcfg-team0 . Inserting a dot in front of the le name makes it “invisible” for
wicked. If you really do not need the configuration anymore, you can also remove the le.
3. Reload the configuration:
wicked ifreload all

16.8.1 Use Case: Loadbalancing with Network Teaming
Loadbalancing is used to improve bandwidth. Use the following configuration le to create a
Network Teaming device with loadbalancing capabilities. Proceed with Procedure 16.1, “General
Procedure” to set up the device. Check the output with teamdctl .
EXAMPLE 16.12: CONFIGURATION FOR LOADBALANCING WITH NETWORK TEAMING
STARTMODE=auto 1
BOOTPROTO=static 2
IPADDRESS="192.168.1.1/24" 2
IPADDR6="fd00:deca:fbad:50::1/64" 2
TEAM_RUNNER="loadbalance" 3
TEAM_LB_TX_HASH="ipv4,ipv6,eth,vlan"
TEAM_LB_TX_BALANCER_NAME="basic"
TEAM_LB_TX_BALANCER_INTERVAL="100"
TEAM_PORT_DEVICE_0="eth0" 4
TEAM_LW_NAME="ethtool" 5
TEAM_LW_ETHTOOL_DELAY_UP="10" 6
TEAM_LW_ETHTOOL_DELAY_DOWN="10" 6
1 Controls the start of the teaming device. The value of auto means, the interface will be set
up when the network service is available and will be started automatically on every reboot.
In case you need to control the device yourself (and prevent it from starting automatically),
set STARTMODE to manual .
2 Sets a static IP address (here 192.168.1.1 for IPv4 and fd00:deca:fbad:50::1 for IPv6).
If the Network Teaming device should use a dynamic IP address, set BOOTPROTO="dhcp"
and remove (or comment) the line with IPADDRESS and IPADDR6 .
3 Sets TEAM_RUNNER to loadbalance to activate the loadbalancing mode.
4 Specifies one or more devices which should be aggregated to create the Network Teaming
device.
5 Defines a link watcher to monitor the state of subordinate devices. The default value eth-
tool checks only if the device is up and accessible. This makes this check fast enough.
However, it does not check if the device can really send or receive packets.
If you need a higher confidence in the connection, use the arp_ping option. This sends
pings to an arbitrary host (configured in the TEAM_LW_ARP_PING_TARGET_HOST variable).
Only if the replies are received, the Network Teaming device is considered to be up.
251 Use Case: Loadbalancing with Network Teaming SLES 12 SP3

6 Defines the delay in milliseconds between the link coming up (or down) and the runner
being notified.
16.8.2 Use Case: Failover with Network Teaming

Failover is used to ensure high availability of a critical Network Teaming device by involving
a parallel backup network device. The backup network device is running all the time and takes
over if and when the main device fails.
Use the following configuration le to create a Network Teaming device with failover capabili-
ties. Proceed with Procedure 16.1, “General Procedure” to set up the device. Check the output with
teamdctl .
EXAMPLE 16.13: CONFIGURATION FOR DHCP NETWORK TEAMING DEVICE
STARTMODE=auto 1
BOOTPROTO=static 2
IPADDR="192.168.1.2/24" 2
IPADDR6="fd00:deca:fbad:50::2/64" 2
TEAM_RUNNER=activebackup 3
TEAM_LW_NAME=ethtool 5
TEAM_LW_ETHTOOL_DELAY_UP="10" 6
TEAM_LW_ETHTOOL_DELAY_DOWN="10" 6
1 Controls the start of the teaming device. The value of auto means, the interface will be set
up when the network service is available and will be started automatically on every reboot.
In case you need to control the device yourself (and prevent it from starting automatically),
set STARTMODE to manual .
2 Sets a static IP address (here 192.168.1.2 for IPv4 and fd00:deca:fbad:50::2 for IPv6).
If the Network Teaming device should use a dynamic IP address, set BOOTPROTO="dhcp"
and remove (or comment) the line with IPADDRESS and IPADDR6 .
3 Sets TEAM_RUNNER to activebackup to activate the failover mode.
4 Specifies one or more devices which should be aggregated to create the Network Teaming
device.
252 Use Case: Failover with Network Teaming SLES 12 SP3

5 Defines a link watcher to monitor the state of subordinate devices. The default value eth-
tool checks only if the device is up and accessible. This makes this check fast enough.
However, it does not check if the device can really send or receive packets.
If you need a higher confidence in the connection, use the arp_ping option. This sends
pings to an arbitrary host (configured in the TEAM_LW_ARP_PING_TARGET_HOST variable).
Only if the replies are received, the Network Teaming device is considered to be up.
6 Defines the delay in milliseconds between the link coming up (or down) and the runner
being notified.
16.8.3 Use Case: VLAN over Team Device

VLAN is an abbreviation of Virtual Local Area Network. It allows the running of multiple logical
(virtual) ethernets over one single physical ethernet. It logically splits the network into different
broadcast domains so that packets are only switched between ports that are designated for the
same VLAN.
The following use case creates two static VLANs on top of a team device:
vlan0 , bound to the IP address 192.168.10.1
vlan1 , bound to the IP address 192.168.20.1
Proceed as follows:
1. Enable the VLAN tags on your switch. If you want to use loadbalancing for your team de-
vice, your switch needs to be capable of Link Aggregation Control Protocol (LACP) (802.3ad).
Consult your hardware manual about the details.
2. Decide if you want to use loadbalancing or failover for your team device. Set up your
team device as described in Section 16.8.1, “Use Case: Loadbalancing with Network Teaming” or
Section 16.8.2, “Use Case: Failover with Network Teaming”.
3. In /etc/sysconfig/network create a le ifcfg-vlan0 with the following content:
STARTMODE="auto"
BOOTPROTO="static" 1
IPADDR='192.168.10.1/24' 2
ETHERDEVICE="team0" 3
VLAN_ID="0" 4
VLAN='yes'
253 Use Case: VLAN over Team Device SLES 12 SP3

1 Defines a xed IP address, specified in IPADDR .
2 Defines the IP address, here with its netmask.
3 Contains the real interface to use for the VLAN interface, here our team device
( team0 ).
4 Specifies a unique ID for the VLAN. Preferably, the le name and the VLAN_ID cor-
responds to the name ifcfg-vlanVLAN_ID . In our case VLAN_ID is 0 which leads
to the filename ifcfg-vlan0 .
4. Copy the le /etc/sysconfig/network/ifcfg-vlan0 to /etc/sysconfig/net-

work/ifcfg-vlan1 and change the following values:
IPADDR from 192.168.10.1/24 to 192.168.20.1/24 .
VLAN_ID from 0 to 1 .
5. Start the two VLANs:
root # wicked ifup vlan0 vlan1
6. Check the output of ifconfig :
root # ifconfig -a
[...]
vlan0 Link encap:Ethernet HWaddr 08:00:27:DC:43:98
inet addr:192.168.10.1 Bcast:192.168.10.255 Mask:255.255.255.0
inet6 addr: fe80::a00:27ff:fedc:4398/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:816 (816.0 b)
vlan1 Link encap:Ethernet HWaddr 08:00:27:DC:43:98

inet addr:192.168.20.1 Bcast:192.168.20.255 Mask:255.255.255.0
inet6 addr: fe80::a00:27ff:fedc:4398/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:816 (816.0 b)
254 Use Case: VLAN over Team Device SLES 12 SP3

16.9 Software-Defined Networking with Open vSwitch
Software-defined networking (SDN) means separating the system that controls where traffic is
sent (the control plane) from the underlying system that forwards traffic to the selected destina-
tion (the data plane, also called the forwarding plane). This means that the functions previously
fulfilled by a single, usually inflexible switch, can now be separated between a switch (data
plane) and its controller (control plane). In this model, the controller is programmable and can
be very flexible and adapt quickly to changing network conditions.
Open vSwitch is software that implements a distributed virtual multilayer switch that is compat-
ible with the OpenFlow protocol. OpenFlow allows a controller application to modify the con-
figuration of a switch. OpenFlow is layered onto the TCP protocol and is implemented in a range
of hardware and software. A single controller can thus drive multiple, very different switches.
16.9.1 Advantages of Open vSwitch

Software-defined networking with Open vSwitch brings several advantages with it, especially
when you used together with virtual machines:
Networking states can be identified easily.
Networks and their live state can be moved from one host to another.
Network dynamics are traceable and external software can be enabled to respond to them.
You can apply and manipulate tags in network packets to identify which machine they
are coming from or going to and maintain other networking context. Tagging rules can
be configured and migrated.
Open vSwitch implements the GRE protocol (Generic Routing Encapsulation). This allows
you, for example, to connect private VM networks to each other.
Open vSwitch can be used on its own, but is designed to integrate with networking hard-
ware and can control hardware switches.
16.9.2 Installing Open vSwitch

1. Install Open vSwitch and supplementary packages:
root # zypper install openvswitch openvswitch-switch
255 Software-Defined Networking with Open vSwitch SLES 12 SP3

If you plan to use Open vSwitch together with the KVM hypervisor, additionally install
tunctl . If you plan to use Open vSwitch together with the Xen hypervisor, additionally
install openvswitch-kmp-xen .
2. Enable the Open vSwitch service:
root # systemctl enable openvswitch
3. Either restart the computer or use systemctl to start the Open vSwitch service imme-
diately:
root # systemctl start openvswitch
4. To check whether Open vSwitch was activated correctly, use:
root # systemctl status openvswitch
16.9.3 Overview of Open vSwitch Daemons and Utilities

Open vSwitch consists of several components. Among them are a kernel module and various
user space components. The kernel module is used for accelerating the data path, but is not
necessary for a minimal Open vSwitch installation.
16.9.3.1 Daemons
The central executables of Open vSwitch are its two daemons. When you start the openvswitch
service, you are indirectly starting them.
The main Open vSwitch daemon ( ovs-vswitchd ) provides the implementation of a switch. The
Open vSwitch database daemon ( ovsdb-server ) serves the database that stores the configura-
tion and state of Open vSwitch.
16.9.3.2 Utilities
Open vSwitch also comes with several utilities that help you work with it. The following list is
not exhaustive, but instead describes important commands only.
256 Overview of Open vSwitch Daemons and Utilities SLES 12 SP3

ovsdb-tool
Create, upgrade, compact, and query Open vSwitch databases. Do transactions on Open
vSwitch databases.
ovs-appctl
Configure a running ovs-vswitchd or ovsdb-server daemon.
ovs-dpctl , ovs-dpctl-top
Create, modify, visualize, and delete data paths. Using this tool can interfere with ovs-
vswitchd also performing data path management. Therefore, it is often used for diagnos-
tics only.
ovs-dpctl-top creates a top -like visualization for data paths.
ovs-ofctl
Manage any switches adhering to the OpenFlow protocol. ovs-ofctl is not limited to
interacting with Open vSwitch.
ovs-vsctl
Provides a high-level interface to the configuration database. It can be used to query and
modify the database. In effect, it shows the status of ovs-vswitchd and can be used to
configure it.
16.9.4 Creating a Bridge with Open vSwitch

The following example configuration uses the Wicked network service that is used by default
on SUSE Linux Enterprise Server. To learn more about Wicked, see Section 16.5, “Configuring a
Network Connection Manually”.
When you have installed and started Open vSwitch, proceed as follows:
1. To configure a bridge for use by your virtual machine, create a le with content like this:
STARTMODE='auto' 1
BOOTPROTO='dhcp' 2
OVS_BRIDGE='yes' 3
OVS_BRIDGE_PORT_DEVICE_1='eth0' 4
1 Set up the bridge automatically when the network service is started.

2 The protocol to use for configuring the IP address.
3 Mark the configuration as an Open vSwitch bridge.
257 Creating a Bridge with Open vSwitch SLES 12 SP3

4 Choose which device/devices should be added to the bridge. To add more devices,
append additional lines for each of them to the le:
OVS_BRIDGE_PORT_DEVICE_SUFFIX='DEVICE'
The SUFFIX can be any alphanumeric string. However, to avoid overwriting a pre-
vious definition, make sure the SUFFIX of each device is unique.
Save the le in the directory /etc/sysconfig/network under the name ifcfg-br0 .
Instead of br0 , you can use any name you want. However, the le name needs to begin
with ifcfg- .
To learn about further options, refer to the man pages of ifcfg ( man 5 ifcfg ) and
ifcfg-ovs-bridge ( man 5 ifcfg-ovs-bridge ).
2. Now start the bridge:
root # wicked ifup br0
When Wicked is done, it should output the name of the bridge and next to it the state up .
16.9.5 Using Open vSwitch Directly with KVM

After having created the bridge as described in Section 16.9.4, “Creating a Bridge with Open vSwitch”,
you can use Open vSwitch to manage the network access of virtual machines created with KVM/
QEMU.
1. To be able to best use the capabilities of Wicked, make some further changes to the bridge
configured before. Open the previously created /etc/sysconfig/network/ifcfg-br0
and append a line for another port device:
OVS_BRIDGE_PORT_DEVICE_2='tap0'
Additionally, set BOOTPROTO to none . The le should now look like this:
STARTMODE='auto'
BOOTPROTO='none'
OVS_BRIDGE='yes'
OVS_BRIDGE_PORT_DEVICE_1='eth0'
OVS_BRIDGE_PORT_DEVICE_2='tap0'
The new port device tap0 will be configured in the next step.
258 Using Open vSwitch Directly with KVM SLES 12 SP3

2. Now add a configuration le for the tap0 device:
STARTMODE='auto'
BOOTPROTO='none'
TUNNEL='tap'
Save the le in the directory /etc/sysconfig/network under the name ifcfg-tap0 .
Tip: Allowing Other Users to Access the Tap Device

To be able to use this tap device from a virtual machine started as a user who is
not root , append:
TUNNEL_SET_OWNER=USER_NAME
To allow access for an entire group, append:
TUNNEL_SET_GROUP=GROUP_NAME
3. Finally, open the configuration for the device defined as the rst OVS_BRIDGE_PORT_DE-
VICE . If you did not change the name, that should be eth0 . Therefore, open /etc/
sysconfig/network/ifcfg-eth0 and make sure that the following options are set:
STARTMODE='auto'
BOOTPROTO='none'
If the le does not exist yet, create it.
4. Restart the bridge interface using Wicked:
root # wicked ifreload br0
This will also trigger a reload of the newly defined bridge port devices.
5. To start a virtual machine, use, for example:
root # qemu-kvm \
-drive file=/PATH/TO/DISK-IMAGE 1 \
-m 512 -net nic,vlan=0,macaddr=00:11:22:EE:EE:EE \
-net tap,ifname=tap0,script=no,downscript=no 2
1 The path to the QEMU disk image you want to start.
259 Using Open vSwitch Directly with KVM SLES 12 SP3

2 Use the tap device ( tap0 ) created before.
For further information on the usage of KVM/QEMU, see Book “Virtualization Guide”.
16.9.6 Using Open vSwitch with libvirt

After having created the bridge as described before in Section 16.9.4, “Creating a Bridge with Open
vSwitch”, you can add the bridge to an existing virtual machine managed with libvirt . Since
libvirt has some support for Open vSwitch bridges already, you can use the bridge created
in Section 16.9.4, “Creating a Bridge with Open vSwitch” without further changes to the networking
configuration.
1. Open the domain XML le for the intended virtual machine:
root # virsh edit VM_NAME
Replace VM_NAME with the name of the desired virtual machine. This will open your de-
fault text editor.
2. Find the networking section of the document by looking for a section starting with <in-
terface type="..."> and ending in </interface> .
Replace the existing section with a networking section that looks somewhat like this:
<interface type='bridge'>
<source bridge='br0'/>
<virtualport type='openvswitch'/>
</interface>
Important: Compatibility of virsh iface-* and Virtual

Machine Manager with Open vSwitch
At the moment, the Open vSwitch compatibility of libvirt is not exposed through
the virsh iface-* tools and Virtual Machine Manager. If you use any of these
tools, your configuration can break.
3. You can now start or restart the virtual machine as usual.
For further information on the usage of libvirt , see Book “Virtualization Guide”.
260 Using Open vSwitch with libvirt SLES 12 SP3

http://openvswitch.org/support/
The documentation section of the Open vSwitch project Web site
https://www.opennetworking.org/images/stories/downloads/sdn-resources/white-papers/wp-
sdn-newnorm.pdf
Whitepaper by the Open Networking Foundation about software-defined networking and
the OpenFlow protocol

17 Printer Operation
SUSE® Linux Enterprise Server supports printing with many types of printers, including remote
network printers. Printers can be configured manually or with YaST. For configuration instruc-
tions, refer to Book “Deployment Guide”, Chapter 11 “Setting Up Hardware Components with YaST”,
Section 11.3 “Setting Up a Printer”. Both graphical and command line utilities are available for
starting and managing print jobs. If your printer does not work as expected, refer to Section 17.8,
“Troubleshooting”.
CUPS (Common Unix Printing System) is the standard print system in SUSE Linux Enterprise
Server.
Printers can be distinguished by interface, such as USB or network, and printer language. When
buying a printer, make sure that the printer has an interface that is supported (USB, Ethernet, or
Wi-Fi) and a suitable printer language. Printers can be categorized on the basis of the following
three classes of printer languages:
PostScript Printers
PostScript is the printer language in which most print jobs in Linux and Unix are generat-
ed and processed by the internal print system. If PostScript documents can be processed
directly by the printer and do not need to be converted in additional stages in the print
system, the number of potential error sources is reduced.
Currently PostScript is being replaced by PDF as the standard print job format. PostScript
+PDF printers that can directly print PDF (in addition to PostScript) already exist. For
traditional PostScript printers PDF needs to be converted to PostScript in the printing
workflow.
Standard Printers (Languages Like PCL and ESC/P)

In the case of known printer languages, the print system can convert PostScript jobs to
the respective printer language with Ghostscript. This processing stage is called interpret-
ing. The best-known languages are PCL (which is mostly used by HP printers and their
clones) and ESC/P (which is used by Epson printers). These printer languages are usually
supported by Linux and produce an adequate print result. Linux may not be able to address
some special printer functions. Except for HP and Epson, there are currently no printer
manufacturers who develop Linux drivers and make them available to Linux distributors
under an open source license.
262 SLES 12 SP3

Proprietary Printers (Also Called GDI Printers)
These printers do not support any of the common printer languages. They use their own
undocumented printer languages, which are subject to change when a new edition of a
model is released. Usually only Windows drivers are available for these printers. See Sec-
tion 17.8.1, “Printers without Standard Printer Language Support” for more information.
Before you buy a new printer, refer to the following sources to check how well the printer you
intend to buy is supported:
http://www.linuxfoundation.org/OpenPrinting/
The OpenPrinting home page with the printer database. The database shows the latest
Linux support status. However, a Linux distribution can only integrate the drivers available
at production time. Accordingly, a printer currently rated as “perfectly supported” may not
have had this status when the latest SUSE Linux Enterprise Server version was released.
Thus, the databases may not necessarily indicate the correct status, but only provide an
approximation.
http://pages.cs.wisc.edu/~ghost/
The Ghostscript Web page.
/usr/share/doc/packages/ghostscript/catalog.devices
List of built-in Ghostscript drivers.
17.1 The CUPS Workflow

The user creates a print job. The print job consists of the data to print plus information for the
spooler. This includes the name of the printer or the name of the print queue, and optionally,
information for the filter, such as printer-specific options.
At least one dedicated print queue exists for every printer. The spooler holds the print job in the
queue until the desired printer is ready to receive data. When the printer is ready, the spooler
sends the data through the filter and back-end to the printer.
The filter converts the data generated by the application that is printing (usually PostScript or
PDF, but also ASCII, JPEG, etc.) into printer-specific data (PostScript, PCL, ESC/P, etc.). The
features of the printer are described in the PPD les. A PPD le contains printer-specific options
with the parameters needed to enable them on the printer. The filter system makes sure that
options selected by the user are enabled.
263 The CUPS Workflow SLES 12 SP3

If you use a PostScript printer, the filter system converts the data into printer-specific PostScript.
This does not require a printer driver. If you use a non-PostScript printer, the filter system con-
verts the data into printer-specific data. This requires a printer driver suitable for your printer.
The back-end receives the printer-specific data from the filter then passes it to the printer.
17.2 Methods and Protocols for Connecting Printers

There are various possibilities for connecting a printer to the system. The configuration of CUPS
does not distinguish between a local printer and a printer connected to the system over the
network. For more information about the printer connection, read the article CUPS in a Nutshell
at http://en.opensuse.org/SDB:CUPS_in_a_Nutshell .
System z Printers and similar devices provided by the z/VM that connect locally with the
IBM z Systems mainframes are not supported by CUPS. On these platforms, printing is only
possible over the network. The cabling for network printers must be installed according to the
instructions of the printer manufacturer.
Warning: Changing Cable Connections in a Running System

When connecting the printer to the machine, do not forget that only USB devices can be
plugged in or unplugged during operation. To avoid damaging your system or printer,
shut down the system before changing any connections that are not USB.
17.3 Installing the Software

PPD (PostScript printer description) is the computer language that describes the properties, like
resolution, and options, such as the availability of a duplex unit. These descriptions are required
for using various printer options in CUPS. Without a PPD le, the print data would be forwarded
to the printer in a “raw” state, which is usually not desired.
To configure a PostScript printer, the best approach is to get a suitable PPD le. Many PPD les
are available in the packages manufacturer-PPDs and OpenPrintingPPDs-postscript . See
Section 17.7.3, “PPD Files in Various Packages” and Section 17.8.2, “No Suitable PPD File Available for a
PostScript Printer”.
264 Methods and Protocols for Connecting Printers SLES 12 SP3

New PPD les can be stored in the directory /usr/share/cups/model/ or added to the print
system with YaST as described in Book “Deployment Guide”, Chapter 11 “Setting Up Hardware Com-
ponents with YaST”, Section 11.3.1.1 “Adding Drivers with YaST”. Subsequently, the PPD le can be
selected during the printer setup.
Be careful if a printer manufacturer wants you to install entire software packages. This kind
of installation may result in the loss of the support provided by SUSE Linux Enterprise Server.
Also, print commands may work differently and the system may no longer be able to address
devices of other manufacturers. For this reason, the installation of manufacturer software is not
recommended.
17.4 Network Printers

A network printer can support various protocols, some even concurrently. Although most of the
supported protocols are standardized, some manufacturers modify the standard. Manufacturers
then provide drivers for only a few operating systems. Unfortunately, Linux drivers are rarely
provided. The current situation is such that you cannot act on the assumption that every protocol
works smoothly in Linux. Therefore, you may need to experiment with various options to achieve
a functional configuration.
CUPS supports the socket , LPD , IPP and smb protocols.
socket
Socket refers to a connection in which the plain print data is sent directly to a TCP sock-
et. Some socket port numbers that are commonly used are 9100 or 35 . The device URI
(uniform resource identifier) syntax is: socket:// IP.OF.THE.PRINTER : PORT , for example:
socket://192.168.2.202:9100/ .
LPD (Line Printer Daemon)

The LPD protocol is described in RFC 1179. Under this protocol, some job-related data,
such as the ID of the print queue, is sent before the actual print data is sent. Therefore, a
print queue must be specified when configuring the LPD protocol. The implementations of
diverse printer manufacturers are flexible enough to accept any name as the print queue. If
necessary, the printer manual should indicate what name to use. LPT, LPT1, LP1 or similar
names are often used. The port number for an LPD service is 515 . An example device URI
is lpd://192.168.2.202/LPT1 .
265 Network Printers SLES 12 SP3

IPP (Internet Printing Protocol)
IPP is a relatively new protocol (1999) based on the HTTP protocol. With IPP, more job-
related data is transmitted than with the other protocols. CUPS uses IPP for internal data
transmission. The name of the print queue is necessary to configure IPP correctly. The
port number for IPP is 631 . Example device URIs are ipp://192.168.2.202/ps and
ipp://192.168.2.202/printers/ps .
SMB (Windows Share)

CUPS also supports printing on printers connected to Windows shares. The protocol used
for this purpose is SMB. SMB uses the port numbers 137 , 138 and 139 . Example de-
vice URIs are smb://user:password@workgroup/smb.example.com/printer , smb://
user:password@smb.example.com/printer , and smb://smb.example.com/printer .
The protocol supported by the printer must be determined before configuration. If the manufac-
turer does not provide the needed information, the command nmap (which comes with the nmap
package) can be used to ascertain the protocol. nmap checks a host for open ports. For example:
nmap -p 35,137-139,515,631,9100-10000 IP.OF.THE.PRINTER
17.5 Configuring CUPS with Command Line Tools

CUPS can be configured with command line tools like lpinfo , lpadmin and lpoptions . You
need a device URI consisting of a back-end, such as USB, and parameters. To determine valid
device URIs on your system use the command lpinfo -v | grep ":/" :
# lpinfo -v | grep ":/"

direct usb://ACME/FunPrinter%20XL
network socket://192.168.2.253
With lpadmin the CUPS server administrator can add, remove or manage print queues. To add
a print queue, use the following syntax:
lpadmin -p QUEUE -v DEVICE-URI -P PPD-FILE -E
Then the device ( -v ) is available as QUEUE ( -p ), using the specified PPD le ( -P ). This means
that you must know the PPD le and the device URI to configure the printer manually.
266 Configuring CUPS with Command Line Tools SLES 12 SP3

Do not use -E as the rst option. For all CUPS commands, -E as the rst argument sets use
of an encrypted connection. To enable the printer, -E must be used as shown in the following
example:
lpadmin -p ps -v usb://ACME/FunPrinter%20XL -P \
/usr/share/cups/model/Postscript.ppd.gz -E
The following example configures a network printer:
lpadmin -p ps -v socket://192.168.2.202:9100/ -P \
/usr/share/cups/model/Postscript-level1.ppd.gz -E
For more options of lpadmin , see the man page of lpadmin(8) .

During printer setup, certain options are set as default. These options can be modified for every
print job (depending on the print tool used). Changing these default options with YaST is also
possible. Using command line tools, set default options as follows:
1. First, list all options:
lpoptions -p QUEUE -l
Example:
Resolution/Output Resolution: 150dpi *300dpi 600dpi
The activated default option is identified by a preceding asterisk ( * ).
2. Change the option with lpadmin :
lpadmin -p QUEUE -o Resolution=600dpi
3. Check the new setting:
lpoptions -p QUEUE -l
Resolution/Output Resolution: 150dpi 300dpi *600dpi
When a normal user runs lpoptions , the settings are written to ~/.cups/lpoptions . How-
ever, root settings are written to /etc/cups/lpoptions .
267 Configuring CUPS with Command Line Tools SLES 12 SP3

17.6 Printing from the Command Line
To print from the command line, enter lp -d QUEUENAME FILENAME , substituting the corre-
sponding names for QUEUENAME and FILENAME .
Some applications rely on the lp command for printing. In this case, enter the correct command
in the application's print dialog, usually without specifying FILENAME , for example, lp -d
QUEUENAME .
17.7 Special Features in SUSE Linux Enterprise Server

Several CUPS features have been adapted for SUSE Linux Enterprise Server. Some of the most
important changes are covered here.
17.7.1 CUPS and Firewall

After having performed a default installation of SUSE Linux Enterprise Server, SuSEFirewall2
is active and the network interfaces are configured to be in the External Zone which blocks
incoming traffic. More information about the SuSEFirewall2 configuration is available in Book
“Security Guide”, Chapter 15 “Masquerading and Firewalls”, Section 15.4 “SuSEFirewall2” and at http://
en.opensuse.org/SDB:CUPS_and_SANE_Firewall_settings .
17.7.1.1 CUPS Client
Normally, a CUPS client runs on a regular workstation located in a trusted network environment
behind a firewall. In this case it is recommended to configure the network interface to be in the
Internal Zone , so the workstation is reachable from within the network.
17.7.1.2 CUPS Server
If the CUPS server is part of a trusted network environment protected by a firewall, the network
interface should be configured to be in the Internal Zone of the firewall. It is not recommend-
ed to set up a CUPS server in an untrusted network environment unless you ensure that it is
protected by special firewall rules and secure settings in the CUPS configuration.
268 Printing from the Command Line SLES 12 SP3

17.7.2 Browsing for Network Printers
CUPS servers regularly announce the availability and status information of shared printers over
the network. Clients can access this information to display a list of available printers in printing
dialogs, for example. This is called “browsing”.
CUPS servers announce their print queues over the network either via the traditional CUPS
browsing protocol or via Bonjour/DND-SD. To be able to browse network print queues, the
service cups-browsed needs to run on all clients that print via CUPS servers. cups-browsed
is not started by default. To start it for the active session, use sudo systemctl start cups-
browsed . To ensure it is automatically started after booting, enable it with sudo systemctl
enable cups-browsed on all clients.
In case browsing does not work after having started cups-browsed , the CUPS server(s) probably
announce the network print queues via Bonjour/DND-SD. In this case you need to additionally
install the package avahi and start the associated service with sudo systemctl start avahi-
daemon on all clients.
17.7.3 PPD Files in Various Packages

The YaST printer configuration sets up the queues for CUPS using the PPD les installed in /
usr/share/cups/model . To nd the suitable PPD les for the printer model, YaST compares
the vendor and model determined during hardware detection with the vendors and models in
all PPD les. For this purpose, the YaST printer configuration generates a database from the
vendor and model information extracted from the PPD les.
The configuration using only PPD les and no other information sources has the advantage that
the PPD les in /usr/share/cups/model can be modified freely. For example, if you have
PostScript printers the PPD les can be copied directly to /usr/share/cups/model (if they do
not already exist in the manufacturer-PPDs or OpenPrintingPPDs-postscript packages) to
achieve an optimum configuration for your printers.
Additional PPD les are provided by the following packages:
gutenprint: the Gutenprint driver and its matching PPDs
splix: the SpliX driver and its matching PPDs
OpenPrintingPPDs-ghostscript: PPDs for Ghostscript built-in drivers
OpenPrintingPPDs-hpijs: PPDs for the HPIJS driver for non-HP printers
269 Browsing for Network Printers SLES 12 SP3

17.8 Troubleshooting
The following sections cover some of the most frequently encountered printer hardware and
software problems and ways to solve or circumvent these problems. Among the topics covered
are GDI printers, PPD les and port configuration. Common network printer problems, defective
printouts, and queue handling are also addressed.
17.8.1 Printers without Standard Printer Language Support
These printers do not support any common printer language and can only be addressed with
special proprietary control sequences. Therefore they can only work with the operating system
versions for which the manufacturer delivers a driver. GDI is a programming interface developed
by Microsoft* for graphics devices. Usually the manufacturer delivers drivers only for Windows,
and since the Windows driver uses the GDI interface these printers are also called GDI printers.
The actual problem is not the programming interface, but that these printers can only be ad-
dressed with the proprietary printer language of the respective printer model.
Some GDI printers can be switched to operate either in GDI mode or in one of the standard
printer languages. See the manual of the printer whether this is possible. Some models require
special Windows software to do the switch (note that the Windows printer driver may always
switch the printer back into GDI mode when printing from Windows). For other GDI printers
there are extension modules for a standard printer language available.
Some manufacturers provide proprietary drivers for their printers. The disadvantage of propri-
etary printer drivers is that there is no guarantee that these work with the installed print system
or that they are suitable for the various hardware platforms. In contrast, printers that support a
standard printer language do not depend on a special print system version or a special hardware
platform.
Instead of spending time trying to make a proprietary Linux driver work, it may be more cost-ef-
fective to purchase a printer which supports a standard printer language (preferably PostScript).
This would solve the driver problem once and for all, eliminating the need to install and con-
figure special driver software and obtain driver updates that may be required because of new
developments in the print system.
270 Troubleshooting SLES 12 SP3

17.8.2 No Suitable PPD File Available for a PostScript Printer
If the manufacturer-PPDs or OpenPrintingPPDs-postscript packages do not contain a suit-
able PPD le for a PostScript printer, it should be possible to use the PPD le from the driver CD
of the printer manufacturer or download a suitable PPD le from the Web page of the printer
manufacturer.
If the PPD le is provided as a zip archive (.zip) or a self-extracting zip archive ( .exe ), unpack
it with unzip . First, review the license terms of the PPD le. Then use the cupstestppd util-
ity to check if the PPD le complies with “Adobe PostScript Printer Description File Format
Specification, version 4.3.” If the utility returns “FAIL,” the errors in the PPD les are serious
and are likely to cause major problems. The problem spots reported by cupstestppd should
be eliminated. If necessary, ask the printer manufacturer for a suitable PPD le.
17.8.3 Network Printer Connections
Identifying Network Problems

Connect the printer directly to the computer. For test purposes, configure the printer as a
local printer. If this works, the problems are related to the network.
Checking the TCP/IP Network

The TCP/IP network and name resolution must be functional.
Checking a Remote lpd

Use the following command to test if a TCP connection can be established to lpd (port
515 ) on HOST :
netcat -z HOST 515 && echo ok || echo failed
If the connection to lpd cannot be established, lpd may not be active or there may be
basic network problems.
Provided that the respective lpd is active and the host accepts queries, run the following
command as root to query a status report for QUEUE on remote HOST :
echo -e "\004queue" \
| netcat -w 2 -p 722 HOST 515
271 No Suitable PPD File Available for a PostScript Printer SLES 12 SP3
If lpd does not respond, it may not be active or there may be basic network problems.
If lpd responds, the response should show why printing is not possible on the queue on
host . If you receive a response like that shown in Example 17.1, “Error Message from lpd”,
the problem is caused by the remote lpd .
EXAMPLE 17.1: ERROR MESSAGE FROM lpd
lpd: your host does not have line printer access

lpd: queue does not exist
printer: spooling disabled
printer: printing disabled
Checking a Remote cupsd

A CUPS network server can broadcast its queues by default every 30 seconds on UDP
port 631 . Accordingly, the following command can be used to test whether there is a
broadcasting CUPS network server in the network. Make sure to stop your local CUPS
daemon before executing the command.
netcat -u -l -p 631 & PID=$! ; sleep 40 ; kill $PID
If a broadcasting CUPS network server exists, the output appears as shown in Example 17.2,
“Broadcast from the CUPS Network Server”.
EXAMPLE 17.2: BROADCAST FROM THE CUPS NETWORK SERVER
ipp://192.168.2.202:631/printers/queue
System z Take into account that IBM z Systems Ethernet devices do not receive broadcasts
by default.
The following command can be used to test if a TCP connection can be established to
cupsd (port 631 ) on HOST :
netcat -z HOST 631 && echo ok || echo failed
If the connection to cupsd cannot be established, cupsd may not be active or there may
be basic network problems. lpstat -h HOST -l -t returns a (possibly very long) status
report for all queues on HOST , provided the respective cupsd is active and the host accepts
queries.
The next command can be used to test if the QUEUE on HOST accepts a print job consisting
of a single carriage-return character. Nothing should be printed. Possibly, a blank page
may be ejected.
echo -en "\r" \

| lp -d queue -h HOST
272 Network Printer Connections SLES 12 SP3

Troubleshooting a Network Printer or Print Server Machine
Spoolers running in a print server machine sometimes cause problems when they need
to deal with multiple print jobs. Since this is caused by the spooler in the print server
machine, there no way to resolve this issue. As a work-around, circumvent the spooler in
the print server machine by addressing the printer connected to the print server machine
directly with the TCP socket. See Section 17.4, “Network Printers”.
In this way, the print server machine is reduced to a converter between the various forms of
data transfer (TCP/IP network and local printer connection). To use this method, you need
to know the TCP port on the print server machine. If the printer is connected to the print
server machine and turned on, this TCP port can usually be determined with the nmap
utility from the nmap package some time after the print server machine is powered up. For
example, nmap IP-address may deliver the following output for a print server machine:
Port State Service

23/tcp open telnet
80/tcp open http
515/tcp open printer
631/tcp open cups
9100/tcp open jetdirect
This output indicates that the printer connected to the print server machine can be ad-
dressed via TCP socket on port 9100 . By default, nmap only checks several commonly
known ports listed in /usr/share/nmap/nmap-services . To check all possible ports, use
the command nmap -p FROM_PORT - TO_PORT IP_ADDRESS . This may take some time.
For further information, refer to the man page of nmap .
Enter a command like
echo -en "\rHello\r\f" | netcat -w 1 IP-address port

cat file | netcat -w 1 IP-address port
to send character strings or les directly to the respective port to test if the printer can
be addressed on this port.
17.8.4 Defective Printouts without Error Message

For the print system, the print job is completed when the CUPS back-end completes the data
transfer to the recipient (printer). If further processing on the recipient fails (for example, if
the printer is not able to print the printer-specific data) the print system does not notice this.
If the printer cannot print the printer-specific data, select a PPD le that is more suitable for
the printer.
273 Defective Printouts without Error Message SLES 12 SP3

17.8.5 Disabled Queues
If the data transfer to the recipient fails entirely after several attempts, the CUPS back-end, such
as USB or socket , reports an error to the print system (to cupsd ). The back-end determines
how many unsuccessful attempts are appropriate until the data transfer is reported as impossible.
As further attempts would be in vain, cupsd disables printing for the respective queue. After
eliminating the cause of the problem, the system administrator must re-enable printing with the
command cupsenable .
17.8.6 CUPS Browsing: Deleting Print Jobs

If a CUPS network server broadcasts its queues to the client hosts via browsing and a suitable
local cupsd is active on the client hosts, the client cupsd accepts print jobs from applications
and forwards them to the cupsd on the server. When cupsd on the server accepts a print job, it
is assigned a new job number. Therefore, the job number on the client host is different from the
job number on the server. As a print job is usually forwarded immediately, it cannot be deleted
with the job number on the client host This is because the client cupsd regards the print job as
completed when it has been forwarded to the server cupsd .
To delete the print job on the server, use a command such as lpstat -h cups.example.com
-o to determine the job number on the server. This assumes that the server has not already
completed the print job (that is, sent it completely to the printer). Use the obtained job number
to delete the print job on the server as follows:
cancel -h cups.example.com QUEUE-JOBNUMBER
17.8.7 Defective Print Jobs and Data Transfer Errors

If you switch the printer o or shut down the computer during the printing process, print jobs
remain in the queue. Printing resumes when the computer (or the printer) is switched back on.
Defective print jobs must be removed from the queue with cancel .
If a print job is corrupted or an error occurs in the communication between the host and the
printer, the printer cannot process the data correctly and prints numerous sheets of paper with
unintelligible characters. To x the problem, follow these steps:
1. To stop printing, remove all paper from ink jet printers or open the paper trays of laser
printers. High-quality printers have a button for canceling the current printout.
274 Disabled Queues SLES 12 SP3

2. The print job may still be in the queue, because jobs are only removed after they are sent
completely to the printer. Use lpstat -o or lpstat -h cups.example.com -o to check
which queue is currently printing. Delete the print job with cancel QUEUE - JOBNUMBER
or cancel -h cups.example.com QUEUE - JOBNUMBER .
3. Some data may still be transferred to the printer even though the print job has been deleted
from the queue. Check if a CUPS back-end process is still running for the respective queue
and terminate it.
4. Reset the printer completely by switching it o for some time. Then insert the paper and
turn on the printer.
17.8.8 Debugging CUPS

Use the following generic procedure to locate problems in CUPS:
1. Set LogLevel debug in /etc/cups/cupsd.conf .
2. Stop cupsd .
3. Remove /var/log/cups/error_log* to avoid having to search through very large log

les.
4. Start cupsd .
5. Repeat the action that led to the problem.
6. Check the messages in /var/log/cups/error_log* to identify the cause of the problem.

In-depth information about printing on SUSE Linux is presented in the openSUSE Support Data-
base at http://en.opensuse.org/Portal:Printing . Solutions to many specific problems are present-
ed in the SUSE Knowledgebase (http://www.suse.com/support/ ). Locate the relevant articles
with a text search for CUPS .
275 Debugging CUPS SLES 12 SP3

18 The X Window System
The X Window System (X11) is the de facto standard for graphical user interfaces in Unix. X
is network-based, enabling applications started on one host to be displayed on another host
connected over any kind of network (LAN or Internet). This chapter provides basic information
on the X configuration, and background information about the use of fonts in SUSE® Linux
Enterprise Server.
Usually, the X Window System needs no configuration. The hardware is dynamically detected
during X start-up. The use of xorg.conf is therefore deprecated. If you still need to specify
custom options to change the way X behaves, you can still do so by modifying configuration
les under /etc/X11/xorg.conf.d/ .
Tip: IBM z Systems: Configuring the Graphical User Interface

IBM z Systems does not have any input or output devices supported by X.Org. Therefore,
none of the configuration procedures described in this section apply. More relevant infor-
mation for IBM z Systems can be found in Book “Deployment Guide”, Chapter 4 “Installation
on IBM z Systems”.
18.1 Installing and Configuring Fonts

Fonts in Linux can be categorized into two parts:
Outline or Vector Fonts

Contains a mathematical description as drawing instructions about the shape of a glyph.
As such, each glyph can be scaled to arbitrary sizes without loss of quality. Before such
a font (or glyph) can be used, the mathematical descriptions need to be transformed into
a raster (grid). This process is called font rasterization. Font hinting (embedded inside the
font) improves and optimizes the rendering result for a particular size. Rasterization and
hinting is done with the FreeType library.
Common formats under Linux are PostScript Type 1 and Type 2, TrueType, and OpenType.
276 Installing and Configuring Fonts SLES 12 SP3

Bitmap or Raster Fonts
Consists of an array of pixels designed for a specific font size. Bitmap fonts are extremely
fast and simple to render. However, compared to vector fonts, bitmap fonts cannot be
scaled without losing quality. As such, these fonts are usually distributed in different sizes.
These days, bitmap fonts are still used in the Linux console and sometimes in terminals.
Under Linux, Portable Compiled Format (PCF) or Glyph Bitmap Distribution Format (BDF)
are the most common formats.
The appearance of these fonts can be influenced by two main aspects:
choosing a suitable font family,
rendering the font with an algorithm that achieves results comfortable for the receiver's
eyes.
The last point is only relevant to vector fonts. Although the above two points are highly subjec-
tive, some defaults need to be created.
Linux font rendering systems consist of several libraries with different relations. The basic font
rendering library is FreeType (http://www.freetype.org/) , which converts font glyphs of support-
ed formats into optimized bitmap glyphs. The rendering process is controlled by an algorithm
and its parameters (which may be subject to patent issues).
Every program or library which uses FreeType should consult the Fontconfig (http://www.font-
config.org/) library. This library gathers font configuration from users and from the system.
When a user amends his Fontconfig setting, this change will result in Fontconfig-aware appli-
cations.
More sophisticated OpenType shaping needed for scripts such as Arabic, Han or Phags-Pa and
other higher level text processing is done using Harfbuzz (http://www.harfbuzz.org/) or Pango
(http://www.pango.org/) .
277 Installing and Configuring Fonts SLES 12 SP3

18.1.1 Showing Installed Fonts
To get an overview about which fonts are installed on your system, ask the commands rpm
or fc-list . Both will give you a good answer, but may return a different list depending on
system and user configuration:
rpm
Invoke rpm to see which software packages containing fonts are installed on your system:
rpm -qa '*fonts*'
Every font package should satisfy this expression. However, the command may return some
false positives like fonts-config (which is neither a font nor does it contain fonts).
fc-list
Invoke fc-list to get an overview about what font families can be accessed, whether
they are installed on the system or in your home:
fc-list ':' family
Note: Command fc-list

The command fc-list is a wrapper to the Fontconfig library. It is possible to query
a lot of interesting information from Fontconfig—or, to be more precise, from its
cache. See man 1 fc-list for more details.
18.1.2 Viewing Fonts

If you want to know what an installed font family looks like, either use the command
ftview (package ft2demos ) or visit http://fontinfo.opensuse.org/ . For example, to display
the FreeMono font in 14 point, use ftview like this:
ftview 14 /usr/share/fonts/truetype/FreeMono.ttf
If you need further information, go to http://fontinfo.opensuse.org/ to nd out which styles

(regular, bold, italic, etc.) and languages are supported.
18.1.3 Querying Fonts

To query which font is used when a pattern is given, use the fc-match command.
278 Showing Installed Fonts SLES 12 SP3

For example, if your pattern contains an already installed font, fc-match returns the le name,
font family, and the style:
tux > fc-match 'Liberation Serif'

LiberationSerif-Regular.ttf: "Liberation Serif" "Regular"
If the desired font does not exist on your system, Fontconfig's matching rules take place and try
to nd the most similar fonts available. This means, your request is substituted:
tux > fc-match 'Foo Family'

DejaVuSans.ttf: "DejaVu Sans" "Book"
Fontconfig supports aliases: a name is substituted with another family name. A typical example
are the generic names such as “sans-serif”, “serif”, and “monospace”. These alias names can be
substituted by real family names or even a preference list of family names:
tux > for font in serif sans mono; do fc-match "$font" ; done
DejaVuSerif.ttf: "DejaVu Serif" "Book"
DejaVuSans.ttf: "DejaVu Sans" "Book"
DejaVuSansMono.ttf: "DejaVu Sans Mono" "Book"
The result may vary on your system, depending on which fonts are currently installed.
Note: Similarity Rules according to Fontconfig

Fontconfig always returns a real family (if at least one is installed) according to the given
request, as similar as possible. “Similarity” depends on Fontconfig's internal metrics and
on the user's or administrator's Fontconfig settings.
18.1.4 Installing Fonts
To install a new font there are these major methods:
1. Manually install the font les such as *.ttf or *.otf to a known font directory. If it
needs to be system-wide, use the standard directory /usr/share/fonts . For installation
in your home directory, use ~/.config/fonts .
279 Installing Fonts SLES 12 SP3

If you want to deviate from the standard directories, Fontconfig allows you to choose
another one. Let Fontconfig know by using the <dir> element, see Section 18.1.5.2, “Diving
into Fontconfig XML” for details.
2. Install fonts using zypper . Lots of fonts are already available as a package, be it on your
SUSE distribution or in the M17N:fonts (http://download.opensuse.org/repositories/M17N:/
fonts/) repository. Add the repository to your list using the following command. For
example, to add a repository for SLE 12:
sudo zypper ar
http://download.opensuse.org/repositories/M17N:/fonts/SLE_12_SP3/
To search for your FONT_FAMILY_NAME use this command:
sudo zypper se 'FONT_FAMILY_NAME*fonts'
18.1.5 Configuring the Appearance of Fonts
Depending on the rendering medium, and font size, the result may be unsatisfactory. For exam-
ple, an average monitor these days has a resolution of 100dpi which makes pixels too big and
glyphs look clunky.
There are several algorithms available to deal with low resolutions, such as anti-aliasing
(grayscale smoothing), hinting (fitting to the grid), or subpixel rendering (tripling resolution in
one direction). These algorithms can also differ from one font format to another.
Important: Patent Issues with Subpixel Rendering

Subpixel rendering is not used in SUSE distributions. Although FreeType2 has support
for this algorithm, it is covered by several patents expiring at the end of the year 2019.
Therefore, setting subpixel rendering options in Fontconfig has no effect unless the system
has a FreeType2 library with subpixel rendering compiled in.
Via Fontconfig, it is possible to select a rendering algorithms for every font individually or for
a set of fonts.
280 Configuring the Appearance of Fonts SLES 12 SP3

18.1.5.1 Configuring Fonts via sysconfig
SUSE Linux Enterprise Server comes with a sysconfig layer above Fontconfig. This is a good
starting point for experimenting with font configuration. To change the default settings, edit the
configuration le /etc/sysconfig/fonts-config . (or use the YaST sysconfig module). After
you have edited the le, run fonts-config :
sudo /usr/sbin/fonts-config
Restart the application to make the effect visible. Keep in mind the following issues:
A few applications do need not to be restarted. For example, Firefox re-reads Fontconfig
configuration from time to time. Newly created or reloaded tabs get new font configura-
tions later.
The fonts-config script is called automatically after every package installation or re-
moval (if not, it is a bug of the font software package).
Every sysconfig variable can be temporarily overridden by the fonts-config command

line option. See fonts-config --help for details.
There are several sysconfig variables which can be altered. See man 1 fonts-config or the
help page of the YaST sysconfig module. The following variables are examples:
Usage of Rendering Algorithms

Consider FORCE_HINTSTYLE , FORCE_AUTOHINT , FORCE_BW , FORCE_BW_MONOSPACE ,
USE_EMBEDDED_BITMAPS and EMBEDDED_BITMAP_LANGAGES
Preference Lists of Generic Aliases

Use PREFER_SANS_FAMILIES , PREFER_SERIF_FAMILIES , PREFER_MONO_FAMILIES and
SEARCH_METRIC_COMPATIBLE
The following list provides some configuration examples, sorted from the “most readable” fonts
(more contrast) to “most beautiful” (more smoothed).
Bitmap Fonts
Prefer bitmap fonts via the PREFER_*_FAMILIES variables. Follow the example in the help
section for these variables. Be aware that these fonts are rendered black and white, not
smoothed and that bitmap fonts are available in several sizes only. Consider using
SEARCH_METRIC_COMPATIBLE="no"
to disable metric compatibility-driven family name substitutions.

Scalable Fonts Rendered Black and White
Scalable fonts rendered without antialiasing can result in a similar outcome to bitmap
fonts, while maintaining font scalability. Use well hinted fonts like the Liberation families.
Unfortunately, there is a lack of well hinted fonts though. Set the following variable to
force this method:
FORCE_BW="yes"
Monospaced Fonts Rendered Black and White

Render monospaced fonts without antialiasing only, otherwise use default settings:
FORCE_BW_MONOSPACE="yes"
Default Settings
All fonts are rendered with antialiasing. Well hinted fonts will be rendered with the byte
code interpreter (BCI) and the rest with autohinter ( hintstyle=hintslight ). Leave all
relevant sysconfig variables to the default setting.
CFF Fonts
Use fonts in CFF format. They can be considered also more readable than the default
TrueType fonts given the current improvements in FreeType2. Try them out by following
the example of PREFER_*_FAMILIES . Possibly make them more dark and bold with:
as they are rendered by hintstyle=hintslight by default. Also consider using:
Autohinter Exclusively
Even for a well hinted font, use FreeType2's autohinter. That can lead to thicker, sometimes
fuzzier letter shapes with lower contrast. Set the following variable to activate this:
FORCE_AUTOHINTER="yes"
Use FORCE_HINTSTYLE to control the level of hinting.
18.1.5.2 Diving into Fontconfig XML

Fontconfig's configuration format is the eXtensible Markup Language (XML). These few examples
are not a complete reference, but a brief overview. Details and other inspiration can be found
in man 5 fonts-conf or in /etc/fonts/conf.d/ .

The central Fontconfig configuration le is /etc/fonts/fonts.conf , which—along other work
—includes the whole /etc/fonts/conf.d/ directory. To customize Fontconfig, there are two
places where you can insert your changes:
FONTCONFIG CONFIGURATION FILES
1. System-wide changes. Edit the le /etc/fonts/local.conf (by default, it contains an

empty fontconfig element).
2. User-specific changes. Edit the le ~/.config/fontconfig/fonts.conf . Place Fontcon-

fig configuration les in the ~/.config/fontconfig/conf.d/ directory.
User-specific changes overwrite any system-wide settings.
Note: Deprecated User Configuration File

The le ~/.fonts.conf is marked as deprecated and should not be used anymore. Use
~/.config/fontconfig/fonts.conf instead.
Every configuration le needs to have a fontconfig element. As such, the minimal le looks
like this:
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>

</fontconfig>
If the default directories are not enough, insert the dir element with the respective directory:
<dir>/usr/share/fonts2</dir>
Fontconfig searches recursively for fonts.

Font-rendering algorithms can be chosen with following Fontconfig snippet (see Example 18.1,
“Specifying Rendering Algorithms”):
EXAMPLE 18.1: SPECIFYING RENDERING ALGORITHMS
<match target="font">
<test name="family">
<string>FAMILY_NAME</string>
</test>
<edit name="antialias" mode="assign">

<bool>true</bool>
</edit>
<edit name="hinting" mode="assign">
<bool>true</bool>
</edit>
<edit name="autohint" mode="assign">
<bool>false</bool>
</edit>
<edit name="hintstyle" mode="assign">
<const>hintfull</const>
</edit>
</match>
Various properties of fonts can be tested. For example, the <test> element can test for the
font family (as shown in the example), size interval, spacing, font format, and others. When
abandoning <test> completely, all <edit> elements will be applied to every font (global
change).
EXAMPLE 18.2: ALIASES AND FAMILY NAME SUBSTITUTIONS
Rule 1
<alias>
<family>Alegreya SC</family>
<default>
<family>serif</family>
</default>
</alias>
Rule 2
<alias>
<prefer>
<family>Droid Serif</family>
</prefer>
</alias>
Rule 3
<alias>
<accept>
<family>STIXGeneral</family>
</accept>
</alias>

The rules from Example 18.2, “Aliases and Family Name Substitutions” create a prioritized family list
(PFL). Depending on the element, different actions are performed:
<default> from Rule 1

This rule adds a serif family name at the end of the PFL.
<prefer> from Rule 2

This rule adds “Droid Serif” just before the rst occurrence of serif in the PFL, whenever
Alegreya SC is in PFL.
<accept> from Rule 3

This rule adds a “STIXGeneral” family name just after the rst occurrence of the serif
family name in the PFL.
Putting this together, when snippets occur in the order Rule 1 - Rule 2 - Rule 3 and the user
requests “Alegreya SC”, then the PFL is created as depicted in Table 18.1, “Generating PFL from
Fontconfig rules”.
TABLE 18.1: GENERATING PFL FROM FONTCONFIG RULES
Order Current PFL
Request Alegreya SC
Rule 1 Alegreya SC , serif
Rule 2 Alegreya SC , Droid Serif , serif
Rule 3 Alegreya SC , Droid Serif , serif , STIXGeneral
In Fontconfig's metrics, the family name has the highest priority over other patterns, like style,
size, etc. Fontconfig checks which family is currently installed on the system. If “Alegreya SC”
is installed, then Fontconfig returns it. If not, it asks for “Droid Serif”, etc.
Be careful. When the order of Fontconfig snippets is changed, Fontconfig can return different
results, as depicted in Table 18.2, “Results from Generating PFL from Fontconfig Rules with Changed
Order”.
TABLE 18.2: RESULTS FROM GENERATING PFL FROM FONTCONFIG RULES WITH CHANGED ORDER
Order Current PFL Note
Request Alegreya SC Same request performed.

Order Current PFL Note
Rule 2 Alegreya SC serif not in FPL, nothing is

substituted
Rule 3 Alegreya SC serif not in FPL, nothing is

substituted
Rule 1 Alegreya SC , serif Alegreya SC present in

FPL, substitution is per-
formed
Note: Implication.
Think of the <default> alias as a classification or inclusion of this group (if not installed).
As the example shows, <default> should always precede the <prefer> and <accept>
aliases of that group.
<default> classification is not limited to the generic aliases serif, sans-serif and
monospace. See /usr/share/fontconfig/conf.avail/30-metric-aliases.conf for
a complex example.
The following Fontconfig snippet in Example 18.3, “Aliases and Family Name Substitutions” creates
a serif group. Every family in this group could substitute others when a former font is not
installed.
EXAMPLE 18.3: ALIASES AND FAMILY NAME SUBSTITUTIONS
<alias>
<default>
</default>
</alias>
<alias>
<default>
</default>
</alias>
<alias>

<default>
</default>
</alias>
<alias>
<accept>
</accept>
</alias>
Priority is given by the order in the <accept> alias. Similarly, stronger <prefer> aliases can
be used.
Example 18.2, “Aliases and Family Name Substitutions” is expanded by Example 18.4, “Aliases and Family
Names Substitutions”.
EXAMPLE 18.4: ALIASES AND FAMILY NAMES SUBSTITUTIONS
Rule 4
<alias>
<accept>
<family>Liberation Serif</family>
</accept>
</alias>
Rule 5
<alias>
<prefer>
<family>DejaVu Serif</family>
</prefer>
</alias>
The expanded configuration from Example 18.4, “Aliases and Family Names Substitutions” would lead
to the following PFL evolution:
TABLE 18.3: RESULTS FROM GENERATING PFL FROM FONTCONFIG RULES
Order Current PFL
Request Alegreya SC

Order Current PFL
Rule 1 Alegreya SC , serif
Rule 2 Alegreya SC , Droid Serif , serif
Rule 3 Alegreya SC , Droid Serif , serif , STIXGeneral
Rule 4 Alegreya SC , Droid Serif , serif , Liberation Serif , STIX-

General
Rule 5 Alegreya SC , Droid Serif , DejaVu Serif , serif , Liberation

Serif , STIXGeneral
Note: Implications.
In case multiple <accept> declarations for the same generic name exist, the dec-
laration that is parsed last “wins”. If possible, do not use <accept> after user ( /
etc/fonts/conf.d/*-user.conf ) when creating a system-wide configuration.
In case multiple <prefer declarations for the same generic name exist, the decla-
ration that is parsed last “wins”. If possible, do not use <prefer> before user in
the system-wide configuration.
Every <prefer> declaration overwrites <accept> declarations for the same gener-
ic name. If the administrator wants to allow the user to utilize even <accept> and
not only <prefer> ,the administrator should not use <prefer> in the system-wide
configuration. On the other hand, as users mostly use <prefer> , this should not
have any detrimental effect. We also see the use of <prefer> also in system wide
configurations.

Install the packages xorg-docs to get more in-depth information about X11. man 5 xorg.conf
tells you more about the format of the manual configuration (if needed). More information on
the X11 development can be found on the project's home page at http://www.x.org .

Drivers are found in xf86-video-* packages, for example xf86-video-nv . Many of the drivers
delivered with these packages are described in detail in the related manual page. For example,
if you use the nv driver, nd more information about this driver in man 4 nv .
Information about third-party drivers should be available in /usr/share/doc/pack-
ages/<package_name> . For example, the documentation of x11-video-nvidiaG03 is avail-
able in /usr/share/doc/packages/x11-video-nvidiaG03 after the package was installed.

19 Accessing File Systems with FUSE
FUSE is the acronym for le system in user space. This means you can configure and
mount a le system as an unprivileged user. Normally, you need to be root for this
task. FUSE alone is a kernel module. Combined with plug-ins, it allows you to ex-
tend FUSE to access almost all le systems like remote SSH connections, ISO im-
ages, and more.
19.1 Configuring FUSE

Before you can use FUSE, you need to install the package fuse . Depending which le system
you want to use, you need additional plug-ins available as separate packages.
Generally you do not need to configure FUSE. However, it is a good idea to create a directory
where all your mount points are combined. For example, you can create a directory ~/mounts
and insert your subdirectories for your different le systems there.
19.2 Mounting an NTFS Partition

NTFS, the New Technology File System, is the default le system of Windows. Since under normal
circumstances the unprivileged user cannot mount NTFS block devices using the external FUSE
library, the process of mounting a Windows partition described below requires root privileges.
1. Become root and install the package ntfs-3g . It is available in SUSE Linux Enterprise
Workstation Extension.
2. Create a directory that is to be used as a mount point, for example ~/mounts/windows .
3. Find out which Windows partition you need. Use YaST and start the partitioner module
to see which partition belongs to Windows, but do not modify anything. Alternatively,
become root and execute /sbin/fdisk -l . Look for partitions with a partition type
of HPFS/NTFS .
4. Mount the partition in read-write mode. Replace the placeholder DEVICE with your re-
spective Windows partition:
ntfs-3g /dev/DEVICE MOUNT POINT
290 Configuring FUSE SLES 12 SP3

To use your Windows partition in read-only mode, append -o ro :
ntfs-3g /dev/DEVICE MOUNT POINT -o ro
The command ntfs-3g uses the current user (UID) and group (GID) to mount the given
device. If you want to set the write permissions to a different user, use the command id
USER to get the output of the UID and GID values. Set it with:
id tux
uid=1000(tux) gid=100(users) groups=100(users),16(dialout),33(video)
ntfs-3g /dev/DEVICE MOUNT POINT -o uid=1000,gid=100
Find additional options in the man page.
To unmount the resource, run fusermount -u MOUNT POINT .

See the home page http://fuse.sourceforge.net of FUSE for more information.

20 Managing Kernel Modules
Although Linux is a monolithic kernel, it can be extended using kernel modules. These are special
objects that can be inserted into the kernel and removed on demand. In practical terms, kernel
modules make it possible to add and remove drivers and interfaces that are not included in the
kernel itself. Linux provides several commands for managing kernel modules.
20.1 Listing Loaded Modules with lsmod and

modinfo
Use the lsmod command to view what kernel modules are currently loaded. The output of the
command may look as follows:
tux > lsmod

Module Size Used by
snd_usb_audio 188416 2
snd_usbmidi_lib 36864 1 snd_usb_audio
hid_plantronics 16384 0
snd_rawmidi 36864 1 snd_usbmidi_lib
snd_seq_device 16384 1 snd_rawmidi
fuse 106496 3
nfsv3 45056 1
nfs_acl 16384 1 nfsv3
The output is divided into three columns. The Module column lists the names of the loaded
modules, while the Size column displays the size of each module. The Used by column shows
the number of referring modules and their names. Note that this list may be incomplete.
To view detailed information about a specific kernel module, use the modinfo MODULE_NAME
command, where MODULE_NAME is the name of the desired kernel module. Note that the mod-
info binary resides in the /sbin directory that is not in the user's PATH environment variable.
This means that you must specify the full path to the binary when running modinfo command
as a regular user:
$ /sbin/modinfo kvm
filename: /lib/modules/4.4.57-18.3-default/kernel/arch/x86/kvm/kvm.ko
license: GPL
author: Qumranet
srcversion: BDFD8098BEEA517CB75959B
depends: irqbypass
292 Listing Loaded Modules with lsmod and modinfo SLES 12 SP3
intree: Y
vermagic: 4.4.57-18.3-default SMP mod_unload modversions
signer: openSUSE Secure Boot Signkey
sig_key: 03:32:FA:9C:BF:0D:88:BF:21:92:4B:0D:E8:2A:09:A5:4D:5D:EF:C8
sig_hashalgo: sha256
parm: ignore_msrs:bool
parm: min_timer_period_us:uint
parm: kvmclock_periodic_sync:bool
parm: tsc_tolerance_ppm:uint
parm: lapic_timer_advance_ns:uint
parm: halt_poll_ns:uint
parm: halt_poll_ns_grow:int
parm: halt_poll_ns_shrink:int
20.2 Adding and Removing Kernel Modules

While it is possible to use insmod and rmmod to add and remove kernel modules, it is recom-
mended to use the modprobe tool instead. modprobe offers several important advantages, in-
cluding automatic dependency resolution and blacklisting.
When used without any parameters, the modprobe command installs a specified kernel module.
modprobe must be run with root privileges:
tux > sudo modprobe acpi
To remove a kernel module, use the -r parameter:
sudo modprobe -r acpi
20.2.1 Loading Kernel Modules Automatically on Boot

Instead of loading kernel modules manually, you can load them automatically during the boot
process using the system-modules-load.service service. To enable a kernel module, add a
.conf le to the /etc/modules-load.d/ directory. It is good practice to give the configuration
le the same name as the module, for example:
/etc/modules-load.d/rt2800usb.conf
The configuration le must contain the name of the desired kernel module (for example,
rt2800usb ).
293 Adding and Removing Kernel Modules SLES 12 SP3

The described technique allows you to load kernel modules without any parameters. If you need
to load a kernel module with specific options, add a configuration le to the /etc/modprobe.d/
directory instead. The le must have the .conf extension. The name of the le should adhere
to the following naming convention: priority-modulename.conf , for example: 50-think-
fan.conf . The configuration le must contain the name of the kernel module and the desired
parameters. You can use the example command below to create a configuration le containing
the name of the kernel module and its parameters:
echo "options thinkpad_acpi fan_control=1" | sudo tee /etc/modprobe.d/thinkfan.conf
Note: Loading Kernel Modules

Most kernel modules are loaded by the system automatically when a device is detected
or user space requests specific functionality. Thus, adding modules manually to /etc/
modules-load.d/ is rarely required.
20.2.2 Blacklisting Kernel Modules with modprobe

Blacklisting a kernel module prevents it from loading during the boot process. This can be useful
when you want to disable a module that you suspect is causing problems on your system. Note
that you can still load blacklisted kernel modules manually using the insmod or modprobe tools.
To blacklist a module, add the blacklist MODULE_NAME line to the /etc/mod-
probe.d/50-blacklist.conf le. For example:
blacklist nouveau
Run the mkinitrd command as root to generate a new initrd image, then reboot your ma-
chine. These steps can be performed using the following command:
su
echo "blacklist nouveau" >> /etc/modprobe.d/50-blacklist.conf && mkinitrd && reboot
To disable a kernel module temporarily only, blacklist it on-the-y during the boot. To do this,
press the E key when you see the boot screen. This drops you into a minimal editor that allows
you to modify boot parameters. Locate the line that looks as follows:
linux /boot/vmlinuz...splash= silent quiet showopts
294 Blacklisting Kernel Modules with modprobe SLES 12 SP3

Add the modprobe.blacklist=MODULE_NAME command to the end of the line. For example:
linux /boot/vmlinuz...splash= silent quiet showopts modprobe.blacklist=nouveau
Press F10 or Ctrl – X to boot with the specified configuration.

To blacklist a kernel module permanently via GRUB, open the /etc/default/grub le for
editing, and add the modprobe.blacklist=MODULE_NAME option to the GRUB_CMD_LINUX com-
mand. Then run the sudo grub2-mkconfig -o /boot/grub2/grub.cfg command to enable
the changes.
295 Blacklisting Kernel Modules with modprobe SLES 12 SP3

21 Dynamic Kernel Device Management with udev
The kernel can add or remove almost any device in a running system. Changes in the device
state (whether a device is plugged in or removed) need to be propagated to user space. Devices
need to be configured when they are plugged in and recognized. Users of a certain device need
to be informed about any changes in this device's recognized state. udev provides the needed
infrastructure to dynamically maintain the device node les and symbolic links in the /dev
directory. udev rules provide a way to plug external tools into the kernel device event process-
ing. This allows you to customize udev device handling by adding certain scripts to execute as
part of kernel device handling, or request and import additional data to evaluate during device
handling.
21.1 The /dev Directory

The device nodes in the /dev directory provide access to the corresponding kernel devices.
With udev , the /dev directory reflects the current state of the kernel. Every kernel device has
one corresponding device le. If a device is disconnected from the system, the device node is
removed.
The content of the /dev directory is kept on a temporary le system and all les are rendered
at every system start-up. Manually created or modified les do not, by design, survive a reboot.
Static les and directories that should always be in the /dev directory regardless of the state of
the corresponding kernel device can be created with systemd-tmpfiles. The configuration les
are found in /usr/lib/tmpfiles.d/ and /etc/tmpfiles.d/ ; for more information, see the
systemd-tmpfiles(8) man page.
21.2 Kernel uevents and udev

The required device information is exported by the sysfs le system. For every device the
kernel has detected and initialized, a directory with the device name is created. It contains
attribute les with device-specific properties.
Every time a device is added or removed, the kernel sends a uevent to notify udev of the change.
The udev daemon reads and parses all provided rules from the /etc/udev/rules.d/*.rules
les once at start-up and keeps them in memory. If rules les are changed, added or removed,
296 The /dev Directory SLES 12 SP3

the daemon can reload the in-memory representation of all rules with the command udevadm
control --reload . For more details on udev rules and their syntax, refer to Section 21.6,
“Influencing Kernel Device Event Handling with udev Rules”.
Every received event is matched against the set of provides rules. The rules can add or change
event environment keys, request a specific name for the device node to create, add symbolic
links pointing to the node or add programs to run after the device node is created. The driver
core uevents are received from a kernel netlink socket.
21.3 Drivers, Kernel Modules and Devices

The kernel bus drivers probe for devices. For every detected device, the kernel creates an internal
device structure while the driver core sends a uevent to the udev daemon. Bus devices identify
themselves by a specially-formatted ID, which tells what kind of device it is. Usually these IDs
consist of vendor and product ID and other subsystem-specific values. Every bus has its own
scheme for these IDs, called MODALIAS . The kernel takes the device information, composes a
MODALIAS ID string from it and sends that string along with the event. For a USB mouse, it
looks like this:
MODALIAS=usb:v046DpC03Ed2000dc00dsc00dp00ic03isc01ip02
Every device driver carries a list of known aliases for devices it can handle. The list is contained
in the kernel module le itself. The program depmod reads the ID lists and creates the le
modules.alias in the kernel's /lib/modules directory for all currently available modules.
With this infrastructure, module loading is as easy as calling modprobe for every event that
carries a MODALIAS key. If modprobe $MODALIAS is called, it matches the device alias composed
for the device with the aliases provided by the modules. If a matching entry is found, that module
is loaded. All this is automatically triggered by udev .
21.4 Booting and Initial Device Setup

All device events happening during the boot process before the udev daemon is running are
lost, because the infrastructure to handle these events resides on the root le system and is
not available at that time. To cover that loss, the kernel provides a uevent le located in the
device directory of every device in the sysfs le system. By writing add to that le, the kernel
resends the same event as the one lost during boot. A simple loop over all uevent les in /sys
triggers all events again to create the device nodes and perform device setup.
297 Drivers, Kernel Modules and Devices SLES 12 SP3

As an example, a USB mouse present during boot may not be initialized by the early boot logic,
because the driver is not available at that time. The event for the device discovery was lost
and failed to nd a kernel module for the device. Instead of manually searching for connected
devices, udev requests all device events from the kernel after the root le system is available, so
the event for the USB mouse device runs again. Now it nds the kernel module on the mounted
root le system and the USB mouse can be initialized.
From user space, there is no visible difference between a device coldplug sequence and a device
discovery during runtime. In both cases, the same rules are used to match and the same config-
ured programs are run.
21.5 Monitoring the Running udev Daemon

The program udevadm monitor can be used to visualize the driver core events and the timing
of the udev event processes.
UEVENT[1185238505.276660] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb)

UDEV [1185238505.279198] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb)
UEVENT[1185238505.279527] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb)
UDEV [1185238505.285573] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb)
UEVENT[1185238505.298878] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/
input10 (input)
UDEV [1185238505.305026] add /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/
input10 (input)
input10/mouse2 (input)
input10/event4 (input)
input10/event4 (input)
input10/mouse2 (input)
The UEVENT lines show the events the kernel has sent over netlink. The UDEV lines show the
finished udev event handlers. The timing is printed in microseconds. The time between UEVENT
and UDEV is the time udev took to process this event or the udev daemon has delayed its
execution to synchronize this event with related and already running events. For example, events
for hard disk partitions always wait for the main disk device event to finish, because the partition
events may rely on the data that the main disk event has queried from the hardware.
298 Monitoring the Running udev Daemon SLES 12 SP3

udevadm monitor --env shows the complete event environment:
ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10
SUBSYSTEM=input
SEQNUM=1181
NAME="Logitech USB-PS/2 Optical Mouse"
PHYS="usb-0000:00:1d.2-1/input0"
UNIQ=""
EV=7
KEY=70000 0 0 0 0
REL=103
MODALIAS=input:b0003v046DpC03Ee0110-e0,1,2,k110,111,112,r0,1,8,amlsfw
udev also sends messages to syslog. The default syslog priority that controls which messages are
sent to syslog is specified in the udev configuration le /etc/udev/udev.conf . The log pri-
ority of the running daemon can be changed with udevadm control --log_priority= LEV-
EL/NUMBER .
21.6 Influencing Kernel Device Event Handling with

udev Rules
A udev rule can match any property the kernel adds to the event itself or any information that
the kernel exports to sysfs . The rule can also request additional information from external
programs. Every event is matched against all provided rules. All rules are located in the /etc/
udev/rules.d directory.
Every line in the rules le contains at least one key value pair. There are two kinds of keys,
match and assignment keys. If all match keys match their values, the rule is applied and the
assignment keys are assigned the specified value. A matching rule may specify the name of the
device node, add symbolic links pointing to the node or run a specified program as part of the
event handling. If no matching rule is found, the default device node name is used to create
the device node. Detailed information about the rule syntax and the provided keys to match or
import data are described in the udev man page. The following example rules provide a basic
introduction to udev rule syntax. The example rules are all taken from the udev default rule
set that is located under /etc/udev/rules.d/50-udev-default.rules .
EXAMPLE 21.1: EXAMPLE udev RULES
# console
299 Influencing Kernel Device Event Handling with udev Rules SLES 12 SP3
KERNEL=="console", MODE="0600", OPTIONS="last_rule"
# serial devices
KERNEL=="ttyUSB*", ATTRS{product}=="[Pp]alm*Handheld*", SYMLINK+="pilot"
# printer
SUBSYSTEM=="usb", KERNEL=="lp*", NAME="usb/%k", SYMLINK+="usb%k", GROUP="lp"
# kernel firmware loader

SUBSYSTEM=="firmware", ACTION=="add", RUN+="firmware.sh"
The console rule consists of three keys: one match key ( KERNEL ) and two assign keys ( MODE ,
OPTIONS ). The KERNEL match rule searches the device list for any items of the type console .
Only exact matches are valid and trigger this rule to be executed. The MODE key assigns special
permissions to the device node, in this case, read and write permissions to the owner of this
device only. The OPTIONS key makes this rule the last rule to be applied to any device of this
type. Any later rule matching this particular device type does not have any effect.
The serial devices rule is not available in 50-udev-default.rules anymore, but it is
still worth considering. It consists of two match keys ( KERNEL and ATTRS ) and one assign key
( SYMLINK ). The KERNEL key searches for all devices of the ttyUSB type. Using the * wild card,
this key matches several of these devices. The second match key, ATTRS , checks whether the
product attribute le in sysfs for any ttyUSB device contains a certain string. The assign
key ( SYMLINK ) triggers the addition of a symbolic link to this device under /dev/pilot . The
operator used in this key ( += ) tells udev to additionally perform this action, even if previous
or later rules add other symbolic links. As this rule contains two match keys, it is only applied
if both conditions are met.
The printer rule deals with USB printers and contains two match keys which must both apply
to get the entire rule applied ( SUBSYSTEM and KERNEL ). Three assign keys deal with the naming
for this device type ( NAME ), the creation of symbolic device links ( SYMLINK ) and the group
membership for this device type ( GROUP ). Using the * wild card in the KERNEL key makes it
match several lp printer devices. Substitutions are used in both, the NAME and the SYMLINK
keys to extend these strings by the internal device name. For example, the symbolic link to the
rst lp USB printer would read /dev/usblp0 .
The kernel firmware loader rule makes udev load additional rmware by an external helper
script during runtime. The SUBSYSTEM match key searches for the firmware subsystem. The
ACTION key checks whether any device belonging to the firmware subsystem has been added.
The RUN+= key triggers the execution of the firmware.sh script to locate the rmware that
is to be loaded.
300 Influencing Kernel Device Event Handling with udev Rules SLES 12 SP3
Some general characteristics are common to all rules:
Each rule consists of one or more key value pairs separated by a comma.
A key's operation is determined by the operator. udev rules support several operators.
Each given value must be enclosed by quotation marks.
Each line of the rules le represents one rule. If a rule is longer than one line, use \ to
join the different lines as you would do in shell syntax.
udev rules support a shell-style pattern that matches the * , ? , and [] patterns.
udev rules support substitutions.
21.6.1 Using Operators in udev Rules

Creating keys you can choose from several operators, depending on the type of key you want
to create. Match keys will normally be used to nd a value that either matches or explicitly
mismatches the search value. Match keys contain either of the following operators:
==
Compare for equality. If the key contains a search pattern, all results matching this pattern
are valid.
!=
Compare for non-equality. If the key contains a search pattern, all results matching this
pattern are valid.
Any of the following operators can be used with assign keys:
=
Assign a value to a key. If the key previously consisted of a list of values, the key resets
and only the single value is assigned.
+=
Add a value to a key that contains a list of entries.
:=
Assign a final value. Disallow any later change by later rules.
301 Using Operators in udev Rules SLES 12 SP3

21.6.2 Using Substitutions in udev Rules
udev rules support the use of placeholders and substitutions. Use them in a similar fashion as
you would do in any other scripts. The following substitutions can be used with udev rules:
%r , $root
The device directory, /dev by default.
%p , $devpath
The value of DEVPATH .
%k , $kernel
The value of KERNEL or the internal device name.
%n , $number
The device number.
%N , $tempnode
The temporary name of the device le.
%M , $major
The major number of the device.
%m , $minor
The minor number of the device.
%s{ATTRIBUTE} , $attr{ATTRIBUTE}
The value of a sysfs attribute (specified by ATTRIBUTE ).
%E{VARIABLE} , $env{VARIABLE}
The value of an environment variable (specified by VARIABLE ).
%c , $result
The output of PROGRAM .
%%
The % character.
$$
The $ character.
302 Using Substitutions in udev Rules SLES 12 SP3

21.6.3 Using udev Match Keys
Match keys describe conditions that must be met before a udev rule can be applied. The fol-
lowing match keys are available:
ACTION
The name of the event action, for example, add or remove when adding or removing a
device.
DEVPATH
The device path of the event device, for example, DEVPATH=/bus/pci/drivers/ipw3945
to search for all events related to the ipw3945 driver.
KERNEL
The internal (kernel) name of the event device.
SUBSYSTEM
The subsystem of the event device, for example, SUBSYSTEM=usb for all events related to
USB devices.
ATTR{FILENAME}
sysfs attributes of the event device. To match a string contained in the vendor attribute
le name, you could use ATTR{vendor}=="On[sS]tream" , for example.
KERNELS
Let udev search the device path upwards for a matching device name.
SUBSYSTEMS
Let udev search the device path upwards for a matching device subsystem name.
DRIVERS
Let udev search the device path upwards for a matching device driver name.
ATTRS{FILENAME}
Let udev search the device path upwards for a device with matching sysfs attribute
values.
ENV{KEY}
The value of an environment variable, for example, ENV{ID_BUS}="ieee1394 to search
for all events related to the FireWire bus ID.
303 Using udev Match Keys SLES 12 SP3

PROGRAM
Let udev execute an external program. To be successful, the program must return with
exit code zero. The program's output, printed to STDOUT, is available to the RESULT key.
RESULT
Match the output string of the last PROGRAM call. Either include this key in the same rule
as the PROGRAM key or in a later one.
21.6.4 Using udev Assign Keys

In contrast to the match keys described above, assign keys do not describe conditions that must
be met. They assign values, names and actions to the device nodes maintained by udev .
NAME
The name of the device node to be created. After a rule has set a node name, all other rules
with a NAME key for this node are ignored.
SYMLINK
The name of a symbolic link related to the node to be created. Multiple matching rules
can add symbolic links to be created with the device node. You can also specify multiple
symbolic links for one node in one rule using the space character to separate the symbolic
link names.
OWNER, GROUP, MODE

The permissions for the new device node. Values specified here overwrite anything that
has been compiled in.
ATTR{KEY}
Specify a value to be written to a sysfs attribute of the event device. If the == operator
is used, this key is also used to match against the value of a sysfs attribute.
ENV{KEY}
Tell udev to export a variable to the environment. If the == operator is used, this key is
also used to match against an environment variable.
RUN
Tell udev to add a program to the list of programs to be executed for this device. Keep in
mind to restrict this to very short tasks to avoid blocking further events for this device.
304 Using udev Assign Keys SLES 12 SP3

LABEL
Add a label where a GOTO can jump to.
GOTO
Tell udev to skip several rules and continue with the one that carries the label referenced
by the GOTO key.
IMPORT{TYPE}
Load variables into the event environment such as the output of an external program.
udev imports variables of several types. If no type is specified, udev tries to determine
the type itself based on the executable bit of the le permissions.
program tells udev to execute an external program and import its output.
file tells udev to import a text le.
parent tells udev to import the stored keys from the parent device.
WAIT_FOR_SYSFS
Tells udev to wait for the specified sysfs le to be created for a certain device. For
example, WAIT_FOR_SYSFS="ioerr_cnt" informs udev to wait until the ioerr_cnt le
has been created.
OPTIONS
The OPTION key may have several values:
last_rule tells udev to ignore all later rules.
ignore_device tells udev to ignore this event completely.
ignore_remove tells udev to ignore all later remove events for the device.
all_partitions tells udev to create device nodes for all available partitions on a
block device.
21.7 Persistent Device Naming

The dynamic device directory and the udev rules infrastructure make it possible to provide
stable names for all disk devices—regardless of their order of recognition or the connection
used for the device. Every appropriate block device the kernel creates is examined by tools
305 Persistent Device Naming SLES 12 SP3

with special knowledge about certain buses, drive types or le systems. Along with the dynamic
kernel-provided device node name, udev maintains classes of persistent symbolic links pointing
to the device:
/dev/disk
|-- by-id
| |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B -> ../../sda
| |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part1 -> ../../sda1
| |-- usb-Generic_STORAGE_DEVICE_02773 -> ../../sdd
| `-- usb-Generic_STORAGE_DEVICE_02773-part1 -> ../../sdd1
|-- by-label
| |-- Photos -> ../../sdd1
| |-- SUSE10 -> ../../sda7
| `-- devel -> ../../sda6
|-- by-path
| |-- pci-0000:00:1f.2-scsi-0:0:0:0 -> ../../sda
| |-- pci-0000:00:1f.2-scsi-0:0:0:0-part1 -> ../../sda1
| |-- pci-0000:00:1f.2-scsi-1:0:0:0 -> ../../sr0
| |-- usb-02773:0:0:2 -> ../../sdd
| |-- usb-02773:0:0:2-part1 -> ../../sdd1
`-- by-uuid
|-- 159a47a4-e6e6-40be-a757-a629991479ae -> ../../sda7
|-- 3e999973-00c9-4917-9442-b7633bd95b9e -> ../../sda6
`-- 4210-8F8C -> ../../sdd1
21.8 Files used by udev

/sys/*
Virtual le system provided by the Linux kernel, exporting all currently known devices.
This information is used by udev to create device nodes in /dev
/dev/*
Dynamically created device nodes and static content created with systemd-tmpfiles; for
more information, see the systemd-tmpfiles(8) man page.
306 Files used by udev SLES 12 SP3

The following les and directories contain the crucial elements of the udev infrastructure:
/etc/udev/udev.conf
Main udev configuration le.
/etc/udev/rules.d/*
udev event matching rules.
/usr/lib/tmpfiles.d/ and /etc/tmpfiles.d/

Responsible for static /dev content.
/usr/lib/udev/*
Helper programs called from udev rules.

For more information about the udev infrastructure, refer to the following man pages:
udev
General information about udev , keys, rules and other important configuration issues.
udevadm
udevadm can be used to control the runtime behavior of udev , request kernel events,
manage the event queue and provide simple debugging mechanisms.
udevd
Information about the udev event managing daemon.

22 Live Patching the Linux Kernel Using kGraft
This document describes the basic principles of the kGraft live patching technology
and provides usage guidelines for the SLE Live Patching service.
kGraft is a live patching technology for runtime patching of the Linux kernel, with-
out stopping the kernel. This maximizes system uptime, and thus system availabili-
ty, which is important for mission-critical systems. By allowing dynamic patching of
the kernel, the technology also encourages users to install critical security updates
without deferring them to a scheduled downtime.
A kGraft patch is a kernel module, intended for replacing whole functions in the
kernel. kGraft primarily offers in-kernel infrastructure for integration of the patched
code with base kernel code at runtime.
SLE Live Patching is a service provided on top of regular SUSE Linux Enterprise
Server maintenance. kGraft patches distributed through SLE Live Patching supple-
ment regular SLES maintenance updates. Common update stack and procedures can
be used for SLE Live Patching deployment.
The information provided in this document related to the AMD64/Intel 64 and
POWER architectures. In case you use a different architecture, the procedures may
differ.
22.1 Advantages of kGraft

Live kernel patching using kGraft is especially useful for quick response in emergencies (when
serious vulnerabilities are known and should be xed when possible or there are serious system
stability issues with a known x). It is not used for scheduled updates where time is not critical.
Typical use cases for kGraft include systems like memory databases with huge amounts of RAM,
where boot-up times of 15 minutes or more are not uncommon, large simulations that need
weeks or months without a restart, or infrastructure building blocks providing continuous ser-
vice to a many consumers.
The main advantage of kGraft is that it never requires stopping the kernel, not even for a short
time period.
308 Advantages of kGraft SLES 12 SP3

A kGraft patch is a .ko kernel module in a RPM package. It is inserted into the kernel using the
insmod command when the package is installed or updated. kGraft replaces whole functions in
the kernel, even if they are being executed. An updated kGraft module can replace an existing
patch if necessary.
kGraft is also lean—it contains only a small amount of code, because it leverages other standard
Linux technologies.
22.2 Low-level Function of kGraft

kGraft uses the ftrace infrastructure to perform patching. The following describes the implemen-
tation on the AMD64/Intel 64 architecture.
To patch a kernel function, kGraft needs some space at the start of the function to insert a jump to
a new function. This space is allocated during kernel compilation by GCC with function profiling
turned on. In particular, a 5-byte call instruction is injected to the start of kernel functions. When
such instrumented kernel is booting, profiling calls are replaced by 5-byte NOP (no operation)
instructions.
After patching starts, the rst byte is replaced by the INT3 (breakpoint) instruction. This ensures
atomicity of the 5-byte instruction replacement. The other four bytes are replaced by the address
to the new function. Finally, the rst byte is replaced by the JMP (long jump) opcode.
Inter-processor non-maskable interrupts (IPI NMI) are used throughout the process to ush spec-
ulative decoding queues of other CPUs in the system. This allows switching to the new function
without ever stopping the kernel, not even for a very short moment. The interruptions by IPI
NMIs can be measured in microseconds and are not considered service interruptions as they
happen while the kernel is running in any case.
Callers are never patched. Instead, the callee's NOPs are replaced by a JMP to the new function.
JMP instructions remain forever. This takes care of function pointers, including in structures,
and does not require saving any old data for the possibility of un-patching.
However, these steps alone would not be good enough: since the functions would be replaced
non-atomically, a new xed function in one part of the kernel could still be calling an old
function elsewhere or vice versa. If the semantics of the function interfaces changed in the patch,
chaos would ensue.
Thus, until all functions are replaced, kGraft uses an approach based on trampolines and similar
to RCU (read-copy-update), to ensure a consistent view of the world to each user space thread,
kernel thread and kernel interrupt. A per-thread ag is set on each kernel entry and exit. This
309 Low-level Function of kGraft SLES 12 SP3

way, an old function would always call another old function and a new function always a new
one. Once all processes have the "new universe" ag set, patching is complete, trampolines can
be removed and the code can operate at full speed without performance impact other than an
extra-long jump for each patched function.
22.3 Installing kGraft Patches

This section describes the activation of the SUSE Linux Enterprise Live Patching extension and
the installation of kGraft patches.
22.3.1 Activation of SLE Live Patching

To activate SLE Live Patching on your system, follow these steps:
1. If your SLES system is not yet registered, register it. Registration can be done during the
system installation or later using the YaST Product Registration module ( yast2 registra-
tion ). After registration, click Yes to see the list of available online updates.
If your SLES system is already registered, but SLE Live Patching is not yet activated, open
the YaST Product Registration module ( yast2 registration ) and click Select Extensions.
2. Select SUSE Linux Enterprise Live Patching 12 in the list of available extensions and click
Next.
3. Confirm the license terms and click Next.
4. Enter the SLE Live Patching registration code and click Next.
5. Check the Installation Summary and selected Patterns. The pattern Live Patching should
be selected for installation.
6. Click Accept to complete the installation. This will install the base kGraft components on
your system together with the initial live patch.
22.3.2 Updating System

1. SLE Live Patching updates are distributed in a form that allows using standard SLE update
stack for patch application. The initial live patch can be updated using zypper patch ,
YaST Online Update or equivalent method.
310 Installing kGraft Patches SLES 12 SP3

2. The kernel is patched automatically during the package installation. However, invocations
of the old kernel functions are not completely eliminated until all sleeping processes wake
up and get out of the way. This can take a considerable amount of time. Despite this,
sleeping processes that use the old kernel functions are not considered a security issue.
Nevertheless, in the current version of kGraft, it is not possible to apply another kGraft
patch until all processes cross the kernel-user space boundary to stop using patched func-
tions from the previous patch.
To see the global status of patching, check the ag in /sys/kernel/kgraft/
in_progress . The value 1 signifies the existence of sleeping processes that still need to
be woken (the patching is still in progress). The value 0 signifies that all processes are
using solely the patched functions and patching has finished already. Alternatively, use
the kgr status command to obtain the same information.
The ag can be checked on a per-process basis too. Check the number in /proc/PRO-
CESS_NUMBER/kgr_in_progress for each process individually. Again, the value 1 signi-
fies sleeping process that still needs to be woken. Alternatively, use the kgr blocking
command to output the list of sleeping processes.
22.4 Patch Lifecycle

Expiration dates of live patches can be accessed with zypper lifecycle . Make sure that the
package lifecycle-data-sle-live-patching is installed.
tux > zypper lifecycle
Product end of support

Codestream: SUSE Linux Enterprise Server 12 2024-10-31
SUSE Linux Enterprise Server 12 SP2 n/a*
Extension end of support

SUSE Linux Enterprise Live Patching 2017-10-31
Package end of support if different from product:

SUSEConnect Now, installed 0.2.41-18.1, update available
0.2.42-19.3.1
apache2-utils Now
*) See https://www.suse.com/lifecycle for latest information
311 Patch Lifecycle SLES 12 SP3

When the expiration date of a patch is reached, no further live patches for this kernel version
will be supplied. Plan an update of your kernel before the end of the live patch lifecycle period.
22.5 Removing a kGraft Patch

To remove a kGraft patch, use the following procedure:
1. First remove the patch itself using Zypper:
zypper rm kgraft-patch-3_12_32-25-default
2. Then reboot the machine.
22.6 Stuck Kernel Execution Threads

Kernel threads need to be prepared to handle kGraft. Third-party software may not be ready for
kGraft adoption and its kernel modules may spawn kernel execution threads. These threads will
block the patching process indefinitely. As an emergency measure kGraft offers the possibility
to force finishing of the patching process without waiting for all execution threads to cross the
safety checkpoint. This can be achieved by writing 0 into /sys/kernel/kgraft/in_progress .
Consult SUSE Support before performing this procedure.
22.7 The kgr Tool

Several kGraft management tasks can be simplified with the kgr tool. The available commands
are:
kgr status
Displays the overall status of kGraft patching ( ready or in_progress ).
kgr patches
Displays the list of loaded kGraft patches.
kgr blocking
Lists processes that are preventing kGraft patching from finishing. By default only the PIDs
are listed. Specifying -v prints command lines if available. Another -v displays also stack
traces.
312 Removing a kGraft Patch SLES 12 SP3

For detailed information, see man kgr .
22.8 Scope of kGraft Technology

kGraft is based on replacing functions. Data structure alteration can be accomplished only in-
directly with kGraft. As a result, changes to kernel data structure require special care and, if
the change is too large, rebooting might be required. kGraft also might not be able to handle
situations where one compiler is used to compile the old kernel and another compiler is used
for compiling the patch.
Because of the way kGraft works, support for third-party modules that are spawning kernel
threads is limited.
22.9 Scope of SLE Live Patching

Fixes for SUSE Common Vulnerability Scoring System (CVSS) level 7+ vulnerabilities and bug
fixes related to system stability or data corruption will be shipped in the scope of SLE Live
Patching. It might not be possible to produce a live patch for all kinds of fixes fulfilling the
above criteria. SUSE reserves the right to skip fixes where production of a kernel live patch is
unviable because of technical reasons. For more information on CVSS 3.0, which is the base for
the SUSE CVSS rating, see https://www.first.org/cvss/ .
22.10 Interaction with the Support Processes

While resolving a technical difficulty with SUSE Support, you may receive a so-called Program
Temporary Fix (PTF). PTFs may be issued for various packages including those forming the base
of SLE Live Patching.
kGraft PTFs complying with the conditions described in the previous section can be installed as
usual and SUSE will ensure that the system in question does not need to be rebooted and that
future live updates are applied cleanly.
PTFs issued for the base kernel disrupt the live patching process. First, installing the PTF kernel
means a reboot as the kernel cannot be replaced as a whole at runtime. Second, another reboot
is needed to replace the PTF with any regular maintenance updates for which the live patches
are issued.
313 Scope of kGraft Technology SLES 12 SP3

PTFs for other packages in SLE Live Patching can be treated like regular PTFs with the usual
guarantees.
314 Interaction with the Support Processes SLES 12 SP3

23 Special System Features
This chapter starts with information about various software packages, the virtual
consoles and the keyboard layout. We talk about software components like bash ,
cron and logrotate , because they were changed or enhanced during the last re-
lease cycles. Even if they are small or considered of minor importance, users should
change their default behavior, because these components are often closely coupled
with the system. The chapter concludes with a section about language and coun-
try-specific settings (I18N and L10N).
23.1 Information about Special Software Packages

The programs bash , cron , logrotate , locate , ulimit and free are very important for
system administrators and many users. Man pages and info pages are two useful sources of
information about commands, but both are not always available. GNU Emacs is a popular and
very configurable text editor.
23.1.1 The bash Package and /etc/profile

Bash is the default system shell. When used as a login shell, it reads several initialization les.
Bash processes them in the order they appear in this list:
1. /etc/profile
2. ~/.profile
3. /etc/bash.bashrc
4. ~/.bashrc
Make custom settings in ~/.profile or ~/.bashrc . To ensure the correct processing of

these les, it is necessary to copy the basic settings from /etc/skel/.profile or /etc/
skel/.bashrc into the home directory of the user. It is recommended to copy the settings from
/etc/skel after an update. Execute the following shell commands to prevent the loss of per-
sonal adjustments:
mv ~/.bashrc ~/.bashrc.old
315 Information about Special Software Packages SLES 12 SP3

cp /etc/skel/.bashrc ~/.bashrc
mv ~/.profile ~/.profile.old
cp /etc/skel/.profile ~/.profile
Then copy personal adjustments back from the *.old les.
23.1.2 The cron Package
Use cron to run commands automatically in the background at predefined time. cron uses spe-
cially formatted time tables, and the tool comes with several default ones. Users can also specify
custom tables, if needed.
The cron tables are located in /var/spool/cron/tabs . /etc/crontab serves as a systemwide
cron table. Enter the user name to run the command directly after the time table and before
the command. In Example 23.1, “Entry in /etc/crontab”, root is entered. Package-specific tables,
located in /etc/cron.d , have the same format. See the cron man page ( man cron ).
EXAMPLE 23.1: ENTRY IN /ETC/CRONTAB
1-59/5 * * * * root test -x /usr/sbin/atrun && /usr/sbin/atrun
You cannot edit /etc/crontab by calling the command crontab -e . This le must be loaded
directly into an editor, then modified and saved.
A number of packages install shell scripts to the directories /etc/cron.hourly , /etc/
cron.daily , /etc/cron.weekly and /etc/cron.monthly , whose execution is controlled by
/usr/lib/cron/run-crons . /usr/lib/cron/run-crons is run every 15 minutes from the
main table ( /etc/crontab ). This guarantees that processes that may have been neglected can
be run at the proper time.
To run the hourly , daily or other periodic maintenance scripts at custom times, remove the
time stamp les regularly using /etc/crontab entries (see Example 23.2, “/etc/crontab: Remove
Time Stamp Files”, which removes the hourly one before every full hour, the daily one once
a day at 2:14 a.m., etc.).
EXAMPLE 23.2: /ETC/CRONTAB: REMOVE TIME STAMP FILES
59 * * * * root rm -f /var/spool/cron/lastrun/cron.hourly
14 2 * * * root rm -f /var/spool/cron/lastrun/cron.daily
29 2 * * 6 root rm -f /var/spool/cron/lastrun/cron.weekly
316 The cron Package SLES 12 SP3

44 2 1 * * root rm -f /var/spool/cron/lastrun/cron.monthly
Or you can set DAILY_TIME in /etc/sysconfig/cron to the time at which cron.daily should
start. The setting of MAX_NOT_RUN ensures that the daily tasks get triggered to run, even if the
user did not turn on the computer at the specified DAILY_TIME for a longer time. The maximum
value of MAX_NOT_RUN is 14 days.
The daily system maintenance jobs are distributed to various scripts for reasons of clarity. They
are contained in the package aaa_base . /etc/cron.daily contains, for example, the compo-
nents suse.de-backup-rpmdb , suse.de-clean-tmp or suse.de-cron-local .
23.1.3 Stopping Cron Status Messages

To avoid the mail-ood caused by cron status messages, the default value of
SEND_MAIL_ON_NO_ERROR in /etc/sysconfig/cron is set to " no " for new installations. Even
with this setting to " no ", cron data output will still be sent to the MAILTO address, as docu-
mented in the cron man page.
In the update case it is recommended to set these values according to your needs.
23.1.4 Log Files: Package logrotate
There are several system services (daemons) that, along with the kernel itself, regularly record
the system status and specific events onto log les. This way, the administrator can regularly
check the status of the system at a certain point in time, recognize errors or faulty functions and
troubleshoot them with pinpoint precision. These log les are normally stored in /var/log as
specified by FHS and grow on a daily basis. The logrotate package helps control the growth of
these les. For more details refer to Book “System Analysis and Tuning Guide”, Chapter 3 “Analyzing
and Managing System Log Files”, Section 3.3 “Managing Log Files with logrotate”.
23.1.5 The locate Command
locate , a command for quickly finding les, is not included in the standard scope of installed
software. If desired, install the package mlocate , the successor of the package findutils-lo-
cate . The updatedb process is started automatically every night or about 15 minutes after boot-
ing the system.
317 Stopping Cron Status Messages SLES 12 SP3

23.1.6 The ulimit Command
With the ulimit (user limits) command, it is possible to set limits for the use of system resources
and to have these displayed. ulimit is especially useful for limiting available memory for
applications. With this, an application can be prevented from co-opting too much of the system
resources and slowing or even hanging up the operating system.
ulimit can be used with various options. To limit memory usage, use the options listed in
Table 23.1, “ulimit: Setting Resources for the User”.
TABLE 23.1: ulimit: SETTING RESOURCES FOR THE USER
-m The maximum resident set size
-v The maximum amount of virtual memory

available to the shell
-s The maximum size of the stack
-c The maximum size of core les created
-a All current limits are reported
Systemwide default entries are set in /etc/profile . Editing this le directly is not recommend-
ed, because changes will be overwritten during system upgrades. To customize systemwide pro-
file settings, use /etc/profile.local . Per-user settings should be made in ~USER/.bashrc .
EXAMPLE 23.3: ULIMIT: SETTINGS IN ~/.BASHRC
# Limits maximum resident set size (physical memory):

ulimit -m 98304
# Limits of virtual memory:

ulimit -v 98304
Memory allocations must be specified in KB. For more detailed information, see man bash .
Important: ulimit Support

Not all shells support ulimit directives. PAM (for example, pam_limits ) offers com-
prehensive adjustment possibilities as an alternative to ulimit .
318 The ulimit Command SLES 12 SP3

23.1.7 The free Command
The free command displays the total amount of free and used physical memory as well as swap
space in the system and the buers and cache consumed by the kernel. The concept of available
RAM dates back to before the days of unified memory management. The slogan free memory is
bad memory applies well to Linux. As a result, Linux has always made the effort to balance out
caches without actually allowing free or unused memory.
The kernel does not have direct knowledge of any applications or user data. Instead, it manages
applications and user data in a page cache. If memory runs short, parts of it are written to the
swap partition or to les, from which they can initially be read using the mmap command (see
man mmap ).
The kernel also contains other caches, such as the slab cache, where the caches used for network
access are stored. This may explain the differences between the counters in /proc/meminfo .
Most, but not all, of them can be accessed via /proc/slabinfo .
However, if your goal is to nd out how much RAM is currently being used, nd this information
in /proc/meminfo .
23.1.8 Man Pages and Info Pages
For some GNU applications (such as tar), the man pages are no longer maintained. For these
commands, use the --help option to get a quick overview of the info pages, which provide
more in-depth instructions. Info is GNU's hypertext system. Read an introduction to this system
by entering info info . Info pages can be viewed with Emacs by entering emacs -f info
or directly in a console with info . You can also use tkinfo, xinfo or the help system to view
info pages.
23.1.9 Selecting Man Pages Using the man Command

To read a man page enter man MAN_PAGE . If a man page with the same name exists in different
sections, they will all be listed with the corresponding section numbers. Select the one to display.
If you do not enter a section number within a few seconds, the rst man page will be displayed.
To change this to the default system behavior, set MAN_POSIXLY_CORRECT=1 in a shell initial-
ization le such as ~/.bashrc .
319 The free Command SLES 12 SP3

23.1.10 Settings for GNU Emacs
GNU Emacs is a complex work environment. The following sections cover the configuration
les processed when GNU Emacs is started. More information is available at http://www.gnu.org/
software/emacs/ .
On start-up, Emacs reads several les containing the settings of the user, system administrator
and distributor for customization or preconfiguration. The initialization le ~/.emacs is in-
stalled to the home directories of the individual users from /etc/skel . .emacs , in turn, reads
the le /etc/skel/.gnu-emacs . To customize the program, copy .gnu-emacs to the home di-
rectory (with cp /etc/skel/.gnu-emacs ~/.gnu-emacs ) and make the desired settings there.
.gnu-emacs defines the le ~/.gnu-emacs-custom as custom-file . If users make settings
with the customize options in Emacs, the settings are saved to ~/.gnu-emacs-custom .
With SUSE Linux Enterprise Server, the emacs package installs the le site-start.el in the
directory /usr/share/emacs/site-lisp . The le site-start.el is loaded before the ini-
tialization le ~/.emacs . Among other things, site-start.el ensures that special configura-
tion les distributed with Emacs add-on packages, such as psgml , are loaded automatically.
Configuration les of this type are located in /usr/share/emacs/site-lisp , too, and always
begin with suse-start- . The local system administrator can specify systemwide settings in
default.el .
More information about these les is available in the Emacs info le under Init File: in-
fo:/emacs/InitFile . Information about how to disable the loading of these les (if necessary)
is also provided at this location.
The components of Emacs are divided into several packages:
The base package emacs .
emacs-x11 (usually installed): the program with X11 support.
emacs-nox : the program without X11 support.
emacs-info : online documentation in info format.
320 Settings for GNU Emacs SLES 12 SP3

emacs-el : the uncompiled library les in Emacs Lisp. These are not required at runtime.
Numerous add-on packages can be installed if needed: emacs-auctex (LaTeX), psgml

(SGML and XML), gnuserv (client and server operation) and others.
23.2 Virtual Consoles

Linux is a multiuser and multitasking system. The advantages of these features can be appreci-
ated even on a stand-alone PC system. In text mode, there are six virtual consoles available.
Switch between them using Alt – F1 through Alt – F6 . The seventh console is reserved for X
and the tenth console shows kernel messages.
To switch to a console from X without shutting it down, use Ctrl – Alt – F1 to Ctrl – Alt – F6 .
To return to X, press Alt – F7 .
23.3 Keyboard Mapping

To standardize the keyboard mapping of programs, changes were made to the following les:
/etc/inputrc
/etc/X11/Xmodmap
/etc/skel/.emacs
/etc/skel/.gnu-emacs
/etc/skel/.vimrc
/etc/csh.cshrc
/etc/termcap
/usr/share/terminfo/x/xterm
/usr/share/X11/app-defaults/XTerm
/usr/share/emacs/VERSION/site-lisp/term/*.el
These changes only affect applications that use terminfo entries or whose configuration les
are changed directly ( vi , emacs , etc.). Applications not shipped with the system should be
adapted to these defaults.
Under X, the compose key (multikey) can be enabled as explained in /etc/X11/Xmodmap .
Further settings are possible using the X Keyboard Extension (XKB). This extension is also used
by the desktop environment GNOME (gswitchit).
321 Virtual Consoles SLES 12 SP3

Tip: For More Information
Information about XKB is available in the documents listed in /usr/share/doc/pack-
ages/xkeyboard-config (part of the xkeyboard-config package).
23.4 Language and Country-Specific Settings

The system is, to a very large extent, internationalized and can be modified for local needs. In-
ternationalization (I18N) allows specific localization (L10N). The abbreviations I18N and L10N
are derived from the rst and last letters of the words and, in between, the number of letters
omitted.
Settings are made with LC_ variables defined in the le /etc/sysconfig/language . This refers
not only to native language support, but also to the categories Messages (Language), Character Set,
Sort Order, Time and Date, Numbers and Money. Each of these categories can be defined directly
with its own variable or indirectly with a master variable in the le language (see the locale
man page).
RC_LC_MESSAGES , RC_LC_CTYPE , RC_LC_COLLATE , RC_LC_TIME , RC_LC_NUMERIC , RC_L-

C_MONETARY
These variables are passed to the shell without the RC_ prefix and represent the listed
categories. The shell profiles concerned are listed below. The current setting can be shown
with the command locale .
RC_LC_ALL
This variable, if set, overwrites the values of the variables already mentioned.
RC_LANG
If none of the previous variables are set, this is the fallback. By default, only RC_LANG is
set. This makes it easier for users to enter their own values.
ROOT_USES_LANG
A yes or no variable. If set to no , root always works in the POSIX environment.
The variables can be set with the YaST sysconfig editor. The value of such a variable contains the
language code, country code, encoding and modifier. The individual components are connected
by special characters:
LANG=<language>[[_<COUNTRY>].<Encoding>[@<Modifier>]]
322 Language and Country-Specific Settings SLES 12 SP3

23.4.1 Some Examples
You should always set the language and country codes together. Language settings follow
the standard ISO 639 available at http://www.evertype.com/standards/iso639/iso639-en.html
and http://www.loc.gov/standards/iso639-2/ . Country codes are listed in ISO 3166, see http://
en.wikipedia.org/wiki/ISO_3166 .
It only makes sense to set values for which usable description les can be found in /usr/lib/
locale . Additional description les can be created from the les in /usr/share/i18n using
the command localedef . The description les are part of the glibc-i18ndata package. A
description le for en_US.UTF-8 (for English and United States) can be created with:
localedef -i en_US -f UTF-8 en_US.UTF-8
LANG=en_US.UTF-8
This is the default setting if American English is selected during installation. If you selected
another language, that language is enabled but still with UTF-8 as the character encoding.
LANG=en_US.ISO-8859-1
This sets the language to English, country to United States and the character set to
ISO-8859-1 . This character set does not support the Euro sign, but it can be useful some-
times for programs that have not been updated to support UTF-8 . The string defining the
charset ( ISO-8859-1 in this case) is then evaluated by programs like Emacs.
LANG=en_IE@euro
The above example explicitly includes the Euro sign in a language setting. This setting
is obsolete now, as UTF-8 also covers the Euro symbol. It is only useful if an application
supports ISO-8859-15 and not UTF-8.
Changes to /etc/sysconfig/language are activated by the following process chain:
For the Bash: /etc/profile reads /etc/profile.d/lang.sh which, in turn, analyzes

/etc/sysconfig/language .
For tcsh: At login, /etc/csh.login reads /etc/profile.d/lang.csh which, in turn,

analyzes /etc/sysconfig/language .
323 Some Examples SLES 12 SP3

This ensures that any changes to /etc/sysconfig/language are available at the next login to
the respective shell, without having to manually activate them.
Users can override the system defaults by editing their ~/.bashrc accordingly. For ex-
ample, if you do not want to use the system-wide en_US for program messages, include
LC_MESSAGES=es_ES so that messages are displayed in Spanish instead.
23.4.2 Locale Settings in ~/.i18n

If you are not satisfied with locale system defaults, change the settings in ~/.i18n according
to the Bash scripting syntax. Entries in ~/.i18n override system defaults from /etc/syscon-
fig/language . Use the same variable names but without the RC_ name space prefixes. For
example, use LANG instead of RC_LANG :
LANG=cs_CZ.UTF-8
LC_COLLATE=C
23.4.3 Settings for Language Support

Files in the category Messages are, as a rule, only stored in the corresponding language direc-
tory (like en ) to have a fallback. If you set LANG to en_US and the message le in /usr/
share/locale/en_US/LC_MESSAGES does not exist, it falls back to /usr/share/locale/en/
LC_MESSAGES .
A fallback chain can also be defined, for example, for Breton to French or for Galician to Spanish
to Portuguese:
LANGUAGE="br_FR:fr_FR"
LANGUAGE="gl_ES:es_ES:pt_PT"
If desired, use the Norwegian variants Nynorsk and Bokmål instead (with additional fallback
to no ):
LANG="nn_NO"
LANGUAGE="nn_NO:nb_NO:no"
or
LANG="nb_NO"
LANGUAGE="nb_NO:nn_NO:no"
Note that in Norwegian, LC_TIME is also treated differently.
324 Locale Settings in ~/.i18n SLES 12 SP3

One problem that can arise is a separator used to delimit groups of digits not being recognized
properly. This occurs if LANG is set to only a two-letter language code like de , but the definition
le glibc uses is located in /usr/share/lib/de_DE/LC_NUMERIC . Thus LC_NUMERIC must be
set to de_DE to make the separator definition visible to the system.
The GNU C Library Reference Manual, Chapter “Locales and Internationalization”. It is in-
cluded in glibc-info . The package is available from the SUSE Linux Enterprise SDK.
The SDK is a module for SUSE Linux Enterprise and is available via an online channel
from the SUSE Customer Center. Alternatively, go to http://download.suse.com/ , search
for SUSE Linux Enterprise Software Development Kit and download it from there.
Refer to Book “Deployment Guide”, Chapter 14 “Installing Modules, Extensions, and Third Party
Add-On Products” for details.
Markus Kuhn, UTF-8 and Unicode FAQ for Unix/Linux, currently at http://www.cl.cam.ac.uk/
~mgk25/unicode.html .
Unicode-HOWTO by Bruno Haible, available at http://tldp.org/HOWTO/Unicode-HOW-

TO-1.html .

IV Services
24 Time Synchronization with NTP 327
25 The Domain Name System 334
26 DHCP 359
27 Sharing File Systems with NFS 375
28 Samba 386
29 On-Demand Mounting with Autofs 408
30 SLP 416
31 The Apache HTTP Server 420
32 Setting Up an FTP Server with YaST 462
33 The Proxy Server Squid 466
34 Web Based Enterprise Management Using SFCB 490

24 Time Synchronization with NTP
The NTP (network time protocol) mechanism is a protocol for synchronizing the
system time over the network. First, a machine can obtain the time from a server
that is a reliable time source. Second, a machine can itself act as a time source for
other computers in the network. The goal is twofold—maintaining the absolute time
and synchronizing the system time of all machines within a network.
Maintaining an exact system time is important in many situations. The built-in hardware clock
does often not meet the requirements of applications such as databases or clusters. Manual
correction of the system time would lead to severe problems because, for example, a backward
leap can cause malfunction of critical applications. Within a network, it is usually necessary to
synchronize the system time of all machines, but manual time adjustment is a bad approach.
NTP provides a mechanism to solve these problems. The NTP service continuously adjusts the
system time with reliable time servers in the network. It further enables the management of
local reference clocks, such as radio-controlled clocks.
24.1 Configuring an NTP Client with YaST

The NTP daemon ( ntpd ) coming with the ntp package is preset to use the local computer clock
as a time reference. Using the hardware clock, however, only serves as a fallback for cases where
no time source of better precision is available. YaST simplifies the configuration of an NTP client.
24.1.1 Basic Configuration

The YaST NTP client configuration (Network Services NTP Configuration) consists of tabs. Set
the start mode of ntpd and the server to query on the General Settings tab.
Only Manually
Select Only Manually, if you want to manually start the ntpd daemon.
Synchronize without Daemon

Select Synchronize without Daemon to set the system time periodically without a perma-
nently running ntpd . You can set the Interval of the Synchronization in Minutes.
327 Configuring an NTP Client with YaST SLES 12 SP3

Now and On Boot
Select Now and On Boot to start ntpd automatically when the system is booted. This setting
is recommended.
24.1.2 Changing Basic Configuration

The servers and other time sources for the client to query are listed in the lower part of the
General Settings tab. Modify this list as needed with Add, Edit, and Delete. Display Log provides
the possibility to view the log les of your client.
Click Add to add a new source of time information. In the following dialog, select the type of
source with which the time synchronization should be made. The following options are available:
FIGURE 24.1: YAST: NTP SERVER
Server
In the drop-down Select list (see Figure 24.1, “YaST: NTP Server”), determine whether to set
up time synchronization using a time server from your local network (Local NTP Server)
or an Internet-based time server that takes care of your time zone (Public NTP Server). For
a local time server, click Lookup to start an SLP query for available time servers in your
network. Select the most suitable time server from the list of search results and exit the
328 Changing Basic Configuration SLES 12 SP3

dialog with OK. For a public time server, select your country (time zone) and a suitable
server from the list under Public NTP Server then exit the dialog with OK. In the main
dialog, test the availability of the selected server with Test. Options allows you to specify
additional options for ntpd .
Using Access Control Options, you can restrict the actions that the remote computer can per-
form with the daemon running on your computer. This eld is enabled only after checking
Restrict NTP Service to Configured Servers Only on the Security Settings tab (see Figure 24.2,
“Advanced NTP Configuration: Security Settings”). The options correspond to the restrict
clauses in /etc/ntp.conf . For example, nomodify notrap noquery disallows the serv-
er to modify NTP settings of your computer and to use the trap facility (a remote event
logging feature) of your NTP daemon. Using these restrictions is recommended for servers
out of your control (for example, on the Internet).
Refer to /usr/share/doc/packages/ntp-doc (part of the ntp-doc package) for detailed
information.
Peer
A peer is a machine to which a symmetric relationship is established: it acts both as a time
server and as a client. To use a peer in the same network instead of a server, enter the
address of the system. The rest of the dialog is identical to the Server dialog.
Radio Clock
To use a radio clock in your system for the time synchronization, enter the clock type, unit
number, device name, and other options in this dialog. Click Driver Calibration to ne-tune
the driver. Detailed information about the operation of a local radio clock is available in
/usr/share/doc/packages/ntp-doc/refclock.html .
Outgoing Broadcast
Time information and queries can also be transmitted by broadcast in the network. In
this dialog, enter the address to which such broadcasts should be sent. Do not activate
broadcasting unless you have a reliable time source like a radio controlled clock.
Incoming Broadcast
If you want your client to receive its information via broadcast, enter the address from
which the respective packets should be accepted in this elds.

FIGURE 24.2: ADVANCED NTP CONFIGURATION: SECURITY SETTINGS
In the Security Settings tab (see Figure 24.2, “Advanced NTP Configuration: Security Settings”), deter-
mine whether ntpd should be started in a chroot jail. By default, Run NTP Daemon in Chroot
Jail is not activated. The chroot jail option increases the security in the event of an attack over
ntpd , as it prevents the attacker from compromising the entire system.
Restrict NTP Service to Configured Servers Only increases the security of your system by disallow-
ing remote computers to view and modify NTP settings of your computer and to use the trap
facility for remote event logging. After being enabled, these restrictions apply to all remote
computers, unless you override the access control options for individual computers in the list
of time sources in the General Settings tab. For all other remote computers, only querying for
local time is allowed.
Enable Open Port in Firewall if SuSEFirewall2 is active (which it is by default). If you leave the
port closed, it is not possible to establish a connection to the time server.

24.2 Manually Configuring NTP in the Network
The easiest way to use a time server in the network is to set server parameters. For example, if
a time server called ntp.example.com is reachable from the network, add its name to the le
/etc/ntp.conf by adding the following line:
server ntp.example.com
To add more time servers, insert additional lines with the keyword server . After initializing
ntpd with the command systemctl start ntp , it takes about one hour until the time is
stabilized and the drift le for correcting the local computer clock is created. With the drift le,
the systematic error of the hardware clock can be computed when the computer is powered on.
The correction is used immediately, resulting in a higher stability of the system time.
There are two possible ways to use the NTP mechanism as a client: First, the client can query
the time from a known server in regular intervals. With many clients, this approach can cause
a high load on the server. Second, the client can wait for NTP broadcasts sent out by broadcast
time servers in the network. This approach has the disadvantage that the quality of the server
is unknown and a server sending out wrong information can cause severe problems.
If the time is obtained via broadcast, you do not need the server name. In this case, enter the
line broadcastclient in the configuration le /etc/ntp.conf . To use one or more known
time servers exclusively, enter their names in the line starting with servers .
24.3 Dynamic Time Synchronization at Runtime

If the system boots without network connection, ntpd starts up, but it cannot resolve DNS names
of the time servers set in the configuration le. This can happen if you use NetworkManager
with an encrypted Wi-Fi.
If you want ntpd to resolve DNS names at runtime, you must set the dynamic option. When a
network connection is established after booting, ntpd looks up the names again and can reach
the time servers to get the time.
Manually edit /etc/ntp.conf and add dynamic to one or more server entries:
server ntp.example.com dynamic
Or use YaST and proceed as follows:
1. In YaST click Network Services NTP Configuration.
331 Manually Configuring NTP in the Network SLES 12 SP3

2. Select the server you want to configure. Then click Edit.
3. Activate the Options eld and add dynamic . Separate it with a space, if there are already
other options entered.
4. Click Ok to close the edit dialog. Repeat the previous step to change all servers as wanted.
5. Finally click Ok to save the settings.
24.4 Setting Up a Local Reference Clock

The software package ntpd contains drivers for connecting local reference clocks. A list of sup-
ported clocks is available in the ntp-doc package in the le /usr/share/doc/packages/ntp-
doc/refclock.html . Every driver is associated with a number. In NTP, the actual configuration
takes place by means of pseudo IP addresses. The clocks are entered in the le /etc/ntp.conf
as though they existed in the network. For this purpose, they are assigned special IP addresses
in the form 127.127.T.U . Here, T stands for the type of the clock and determines which driver
is used and U for the unit, which determines the interface used.
Normally, the individual drivers have special parameters that describe configuration details. The
le /usr/share/doc/packages/ntp-doc/drivers/driverNN.html (where NN is the number
of the driver) provides information about the particular type of clock. For example, the “type 8”
clock (radio clock over serial interface) requires an additional mode that specifies the clock
more precisely. The Conrad DCF77 receiver module, for example, has mode 5. To use this clock
as a preferred reference, specify the keyword prefer . The complete server line for a Conrad
DCF77 receiver module would be:
server 127.127.8.0 mode 5 prefer
Other clocks follow the same pattern. Following the installation of the ntp-doc package, the
documentation for NTP is available in the directory /usr/share/doc/packages/ntp-doc . The
le /usr/share/doc/packages/ntp-doc/refclock.html provides links to the driver pages
describing the driver parameters.
332 Setting Up a Local Reference Clock SLES 12 SP3

24.5 Clock Synchronization to an External Time
Reference (ETR)
Support for clock synchronization to an external time reference (ETR) is available. The external
time reference sends an oscillator signal and a synchronization signal every 2**20 (2 to the
power of 20) microseconds to keep TOD clocks of all connected servers synchronized.
For availability two ETR units can be connected to a machine. If the clock deviates for more
than the sync-check tolerance all CPUs get a machine check that indicates that the clock is
out of sync. If this happens, all DASD I/O to XRC enabled devices is stopped until the clock is
synchronized again.
The ETR support is activated via two sysfs attributes; run the following commands as root :
echo 1 > /sys/devices/system/etr/etr0/online

echo 1 > /sys/devices/system/etr/etr1/online
333 Clock Synchronization to an External Time Reference (ETR) SLES 12 SP3

25 The Domain Name System
DNS (domain name system) is needed to resolve the domain names and host names
into IP addresses. In this way, the IP address 192.168.2.100 is assigned to the host
name jupiter , for example. Before setting up your own name server, read the gen-
eral information about DNS in Section 16.3, “Name Resolution”. The following configu-
ration examples refer to BIND, the default DNS server.
25.1 DNS Terminology
Zone
The domain name space is divided into regions called zones. For example, if you have
example.com , you have the example section (or zone) of the com domain.
DNS server
The DNS server is a server that maintains the name and IP information for a domain. You
can have a primary DNS server for master zone, a secondary server for slave zone, or a
slave server without any zones for caching.
Master zone DNS server

The master zone includes all hosts from your network and a DNS server master zone
stores up-to-date records for all the hosts in your domain.
Slave zone DNS server

A slave zone is a copy of the master zone. The slave zone DNS server obtains its zone
data with zone transfer operations from its master server. The slave zone DNS server
responds authoritatively for the zone as long as it has valid (not expired) zone data. If
the slave cannot obtain a new copy of the zone data, it stops responding for the zone.
Forwarder
Forwarders are DNS servers to which your DNS server should send queries it cannot an-
swer. To enable different configuration sources in one configuration, netconfig is used
(see also man 8 netconfig ).
334 DNS Terminology SLES 12 SP3

Record
The record is information about name and IP address. Supported records and their syntax
are described in BIND documentation. Some special records are:
NS record
An NS record tells name servers which machines are in charge of a given domain
zone.
MX record
The MX (mail exchange) records describe the machines to contact for directing mail
across the Internet.
SOA record
SOA (Start of Authority) record is the rst record in a zone le. The SOA record is
used when using DNS to synchronize data between multiple computers.
25.2 Installation
To install a DNS server, start YaST and select Software Software Management. Choose View Pat-
terns and select DHCP and DNS Server. Confirm the installation of the dependent packages to
finish the installation process.
Alternatively use the following command on the command line:
zypper in -t pattern dhcp_dns_server
25.3 Configuration with YaST

Use the YaST DNS module to configure a DNS server for the local network. When starting the
module for the rst time, a wizard starts, prompting you to make a few decisions concerning
administration of the server. Completing this initial setup produces a basic server configuration.
Use the expert mode to deal with more advanced configuration tasks, such as setting up ACLs,
logging, TSIG keys, and other options.
335 Installation SLES 12 SP3

25.3.1 Wizard Configuration
The wizard consists of three steps or dialogs. At the appropriate places in the dialogs, you can
enter the expert configuration mode.
1. When starting the module for the rst time, the Forwarder Settings dialog, shown in Fig-
ure 25.1, “DNS Server Installation: Forwarder Settings”, opens. The Local DNS Resolution Policy
allows to set the following options:
Merging forwarders is disabled
Automatic merging
Merging forwarders is enabled
Custom configuration—If Custom configuration is selected, Custom policy can be speci-

fied; by default (with Automatic merging selected), Custom policy is set to auto , but
here you can either set interface names or select from the two special policy names
STATIC and STATIC_FALLBACK .
In Local DNS Resolution Forwarder, specify which service to use: Using system name servers,
This name server (bind), or Local dnsmasq server.
For more information about all these settings, see man 8 netconfig .
FIGURE 25.1: DNS SERVER INSTALLATION: FORWARDER SETTINGS
336 Wizard Configuration SLES 12 SP3

Forwarders are DNS servers to which your DNS server sends queries it cannot answer
itself. Enter their IP address and click Add.
2. The DNS Zones dialog consists of several parts and is responsible for the management of
zone les, described in Section 25.6, “Zone Files”. For a new zone, provide a name for it in
Name. To add a reverse zone, the name must end in .in-addr.arpa . Finally, select the
Type (master, slave, or forward). See Figure 25.2, “DNS Server Installation: DNS Zones”. Click
Edit to configure other settings of an existing zone. To remove a zone, click Delete.
FIGURE 25.2: DNS SERVER INSTALLATION: DNS ZONES
3. In the final dialog, you can open the DNS port in the firewall by clicking Open Port in
Firewall. Then decide whether to start the DNS server when booting (On or O). You can
also activate LDAP support. See Figure 25.3, “DNS Server Installation: Finish Wizard”.
337 Wizard Configuration SLES 12 SP3

FIGURE 25.3: DNS SERVER INSTALLATION: FINISH WIZARD
25.3.2 Expert Configuration

After starting the module, YaST opens a window displaying several configuration options. Com-
pleting it results in a DNS server configuration with the basic functions in place:
25.3.2.1 Start-Up
Under Start-Up, define whether the DNS server should be started when the booting the system
or manually. To start the DNS server immediately, click Start DNS Server Now. To stop the DNS
server, click Stop DNS Server Now. To save the current settings, select Save Settings and Reload
DNS Server Now. You can open the DNS port in the firewall with Open Port in Firewall and modify
the firewall settings with Firewall Details.
By selecting LDAP Support Active, the zone les are managed by an LDAP database. Any changes
to zone data written to the LDAP database are picked up by the DNS server when it is restarted
or prompted to reload its configuration.
338 Expert Configuration SLES 12 SP3

25.3.2.2 Forwarders
If your local DNS server cannot answer a request, it tries to forward the request to a Forwarder,
if configured so. This forwarder may be added manually to the Forwarder List. If the forwarder is
not static like in dial-up connections, netconfig handles the configuration. For more information
about netconfig, see man 8 netconfig .
25.3.2.3 Basic Options
In this section, set basic server options. From the Option menu, select the desired item then
specify the value in the corresponding text box. Include the new entry by selecting Add.
25.3.2.4 Logging
To set what the DNS server should log and how, select Logging. Under Log Type, specify where the
DNS server should write the log data. Use the system-wide log by selecting System Log or specify
a different le by selecting File. In the latter case, additionally specify a name, the maximum
le size in megabytes and the number of log le versions to store.
Further options are available under Additional Logging. Enabling Log All DNS Queries causes every
query to be logged, in which case the log le could grow extremely large. For this reason, it is
not a good idea to enable this option for other than debugging purposes. To log the data traffic
during zone updates between DHCP and DNS server, enable Log Zone Updates. To log the data
traffic during a zone transfer from master to slave, enable Log Zone Transfer. See Figure 25.4,
“DNS Server: Logging”.

FIGURE 25.4: DNS SERVER: LOGGING
25.3.2.5 ACLs
Use this dialog to define ACLs (access control lists) to enforce access restrictions. After providing
a distinct name under Name, specify an IP address (with or without netmask) under Value in
the following fashion:
{ 192.168.1/24; }
The syntax of the configuration le requires that the address ends with a semicolon and is put
into curly braces.
25.3.2.6 TSIG Keys

The main purpose of TSIGs (transaction signatures) is to secure communications between DHCP
and DNS servers. They are described in Section 25.8, “Secure Transactions”.
To generate a TSIG key, enter a distinctive name in the eld labeled Key ID and specify the le
where the key should be stored (Filename). Confirm your choices with Generate.
To use a previously created key, leave the Key ID eld blank and select the le where it is stored
under Filename. After that, confirm with Add.

25.3.2.7 DNS Zones (Adding a Slave Zone)
To add a slave zone, select DNS Zones, choose the zone type Slave, write the name of the new
zone, and click Add.
In the Zone Editor sub-dialog under Master DNS Server IP, specify the master from which the
slave should pull its data. To limit access to the server, select one of the ACLs from the list.
25.3.2.8 DNS Zones (Adding a Master Zone)
To add a master zone, select DNS Zones, choose the zone type Master, write the name of the new
zone, and click Add. When adding a master zone, a reverse zone is also needed. For example,
when adding the zone example.com that points to hosts in a subnet 192.168.1.0/24 , you
should also add a reverse zone for the IP-address range covered. By definition, this should be
named 1.168.192.in-addr.arpa .
25.3.2.9 DNS Zones (Editing a Master Zone)
To edit a master zone, select DNS Zones, select the master zone from the table, and click Edit.
The dialog consists of several pages: Basics (the one opened rst), NS Records, MX Records, SOA,
and Records.
The basic dialog, shown in Figure 25.5, “DNS Server: Zone Editor (Basics)”, lets you define settings for
dynamic DNS and access options for zone transfers to clients and slave name servers. To permit
the dynamic updating of zones, select Allow Dynamic Updates as well as the corresponding TSIG
key. The key must have been defined before the update action starts. To enable zone transfers,
select the corresponding ACLs. ACLs must have been defined already.
In the Basics dialog, select whether to enable zone transfers. Use the listed ACLs to define who
can download zones.

FIGURE 25.5: DNS SERVER: ZONE EDITOR (BASICS)
Zone Editor (NS Records)

The NS Records dialog allows you to define alternative name servers for the zones specified.
Make sure that your own name server is included in the list. To add a record, enter its
name under Name Server to Add then confirm with Add. See Figure 25.6, “DNS Server: Zone
Editor (NS Records)”.
FIGURE 25.6: DNS SERVER: ZONE EDITOR (NS RECORDS)

Zone Editor (MX Records)
To add a mail server for the current zone to the existing list, enter the corresponding
address and priority value. After doing so, confirm by selecting Add. See Figure 25.7, “DNS
Server: Zone Editor (MX Records)”.
FIGURE 25.7: DNS SERVER: ZONE EDITOR (MX RECORDS)
Zone Editor (SOA)

This page allows you to create SOA (start of authority) records. For an explanation of the
individual options, refer to Example 25.6, “The /var/lib/named/example.com.zone File”. Chang-
ing SOA records is not supported for dynamic zones managed via LDAP.

FIGURE 25.8: DNS SERVER: ZONE EDITOR (SOA)
Zone Editor (Records)

This dialog manages name resolution. In Record Key, enter the host name then select its
type. The A type represents the main entry. The value for this should be an IP address
(IPv4). Use AAAA for IPv6 addresses. CNAME is an alias. Use the types NS and MX for
detailed or partial records that expand on the information provided in the NS Records and
MX Records tabs. These three types resolve to an existing A record. PTR is for reverse
zones. It is the opposite of an A record, for example:
hostname.example.com. IN A 192.168.0.1
1.0.168.192.in-addr.arpa IN PTR hostname.example.com.
25.3.2.9.1 Adding Reverse Zones
To add a reverse zone, follow this procedure:
1. Start YaST DNS Server DNS Zones.
2. If you have not added a master forward zone, add it and Edit it.
3. In the Records tab, ll the corresponding Record Key and Value, then add the record with
Add and confirm with OK. If YaST complains about a non-existing record for a name server,
add it in the NS Records tab.

FIGURE 25.9: ADDING A RECORD FOR A MASTER ZONE
4. Back in the DNS Zones window, add a reverse master zone.
FIGURE 25.10: ADDING A REVERSE ZONE
5. Edit the reverse zone, and in the Records tab, you can see the PTR: Reverse translation record
type. Add the corresponding Record Key and Value, then click Add and confirm with OK.

FIGURE 25.11: ADDING A REVERSE RECORD
Add a name server record if needed.
Tip: Editing the Reverse Zone

After adding a forward zone, go back to the main menu and select the reverse zone for
editing. There in the tab Basics activate the check box Automatically Generate Records From
and select your forward zone. That way, all changes to the forward zone are automatically
updated in the reverse zone.
25.4 Starting the BIND Name Server

On a SUSE® Linux Enterprise Server system, the name server BIND (Berkeley Internet Name
Domain) comes preconfigured, so it can be started right after installation without any problems.
Normally, if you already have an Internet connection and entered 127.0.0.1 as the name server
address for localhost in /etc/resolv.conf , you already have a working name resolution
without needing to know the DNS of the provider. BIND carries out name resolution via the root
name server, a notably slower process. Normally, the DNS of the provider should be entered
with its IP address in the configuration le /etc/named.conf under forwarders to ensure
346 Starting the BIND Name Server SLES 12 SP3

effective and secure name resolution. If this works so far, the name server runs as a pure caching-
only name server. Only when you configure its own zones it becomes a proper DNS. Find a
simple example documented in /usr/share/doc/packages/bind/config .
Tip: Automatic Adaptation of the Name Server Information

Depending on the type of Internet connection or the network connection, the name serv-
er information can automatically be adapted to the current conditions. To do this, set
the NETCONFIG_DNS_POLICY variable in the /etc/sysconfig/network/config le to
auto .
However, do not set up an official domain until one is assigned to you by the responsible insti-
tution. Even if you have your own domain and it is managed by the provider, you are better
o not using it, because BIND would otherwise not forward requests for this domain. The Web
server at the provider, for example, would not be accessible for this domain.
To start the name server, enter the command systemctl start named as root . Check with
systemctl status named whether named (as the name server process is called) has been
started successfully. Test the name server immediately on the local system with the host or dig
programs, which should return localhost as the default server with the address 127.0.0.1 .
If this is not the case, /etc/resolv.conf probably contains an incorrect name server entry or
the le does not exist. For the rst test, enter host 127.0.0.1 , which should always work.
If you get an error message, use systemctl status named to see whether the server is actu-
ally running. If the name server does not start or behaves unexpectedly, check the output of
journalctl -e .
To use the name server of the provider (or one already running on your network) as the for-
warder, enter the corresponding IP address or addresses in the options section under for-
warders . The addresses included in Example 25.1, “Forwarding Options in named.conf” are exam-
ples only. Adjust these entries to your own setup.
EXAMPLE 25.1: FORWARDING OPTIONS IN NAMED.CONF
options {
directory "/var/lib/named";
forwarders { 10.11.12.13; 10.11.12.14; };
listen-on { 127.0.0.1; 192.168.1.116; };
allow-query { 127/8; 192.168/16 };
notify no;
};
347 Starting the BIND Name Server SLES 12 SP3

The options entry is followed by entries for the zone, localhost , and 0.0.127.in-ad-
dr.arpa . The type hint entry under “.” should always be present. The corresponding les do
not need to be modified and should work as they are. Also make sure that each entry is closed
with a “;” and that the curly braces are in the correct places. After changing the configuration
le /etc/named.conf or the zone les, tell BIND to reread them with systemctl reload
named . Achieve the same by stopping and restarting the name server with systemctl restart
named . Stop the server at any time by entering systemctl stop named .
25.5 The /etc/named.conf Configuration File

All the settings for the BIND name server itself are stored in the /etc/named.conf le. How-
ever, the zone data for the domains to handle (consisting of the host names, IP addresses, and
so on) are stored in separate les in the /var/lib/named directory. The details of this are
described later.
/etc/named.conf is roughly divided into two areas. One is the options section for general
settings and the other consists of zone entries for the individual domains. A logging section
and acl (access control list) entries are optional. Comment lines begin with a # sign or // . A
minimal /etc/named.conf is shown in Example 25.2, “A Basic /etc/named.conf”.
EXAMPLE 25.2: A BASIC /ETC/NAMED.CONF
options {
directory "/var/lib/named";
forwarders { 10.0.0.1; };
notify no;
};
zone "localhost" in {
type master;
file "localhost.zone";
};
zone "0.0.127.in-addr.arpa" in {
type master;
file "127.0.0.zone";
};
zone "." in {
type hint;
file "root.hint";
};
348 The /etc/named.conf Configuration File SLES 12 SP3

25.5.1 Important Configuration Options
directory " FILENAME ";

Specifies the directory in which BIND can nd the les containing the zone data. Usually,
this is /var/lib/named .
forwarders { IP-ADDRESS ; };
Specifies the name servers (mostly of the provider) to which DNS requests should be for-
warded if they cannot be resolved directly. Replace IP-ADDRESS with an IP address like
192.168.1.116 .
forward first;
Causes DNS requests to be forwarded before an attempt is made to resolve them via the
root name servers. Instead of forward first , forward only can be written to have all
requests forwarded and none sent to the root name servers. This makes sense for firewall
configurations.
listen-on port 53 { 127.0.0.1; IP-ADDRESS ; };

Tells BIND on which network interfaces and port to accept client queries. port 53 does
not need to be specified explicitly, because 53 is the default port. Enter 127.0.0.1 to
permit requests from the local host. If you omit this entry entirely, all interfaces are used
by default.
listen-on-v6 port 53 {any; };

Tells BIND on which port it should listen for IPv6 client requests. The only alternative to
any is none . As far as IPv6 is concerned, the server only accepts wild card addresses.
query-source address * port 53;

This entry is necessary if a firewall is blocking outgoing DNS requests. This tells BIND to
post requests externally from port 53 and not from any of the high ports above 1024.
query-source-v6 address * port 53;

Tells BIND which port to use for IPv6 queries.
allow-query { 127.0.0.1; NET ; };

Defines the networks from which clients can post DNS requests. Replace NET with address
information like 192.168.2.0/24 . The /24 at the end is an abbreviated expression for
the netmask (in this case 255.255.255.0 ).
349 Important Configuration Options SLES 12 SP3

allow-transfer ! *;;
Controls which hosts can request zone transfers. In the example, such requests are com-
pletely denied with ! * . Without this entry, zone transfers can be requested from any-
where without restrictions.
statistics-interval 0;
In the absence of this entry, BIND generates several lines of statistical information per
hour in the system's journal. Set it to 0 to suppress these statistics completely or set an
interval in minutes.
cleaning-interval 720;
This option defines at which time intervals BIND clears its cache. This triggers an entry in
the system's journal each time it occurs. The time specification is in minutes. The default
is 60 minutes.
interface-interval 0;
BIND regularly searches the network interfaces for new or nonexistent interfaces. If this
value is set to 0 , this is not done and BIND only listens at the interfaces detected at start-
up. Otherwise, the interval can be defined in minutes. The default is sixty minutes.
notify no;
no prevents other name servers from being informed when changes are made to the zone
data or when the name server is restarted.
For a list of available options, read the manual page man 5 named.conf .
25.5.2 Logging
What, how, and where logging takes place can be extensively configured in BIND. Normally, the
default settings should be sufficient. Example 25.3, “Entry to Disable Logging”, shows the simplest
form of such an entry and completely suppresses any logging.
EXAMPLE 25.3: ENTRY TO DISABLE LOGGING
logging {
category default { null; };
};
350 Logging SLES 12 SP3

25.5.3 Zone Entries
EXAMPLE 25.4: ZONE ENTRY FOR EXAMPLE.COM
zone "example.com" in {
type master;
file "example.com.zone";
notify no;
};
After zone , specify the name of the domain to administer ( example.com ) followed by in and
a block of relevant options enclosed in curly braces, as shown in Example 25.4, “Zone Entry for
example.com”. To define a slave zone, switch the type to slave and specify a name server that
administers this zone as master (which, in turn, may be a slave of another master), as shown
in Example 25.5, “Zone Entry for example.net”.
EXAMPLE 25.5: ZONE ENTRY FOR EXAMPLE.NET
zone "example.net" in {
type slave;
file "slave/example.net.zone";
masters { 10.0.0.1; };
};
The zone options:
type master;
By specifying master , tell BIND that the zone is handled by the local name server. This
assumes that a zone le has been created in the correct format.
type slave;
This zone is transferred from another name server. It must be used together with masters .
type hint;
The zone . of the hint type is used to set the root name servers. This zone definition
can be left as is.
file example.com.zone or file “slave/example.net.zone”;

This entry specifies the le where zone data for the domain is located. This le is not
required for a slave, because this data is pulled from another name server. To differentiate
master and slave les, use the directory slave for the slave les.
351 Zone Entries SLES 12 SP3

masters { SERVER_IP_ADDRESS ; };
This entry is only needed for slave zones. It specifies from which name server the zone
le should be transferred.
allow-update {! *; };
This option controls external write access, which would allow clients to make a DNS en-
try—something not normally desirable for security reasons. Without this entry, zone up-
dates are not allowed. The above entry achieves the same because ! * effectively bans
any such activity.
25.6 Zone Files

Two types of zone les are needed. One assigns IP addresses to host names and the other does
the reverse: it supplies a host name for an IP address.
Tip: Using the Dot (Period, Fullstop) in Zone Files

The "." has an important meaning in the zone les. If host names are given without a
final dot ( . ), the zone is appended. Complete host names specified with a full domain
name must end with a dot ( . ) to avoid having the domain added to it again. A missing
or wrongly placed "." is probably the most frequent cause of name server configuration
errors.
The rst case to consider is the zone le example.com.zone , responsible for the domain ex-
ample.com , shown in Example 25.6, “The /var/lib/named/example.com.zone File”.
EXAMPLE 25.6: THE /VAR/LIB/NAMED/EXAMPLE.COM.ZONE FILE
1. $TTL 2D
2. example.com. IN SOA dns root.example.com. (
3. 2003072441 ; serial
4. 1D ; refresh
5. 2H ; retry
6. 1W ; expiry
7. 2D ) ; minimum
8.
9. IN NS dns
10. IN MX 10 mail
11.
12. gate IN A 192.168.5.1
352 Zone Files SLES 12 SP3

13. IN A 10.0.0.1
14. dns IN A 192.168.1.116
15. mail IN A 192.168.3.108
16. jupiter IN A 192.168.2.100
17. venus IN A 192.168.2.101
18. saturn IN A 192.168.2.102
19. mercury IN A 192.168.2.103
20. ntp IN CNAME dns
21. dns6 IN A6 0 2002:c0a8:174::
Line 1:
$TTL defines the default time to live that should apply to all the entries in this le. In this
example, entries are valid for a period of two days ( 2 D ).
Line 2:
This is where the SOA (start of authority) control record begins:
The name of the domain to administer is example.com in the rst position. This
ends with "." , because otherwise the zone would be appended a second time. Al-
ternatively, @ can be entered here, in which case the zone would be extracted from
the corresponding entry in /etc/named.conf .
After IN SOA is the name of the name server in charge as master for this zone. The
name is expanded from dns to dns.example.com , because it does not end with a
"." .
An e-mail address of the person in charge of this name server follows. Because the
@ sign already has a special meaning, "." is entered here instead. For root@exam-
ple.com the entry must read root.example.com. . The "." must be included at
the end to prevent the zone from being added.
The ( includes all lines up to ) into the SOA record.
Line 3:
The serial number is an arbitrary number that is increased each time this le is changed.
It is needed to inform the secondary name servers (slave servers) of changes. For this, a
10 digit number of the date and run number, written as YYYYMMDDNN, has become the
customary format.
Line 4:
The refresh rate specifies the time interval at which the secondary name servers verify
the zone serial number . In this case, one day.

Line 5:
The retry rate specifies the time interval at which a secondary name server, in case of
error, attempts to contact the primary server again. Here, two hours.
Line 6:
The expiration time specifies the time frame after which a secondary name server
discards the cached data if it has not regained contact to the primary server. Here, a week.
Line 7:
The last entry in the SOA record specifies the negative caching TTL —the time for which
results of unresolved DNS queries from other servers may be cached.
Line 9:
The IN NS specifies the name server responsible for this domain. dns is extended to
dns.example.com because it does not end with a "." . There can be several lines like
this—one for the primary and one for each secondary name server. If notify is not set
to no in /etc/named.conf , all the name servers listed here are informed of the changes
made to the zone data.
Line 10:
The MX record specifies the mail server that accepts, processes, and forwards e-mails for
the domain example.com . In this example, this is the host mail.example.com . The num-
ber in front of the host name is the preference value. If there are multiple MX entries, the
mail server with the smallest value is taken rst. If mail delivery to this server fails, the
next entry with higher value is used.
Lines 12–19:
These are the actual address records where one or more IP addresses are assigned to host
names. The names are listed here without a "." because they do not include their domain,
so example.com is added to all of them. Two IP addresses are assigned to the host gate ,
as it has two network cards. Wherever the host address is a traditional one (IPv4), the
record is marked with A . If the address is an IPv6 address, the entry is marked with AAAA .
Note: IPv6 Syntax

The IPv6 record has a slightly different syntax than IPv4. Because of the fragmen-
tation possibility, it is necessary to provide information about missed bits before the
address. To ll up the IPv6 address with the needed number of “0”, add two colons
at the correct place in the address.

pluto AAAA 2345:00C1:CA11::1234:5678:9ABC:DEF0
pluto AAAA 2345:00D2:DA11::1234:5678:9ABC:DEF0
Line 20:
The alias ntp can be used to address dns ( CNAME means canonical name).
The pseudo domain in-addr.arpa is used for the reverse lookup of IP addresses into host
names. It is appended to the network part of the address in reverse notation. So 192.168 is
resolved into 168.192.in-addr.arpa . See Example 25.7, “Reverse Lookup”.
EXAMPLE 25.7: REVERSE LOOKUP
1. $TTL 2D
2. 168.192.in-addr.arpa. IN SOA dns.example.com. root.example.com. (
3. 2003072441 ; serial
4. 1D ; refresh
5. 2H ; retry
6. 1W ; expiry
7. 2D ) ; minimum
8.
9. IN NS dns.example.com.
10.
11. 1.5 IN PTR gate.example.com.
12. 100.3 IN PTR www.example.com.
13. 253.2 IN PTR cups.example.com.
Line 1:
$TTL defines the standard TTL that applies to all entries here.
Line 2:
The configuration le should activate reverse lookup for the network 192.168 . Given that
the zone is called 168.192.in-addr.arpa , it should not be added to the host names.
Therefore, all host names are entered in their complete form—with their domain and with
a "." at the end. The remaining entries correspond to those described for the previous
example.com example.
Lines 3–7:
See the previous example for example.com .
Line 9:
Again this line specifies the name server responsible for this zone. This time, however, the
name is entered in its complete form with the domain and a "." at the end.

Lines 11–13:
These are the pointer records hinting at the IP addresses on the respective hosts. Only the
last part of the IP address is entered at the beginning of the line, without the "." at the
end. Appending the zone to this (without the .in-addr.arpa ) results in the complete IP
address in reverse order.
Normally, zone transfers between different versions of BIND should be possible without any
problems.
25.7 Dynamic Update of Zone Data

The term dynamic update refers to operations by which entries in the zone les of a master
server are added, changed, or deleted. This mechanism is described in RFC 2136. Dynamic
update is configured individually for each zone entry by adding an optional allow-update or
update-policy rule. Zones to update dynamically should not be edited by hand.
Transmit the entries to update to the server with the command nsupdate . For the exact syntax
of this command, check the manual page for nsupdate ( man 8 nsupdate ). For security rea-
sons, any such update should be performed using TSIG keys as described in Section 25.8, “Secure
Transactions”.
25.8 Secure Transactions

Secure transactions can be made with transaction signatures (TSIGs) based on shared secret keys
(also called TSIG keys). This section describes how to generate and use such keys.
Secure transactions are needed for communication between different servers and for the dynamic
update of zone data. Making the access control dependent on keys is much more secure than
merely relying on IP addresses.
Generate a TSIG key with the following command (for details, see man dnssec-keygen ):
dnssec-keygen -a hmac-md5 -b 128 -n HOST host1-host2
This creates two les with names similar to these:
Khost1-host2.+157+34265.private Khost1-host2.+157+34265.key
356 Dynamic Update of Zone Data SLES 12 SP3

The key itself (a string like ejIkuCyyGJwwuN3xAteKgg== ) is found in both les. To use it for
transactions, the second le ( Khost1-host2.+157+34265.key ) must be transferred to the re-
mote host, preferably in a secure way (using scp, for example). On the remote server, the key
must be included in the /etc/named.conf le to enable a secure communication between
host1 and host2 :
key host1-host2 {
algorithm hmac-md5;
secret "ejIkuCyyGJwwuN3xAteKgg==";
};
Warning: File Permissions of /etc/named.conf

Make sure that the permissions of /etc/named.conf are properly restricted. The default
for this le is 0640 , with the owner being root and the group named . As an alternative,
move the keys to an extra le with specially limited permissions, which is then included
from /etc/named.conf . To include an external le, use:
include "filename"
Replace filename with an absolute path to your le with keys.
To enable the server host1 to use the key for host2 (which has the address 10.1.2.3 in this
example), the server's /etc/named.conf must include the following rule:
server 10.1.2.3 {
keys { host1-host2. ;};
};
Analogous entries must be included in the configuration les of host2 .

Add TSIG keys for any ACLs (access control lists, not to be confused with le system ACLs) that
are defined for IP addresses and address ranges to enable transaction security. The corresponding
entry could look like this:
allow-update { key host1-host2. ;};
This topic is discussed in more detail in the BIND Administrator Reference Manual under up-
date-policy .
357 Secure Transactions SLES 12 SP3

25.9 DNS Security
DNSSEC, or DNS security, is described in RFC 2535. The tools available for DNSSEC are discussed
in the BIND Manual.
A zone considered secure must have one or several zone keys associated with it. These are
generated with dnssec-keygen , as are the host keys. The DSA encryption algorithm is currently
used to generate these keys. The public keys generated should be included in the corresponding
zone le with an $INCLUDE rule.
With the command dnssec-signzone , you can create sets of generated keys ( keyset- les),
transfer them to the parent zone in a secure manner, and sign them. This generates the les to
include for each zone in /etc/named.conf .

For more information, see the BIND Administrator Reference Manual from the bind-doc package,
which is installed under /usr/share/doc/packages/bind/arm . Consider additionally consult-
ing the RFCs referenced by the manual and the manual pages included with BIND. /usr/share/
doc/packages/bind/README.SUSE contains up-to-date information about BIND in SUSE Linux
Enterprise Server.
358 DNS Security SLES 12 SP3

26 DHCP
The purpose of the Dynamic Host Configuration Protocol (DHCP) is to assign network
settings centrally (from a server) rather than configuring them locally on every
workstation. A host configured to use DHCP does not have control over its own sta-
tic address. It is enabled to configure itself completely and automatically accord-
ing to directions from the server. If you use the NetworkManager on the client side,
you do not need to configure the client. This is useful if you have changing environ-
ments and only one interface active at a time. Never use NetworkManager on a ma-
chine that runs a DHCP server.
Tip: IBM z Systems: DHCP Support

On IBM z Systems platforms, DHCP only works on interfaces using the OSA and OSA
Express network cards. These cards are the only ones with a MAC, which is required for
the DHCP autoconfiguration features.
One way to configure a DHCP server is to identify each client using the hardware address of
its network card (which should be xed in most cases), then supply that client with identical
settings each time it connects to the server. DHCP can also be configured to assign addresses to
each relevant client dynamically from an address pool set up for this purpose. In the latter case,
the DHCP server tries to assign the same address to the client each time it receives a request,
even over extended periods. This works only if the network does not have more clients than
addresses.
DHCP makes life easier for system administrators. Any changes, even bigger ones, related to
addresses and the network configuration in general can be implemented centrally by editing the
server's configuration le. This is much more convenient than reconfiguring numerous worksta-
tions. It is also much easier to integrate machines, particularly new machines, into the network,
because they can be given an IP address from the pool. Retrieving the appropriate network
settings from a DHCP server is especially useful in case of laptops regularly used in different
networks.
In this chapter, the DHCP server will run in the same subnet as the workstations,
192.168.2.0/24 with 192.168.2.1 as gateway. It has the xed IP address 192.168.2.254
and serves two address ranges, 192.168.2.10 to 192.168.2.20 and 192.168.2.100 to
192.168.2.200 .
359 SLES 12 SP3

A DHCP server supplies not only the IP address and the netmask, but also the host name, domain
name, gateway, and name server addresses for the client to use. In addition to that, DHCP allows
several other parameters to be configured in a centralized way, for example, a time server from
which clients may poll the current time or even a print server.
26.1 Configuring a DHCP Server with YaST

To install a DHCP server, start YaST and select Software Software Management. Choose Fil-
ter Patterns and select DHCP and DNS Server. Confirm the installation of the dependent pack-
ages to finish the installation process.
Important: LDAP Support

The YaST DHCP module can be set up to store the server configuration locally (on the
host that runs the DHCP server) or to have its configuration data managed by an LDAP
server. To use LDAP, set up your LDAP environment before configuring the DHCP server.
For more information about LDAP, see Book “Security Guide”, Chapter 5 “LDAP—A Directory
Service”.
The YaST DHCP module ( yast2-dhcp-server ) allows you to set up your own DHCP server for
the local network. The module can run in wizard mode or expert configuration mode.
26.1.1 Initial Configuration (Wizard)

When the module is started for the rst time, a wizard starts, prompting you to make a few basic
decisions concerning server administration. Completing this initial setup produces a very basic
server configuration that should function in its essential aspects. The expert mode can be used
to deal with more advanced configuration tasks. Proceed as follows:
1. Select the interface from the list to which the DHCP server should listen and click Select.
After this, select Open Firewall for Selected Interfaces to open the firewall for this interface,
and click Next. See Figure 26.1, “DHCP Server: Card Selection”.
360 Configuring a DHCP Server with YaST SLES 12 SP3

FIGURE 26.1: DHCP SERVER: CARD SELECTION
2. Use the check box to determine whether your DHCP settings should be automatically
stored by an LDAP server. In the text boxes, provide the network specics for all clients
the DHCP server should manage. These specics are the domain name, address of a time
server, addresses of the primary and secondary name server, addresses of a print and a
WINS server (for a mixed network with both Windows and Linux clients), gateway address,
and lease time. See Figure 26.2, “DHCP Server: Global Settings”.
361 Initial Configuration (Wizard) SLES 12 SP3

FIGURE 26.2: DHCP SERVER: GLOBAL SETTINGS
3. Configure how dynamic IP addresses should be assigned to clients. To do so, specify an IP

range from which the server can assign addresses to DHCP clients. All these addresses must
be covered by the same netmask. Also specify the lease time during which a client may
keep its IP address without needing to request an extension of the lease. Optionally, specify
the maximum lease time—the period during which the server reserves an IP address for
a particular client. See Figure 26.3, “DHCP Server: Dynamic DHCP”.

FIGURE 26.3: DHCP SERVER: DYNAMIC DHCP
4. Define how the DHCP server should be started. Specify whether to start the DHCP server
automatically when the system is booted or manually when needed (for example, for
testing purposes). Click Finish to complete the configuration of the server. See Figure 26.4,
“DHCP Server: Start-Up”.

FIGURE 26.4: DHCP SERVER: START-UP
5. Instead of using dynamic DHCP in the way described in the preceding steps, you can also
configure the server to assign addresses in quasi-static fashion. Use the text boxes provided
in the lower part to specify a list of the clients to manage in this way. Specifically, provide
the Name and the IP Address to give to such a client, the Hardware Address, and the Network
Type (token ring or Ethernet). Modify the list of clients, which is shown in the upper part
with Add, Edit, and Delete from List. See Figure 26.5, “DHCP Server: Host Management”.

FIGURE 26.5: DHCP SERVER: HOST MANAGEMENT
26.1.2 DHCP Server Configuration (Expert)

In addition to the configuration method discussed earlier, there is also an expert configuration
mode that allows you to change the DHCP server setup in every detail. Start the expert configu-
ration by clicking DHCP Server Expert Configuration in the Start-Up dialog (see Figure 26.4, “DHCP
Server: Start-Up”).
Chroot Environment and Declarations

In this rst dialog, make the existing configuration editable by selecting Start DHCP Server.
An important feature of the behavior of the DHCP server is its ability to run in a chroot
environment, or chroot jail, to secure the server host. If the DHCP server should ever
be compromised by an outside attack, the attacker will still be in the chroot jail, which
prevents him from accessing the rest of the system. The lower part of the dialog displays
a tree view with the declarations that have already been defined. Modify these with Add,
Delete, and Edit. Selecting Advanced takes you to additional expert dialogs. See Figure 26.6,
“DHCP Server: Chroot Jail and Declarations”. After selecting Add, define the type of declaration
to add. With Advanced, view the log le of the server, configure TSIG key management,
and adjust the configuration of the firewall according to the setup of the DHCP server.
365 DHCP Server Configuration (Expert) SLES 12 SP3

FIGURE 26.6: DHCP SERVER: CHROOT JAIL AND DECLARATIONS
Selecting the Declaration Type

The Global Options of the DHCP server are made up of several declarations. This dialog
lets you set the declaration types Subnet, Host, Shared Network, Group, Pool of Addresses,
and Class. This example shows the selection of a new subnet (see Figure 26.7, “DHCP Server:
Selecting a Declaration Type”).

FIGURE 26.7: DHCP SERVER: SELECTING A DECLARATION TYPE
Subnet Configuration
This dialog allows you specify a new subnet with its IP address and netmask. In the middle
part of the dialog, modify the DHCP server start options for the selected subnet using Add,
Edit, and Delete. To set up dynamic DNS for the subnet, select Dynamic DNS.
FIGURE 26.8: DHCP SERVER: CONFIGURING SUBNETS

TSIG Key Management
If you chose to configure dynamic DNS in the previous dialog, you can now configure the
key management for a secure zone transfer. Selecting OK takes you to another dialog in
which to configure the interface for dynamic DNS (see Figure 26.10, “DHCP Server: Interface
Configuration for Dynamic DNS”).
FIGURE 26.9: DHCP SERVER: TSIG CONFIGURATION
Dynamic DNS: Interface Configuration

You can now activate dynamic DNS for the subnet by selecting Enable Dynamic DNS for This
Subnet. After doing so, use the drop-down box to activate the TSIG keys for forward and
reverse zones, making sure that the keys are the same for the DNS and the DHCP server.
With Update Global Dynamic DNS Settings, enable the automatic update and adjustment
of the global DHCP server settings according to the dynamic DNS environment. Finally,
define which forward and reverse zones should be updated per dynamic DNS, specifying
the name of the primary name server for each of the two zones. Selecting OK returns to the
subnet configuration dialog (see Figure 26.8, “DHCP Server: Configuring Subnets”). Selecting OK
again returns to the original expert configuration dialog.

FIGURE 26.10: DHCP SERVER: INTERFACE CONFIGURATION FOR DYNAMIC DNS
Network Interface Configuration

To define the interfaces the DHCP server should listen to and to adjust the firewall con-
figuration, select Advanced Interface Configuration from the expert configuration dialog.
From the list of interfaces displayed, select one or more that should be attended by the
DHCP server. If clients in all subnets need to be able to communicate with the server and
the server host also runs a firewall, adjust the firewall accordingly. To do so, select Adapt
Firewall Settings. YaST then adjusts the rules of SuSEFirewall2 to the new conditions (see
Figure 26.11, “DHCP Server: Network Interface and Firewall”), after which you can return to the
original dialog by selecting OK.

FIGURE 26.11: DHCP SERVER: NETWORK INTERFACE AND FIREWALL
After completing all configuration steps, close the dialog with OK. The server is now started
with its new configuration.
26.2 DHCP Software Packages

Both the DHCP server and the DHCP clients are available for SUSE Linux Enterprise Server. The
DHCP server available is dhcpd (published by the Internet Systems Consortium). On the client
side, there is dhcp-client (also from ISC) and tools coming with the wicked package.
370 DHCP Software Packages SLES 12 SP3

By default, the wicked tools are installed with the services wickedd-dhcp4 and wickedd-
dhcp6 . Both are launched automatically on each system boot to watch for a DHCP server. They
do not need a configuration le to do their job and work out of the box in most standard setups.
For more complex situations, use the ISC dhcp-client , which is controlled by means of the
configuration les /etc/dhclient.conf and /etc/dhclient6.conf .
26.3 The DHCP Server dhcpd

The core of any DHCP system is the dynamic host configuration protocol daemon. This server
leases addresses and watches how they are used, according to the settings defined in the con-
figuration le /etc/dhcpd.conf . By changing the parameters and values in this le, a system
administrator can influence the program's behavior in numerous ways. Look at the basic sample
/etc/dhcpd.conf le in Example 26.1, “The Configuration File /etc/dhcpd.conf”.
EXAMPLE 26.1: THE CONFIGURATION FILE /ETC/DHCPD.CONF
default-lease-time 600; # 10 minutes

max-lease-time 7200; # 2 hours
option domain-name "example.com";

option domain-name-servers 192.168.1.116;
option broadcast-address 192.168.2.255;
option routers 192.168.2.1;
option subnet-mask 255.255.255.0;
subnet 192.168.2.0 netmask 255.255.255.0

{
range 192.168.2.10 192.168.2.20;
range 192.168.2.100 192.168.2.200;
}
This simple configuration le should be sufficient to get the DHCP server to assign IP addresses
in the network. Make sure that a semicolon is inserted at the end of each line, because otherwise
dhcpd is not started.
The sample le can be divided into three sections. The rst one defines how many seconds an
IP address is leased to a requesting client by default ( default-lease-time ) before it should
apply for renewal. This section also includes a statement of the maximum period for which a
machine may keep an IP address assigned by the DHCP server without applying for renewal
( max-lease-time ).
371 The DHCP Server dhcpd SLES 12 SP3

In the second part, some basic network parameters are defined on a global level:
The line option domain-name defines the default domain of your network.
With the entry option domain-name-servers , specify up to three values for the DNS
servers used to resolve IP addresses into host names and vice versa. Ideally, configure a
name server on your machine or somewhere else in your network before setting up DHCP.
That name server should also define a host name for each dynamic address and vice versa.
To learn how to configure your own name server, read Chapter 25, The Domain Name System.
The line option broadcast-address defines the broadcast address the requesting client
should use.
With option routers , set where the server should send data packets that cannot be de-
livered to a host on the local network (according to the source and target host address and
the subnet mask provided). Usually, especially in smaller networks, this router is identical
to the Internet gateway.
With option subnet-mask , specify the netmask assigned to clients.
The last section of the le defines a network, including a subnet mask. To finish, specify the
address range that the DHCP daemon should use to assign IP addresses to interested clients. In
Example 26.1, “The Configuration File /etc/dhcpd.conf”, clients may be given any address between
192.168.2.10 and 192.168.2.20 or 192.168.2.100 and 192.168.2.200 .
After editing these few lines, you should be able to activate the DHCP daemon with the com-
mand systemctl start dhcpd . It will be ready for use immediately. Use the command rcd-
hcpd check-syntax to perform a brief syntax check. If you encounter any unexpected problems
with your configuration (the server aborts with an error or does not return done on start), you
should be able to nd out what has gone wrong by looking for information either in the main
system log that can be queried with the command journalctl (see Chapter 15, journalctl:
Query the systemd Journal for more information).
372 The DHCP Server dhcpd SLES 12 SP3

On a default SUSE Linux Enterprise Server system, the DHCP daemon is started in a chroot
environment for security reasons. The configuration les must be copied to the chroot environ-
ment so the daemon can nd them. Normally, there is no need to worry about this because the
command systemctl start dhcpd automatically copies the les.
26.3.1 Clients with Fixed IP Addresses
DHCP can also be used to assign a predefined, static address to a specific client. Addresses as-
signed explicitly always take priority over dynamic addresses from the pool. A static address
never expires in the way a dynamic address would, for example, if there were not enough ad-
dresses available and the server needed to redistribute them among clients.
To identify a client configured with a static address, dhcpd uses the hardware address (which
is a globally unique, xed numerical code consisting of six octet pairs) for the identification of
all network devices (for example, 00:30:6E:08:EC:80 ). If the respective lines, like the ones in
Example 26.2, “Additions to the Configuration File”, are added to the configuration le of Example 26.1,
“The Configuration File /etc/dhcpd.conf”, the DHCP daemon always assigns the same set of data to
the corresponding client.
EXAMPLE 26.2: ADDITIONS TO THE CONFIGURATION FILE
host jupiter {
hardware ethernet 00:30:6E:08:EC:80;
fixed-address 192.168.2.100;
}
The name of the respective client ( host HOSTNAME , here jupiter ) is entered in the rst line
and the MAC address in the second line. On Linux hosts, nd the MAC address with the command
ip link show followed by the network device (for example, eth0 ). The output should contain
something like
link/ether 00:30:6E:08:EC:80
In the preceding example, a client with a network card having the MAC address
00:30:6E:08:EC:80 is assigned the IP address 192.168.2.100 and the host name jupiter
automatically. The type of hardware to enter is ethernet in nearly all cases, although to-
ken-ring , which is often found on IBM systems, is also supported.
373 Clients with Fixed IP Addresses SLES 12 SP3

26.3.2 The SUSE Linux Enterprise Server Version
To improve security, the SUSE Linux Enterprise Server version of the ISC's DHCP server comes
with the non-root/chroot patch by Ari Edelkind applied. This enables dhcpd to run with the
user ID nobody and run in a chroot environment ( /var/lib/dhcp ). To make this possible,
the configuration le dhcpd.conf must be located in /var/lib/dhcp/etc . The init script
automatically copies the le to this directory when starting.
Control the server's behavior regarding this feature by means of entries in the le /etc/syscon-
fig/dhcpd . To run dhcpd without the chroot environment, set the variable DHCPD_RUN_CH-
ROOTED in /etc/sysconfig/dhcpd to “no”.
To enable dhcpd to resolve host names even from within the chroot environment, some other
configuration les must be copied as well:
/etc/localtime
/etc/host.conf
/etc/hosts
/etc/resolv.conf
These les are copied to /var/lib/dhcp/etc/ when starting the init script. Take these copies
into account for any changes that they require if they are dynamically modified by scripts like
/etc/ppp/ip-up . However, there should be no need to worry about this if the configuration
le only specifies IP addresses (instead of host names).
If your configuration includes additional les that should be copied into the chroot environment,
set these under the variable DHCPD_CONF_INCLUDE_FILES in the le /etc/sysconfig/dhcpd .
To ensure that the DHCP logging facility keeps working even after a restart of the syslog dae-
mon, there is an additional entry SYSLOGD_ADDITIONAL_SOCKET_DHCP in the le /etc/syscon-
fig/syslog .

More information about DHCP is available at the Web site of the Internet Systems Con-
sortium (http://www.isc.org/products/DHCP/ ). Information is also available in the dhcpd ,
dhcpd.conf , dhcpd.leases , and dhcp-options man pages.
374 The SUSE Linux Enterprise Server Version SLES 12 SP3

27 Sharing File Systems with NFS
Distributing and sharing le systems over a network is a common task in corporate
environments. The well-proven network le system (NFS) works with NIS, the yel-
low pages protocol. For a more secure protocol that works with LDAP and Kerberos,
check NFSv4 (default). Combined with pNFS, you can eliminate performance bottle-
necks.
NFS with NIS makes a network transparent to the user. With NFS, it is possible to
distribute arbitrary le systems over the network. With an appropriate setup, users
always nd themselves in the same environment regardless of the terminal they
currently use.
Important: Need for DNS

In principle, all exports can be made using IP addresses only. To avoid time-outs, you
need a working DNS system. DNS is necessary at least for logging purposes, because the
mountd daemon does reverse lookups.
27.1 Terminology
The following are terms used in the YaST module.
Exports
A directory exported by an NFS server, which clients can integrate it into their system.
NFS Client
The NFS client is a system that uses NFS services from an NFS server over the Network File
System protocol. The TCP/IP protocol is already integrated into the Linux kernel; there is
no need to install any additional software.
NFS Server
The NFS server provides NFS services to clients. A running server depends on the following
daemons: nfsd (worker), idmapd (ID-to-name mapping for NFSv4, needed for certain
scenarios only), statd (le locking), and mountd (mount requests).
375 Terminology SLES 12 SP3

NFSv3
NFSv3 is the version 3 implementation, the “old” stateless NFS that supports client au-
thentication.
NFSv4
NFSv4 is the new version 4 implementation that supports secure user authentication via
kerberos. NFSv4 requires one single port only and thus is better suited for environments
behind a firewall than NFSv3.
The protocol is specified as http://tools.ietf.org/html/rfc3530 .
pNFS
Parallel NFS, a protocol extension of NFSv4. Any pNFS clients can directly access the data
on an NFS server.
27.2 Installing NFS Server

The NFS server is not part of the default installation. To install the NFS server using YaST, choose
Software Software Management, select Patterns, and enable the File Server option in the Server
Functions section. Press Accept to install the required packages.
Like NIS, NFS is a client/server system. However, a machine can be both—it can supply le
systems over the network (export) and mount le systems from other hosts (import).
Note: Mounting NFS Volumes Locally on the Exporting Server

Mounting NFS volumes locally on the exporting server is not supported on SUSE Linux
Enterprise Server.
27.3 Configuring NFS Server

Configuring an NFS server can be done either through YaST or manually. For authentication,
NFS can also be combined with Kerberos.
376 Installing NFS Server SLES 12 SP3

27.3.1 Exporting File Systems with YaST
With YaST, turn a host in your network into an NFS server—a server that exports directories
and les to all hosts granted access to it or to all members of a group. Thus, the server can also
provide applications without installing the applications locally on every host.
To set up such a server, proceed as follows:
PROCEDURE 27.1: SETTING UP AN NFS SERVER
1. Start YaST and select Network Services NFS Server; see Figure 27.1, “NFS Server Configuration
Tool”. You may be prompted to install additional software.
FIGURE 27.1: NFS SERVER CONFIGURATION TOOL
2. Activate the Start radio button.
3. If a firewall is active on your system (SuSEFirewall2), check Open Ports in Firewall. YaST
adapts its configuration for the NFS server by enabling the nfs service.
4. Check whether you want to Enable NFSv4. If you deactivate NFSv4, YaST will only support
NFSv3. For information about enabling NFSv2, see Note: NFSv2.
377 Exporting File Systems with YaST SLES 12 SP3

If NFSv4 is selected, additionally enter the appropriate NFSv4 domain name. This
parameter is used by the idmapd daemon that is required for Kerberos setups or
if clients cannot work with numeric user names. Leave it as localdomain (the de-
fault) if you do not run idmapd or do not have any special requirements. For more
information on the idmapd daemon see /etc/idmapd.conf .
5. Click Enable GSS Security if you need secure access to the server. A prerequisite for this
is to have Kerberos installed on your domain and to have both the server and the clients
kerberized. Click Next to proceed with the next configuration dialog.
6. Click Add Directory in the upper half of the dialog to export your directory.
7. If you have not configured the allowed hosts already, another dialog for entering the client
information and options pops up automatically. Enter the host wild card (usually you can
leave the default settings as they are).
There are four possible types of host wild cards that can be set for each host: a single host
(name or IP address), netgroups, wild cards (such as * indicating all machines can access
the server), and IP networks.
For more information about these options, see the exports man page.
8. Click Finish to complete the configuration.
27.3.2 Exporting File Systems Manually
The configuration les for the NFS export service are /etc/exports and /etc/syscon-
fig/nfs . In addition to these les, /etc/idmapd.conf is needed for the NFSv4 server config-
uration with kerberized NFS or if the clients cannot work with numeric user names.
To start or restart the services, run the command systemctl restart nfsserver . This also
restarts the RPC portmapper that is required by the NFS server.
To make sure the NFS server always starts at boot time, run sudo systemctl enable nf-
sserver .
Note: NFSv4
NFSv4 is the latest version of NFS protocol available on SUSE Linux Enterprise Server.
Configuring directories for export with NFSv4 is now the same as with NFSv3.
378 Exporting File Systems Manually SLES 12 SP3

On SUSE Linux Enterprise Server 11, the bind mount in /etc/exports was mandatory.
It is still supported, but now deprecated.
/etc/exports
The /etc/exports le contains a list of entries. Each entry indicates a directory that is
shared and how it is shared. A typical entry in /etc/exports consists of:
/SHARED/DIRECTORY HOST(OPTION_LIST)
For example:
/export/data 192.168.1.2(rw,sync)
Here the IP address 192.168.1.2 is used to identify the allowed client. You can also
use the name of the host, a wild card indicating a set of hosts ( *.abc.com , * , etc.), or
netgroups ( @my-hosts ).
For a detailed explanation of all options and their meaning, refer to the man page of
exports ( man exports ).
In case you have modified /etc/exports while the NFS server was running, you need to
restart it for the changes to become active: sudo systemctl restart nfsserver .
/etc/sysconfig/nfs
The /etc/sysconfig/nfs le contains a few parameters that determine NFSv4 server
daemon behavior. It is important to set the parameter NFS4_SUPPORT to yes (default).
NFS4_SUPPORT determines whether the NFS server supports NFSv4 exports and clients.
In case you have modified /etc/sysconfig/nfs while the NFS server was running, you
need to restart it for the changes to become active: sudo systemctl restart nfsserver .
Tip: Mount Options

On SUSE Linux Enterprise Server 11, the --bind mount in /etc/exports was
mandatory. It is still supported, but now deprecated. Configuring directories for
export with NFSv4 is now the same as with NFSv3.
Note: NFSv2
If NFS clients still depend on NFSv2, enable it on the server in /etc/syscon-
fig/nfs by setting:
NFSD_OPTIONS="-V2"

MOUNTD_OPTIONS="-V2"
After restarting the service, check whether version 2 is available with the command:
tux > cat /proc/fs/nfsd/versions

+2 +3 +4 +4.1 -4.2
/etc/idmapd.conf
Starting with SLE 12 SP1, the idmapd daemon is only required if Kerberos authentication
is used, or if clients cannot work with numeric user names. Linux clients can work with
numeric user names since Linux kernel 2.6.39. The idmapd daemon does the name-to-ID
mapping for NFSv4 requests to the server and replies to the client.
If required, idmapd needs to run on the NFSv4 server. Name-to-ID mapping on the client
will be done by nfsidmap provided by the package nfs-client .
Make sure that there is a uniform way in which user names and IDs (uid) are assigned to
users across machines that might probably be sharing le systems using NFS. This can be
achieved by using NIS, LDAP, or any uniform domain authentication mechanism in your
domain.
The parameter Domain must be set the same for both, client and server in the /etc/
idmapd.conf le. If you are not sure, leave the domain as localdomain in the server and
client les. A sample configuration le looks like the following:
[General]
Verbosity = 0
Pipefs-Directory = /var/lib/nfs/rpc_pipefs
Domain = localdomain
[Mapping]
Nobody-User = nobody
Nobody-Group = nobody
To start the idmapd daemon, run systemctl start nfs-idmapd . In case you have mod-
ified /etc/idmapd.conf while the daemon was running, you need to restart it for the
changes to become active: systemctl start nfs-idmapd .
For more information, see the man pages of idmapd and idmapd.conf ( man idmapd and
man idmapd.conf ).

27.3.3 NFS with Kerberos
To use Kerberos authentication for NFS, GSS security must be enabled. Select Enable GSS Security
in the initial YaST NFS Server dialog. You must have a working Kerberos server to use this
feature. YaST does not set up the server but only uses the provided functionality. If you want
to use Kerberos authentication in addition to the YaST configuration, complete at least the
following steps before running the NFS configuration:
1. Make sure that both the server and the client are in the same Kerberos domain. They must
access the same KDC (Key Distribution Center) server and share their krb5.keytab le
(the default location on any machine is /etc/krb5.keytab ). For more information about
Kerberos, see Book “Security Guide”, Chapter 6 “Network Authentication with Kerberos”.
2. Start the gssd service on the client with systemctl start rpc-gssd.service .
3. Start the svcgssd service on the server with systemctl start rpc-svcgssd.service .
Kerberos authentication also requires the idmapd daemon to run on the server. For more infor-
mation refer to /etc/idmapd.conf .
For more information about configuring kerberized NFS, refer to the links in Section 27.5, “For
More Information”.
27.4 Configuring Clients

To configure your host as an NFS client, you do not need to install additional software. All
needed packages are installed by default.
27.4.1 Importing File Systems with YaST
Authorized users can mount NFS directories from an NFS server into the local le tree using the
YaST NFS client module. Proceed as follows:
PROCEDURE 27.2: IMPORTING NFS DIRECTORIES
1. Start the YaST NFS client module.
2. Click Add in the NFS Shares tab. Enter the host name of the NFS server, the directory to
import, and the mount point at which to mount this directory locally.
381 NFS with Kerberos SLES 12 SP3

3. When using NFSv4, select Enable NFSv4 in the NFS Settings tab. Additionally, the NFSv4
Domain Name must contain the same value as used by the NFSv4 server. The default do-
main is localdomain .
4. To use Kerberos authentication for NFS, GSS security must be enabled. Select Enable GSS
Security.
5. Enable Open Port in Firewall in the NFS Settings tab if you use a Firewall and want to allow
access to the service from remote computers. The firewall status is displayed next to the
check box.
6. Click OK to save your changes.
The configuration is written to /etc/fstab and the specified le systems are mounted. When
you start the YaST configuration client at a later time, it also reads the existing configuration
from this le.
Tip: NFS as a Root File System

On (diskless) systems, where the root partition is mounted via network as an NFS share,
you need to be careful when configuring the network device with which the NFS share
is accessible.
When shutting down or rebooting the system, the default processing order is to turn o
network connections, then unmount the root partition. With NFS root, this order causes
problems as the root partition cannot be cleanly unmounted as the network connection
to the NFS share is already not activated. To prevent the system from deactivating the
relevant network device, open the network device configuration tab as described in Sec-
tion 16.4.1.2.5, “Activating the Network Device” and choose On NFSroot in the Device Activation
pane.
27.4.2 Importing File Systems Manually

The prerequisite for importing le systems manually from an NFS server is a running RPC port
mapper. The nfs service takes care to start it properly; thus, start it by entering systemctl
start nfs as root . Then remote le systems can be mounted in the le system like local
partitions using mount :
tux > sudo mount HOST:REMOTE-PATHLOCAL-PATH
382 Importing File Systems Manually SLES 12 SP3

To import user directories from the nfs.example.com machine, for example, use:
tux > sudo mount nfs.example.com:/home /home
27.4.2.1 Using the Automount Service

The autofs daemon can be used to mount remote le systems automatically. Add the following
entry to the /etc/auto.master le:
/nfsmounts /etc/auto.nfs
Now the /nfsmounts directory acts as the root for all the NFS mounts on the client if the au-
to.nfs le is lled appropriately. The name auto.nfs is chosen for the sake of convenience—
you can choose any name. In auto.nfs add entries for all the NFS mounts as follows:
localdata -fstype=nfs server1:/data

nfs4mount -fstype=nfs4 server2:/
Activate the settings with systemctl start autofs as root . In this example, /nfs-
mounts/localdata , the /data directory of server1 , is mounted with NFS and /nfs-
mounts/nfs4mount from server2 is mounted with NFSv4.
If the /etc/auto.master le is edited while the service autofs is running, the automounter
must be restarted for the changes to take effect with systemctl restart autofs .
27.4.2.2 Manually Editing /etc/fstab

A typical NFSv3 mount entry in /etc/fstab looks like this:
nfs.example.com:/data /local/path nfs rw,noauto 0 0
For NFSv4 mounts, use nfs4 instead of nfs in the third column:
nfs.example.com:/data /local/pathv4 nfs4 rw,noauto 0 0
The noauto option prevents the le system from being mounted automatically at start-up. If you
want to mount the respective le system manually, it is possible to shorten the mount command
specifying the mount point only:
tux > sudo mount /local/path
383 Importing File Systems Manually SLES 12 SP3

Note: Mounting at Start-Up
If you do not enter the noauto option, the init scripts of the system will handle the mount
of those le systems at start-up.
27.4.3 Parallel NFS (pNFS)

NFS is one of the oldest protocols, developed in the '80s. As such, NFS is usually sufficient if
you want to share small les. However, when you want to transfer big les or large numbers
of clients want to access data, an NFS server becomes a bottleneck and has a significant impact
on the system performance. This is because of les quickly getting bigger, whereas the relative
speed of your Ethernet has not fully kept up.
When you request a le from a regular NFS server, the server looks up the le metadata, collects
all the data and transfers it over the network to your client. However, the performance bottleneck
becomes apparent no matter how small or big the les are:
With small les most of the time is spent collecting the metadata.
With big les most of the time is spent on transferring the data from server to client.
pNFS, or parallel NFS, overcomes this limitation as it separates the le system metadata from
the location of the data. As such, pNFS requires two types of servers:
A metadata or control server that handles all the non-data traffic
One or more storage server(s) that hold(s) the data
The metadata and the storage servers form a single, logical NFS server. When a client wants to
read or write, the metadata server tells the NFSv4 client which storage server to use to access
the le chunks. The client can access the data directly on the server.
SUSE Linux Enterprise Server supports pNFS on the client side only.
27.4.3.1 Configuring pNFS Client With YaST
Proceed as described in Procedure 27.2, “Importing NFS Directories”, but click the pNFS (v4.1) check
box and optionally NFSv4 share. YaST will do all the necessary steps and will write all the
required options in the le /etc/exports .
384 Parallel NFS (pNFS) SLES 12 SP3

27.4.3.2 Configuring pNFS Client Manually
Refer to Section 27.4.2, “Importing File Systems Manually” to start. Most of the configuration is done
by the NFSv4 server. For pNFS, the only difference is to add the minorversion option and the
metadata server MDS_SERVER to your mount command:
tux > sudo mount -t nfs4 -o minorversion=1 MDS_SERVER MOUNTPOINT
To help with debugging, change the value in the /proc le system:
tux > sudo echo 32767 > /proc/sys/sunrpc/nfsd_debug

tux > sudo echo 32767 > /proc/sys/sunrpc/nfs_debug

In addition to the man pages of exports , nfs , and mount , information about configuring
an NFS server and client is available in /usr/share/doc/packages/nfsidmap/README . For
further documentation online refer to the following Web sites:
Find the detailed technical documentation online at SourceForge (http://nfs.source-

forge.net/) .
For instructions for setting up kerberized NFS, refer to NFS Version 4 Open Source Reference
Implementation (http://www.citi.umich.edu/projects/nfsv4/linux/krb5-setup.html) .
If you have questions on NFSv4, refer to the Linux NFSv4 FAQ (http://www.citi.umich.e-
du/projects/nfsv4/linux/faq/) .

28 Samba
Using Samba, a Unix machine can be configured as a le and print server for ma-
cOS, Windows, and OS/2 machines. Samba has developed into a fully-edged and
rather complex product. Configure Samba with YaST, or by editing the configura-
tion le manually.
28.1 Terminology
The following are some terms used in Samba documentation and in the YaST module.
SMB protocol
Samba uses the SMB (server message block) protocol that is based on the NetBIOS services.
Microsoft released the protocol so other software manufacturers could establish connec-
tions to a Microsoft domain network. With Samba, the SMB protocol works on top of the
TCP/IP protocol, so the TCP/IP protocol must be installed on all clients.
Tip: IBM z Systems: NetBIOS Support

IBM z Systems merely supports SMB over TCP/IP. NetBIOS support is not available
on these systems.
CIFS protocol
CIFS (common Internet le system) protocol is another protocol supported by Samba. CIFS
defines a standard remote le system access protocol for use over the network, enabling
groups of users to work together and share documents across the network.
NetBIOS
NetBIOS is a software interface (API) designed for communication between machines pro-
viding a name service. It enables machines connected to the network to reserve names for
themselves. After reservation, these machines can be addressed by name. There is no cen-
tral process that checks names. Any machine on the network can reserve as many names
as it wants as long as the names are not already in use. The NetBIOS interface can be
implemented for different network architectures. An implementation that works relatively
386 Terminology SLES 12 SP3

closely with network hardware is called NetBEUI, but this is often called NetBIOS. Net-
work protocols implemented with NetBIOS are IPX from Novell (NetBIOS via TCP/IP) and
TCP/IP.
The NetBIOS names sent via TCP/IP have nothing in common with the names used in
/etc/hosts or those defined by DNS. NetBIOS uses its own, completely independent
naming convention. However, it is recommended to use names that correspond to DNS
host names to make administration easier or use DNS natively. This is the default used
by Samba.
Samba server
Samba server provides SMB/CIFS services and NetBIOS over IP naming services to clients.
For Linux, there are three daemons for Samba server: smbd for SMB/CIFS services, nmbd
for naming services, and winbind for authentication.
Samba client
The Samba client is a system that uses Samba services from a Samba server over the SMB
protocol. Common operating systems, such as Windows and macOS support the SMB pro-
tocol. The TCP/IP protocol must be installed on all computers. Samba provides a client
for the different Unix flavors. For Linux, there is a kernel module for SMB that allows
the integration of SMB resources on the Linux system level. You do not need to run any
daemon for the Samba client.
Shares
SMB servers provide resources to the clients by means of shares. Shares are printers and
directories with their subdirectories on the server. It is exported by means of a name and
can be accessed by its name. The share name can be set to any name—it does not need to
be the name of the export directory. A printer is also assigned a name. Clients can access
the printer by its name.
DC
A domain controller (DC) is a server that handles accounts in a domain. For data replica-
tion, additional domain controllers are available in one domain.
28.2 Installing a Samba Server

To install a Samba server, start YaST and select Software Software Management. Choose
View Patterns and select File Server. Confirm the installation of the required packages to finish
the installation process.
387 Installing a Samba Server SLES 12 SP3

28.3 Starting and Stopping Samba
You can start or stop the Samba server automatically (during boot) or manually. Starting and
stopping policy is a part of the YaST Samba server configuration described in Section 28.4.1,
“Configuring a Samba Server with YaST”.
From a command line, stop services required for Samba with systemctl stop smb nmb and
start them with systemctl start nmb smb . The smb service cares about winbind if needed.
Tip: winbind
winbind is an independent service, and as such is also offered as an individual sam-
ba-winbind package.
28.4 Configuring a Samba Server

A Samba server in SUSE® Linux Enterprise Server can be configured in two different ways: with
YaST or manually. Manual configuration offers a higher level of detail, but lacks the convenience
of the YaST GUI.
28.4.1 Configuring a Samba Server with YaST

To configure a Samba server, start YaST and select Network Services Samba Server.
28.4.1.1 Initial Samba Configuration
When starting the module for the rst time, the Samba Installation dialog starts, prompting you
to make a few basic decisions concerning administration of the server. At the end of the con-
figuration it prompts for the Samba administrator password (Samba Root Password). For later
starts, the Samba Configuration dialog appears.
The Samba Installation dialog consists of two steps and optional detailed settings:
Workgroup or Domain Name

Select an existing name from Workgroup or Domain Name or enter a new one and click Next.
388 Starting and Stopping Samba SLES 12 SP3

Samba Server Type
In the next step, specify whether your server should act as a primary domain controller
(PDC), backup domain controller (BDC), or not act as a domain controller. Continue with
Next.
If you do not want to proceed with a detailed server configuration, confirm with OK. Then in
the final pop-up box, set the Samba root Password.
You can change all settings later in the Samba Configuration dialog with the Start-Up, Shares,
Identity, Trusted Domains, and LDAP Settings tabs.
28.4.1.2 Advanced Samba Configuration
During the rst start of the Samba server module the Samba Configuration dialog appears directly
after the two initial steps described in Section 28.4.1.1, “Initial Samba Configuration”. Use it to adjust
your Samba server configuration.
After editing your configuration, click OK to save your settings.
28.4.1.2.1 Starting the Server
In the Start Up tab, configure the start of the Samba server. To start the service every time your
system boots, select During Boot. To activate manual start, choose Manually. More information
about starting a Samba server is provided in Section 28.3, “Starting and Stopping Samba”.
In this tab, you can also open ports in your firewall. To do so, select Open Port in Firewall. If you
have multiple network interfaces, select the network interface for Samba services by clicking
Firewall Details, selecting the interfaces, and clicking OK.
28.4.1.2.2 Shares
In the Shares tab, determine the Samba shares to activate. There are some predefined shares,
like homes and printers. Use Toggle Status to switch between Active and Inactive. Click Add to
add new shares and Delete to delete the selected share.
389 Configuring a Samba Server with YaST SLES 12 SP3

Allow Users to Share Their Directories enables members of the group in Permitted Group to share
directories they own with other users. For example, users for a local scope or DOMAIN\Users
for a domain scope. The user also must make sure that the le system permissions allow access.
With Maximum Number of Shares, limit the total amount of shares that may be created. To permit
access to user shares without authentication, enable Allow Guest Access.
28.4.1.2.3 Identity
In the Identity tab, you can determine the domain with which the host is associated (Base Settings)
and whether to use an alternative host name in the network (NetBIOS Hostname). It is also
possible to use Microsoft Windows Internet Name Service (WINS) for name resolution. In this
case, activate Use WINS for Hostname Resolution and decide whether to Retrieve WINS server via
DHCP. To set expert global settings or set a user authentication source, for example LDAP instead
of TDB database, click Advanced Settings.
28.4.1.2.4 Trusted Domains
To enable users from other domains to access your domain, make the appropriate settings in
the Trusted Domains tab. To add a new domain, click Add. To remove the selected domain, click
Delete.
28.4.1.2.5 LDAP Settings
In the tab LDAP Settings, you can determine the LDAP server to use for authentication. To test
the connection to your LDAP server, click Test Connection. To set expert LDAP settings or use
default values, click Advanced Settings.
For more information about LDAP configuration, see Book “Security Guide”, Chapter 5 “LDAP—A
Directory Service”.
390 Configuring a Samba Server with YaST SLES 12 SP3

28.4.2 Configuring the Server Manually
If you intend to use Samba as a server, install samba . The main configuration le for Samba is
/etc/samba/smb.conf . This le can be divided into two logical parts. The [global] section
contains the central and global settings. The following default sections contain the individual
le and printer shares:
[homes]
[profiles]
[users]
[groups]
[printers]
[print$]
Using this approach, options of the shares can be set differently or globally in the [global]
section, which makes the configuration le easier to understand.
28.4.2.1 The global Section

The following parameters of the [global] section should be modified to match the require-
ments of your network setup, so other machines can access your Samba server via SMB in a
Windows environment.
workgroup = WORKGROUP
This line assigns the Samba server to a workgroup. Replace WORKGROUP with an appropri-
ate workgroup of your networking environment. Your Samba server appears under its DNS
name unless this name has been assigned to some other machine in the network. If the
DNS name is not available, set the server name using netbiosname=MYNAME . For more
details about this parameter, see the smb.conf man page.
os level = 20
This parameter triggers whether your Samba server tries to become LMB (local master
browser) for its workgroup. Choose a very low value such as 2 to spare the existing Win-
dows network from any interruptions caused by a misconfigured Samba server. More in-
formation about this topic can be found in the Network Browsing chapter of the Samba 3
Howto; for more information on the Samba 3 Howto, see Section 28.9, “For More Information”.
391 Configuring the Server Manually SLES 12 SP3

If no other SMB server is in your network (such as a Windows 2000 server) and you want
the Samba server to keep a list of all systems present in the local environment, set the os
level to a higher value (for example, 65 ). Your Samba server is then chosen as LMB for
your local network.
When changing this setting, consider carefully how this could affect an existing Windows
network environment. First test the changes in an isolated network or at a noncritical time
of day.
wins support and wins server

To integrate your Samba server into an existing Windows network with an active WINS
server, enable the wins server option and set its value to the IP address of that WINS
server.
If your Windows machines are connected to separate subnets and need to still be aware of
each other, you have to set up a WINS server. To turn a Samba server into such a WINS
server, set the option wins support = Yes . Make sure that only one Samba server of
the network has this setting enabled. The options wins server and wins support must
never be enabled at the same time in your smb.conf le.
28.4.2.2 Shares
The following examples illustrate how a CD-ROM drive and the user directories ( homes ) are
made available to the SMB clients.
[cdrom]
To avoid having the CD-ROM drive accidentally made available, these lines are deactivated
with comment marks (semicolons in this case). Remove the semicolons in the rst column
to share the CD-ROM drive with Samba.
EXAMPLE 28.1: A CD-ROM SHARE
[cdrom]
comment = Linux CD-ROM
path = /media/cdrom
locking = No
[cdrom] and comment

The [cdrom] section entry is the name of the share that can be seen by all SMB clients
on the network. An additional comment can be added to further describe the share.

path = /media/cdrom
path exports the directory /media/cdrom .
By means of a very restrictive default configuration, this kind of share is only made avail-
able to the users present on this system. If this share should be made available to every-
body, add a line guest ok = yes to the configuration. This setting gives read permissions
to anyone on the network. It is recommended to handle this parameter with great care.
This applies even more to the use of this parameter in the [global] section.
[homes]
The [homes] share is of special importance here. If the user has a valid account and
password for the Linux le server and his own home directory, he can be connected to it.
EXAMPLE 28.2: [HOMES] SHARE
[homes]
comment = Home Directories
valid users = %S
browseable = No
read > inherit acls = Yes
[homes]
As long as there is no other share using the share name of the user connecting to the
SMB server, a share is dynamically generated using the [homes] share directives.
The resulting name of the share is the user name.
valid users = %S
%S is replaced with the concrete name of the share when a connection has been
successfully established. For a [homes] share, this is always the user name. As a
consequence, access rights to a user's share are restricted exclusively to that user.
browseable = No
This setting makes the share invisible in the network environment.
read > By default, Samba prohibits write access to any exported share by means of the read
parameter. To make a share writable, set the value read ,
which is synonymous with writable = Yes .

create mask = 0640
Systems that are not based on MS Windows NT do not understand the concept of Unix
permissions, so they cannot assign permissions when creating a le. The parameter
create mask defines the access permissions assigned to newly created les. This on-
ly applies to writable shares. In effect, this setting means the owner has read and write
permissions and the members of the owner's primary group have read permissions.
valid users = %S prevents read access even if the group has read permissions. For
the group to have read or write access, deactivate the line valid users = %S .
Warning: Do not share NFS mounts with Samba

Sharing NFS mounts with samba may result in data loss and is not supported. Install
Samba directly on the le server or consider using alternatives such as iSCSI .
28.4.2.3 Security Levels
To improve security, each share access can be protected with a password. SMB offers the fol-
lowing ways of checking permissions:
User Level Security ( security = user )

This variant introduces the concept of the user to SMB. Each user must register with the
server with his or her own password. After registration, the server can grant access to
individual exported shares dependent on user names.
ADS Level Security ( security = ADS )

In this mode, Samba will act as a domain member in an Active Directory environment. To
operate in this mode, the machine running Samba needs Kerberos installed and configured.
You must join the machine using Samba to the ADS realm. This can be done using the
YaST Windows Domain Membership module.
Domain Level Security ( security = domain )

This mode will only work correctly if the machine has been joined into a Windows NT
Domain. Samba will try to validate user name and password by passing it to a Windows
NT Primary or Backup Domain Controller. The same way as a Windows NT Server would
do. It expects the encrypted passwords parameter to be set to yes .

The selection of share, user, server, or domain level security applies to the entire server. It is not
possible to offer individual shares of a server configuration with share level security and others
with user level security. However, you can run a separate Samba server for each configured IP
address on a system.
More information about this subject can be found in the Samba 3 HOWTO. For multiple servers
on one system, pay attention to the options interfaces and bind interfaces only .
28.5 Configuring Clients

Clients can only access the Samba server via TCP/IP. NetBEUI and NetBIOS via IPX cannot be
used with Samba.
28.5.1 Configuring a Samba Client with YaST

Configure a Samba client to access resources (les or printers) on the Samba or Windows server.
Enter the NT or Active Directory domain or workgroup in the dialog Network Services Windows
Domain Membership. If you activate Also Use SMB Information for Linux Authentication, the user
authentication runs over the Samba, NT or Kerberos server.
Click Expert Settings for advanced configuration options. For example, use the Mount Server Di-
rectories table to enable mounting server home directory automatically with authentication. This
way users can access their home directories when hosted on CIFS. For details, see the pam_mount
man page.
After completing all settings, confirm the dialog to finish the configuration.
28.6 Samba as Login Server

In networks where predominantly Windows clients are found, it is often preferable that users
may only register with a valid account and password. In a Windows-based network, this task is
handled by a primary domain controller (PDC). You can use a Windows NT server configured
as PDC, but this task can also be done with a Samba server. The entries that must be made in
the [global] section of smb.conf are shown in Example 28.3, “Global Section in smb.conf”.
EXAMPLE 28.3: GLOBAL SECTION IN SMB.CONF
[global]
395 Configuring Clients SLES 12 SP3

workgroup = WORKGROUP
domain logons = Yes
domain master = Yes
It is necessary to prepare user accounts and passwords in an encryption format that conforms
with Windows. Do this with the command smbpasswd -a name . Create the domain account
for the computers, required by the Windows domain concept, with the following commands:
useradd hostname\$
smbpasswd -a -m hostname
With the useradd command, a dollar sign is added. The command smbpasswd inserts this
automatically when the parameter -m is used. The commented configuration example ( /usr/
share/doc/packages/samba/examples/smb.conf.SUSE ) contains settings that automate this
task.
add machine script = /usr/sbin/useradd -g nogroup -c "NT Machine Account" \

-s /bin/false %m\$
To make sure that Samba can execute this script correctly, choose a Samba user with the required
administrator permissions and add it to the ntadmin group. Then all users belonging to this
Linux group can be assigned Domain Admin status with the command:
net groupmap add ntgroup="Domain Admins" unixgroup=ntadmin
28.7 Samba Server in the Network with Active

Directory
If you run Linux servers and Windows servers together, you can build two independent authen-
tication systems and networks or connect servers to one network with one central authentication
system. Because Samba can cooperate with an active directory domain, you can join your SUSE
Linux Enterprise Server to Active Directory (AD).
To join an AD domain proceed as follows:
1. Log in as root and start YaST.
2. Start Network Services Windows Domain Membership.
396 Samba Server in the Network with Active Directory SLES 12 SP3
3. Enter the domain to join at Domain or Workgroup in the Windows Domain Membership
screen.
FIGURE 28.1: DETERMINING WINDOWS DOMAIN MEMBERSHIP
4. Check Also Use SMB Information for Linux Authentication to use the SMB source for Linux
authentication on your server.
5. Click OK and confirm the domain join when prompted for it.
6. Provide the password for the Windows Administrator on the AD server and click OK.
Your server is now set up to pull in all authentication data from the Active Directory
domain controller.
Tip: Identity Mapping

In an environment with more than one Samba server, UIDs and GIDs will not be creat-
ed consistently. The UIDs that get assigned to users will be dependent on the order in
which they rst log in, which results in UID conflicts across servers. To x this, you
need to use identity mapping. See https://www.samba.org/samba/docs/man/Samba-HOW-
TO-Collection/idmapper.html for more details.
397 Samba Server in the Network with Active Directory SLES 12 SP3
28.8 Advanced Topics
This section introduces more advanced techniques to manage both the client and server part
of the Samba suite.
28.8.1 Transparent File Compression on Btrfs

Samba allows clients to remotely manipulate le and directory compression ags for shares
placed on the Btrfs le system. Windows Explorer provides the ability to ag les/directories
for transparent compression via the File Properties Advanced dialog:
FIGURE 28.2: WINDOWS EXPLORER ADVANCED ATTRIBUTES DIALOG
Files agged for compression are transparently compressed and decompressed by the underlying
le system when accessed or modified. This normally results in storage capacity savings at the
expense of extra CPU overhead when accessing the le. New les and directories inherit the
compression ag from the parent directory, unless created with the FILE_NO_COMPRESSION
option.
Windows Explorer presents compressed les and directories visually differently to those that
are not compressed:
FIGURE 28.3: WINDOWS EXPLORER DIRECTORY LISTING WITH COMPRESSED FILES
You can enable Samba share compression either manually by adding
vfs objects = btrfs
to the share configuration in /etc/samba/smb.conf , or using YaST: Network Services Samba

Server Add, and checking Utilize Btrfs Features.
398 Advanced Topics SLES 12 SP3

A general overview of compression on Btrfs can be found in Book “Storage Administration Guide”,
Chapter 1 “Overview of File Systems in Linux”, Section 1.2.2.1 “Mounting Compressed Btrfs File Systems”.
28.8.2 Snapshots
Snapshots, also called Shadow Copies, are copies of the state of a le system subvolume at a
certain point of time. Snapper is the tool to manage these snapshots in Linux. Snapshots are
supported on the Btrfs le system or thin-provisioned LVM volumes. The Samba suite supports
managing of remote snapshots through the FSRVP protocol on both the server and client side.
28.8.2.1 Previous Versions
Snapshots on a Samba server can be exposed to remote Windows clients as le or directory
previous versions.
To enable snapshots on a Samba server, the following conditions must be fulfilled:
The SMB network share resides on a Btrfs subvolume.
The SMB network share path has a related snapper configuration le. You can create the
snapper le with
snapper -c <cfg_name> create-config /path/to/share
For more information on snapper, see Chapter 7, System Recovery and Snapshot Management
with Snapper.
The snapshot directory tree must allow access for relevant users. For more information,
see the PERMISSIONS section of the vfs_snapper manual page ( man 8 vfs_snapper ).
To support remote snapshots, you need to modify the /etc/samba/smb.conf le. You can do
it either with YaST Network Services Samba Server, or manually by enhancing the relevant
share section with
vfs objects = snapper
Note that you need to restart the Samba service for manual smb.conf changes to take effect:
systemctl restart nmb smb
399 Snapshots SLES 12 SP3

FIGURE 28.4: ADDING A NEW SAMBA SHARE WITH SNAPSHOTTING ENABLED
After being configured, snapshots created by snapper for the Samba share path can be accessed
from Windows Explorer from a le or directory's Previous Versions tab.

FIGURE 28.5: THE PREVIOUS VERSIONS TAB IN WINDOWS EXPLORER
28.8.2.2 Remote Share Snapshots
By default, snapshots can only be created and deleted on the Samba server locally, via the
snapper command line utility, or using snapper's time line feature.
Samba can be configured to process share snapshot creation and deletion requests from remote
hosts using the File Server Remote VSS Protocol (FSRVP).

In addition to the configuration and prerequisites documented in Section 28.8.2.1, “Previous Ver-
sions”, the following global configuration is required in /etc/samba/smb.conf :
[global]
rpc_daemon:fssd = fork
registry shares = yes
include = registry
FSRVP clients, including Samba's rpcclient and Windows Server 2012 DiskShadow.exe , can
then instruct Samba to create or delete a snapshot for a given share, and expose the snapshot
as a new share.
28.8.2.3 Managing Snapshots Remotely from Linux with rpcclient

The samba-client package contains an FSRVP client that can remotely request a Win-
dows/Samba server to create and expose a snapshot of a given share. You can then use existing
tools in SUSE Linux Enterprise Server to mount the exposed share and back up its les. Requests
to the server are sent using the rpcclient binary.
EXAMPLE 28.4: USING rpcclient TO REQUEST A WINDOWS SERVER 2012 SHARE SNAPSHOT
Connect to win-server.example.com server as an administrator in an EXAMPLE domain:
# rpcclient -U 'EXAMPLE\Administrator' ncacn_np:win-server.example.com[ndr64,sign]

Enter EXAMPLE/Administrator's password:
Check that the SMB share is visible for rpcclient :
rpcclient $> netshareenum

netname: windows_server_2012_share
remark:
path: C:\Shares\windows_server_2012_share
password: (null)
Check that the SMB share supports snapshot creation:
rpcclient $> fss_is_path_sup windows_server_2012_share \

UNC \\WIN-SERVER\windows_server_2012_share\ supports shadow copy requests
Request the creation of a share snapshot:
rpcclient $> fss_create_expose backup ro windows_server_2012_share

13fe880e-e232-493d-87e9-402f21019fb6: shadow-copy set created
13fe880e-e232-493d-87e9-402f21019fb6(1c26544e-8251-445f-be89-d1e0a3938777): \

\\WIN-SERVER\windows_server_2012_share\ shadow-copy added to set
13fe880e-e232-493d-87e9-402f21019fb6: prepare completed in 0 secs
13fe880e-e232-493d-87e9-402f21019fb6: commit completed in 1 secs
share windows_server_2012_share@{1C26544E-8251-445F-BE89-D1E0A3938777} \
exposed as a snapshot of \\WIN-SERVER\windows_server_2012_share\
Confirm that the snapshot share is exposed by the server:

remark:
password: (null)
netname: windows_server_2012_share@{1C26544E-8251-445F-BE89-D1E0A3938777}
remark: (null)
path: \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy{F6E6507E-F537-11E3-9404-
B8AC6F927453}\Shares\windows_server_2012_share\
password: (null)
Attempt to delete the snapshot share:
rpcclient $> fss_delete windows_server_2012_share \

13fe880e-e232-493d-87e9-402f21019fb6 1c26544e-8251-445f-be89-d1e0a3938777
\\WIN-SERVER\windows_server_2012_share\ shadow-copy deleted
Confirm that the snapshot share has been removed by the server:

remark:
password: (null)
28.8.2.4 Managing Snapshots Remotely from Windows with

DiskShadow.exe
You can manage snapshots of SMB shares on the Linux Samba server from the Windows envi-
ronment acting as a client as well. Windows Server 2012 includes the DiskShadow.exe utility
that can manage remote shares similar to the rpcclient described in Section 28.8.2.3, “Managing
Snapshots Remotely from Linux with rpcclient”. Note that you need to carefully set up the Samba
server rst.

Following is an example procedure to set up the Samba server so that the Windows Server client
can manage its share's snapshots. Note that EXAMPLE is the Active Directory domain used in the
testing environment, fsrvp-server.example.com is the host name of the Samba server, and
/srv/smb is the path to the SMB share.
PROCEDURE 28.1: DETAILED SAMBA SERVER CONFIGURATION
1. Join Active Directory domain via YaST. For more information, Section 28.7, “Samba Server
in the Network with Active Directory”.
2. Ensure that the Active Domain DNS entry was correct:
fsrvp-server:~ # net -U 'Administrator' ads dns register \

fsrvp-server.example.com <IP address>
Successfully registered hostname with DNS
3. Create Btrfs subvolume at /srv/smb
fsrvp-server:~ # btrfs subvolume create /srv/smb
4. Create snapper configuration le for path /srv/smb
fsrvp-server:~ # snapper -c <snapper_config> create-config /srv/smb
5. Create new share with path /srv/smb , and YaST Expose Snapshots check box enabled.
Make sure to add the following snippets to the global section of /etc/samba/smb.conf
as mentioned in Section 28.8.2.2, “Remote Share Snapshots”:
[global]
rpc_daemon:fssd = fork
registry shares = yes
include = registry
6. Restart Samba with systemctl restart nmb smb
7. Configure snapper permissions:
fsrvp-server:~ # snapper -c <snapper_config> set-config \

ALLOW_USERS="EXAMPLE\\\\Administrator EXAMPLE\\\\win-client$"
Ensure that any ALLOW_USERS are also permitted traversal of the .snapshots subdirec-
tory.
fsrvp-server:~ # snapper -c <snapper_config> set-config SYNC_ACL=yes

Important: Path Escaping
Be careful about the '\' escapes! Escape twice to ensure that the value stored in /
etc/snapper/configs/<snapper_config> is escaped once.
"EXAMPLE\win-client$" corresponds to the Windows client computer account. Windows

issues initial FSRVP requests while authenticated with this account.
8. Grant Windows client account necessary privileges:
fsrvp-server:~ # net -U 'Administrator' rpc rights grant \

"EXAMPLE\\win-client$" SeBackupPrivilege
Successfully granted rights.
The previous command is not needed for the "EXAMPLE\Administrator" user, which has
privileges already granted.
PROCEDURE 28.2: WINDOWS CLIENT SETUP AND DiskShadow.exe IN ACTION
1. Boot Windows Server 2012 (example host name WIN-CLIENT).
2. Join the same Active Directory domain EXAMPLE as with the SUSE Linux Enterprise Serv-
er.
3. Reboot.
4. Open Powershell.
5. Start DiskShadow.exe and begin the backup procedure:
PS C:\Users\Administrator.EXAMPLE> diskshadow.exe
Microsoft DiskShadow version 1.0
Copyright (C) 2012 Microsoft Corporation
On computer: WIN-CLIENT, 6/17/2014 3:53:54 PM
DISKSHADOW> begin backup
6. Specify that shadow copy persists across program exit, reset or reboot:
DISKSHADOW> set context PERSISTENT
7. Check whether the specified share supports snapshots, and create one:
DISKSHADOW> add volume \\fsrvp-server\sles_snapper

DISKSHADOW> create
Alias VSS_SHADOW_1 for shadow ID {de4ddca4-4978-4805-8776-cdf82d190a4a} set as \
environment variable.
Alias VSS_SHADOW_SET for shadow set ID {c58e1452-c554-400e-a266-d11d5c837cb1} \
set as environment variable.
Querying all shadow copies with the shadow copy set ID \

{c58e1452-c554-400e-a266-d11d5c837cb1}
* Shadow copy ID = {de4ddca4-4978-4805-8776-cdf82d190a4a} %VSS_SHADOW_1%

- Shadow copy set: {c58e1452-c554-400e-a266-d11d5c837cb1} %VSS_SHADOW_SET%
- Original count of shadow copies = 1
- Original volume name: \\FSRVP-SERVER\SLES_SNAPPER\ \
[volume not on this machine]
- Creation time: 6/17/2014 3:54:43 PM
- Shadow copy device name:
\\FSRVP-SERVER\SLES_SNAPPER@{31afd84a-44a7-41be-b9b0-751898756faa}
- Originating machine: FSRVP-SERVER
- Service machine: win-client.example.com
- Not exposed
- Provider ID: {89300202-3cec-4981-9171-19f59559e0f2}
- Attributes: No_Auto_Release Persistent FileShare
Number of shadow copies listed: 1
8. Finish the backup procedure:
DISKSHADOW> end backup
9. After the snapshot was created, try to delete it and verify the deletion:
DISKSHADOW> delete shadows volume \\FSRVP-SERVER\SLES_SNAPPER\

Deleting shadow copy {de4ddca4-4978-4805-8776-cdf82d190a4a} on volume \
\\FSRVP-SERVER\SLES_SNAPPER\ from provider \
{89300202-3cec-4981-9171-19f59559e0f2} [Attributes: 0x04000009]...
Number of shadow copies deleted: 1
DISKSHADOW> list shadows all
Querying all shadow copies on the computer ...

No shadow copies found in system.

Documentation for Samba ships with the samba-doc package which is not installed by de-
fault. Install it with zypper install samba-doc . Enter apropos samba at the command
line to display some manual pages or browse the /usr/share/doc/packages/samba directory
for more online documentation and examples. Find a commented example configuration ( sm-
b.conf.SUSE ) in the examples subdirectory. Another le to look for Samba related informa-
tion is /usr/share/doc/packages/samba/README.SUSE .
The Samba HOWTO (see https://wiki.samba.org ) provided by the Samba team includes a sec-
tion about troubleshooting. In addition to that, Part V of the document provides a step-by-step
guide to checking your configuration.

29 On-Demand Mounting with Autofs
autofs is a program that automatically mounts specified directories on an on-de-

mand basis. It is based on a kernel module for high efficiency, and can manage both
local directories and network shares. These automatic mount points are mounted
only when they are accessed, and unmounted after a certain period of inactivity.
This on-demand behavior saves bandwidth and results in better performance than
static mounts managed by /etc/fstab . While autofs is a control script, auto-
mount is the command (daemon) that does the actual auto-mounting.
29.1 Installation
autofs is not installed on SUSE Linux Enterprise Server by default. To use its auto-mounting
capabilities, rst install it with
sudo zypper install autofs
29.2 Configuration
You need to configure autofs manually by editing its configuration les with a text editor,
such as vim . There are two basic steps to configure autofs —the master map le, and specific
map les.
29.2.1 The Master Map File

The default master configuration le for autofs is /etc/auto.master . You can change its
location by changing the value of the DEFAULT_MASTER_MAP_NAME option in /etc/syscon-
fig/autofs . Here is the content of the default one for SUSE Linux Enterprise Server:
#
# Sample auto.master file
# This is an automounter map and it has the following format
# key [ -mount-options-separated-by-comma ] location

# For details of the format look at autofs(5). 1
#
#/misc /etc/auto.misc 2
#/net -hosts
#
# Include /etc/auto.master.d/*.autofs 3
#
#+dir:/etc/auto.master.d
#
# Include central master map if it can be found using
# nsswitch sources.
#
# Note that if there are entries for /net or /misc (as
# above) in the included master map any keys that are the
# same will not be seen as the first read key seen takes
# precedence.
#
+auto.master 4
1 The autofs manual page ( man 5 autofs ) offers a lot of valuable information on the
format of the automounter maps.
2 Although commented out (#) by default, this is an example of a simple automounter map-
ping syntax.
3 In case you need to split the master map into several les, uncomment the line, and put
the mappings (suffixed with .autofs ) in the /etc/auto.master.d/ directory.
4 +auto.master ensures that those using NIS (see Book “Security Guide”, Chapter 3 “Using NIS”,
Section 3.1 “Configuring NIS Servers” for more information on NIS) will still nd their master
map.
Entries in auto.master have three elds with the following syntax:
mount point map name options
mount point
The base location where to mount the autofs le system, such as /home .
map name
The name of a map source to use for mounting. For the syntax of the maps les, see
Section 29.2.2, “Map Files”.
options
These options (if specified) will apply as defaults to all entries in the given map.
409 The Master Map File SLES 12 SP3

For more detailed information on the specific values of the optional map-type , format ,
and options , see the auto.master manual page ( man 5 auto.master ).
The following entry in auto.master tells autofs to look in /etc/auto.smb , and create mount
points in the /smb directory.
/smb /etc/auto.smb
29.2.1.1 Direct Mounts
Direct mounts create a mount point at the path specified inside the relevant map le. Instead of
specifying the mount point in auto.master , replace the mount point eld with /- . For exam-
ple, the following line tells autofs to create a mount point at the place specified in auto.smb :
/- /etc/auto.smb
Tip: Maps without Full Path

If the map le is not specified with its full local or network path, it is located using the
Name Service Switch (NSS) configuration:
/- auto.smb
29.2.2 Map Files
Important: Other Types of Maps

Although les are the most common types of maps for auto-mounting with autofs , there
are other types as well. A map specification can be the output of a command, or a result
of a query in LDAP or database. For more detailed information on map types, see the
manual page man 5 auto.master .
410 Map Files SLES 12 SP3

Map les specify the (local or network) source location, and the mount point where to mount the
source locally. The general format of maps is similar to the master map. The difference is that
the options appear between the mount point and the location instead of at the end of the entry:
mount point options location
mount point
Specifies where to mount the source location. This can be either a single directory name
(so-called indirect mount) to be added to the base mount point specified in auto.master ,
or the full path of the mount point (direct mount, see Section 29.2.1.1, “Direct Mounts”).
options
Specifies optional comma-separated list of mount options for the relevant entries. If au-
to.master contains options for this map le as well, theses are appended.
location
Specifies from where the le system is to be mounted. It is usually an NFS or SMB volume
in the usual notation host_name:path_name . If the le system to be mounted begins with
a '/' (such as local /dev entries or smbfs shares), a colon symbol ':' needs to be prefixed,
such as :/dev/sda1 .
29.3 Operation and Debugging

This section introduces information on how to control the autofs service operation, and how
to view more debugging information when tuning the automounter operation.
29.3.1 Controlling the autofs Service

The operation of the autofs service is controlled by systemd . The general syntax of the sys-
temctl command for autofs is
sudo systemctl SUB_COMMAND autofs
where SUB_COMMAND is one of:
enable
Starts the automounter daemon at boot.
411 Operation and Debugging SLES 12 SP3

start
Starts the automounter daemon.
stop
Stops the automounter daemon. Automatic mount points are not accessible.
status
Prints the current status of the autofs service together with a part of a relevant log le.
restart
Stops and starts the automounter, terminating all running daemons and starting new ones.
reload
Checks the current auto.master map, restarts those daemons whose entries have
changed, and starts new ones for new entries.
29.3.2 Debugging the Automounter Problems

If you experience problems when mounting directories with autofs , it is useful to run the
automount daemon manually and watch its output messages:
1. Stop autofs .
sudo systemctl stop autofs
2. From one terminal, run automount manually in the foreground, producing verbose out-
put.
sudo automount -f -v
3. From another terminal, try to mount the auto-mounting le systems by accessing the
mount points (for example by cd or ls ).
4. Check the output of automount from the rst terminal for more information why the
mount failed, or why it was not even attempted.
412 Debugging the Automounter Problems SLES 12 SP3

29.4 Auto-Mounting an NFS Share
The following procedure illustrates how to configure autofs to auto-mount an NFS share avail-
able on your network. It makes use of the information mentioned above, and assumes you are
familiar with NFS exports. For more information on NFS, see Chapter 27, Sharing File Systems with
NFS.
1. Edit the master map le /etc/auto.master :
sudo vim /etc/auto.master
Add a new entry for the new NFS mount at the end of /etc/auto.master :
/nfs /etc/auto.nfs --timeout=10
It tells autofs that the base mount point is /nfs , the NFS shares are specified in the
/etc/auto.nfs map, and that all shares in this map will be automatically unmounted
after 10 seconds of inactivity.
2. Create a new map le for NFS shares:
sudo vim /etc/auto.nfs
/etc/auto.nfs normally contains a separate line for each NFS share. Its format is de-
scribed in Section 29.2.2, “Map Files”. Add the line describing the mount point and the NFS
share network address:
export jupiter.com:/home/geeko/doc/export
The above line means that the /home/geeko/doc/export directory on the jupiter.com
host will be auto-mounted to the /nfs/export directory on the local host ( /nfs is taken
from the auto.master map) when requested. The /nfs/export directory will be created
automatically by autofs .
3. Optionally comment out the related line in /etc/fstab if you previously mounted the
same NFS share statically. The line should look similar to this:
#jupiter.com:/home/geeko/doc/export /nfs/export nfs defaults 0 0
4. Reload autofs and check if it works:
sudo systemctl restart autofs
413 Auto-Mounting an NFS Share SLES 12 SP3

# ls -l /nfs/export
total 20
drwxr-xr-x 6 1001 users 4096 Oct 25 08:56 ./
drwxr-xr-x 3 root root 0 Apr 1 09:47 ../
drwxr-xr-x 5 1001 users 4096 Jan 14 2013 .images/
drwxr-xr-x 10 1001 users 4096 Aug 16 2013 .profiled/
drwxr-xr-x 3 1001 users 4096 Aug 30 2013 .tmp/
drwxr-xr-x 4 1001 users 4096 Oct 25 08:56 SLE-12-manual/
If you can see the list of les on the remote share, then autofs is functioning.
29.5 Advanced Topics

This section describes topics that are beyond the basic introduction to autofs —auto-mounting
of NFS shares that are available on your network, using wild cards in map les, and information
specific to the CIFS le system.
29.5.1 /net Mount Point

This helper mount point is useful if you use a lot of NFS shares. /net auto-mounts all NFS
shares on your local network on demand. The entry is already present in the auto.master le,
so all you need to do is uncomment it and restart autofs :
/net -hosts
systemctl restart autofs
For example, if you have a server named jupiter with an NFS share called /export , you can
mount it by typing
# cd /net/jupiter/export
on the command line.
29.5.2 Using Wild Cards to Auto-Mount Subdirectories

If you have a directory with subdirectories that you need to auto-mount individually—the typical
case is the /home directory with individual users' home directories inside— autofs offers a
clever solution for that.
414 Advanced Topics SLES 12 SP3

In case of home directories, add the following line in auto.master :
/home /etc/auto.home
Now you need to add the correct mapping to the /etc/auto.home le, so that the users' home
directories are mounted automatically. One solution is to create separate entries for each direc-
tory:
wilber jupiter.com:/home/wilber
penguin jupiter.com:/home/penguin
tux jupiter.com:/home/tux
[...]
This is very awkward as you need to manage the list of users inside auto.home . You can use
the asterisk '*' instead of the mount point, and the ampersand '&' instead of the directory to
be mounted:
* jupiter:/home/&
29.5.3 Auto-Mounting CIFS File System

If you want to auto-mount an SMB/CIFS share (see Chapter 28, Samba for more information on
the SMB/CIFS protocol), you need to modify the syntax of the map le. Add -fstype=cifs in
the option eld, and prefix the share location with a colon ':'.
mount point -fstype=cifs ://jupiter.com/export
415 Auto-Mounting CIFS File System SLES 12 SP3

30 SLP
Configuring a network client requires detailed knowledge about services provided

over the network (such as printing or LDAP, for example). To make it easier to con-
figure such services on a network client, the “service location protocol” (SLP) was
developed. SLP makes the availability and configuration data of selected services
known to all clients in the local network. Applications that support SLP can use this
information to be configured automatically.
SUSE® Linux Enterprise Server supports installation using installation sources provided with
SLP and contains many system services with integrated support for SLP. You can use SLP to
provide networked clients with central functions, such as an installation server, le server, or
print server on your system. Services that offer SLP support include cupsd, login, ntp, openldap2,
postfix, rpasswd, rsyncd, saned, sshd (via sh), vnc, and ypserv.
All packages necessary to use SLP services on a network client are installed by default. However,
if you want to provide services via SLP, check that the openslp-server package is installed.
30.1 The SLP Front-End slptool

slptool is a command line tool to query and register SLP services. The query functions are
useful for diagnostic purposes. The most important slptool subcommands are listed below.
slptool --help lists all available options and functions.
findsrvtypes
List all service types available on the network.
tux > slptool findsrvtypes

service:install.suse:nfs
service:install.suse:ftp
service:install.suse:http
service:install.suse:smb
service:ssh
service:fish
service:YaST.installation.suse:vnc
service:smtp
service:domain
service:management-software.IBM:hardware-management-console
service:rsync
416 The SLP Front-End slptool SLES 12 SP3

service:ntp
service:ypserv
findsrvs SERVICE_TYPE
List all servers providing SERVICE_TYPE
tux > slptool findsrvs service:ntp

service:ntp://ntp.example.com:123,57810
service:ntp://ntp2.example.com:123,57810
findattrs SERVICE_TYPE // HOST

List attributes for SERVICE_TYPE on HOST
tux > slptool findattrs service:ntp://ntp.example.com

(owner=tux),(email=tux@example.com)
register SERVICE type // HOST : PORT "( ATTRIBUTE=VALUE ),( ATTRIBUTE=VALUE )"
Registers SERVICE_TYPE on HOST with an optional list of attributes
slptool register service:ntp://ntp.example.com:57810 \

"(owner=tux),(email=tux@example.com)"
deregister SERVICE_TYPE // host

De-registers SERVICE_TYPE on HOST
slptool deregister service:ntp://ntp.example.com
For more information run slptool --help .
30.2 Providing Services via SLP

To provide SLP services, the SLP daemon ( slpd ) must be running. Like most system services in
SUSE Linux Enterprise Server, slpd is controlled by means of a separate start script. After the
installation, the daemon is inactive by default. To activate it for the current session, run sudo
systemctl start slpd . If slpd should be activated on system start-up, run sudo systemctl
enable slpd .
417 Providing Services via SLP SLES 12 SP3

Many applications in SUSE Linux Enterprise Server have integrated SLP support via the libslp
library. If a service has not been compiled with SLP support, use one of the following methods
to make it available via SLP:
Static Registration with /etc/slp.reg.d

Create a separate registration le for each new service. The following example registers
a scanner service:
## Register a saned service on this system

## en means english language
## 65535 disables the timeout, so the service registration does
## not need refreshes
service:scanner.sane://$HOSTNAME:6566,en,65535
watch-port-tcp=6566
description=SANE scanner daemon
The most important line in this le is the service URL, which begins with service: . This
contains the service type ( scanner.sane ) and the address under which the service is
available on the server. $HOSTNAME is automatically replaced with the full host name. The
name of the TCP port on which the relevant service can be found follows, separated by
a colon. Then enter the language in which the service should appear and the duration of
registration in seconds. These should be separated from the service URL by commas. Set
the value for the duration of registration between 0 and 65535 . 0 prevents registration.
65535 removes all restrictions.
The registration le also contains the two variables watch-port-tcp and description .
watch-port-tcp links the SLP service announcement to whether the relevant service is
active by having slpd check the status of the service. The second variable contains a more
precise description of the service that is displayed in suitable browsers.
Tip: YaST and SLP

Some services brokered by YaST, such as an installation server or YOU server, per-
form this registration automatically when you activate SLP in the module dialogs.
YaST then creates registration les for these services.
Static Registration with /etc/slp.reg

The only difference between this method and the procedure with /etc/slp.reg.d is that
all services are grouped within a central le.
418 Providing Services via SLP SLES 12 SP3

Dynamic Registration with slptool
If a service needs to be registered dynamically without the need of configuration les, use
the slptool command line utility. The same utility can also be used to de-register an existing
service offering without restarting slpd . See Section 30.1, “The SLP Front-End slptool” for
details.
30.2.1 Setting up an SLP Installation Server

Announcing the installation data via SLP within your network makes the network installation
much easier, since the installation data such as IP address of the server or the path to the
installation media are automatically required via SLP query. Refer to Book “Deployment Guide”,
Chapter 8 “Setting Up the Server Holding the Installation Sources” for instructions.

RFC 2608, 2609, 2610
RFC 2608 generally deals with the definition of SLP. RFC 2609 deals with the syntax of
the service URLs used in greater detail and RFC 2610 deals with DHCP via SLP.
http://www.openslp.org
The home page of the OpenSLP project.
/usr/share/doc/packages/openslp
This directory contains the documentation for SLP coming with the openslp-server
package, including a README.SUSE containing the SUSE Linux Enterprise Server details,
the RFCs, and two introductory HTML documents. Programmers who want to use the
SLP functions will nd more information in the Programmers Guide that is included in the
openslp-devel package that is provided with the SUSE Software Development Kit.
419 Setting up an SLP Installation Server SLES 12 SP3

31 The Apache HTTP Server
According to the survey from http://www.netcraft.com/ , the Apache HTTP Serv-

er (Apache) is the world's most widely-used Web server. Developed by the Apache
Software Foundation (http://www.apache.org/ ), it is available for most operating
systems. SUSE® Linux Enterprise Server includes Apache version 2.4. In this chap-
ter, learn how to install, configure and set up a Web server; how to use SSL, CGI,
and additional modules; and how to troubleshoot Apache.
31.1 Quick Start

With this section, quickly set up and start Apache. You must be root to install and configure
Apache.
31.1.1 Requirements
Make sure the following requirements are met before trying to set up the Apache Web server:
1. The machine's network is configured properly. For more information about this topic, refer
to Chapter 16, Basic Networking.
2. The machine's exact system time is maintained by synchronizing with a time server. This is
necessary because parts of the HTTP protocol depend on the correct time. See Chapter 24,
Time Synchronization with NTP to learn more about this topic.
3. The latest security updates are installed. If in doubt, run a YaST Online Update.
4. The default Web server port ( 80 ) is opened in the firewall. For this, configure the SuSE-
Firewall2 to allow the service HTTP Server in the external zone. This can be done using
YaST. See Book “Security Guide”, Chapter 15 “Masquerading and Firewalls”, Section 15.4.1 “Con-
figuring the Firewall with YaST” for details.
420 Quick Start SLES 12 SP3

31.1.2 Installation
Apache on SUSE Linux Enterprise Server is not installed by default. To install it with a standard,
predefined configuration that runs “out of the box”, proceed as follows:
PROCEDURE 31.1: INSTALLING APACHE WITH THE DEFAULT CONFIGURATION
1. Start YaST and select Software Software Management.
2. Choose View Patterns and select Web and LAMP Server.
3. Confirm the installation of the dependent packages to finish the installation process.
31.1.3 Start
You can start Apache automatically at boot time or start it manually.
To make sure that Apache is automatically started during boot in the targets multi-user.tar-
get and graphical.target , execute the following command:
root # systemctl enable apache2
For more information about the systemd targets in SUSE Linux Enterprise Server and a descrip-
tion of the YaST Services Manager, refer to Section 13.4, “Managing Services with YaST”.
To manually start Apache using the shell, run systemctl start apache2 .
PROCEDURE 31.2: CHECKING IF APACHE IS RUNNING
If you do not receive error messages when starting Apache, this usually indicates that the
Web server is running. To test this:
1. Start a browser and open http://localhost/ .

If Apache is up and running, you get a test page stating “It works!”.
2. If you do not see this page, refer to Section 31.9, “Troubleshooting”.
Now that the Web server is running, you can add your own documents, adjust the configuration
according to your needs, or add functionality by installing modules.

31.2 Configuring Apache
SUSE Linux Enterprise Server offers two configuration options:
Configuring Apache Manually
Configuring Apache with YaST
Manual configuration offers a higher level of detail, but lacks the convenience of the YaST GUI.
Important: Reload or Restart Apache after Configuration Changes

Most configuration changes require a reload (some also a restart) of Apache to take effect.
Manually reload Apache with systemctl reload apache2 or use one of the restart
options as described in Section 31.3, “Starting and Stopping Apache”.
If you configure Apache with YaST, this can be taken care of automatically if you set
HTTP Service to Enabled as described in Section 31.2.3.2, “HTTP Server Configuration”.
31.2.1 Apache Configuration Files
This section gives an overview of the Apache configuration les. If you use YaST for configura-
tion, you do not need to touch these les—however, the information might be useful for you if
you want to switch to manual configuration later on.
Apache configuration les can be found in two different locations:
/etc/sysconfig/apache2
/etc/apache2/
31.2.1.1 /etc/sysconfig/apache2
/etc/sysconfig/apache2 controls some global settings of Apache, like modules to load, ad-
ditional configuration les to include, ags with which the server should be started, and ags
that should be added to the command line. Every configuration option in this le is extensively
documented and therefore not mentioned here. For a general-purpose Web server, the settings
in /etc/sysconfig/apache2 should be sufficient for any configuration needs.
422 Configuring Apache SLES 12 SP3

31.2.1.2 /etc/apache2/
/etc/apache2/ hosts all configuration les for Apache. In the following, the purpose of each
le is explained. Each le includes several configuration options (also called directives). Every
configuration option in these les is extensively documented and therefore not mentioned here.
The Apache configuration les are organized as follows:
/etc/apache2/
|
|- charset.conv
|- conf.d/
| |
| |- *.conf
|
|- default-server.conf
|- errors.conf
|- httpd.conf
|- listen.conf
|- magic
|- mime.types
|- mod_*.conf
|- server-tuning.conf
|- ssl.*
|- ssl-global.conf
|- sysconfig.d
| |
| |- global.conf
| |- include.conf
| |- loadmodule.conf . .
|
|- uid.conf
|- vhosts.d
| |- *.conf
APACHE CONFIGURATION FILES IN /ETC/APACHE2/
charset.conv
Specifies which character sets to use for different languages. Do not edit this le.
conf.d/*.conf
Configuration les added by other modules. These configuration les can be included into
your virtual host configuration where needed. See vhosts.d/vhost.template for exam-
ples. By doing so, you can provide different module sets for different virtual hosts.
423 Apache Configuration Files SLES 12 SP3

default-server.conf
Global configuration for all virtual hosts with reasonable defaults. Instead of changing the
values, overwrite them with a virtual host configuration.
errors.conf
Defines how Apache responds to errors. To customize these messages for all virtual hosts,
edit this le. Otherwise overwrite these directives in your virtual host configurations.
httpd.conf
The main Apache server configuration le. Avoid changing this le. It primarily contains
include statements and global settings. Overwrite global settings in the pertinent configu-
ration les listed here. Change host-specific settings (such as document root) in your vir-
tual host configuration.
listen.conf
Binds Apache to specific IP addresses and ports. Name-based virtual hosting is also con-
figured here. For details, see Section 31.2.2.1.1, “Name-Based Virtual Hosts”.
magic
Data for the mime_magic module that helps Apache automatically determine the MIME
type of an unknown le. Do not change this le.
mime.types
MIME types known by the system (this actually is a link to /etc/mime.types ). Do not
edit this le. If you need to add MIME types not listed here, add them to mod_mime-
defaults.conf .
mod_*.conf
Configuration les for the modules that are installed by default. Refer to Section 31.4, “In-
stalling, Activating, and Configuring Modules” for details. Note that configuration les for op-
tional modules reside in the directory conf.d .
server-tuning.conf
Contains configuration directives for the different MPMs (see Section 31.4.4, “Multiprocessing
Modules”) and general configuration options that control Apache's performance. Properly
test your Web server when making changes here.
ssl-global.conf and ssl.*

Global SSL configuration and SSL certificate data. Refer to Section 31.6, “Setting Up a Secure
Web Server with SSL” for details.
424 Apache Configuration Files SLES 12 SP3

sysconfig.d/*.conf
Configuration les automatically generated from /etc/sysconfig/apache2 . Do not
change any of these les—edit /etc/sysconfig/apache2 instead. Do not put other con-
figuration les in this directory.
uid.conf
Specifies under which user and group ID Apache runs. Do not change this le.
vhosts.d/*.conf
Your virtual host configuration should be located here. The directory contains template
les for virtual hosts with and without SSL. Every le in this directory ending with .conf
is automatically included in the Apache configuration. Refer to Section 31.2.2.1, “Virtual Host
Configuration” for details.
31.2.2 Configuring Apache Manually

Configuring Apache manually involves editing plain text configuration les as user root .
31.2.2.1 Virtual Host Configuration
The term virtual host refers to Apache's ability to serve multiple universal resource identifiers
(URIs) from the same physical machine. This means that several domains, such as www.exam-
ple.com and www.example.net, are run by a single Web server on one physical machine.
It is common practice to use virtual hosts to save administrative effort (only a single Web server
needs to be maintained) and hardware expenses (each domain does not require a dedicated
server). Virtual hosts can be name based, IP based, or port based.
To list all existing virtual hosts, use the command apache2ctl -S . This outputs a list showing
the default server and all virtual hosts together with their IP addresses and listening ports.
Furthermore, the list also contains an entry for each virtual host showing its location in the
configuration les.
Virtual hosts can be configured via YaST as described in Section 31.2.3.1.4, “Virtual Hosts” or by
manually editing a configuration le. By default, Apache in SUSE Linux Enterprise Server is
prepared for one configuration le per virtual host in /etc/apache2/vhosts.d/ . All les in
this directory with the extension .conf are automatically included to the configuration. A
basic template for a virtual host is provided in this directory ( vhost.template or vhost-
ssl.template for a virtual host with SSL support).
425 Configuring Apache Manually SLES 12 SP3

Tip: Always Create a Virtual Host Configuration
It is recommended to always create a virtual host configuration le, even if your Web
server only hosts one domain. By doing so, you not only have the domain-specific con-
figuration in one le, but you can always fall back to a working basic configuration by
simply moving, deleting, or renaming the configuration le for the virtual host. For the
same reason, you should also create separate configuration les for each virtual host.
When using name-based virtual hosts it is recommended to set up a default configuration
that will be used when a domain name does not match a virtual host configuration. The
default virtual host is the one whose configuration is loaded rst. Since the order of the
configuration les is determined by le name, start the le name of the default virtual
host configuration with an underscore character ( _ ) to make sure it is loaded rst (for
example: _default_vhost.conf ).
The <VirtualHost> </VirtualHost> block holds the information that applies to a particu-
lar domain. When Apache receives a client request for a defined virtual host, it uses the di-
rectives enclosed in this section. Almost all directives can be used in a virtual host context.
See http://httpd.apache.org/docs/2.4/mod/quickreference.html for further information about
Apache's configuration directives.
31.2.2.1.1 Name-Based Virtual Hosts
With name-based virtual hosts, more than one Web site is served per IP address. Apache uses
the host eld in the HTTP header that is sent by the client to connect the request to a matching
ServerName entry of one of the virtual host declarations. If no matching ServerName is found,
the rst specified virtual host is used as a default.
The rst step is to create a <VirtualHost> block for each different name-based host that you
want to serve. Inside each <VirtualHost> block, you will need at minimum a ServerName
directive to designate which host is served and a DocumentRoot directive to show where in the
le system the content for that host resides.
EXAMPLE 31.1: BASIC EXAMPLES OF NAME-BASED VirtualHost ENTRIES
<VirtualHost *:80>
# This first-listed virtual host is also the default for *:80
ServerName www.example.com
ServerAlias example.com
DocumentRoot /srv/www/htdocs/domain

</VirtualHost>
<VirtualHost *:80>
ServerName other.example.com
DocumentRoot /srv/www/htdocs/otherdomain
</VirtualHost>
The opening VirtualHost tag takes the IP address (or fully qualified domain name) as an
argument in a name-based virtual host configuration. A port number directive is optional.
The wild card * is also allowed as a substitute for the IP address. When using IPv6 addresses,
the address must be included in square brackets.
EXAMPLE 31.2: NAME-BASED VirtualHost DIRECTIVES
<VirtualHost 192.168.3.100:80>
...
</VirtualHost>
<VirtualHost 192.168.3.100>
...
</VirtualHost>
<VirtualHost *:80>
...
</VirtualHost>
<VirtualHost *>
...
</VirtualHost>
<VirtualHost [2002:c0a8:364::]>
...
</VirtualHost>
31.2.2.1.2 IP-Based Virtual Hosts
This alternative virtual host configuration requires the setup of multiple IPs for a machine. One
instance of Apache hosts several domains, each of which is assigned a different IP.
The physical server must have one IP address for each IP-based virtual host. If the machine does
not have multiple network cards, virtual network interfaces (IP aliasing) can also be used.
The following example shows Apache running on a machine with the IP 192.168.3.100 , host-
ing two domains on the additional IPs 192.168.3.101 and 192.168.3.102 . A separate Vir-
tualHost block is needed for every virtual server.

EXAMPLE 31.3: IP-BASED VirtualHost DIRECTIVES
...
</VirtualHost>
...
</VirtualHost>
Here, VirtualHost directives are only specified for interfaces other than 192.168.3.100 .
When a Listen directive is also configured for 192.168.3.100 , a separate IP-based virtual
host must be created to answer HTTP requests to that interface—otherwise the directives found
in the default server configuration ( /etc/apache2/default-server.conf ) are applied.
31.2.2.1.3 Basic Virtual Host Configuration
At least the following directives should be in each virtual host configuration to set up a virtual
host. See /etc/apache2/vhosts.d/vhost.template for more options.
ServerName
The fully qualified domain name under which the host should be addressed.
DocumentRoot
Path to the directory from which Apache should serve les for this host. For security rea-
sons, access to the entire le system is forbidden by default, so you must explicitly unlock
this directory within a Directory container.
ServerAdmin
E-mail address of the server administrator. This address is, for example, shown on error
pages Apache creates.
ErrorLog
The error log le for this virtual host. Although it is not necessary to create separate error
log les for each virtual host, it is common practice to do so, because it makes the debug-
ging of errors much easier. /var/log/apache2/ is the default directory for Apache's log
les.

CustomLog
The access log le for this virtual host. Although it is not necessary to create separate
access log les for each virtual host, it is common practice to do so, because it allows
the separate analysis of access statistics for each host. /var/log/apache2/ is the default
directory for Apache's log les.
As mentioned above, access to the whole le system is forbidden by default for security reasons.
Therefore, explicitly unlock the directories in which you have placed the les Apache should
serve—for example the DocumentRoot :
<Directory "/srv/www/www.example.com/htdocs">
Require all granted
</Directory>
Note: Require all granted

In previous versions of Apache, the statement Require all granted was expressed as:
Order allow,deny
Allow from all
This old syntax is still supported by the mod_access_compat module.
The complete configuration le looks like this:
EXAMPLE 31.4: BASIC VirtualHost CONFIGURATION
ServerName www.example.com
DocumentRoot /srv/www/www.example.com/htdocs
ServerAdmin webmaster@example.com
ErrorLog /var/log/apache2/www.example.com_log
CustomLog /var/log/apache2/www.example.com-access_log common
<Directory "/srv/www/www.example.com/htdocs">
Require all granted
</Directory>

</VirtualHost>
31.2.3 Configuring Apache with YaST
To configure your Web server with YaST, start YaST and select Network Services HTTP Server.
When starting the module for the rst time, the HTTP Server Wizard starts, prompting you to
make a few basic decisions concerning administration of the server. After having finished the
wizard, the HTTP Server Configuration dialog starts each time you call the HTTP Server module.
For more information, see Section 31.2.3.2, “HTTP Server Configuration”.
31.2.3.1 HTTP Server Wizard

The HTTP Server Wizard consists of ve steps. In the last step of the dialog, you may enter the
expert configuration mode to make even more specific settings.
31.2.3.1.1 Network Device Selection
Here, specify the network interfaces and ports Apache uses to listen for incoming requests. You
can select any combination of existing network interfaces and their respective IP addresses. Ports
from all three ranges (well-known ports, registered ports, and dynamic or private ports) that
are not reserved by other services can be used. The default setting is to listen on all network
interfaces (IP addresses) on port 80 .
Check Open Port In Firewall to open the ports in the firewall that the Web server listens on. This
is necessary to make the Web server available on the network, which can be a LAN, WAN, or the
public Internet. Keeping the port closed is only useful in test situations where no external access
to the Web server is necessary. If you have multiple network interfaces, click Firewall Details to
specify on which interface(s) the port(s) should be opened.
Click Next to continue with the configuration.
31.2.3.1.2 Modules
The Modules configuration option allows for the activation or deactivation of the script languages
that the Web server should support. For the activation or deactivation of other modules, refer
to Section 31.2.3.2.2, “Server Modules”. Click Next to advance to the next dialog.
430 Configuring Apache with YaST SLES 12 SP3

31.2.3.1.3 Default Host
This option pertains to the default Web server. As explained in Section 31.2.2.1, “Virtual Host Con-
figuration”, Apache can serve multiple virtual hosts from a single physical machine. The rst
declared virtual host in the configuration le is commonly called the default host. Each virtual
host inherits the default host's configuration.
To edit the host settings (also called directives), select the appropriate entry in the table then
click Edit. To add new directives, click Add. To delete a directive, select it and click Delete.
FIGURE 31.1: HTTP SERVER WIZARD: DEFAULT HOST
Here is list of the default settings of the server:
Document Root
Path to the directory from which Apache serves les for this host. /srv/www/htdocs is
the default location.
Alias
Using Alias directives, URLs can be mapped to physical le system locations. This means
that a certain path even outside the Document Root in the le system can be accessed
via a URL aliasing that path.
The default SUSE Linux Enterprise Server Alias /icons points to /usr/share/apache2/
icons for the Apache icons displayed in the directory index view.

ScriptAlias
Similar to the Alias directive, the ScriptAlias directive maps a URL to a le system
location. The difference is that ScriptAlias designates the target directory as a CGI
location, meaning that CGI scripts should be executed in that location.
Directory
With Directory settings, you can enclose a group of configuration options that will only
apply to the specified directory.
Access and display options for the directories /srv/www/htdocs , /usr/share/apache2/
icons and /srv/www/cgi-bin are configured here. It should not be necessary to change
the defaults.
Include
With include, additional configuration les can be specified. Two Include directives are
already preconfigured: /etc/apache2/conf.d/ is the directory containing the configura-
tion les that come with external modules. With this directive, all les in this directory end-
ing in .conf are included. With the second directive, /etc/apache2/conf.d/apache2-
manual.conf , the apache2-manual configuration le is included.
Server Name
This specifies the default URL used by clients to contact the Web server. Use a fully qualified
domain name (FQDN) to reach the Web server at http://FQDN/ or its IP address. You
cannot choose an arbitrary name here—the server must be “known” under this name.
Server Administrator E-Mail

E-mail address of the server administrator. This address is, for example, shown on error
pages Apache creates.
After finishing with the Default Host step, click Next to continue with the configuration.
31.2.3.1.4 Virtual Hosts
In this step, the wizard displays a list of already configured virtual hosts (see Section 31.2.2.1,
“Virtual Host Configuration”). If you have not made manual changes prior to starting the YaST
HTTP wizard, no virtual host is present.
To add a host, click Add to open a dialog in which to enter basic information about the host,
such as Server Name, Server Contents Root ( DocumentRoot ), and the Administrator E-Mail. Server
Resolution is used to determine how a host is identified (name based or IP based). Specify the
name or IP address with Change Virtual Host ID

Clicking Next advances to the second part of the virtual host configuration dialog.
In part two of the virtual host configuration you can specify whether to enable CGI scripts and
which directory to use for these scripts. It is also possible to enable SSL. If you do so, you
must specify the path to the certificate as well. See Section 31.6.2, “Configuring Apache with SSL”
for details on SSL and certificates. With the Directory Index option, you can specify which le
to display when the client requests a directory (by default, index.html ). Add one or more le
names (space-separated) to change this. With Enable Public HTML, the content of the users public
directories ( ~USER/public_html/ ) is made available on the server under http://www.exam-
ple.com/~USER .
Important: Creating Virtual Hosts

It is not possible to add virtual hosts at will. If using name-based virtual hosts, each host
name must be resolved on the network. If using IP-based virtual hosts, you can assign
only one host to each IP address available.
31.2.3.1.5 Summary
This is the final step of the wizard. Here, determine how and when the Apache server is started:
when booting or manually. Also see a short summary of the configuration made so far. If you
are satisfied with your settings, click Finish to complete configuration. To change something,
click Back until you have reached the desired dialog. Clicking HTTP Server Expert Configuration
opens the dialog described in Section 31.2.3.2, “HTTP Server Configuration”.

FIGURE 31.2: HTTP SERVER WIZARD: SUMMARY
31.2.3.2 HTTP Server Configuration
The HTTP Server Configuration dialog also lets you make even more adjustments to the config-
uration than the wizard (which only runs if you configure your Web server for the rst time).
It consists of four tabs described in the following. No configuration option you change here is
effective immediately—you always must confirm your changes with Finish to make them effec-
tive. Clicking Abort leaves the configuration module and discards your changes.
31.2.3.2.1 Listen Ports and Addresses
In HTTP Service, select whether Apache should be running (Enabled) or stopped (Disabled). In
Listen on Ports, Add, Edit, or Delete addresses and ports on which the server should be available.
The default is to listen on all interfaces on port 80 . You should always check Open Port In
Firewall, because otherwise the Web server is not reachable from outside. Keeping the port
closed is only useful in test situations where no external access to the Web server is necessary.
If you have multiple network interfaces, click Firewall Details to specify on which interface(s)
the port(s) should be opened.

With Log Files, watch either the access log le or the error log le. This is useful if you want
to test your configuration. The log le opens in a separate window from which you can also
restart or reload the Web server. For details, see Section 31.3, “Starting and Stopping Apache”. These
commands are effective immediately and their log messages are also displayed immediately.
FIGURE 31.3: HTTP SERVER CONFIGURATION: LISTEN PORTS AND ADDRESSES
31.2.3.2.2 Server Modules
You can change the status (enabled or disabled) of Apache2 modules by clicking Toggle Status.
Click Add Module to add a new module that is already installed but not yet listed. Learn more
about modules in Section 31.4, “Installing, Activating, and Configuring Modules”.

FIGURE 31.4: HTTP SERVER CONFIGURATION: SERVER MODULES
31.2.3.2.3 Main Host or Hosts
These dialogs are identical to the ones already described. Refer to Section 31.2.3.1.3, “Default Host”
and Section 31.2.3.1.4, “Virtual Hosts”.
31.3 Starting and Stopping Apache

If configured with YaST as described in Section 31.2.3, “Configuring Apache with YaST”, Apache is
started at boot time in the multi-user.target and graphical.target . You can change this
behavior using YaST's Services Manager or with the systemctl command line tool ( systemctl
enable or systemctl disable ).
To start, stop, or manipulate Apache on a running system, use either the systemctl or the
apachectl commands as described below.
For general information about systemctl commands, refer to Section 13.2.1, “Managing Services
in a Running System”.
systemctl status apache2

Checks if Apache is started.
436 Starting and Stopping Apache SLES 12 SP3

systemctl start apache2
Starts Apache if it is not already running.
systemctl stop apache2

Stops Apache by terminating the parent process.
systemctl restart apache2

Stops and then restarts Apache. Starts the Web server if it was not running before.
systemctl try-restart apache2

Stops then restarts Apache only if it is already running.
systemctl reload apache2

Stops the Web server by advising all forked Apache processes to rst finish their requests
before shutting down. As each process dies, it is replaced by a newly started one, resulting
in a complete “restart” of Apache.
Tip: Restarting Apache in Production Environments

This command allows activating changes in the Apache configuration without caus-
ing connection break-os.
systemctl stop apache2

Stops the Web server after a defined period of time configured with GracefulShutdown-
Timeout to ensure that existing requests can be finished.
apachectl configtest
Checks the syntax of the configuration les without affecting a running Web server. Be-
cause this check is forced every time the server is started, reloaded, or restarted, it is usu-
ally not necessary to run the test explicitly (if a configuration error is found, the Web server
is not started, reloaded, or restarted).
apachectl status and apachectl fullstatus

Dumps a short or full status screen, respectively. Requires the module mod_status to be
enabled and a text-based browser (such as links or w3m ) installed. In addition to that,
status must be added to APACHE_SERVER_FLAGS in the le /etc/sysconfig/apache2 .
437 Starting and Stopping Apache SLES 12 SP3

Tip: Additional Flags
If you specify additional ags to the commands, these are passed through to the Web
server.
31.4 Installing, Activating, and Configuring Modules

The Apache software is built in a modular fashion: all functionality except some core tasks
are handled by modules. This has progressed so far that even HTTP is processed by a module
( http_core ).
Apache modules can be compiled into the Apache binary at build time or be dynamically loaded
at runtime. Refer to Section 31.4.2, “Activation and Deactivation” for details of how to load modules
dynamically.
Apache modules can be divided into four different categories:
Base Modules
Base modules are compiled into Apache by default. Apache in SUSE Linux Enterprise Server
has only mod_so (needed to load other modules) and http_core compiled in. All others
are available as shared objects: rather than being included in the server binary itself, they
can be included at runtime.
Extension Modules
In general, modules labeled as extensions are included in the Apache software package,
but are usually not compiled into the server statically. In SUSE Linux Enterprise Server,
they are available as shared objects that can be loaded into Apache at runtime.
External Modules
Modules labeled external are not included in the official Apache distribution. However,
SUSE Linux Enterprise Server provides several of them.
Multiprocessing Modules (MPMs)

MPMs are responsible for accepting and handling requests to the Web server, representing
the core of the Web server software.
438 Installing, Activating, and Configuring Modules SLES 12 SP3

31.4.1 Module Installation
If you have done a default installation as described in Section 31.1.2, “Installation”, the following
modules are already installed: all base and extension modules, the multiprocessing module Pre-
fork MPM, and the external module mod_python .
You can install additional external modules by starting YaST and choosing Software Software
Management. Now choose View Search and search for apache. Among other packages, the results
list contains all available external Apache modules.
31.4.2 Activation and Deactivation

Activate or deactivate particular modules either manually or with YaST. In YaST, script language
modules (PHP5, Perl, and Python) need to be enabled or disabled with the module configuration
described in Section 31.2.3.1, “HTTP Server Wizard”. All other modules can be enabled or disabled
as described in Section 31.2.3.2.2, “Server Modules”.
If you prefer to activate or deactivate the modules manually, use the commands a2enmod MOD-
ULE or a2dismod MODULE , respectively. a2enmod -l outputs a list of all currently active mod-
ules.
Important: Including Configuration Files for External Modules

If you have activated external modules manually, make sure to load their configuration
les in all virtual host configurations. Configuration les for external modules are lo-
cated under /etc/apache2/conf.d/ and are loaded in /etc/apache2/default-serv-
er.conf by default. For more ne-grained control you can comment out the inclusion
in /etc/apache2/default-server.conf and add it to specific virtual hosts only. See /
etc/apache2/vhosts.d/vhost.template for examples.
31.4.3 Base and Extension Modules
All base and extension modules are described in detail in the Apache documentation. Only
a brief description of the most important modules is available here. Refer to http://httpd.a-
pache.org/docs/2.4/mod/ to learn details about each module.
439 Module Installation SLES 12 SP3

mod_actions
Provides methods to execute a script whenever a certain MIME type (such as applica-
tion/pdf ), a le with a specific extension (like .rpm ), or a certain request method (such
as GET ) is requested. This module is enabled by default.
mod_alias
Provides Alias and Redirect directives with which you can map a URl to a specific
directory ( Alias ) or redirect a requested URL to another location. This module is enabled
by default.
mod_auth*
The authentication modules provide different authentication methods: basic authentica-
tion with mod_auth_basic or digest authentication with mod_auth_digest .
mod_auth_basic and mod_auth_digest must be combined with an authentication
provider module, mod_authn_* (for example, mod_authn_file for text le–based au-
thentication) and with an authorization module mod_authz_* (for example, mod_au-
thz_user for user authorization).
More information about this topic is available in the Authentication HOWTO at http://
httpd.apache.org/docs/2.4/howto/auth.html .
mod_autoindex
Autoindex generates directory listings when no index le (for example, index.html ) is
present. The look and feel of these indexes is configurable. This module is enabled by
default. However, directory listings are disabled by default via the Options directive—
overwrite this setting in your virtual host configuration. The default configuration le for
this module is located at /etc/apache2/mod_autoindex-defaults.conf .
mod_cgi
mod_cgi is needed to execute CGI scripts. This module is enabled by default.
mod_deflate
Using this module, Apache can be configured to compress given le types on the y before
delivering them.
mod_dir
mod_dir provides the DirectoryIndex directive with which you can configure which
les are automatically delivered when a directory is requested ( index.html by default).
It also provides an automatic redirect to the correct URL when a directory request does
not contain a trailing slash. This module is enabled by default.
440 Base and Extension Modules SLES 12 SP3

mod_env
Controls the environment that is passed to CGI scripts or SSI pages. Environment variables
can be set or unset or passed from the shell that invoked the httpd process. This module
is enabled by default.
mod_expires
With mod_expires , you can control how often proxy and browser caches refresh your
documents by sending an Expires header. This module is enabled by default.
mod_http2
With mod_http2 , Apache gains support for the HTTP/2 protocol. It can be enabled by
specifying Protocols h2 http/1.1 in a VirtualHost .
mod_include
mod_include lets you use Server Side Includes (SSI), which provide a basic functionality
to generate HTML pages dynamically. This module is enabled by default.
mod_info
Provides a comprehensive overview of the server configuration under http://local-
host/server-info/. For security reasons, you should always limit access to this URL. By
default only localhost is allowed to access this URL. mod_info is configured at /etc/
apache2/mod_info.conf .
mod_log_config
With this module, you can configure the look of the Apache log les. This module is enabled
by default.
mod_mime
The mime module ensures that a le is delivered with the correct MIME header based on
the le name's extension (for example text/html for HTML documents). This module is
enabled by default.
mod_negotiation
Necessary for content negotiation. See http://httpd.apache.org/docs/2.4/content-negotia-
tion.html for more information. This module is enabled by default.
mod_rewrite
Provides the functionality of mod_alias , but offers more features and flexibility. With
mod_rewrite , you can redirect URLs based on multiple rules, request headers, and more.
441 Base and Extension Modules SLES 12 SP3

mod_setenvif
Sets environment variables based on details of the client's request, such as the browser
string the client sends, or the client's IP address. This module is enabled by default.
mod_spelling
mod_spelling attempts to automatically correct typographical errors in URLs, such as
capitalization errors.
mod_ssl
Enables encrypted connections between Web server and clients. See Section 31.6, “Setting Up
a Secure Web Server with SSL” for details. This module is enabled by default.
mod_status
Provides information on server activity and performance under http://localhost/serv-
er-status/. For security reasons, you should always limit access to this URL. By default, only
localhost is allowed to access this URL. mod_status is configured at /etc/apache2/
mod_status.conf .
mod_suexec
mod_suexec lets you run CGI scripts under a different user and group. This module is
enabled by default.
mod_userdir
Enables user-specific directories available under ~USER/ . The UserDir directive must be
specified in the configuration. This module is enabled by default.
31.4.4 Multiprocessing Modules
SUSE Linux Enterprise Server provides two different multiprocessing modules (MPMs) for use
with Apache:
Prefork MPM
Worker MPM
442 Multiprocessing Modules SLES 12 SP3

31.4.4.1 Prefork MPM
The prefork MPM implements a non-threaded, preforking Web server. It makes the Web server
behave similarly to Apache version 1.x. In this version it isolates each request and handles it
by forking a separate child process. Thus problematic requests cannot affect others, avoiding
a lockup of the Web server.
While providing stability with this process-based approach, the prefork MPM consumes more
system resources than its counterpart, the worker MPM. The prefork MPM is considered the
default MPM for Unix-based operating systems.
Important: MPMs in This Document

This document assumes Apache is used with the prefork MPM.
31.4.4.2 Worker MPM
The worker MPM provides a multi-threaded Web server. A thread is a “lighter” form of a process.
The advantage of a thread over a process is its lower resource consumption. Instead of only
forking child processes, the worker MPM serves requests by using threads with server processes.
The preforked child processes are multi-threaded. This approach makes Apache perform better
by consuming fewer system resources than the prefork MPM.
One major disadvantage is the stability of the worker MPM: if a thread becomes corrupt, all
threads of a process can be affected. In the worst case, this may result in a server crash. Especially
when using the Common Gateway Interface (CGI) with Apache under heavy load, internal server
errors might occur because of threads being unable to communicate with system resources.
Another argument against using the worker MPM with Apache is that not all available Apache
modules are thread-safe and thus cannot be used with the worker MPM.
Warning: Using PHP Modules with MPMs

Not all available PHP modules are thread-safe. Using the worker MPM with mod_php is
strongly discouraged.
443 Multiprocessing Modules SLES 12 SP3

31.4.5 External Modules
Find a list of all external modules shipped with SUSE Linux Enterprise Server here. Find the
module's documentation in the listed directory.
mod_apparmor
Adds support to Apache to provide AppArmor confinement to individual CGI scripts han-
dled by modules like mod_php5 and mod_perl .
Package Name: apache2-mod_apparmor

More Information: Book “Security Guide”
mod_perl
mod_perl enables you to run Perl scripts in an embedded interpreter. The persistent in-
terpreter embedded in the server avoids the overhead of starting an external interpreter
and the penalty of Perl start-up time.
Package Name: apache2-mod_perl

Configuration File: /etc/apache2/conf.d/mod_perl.conf
More Information: /usr/share/doc/packages/apache2-mod_perl
mod_php5
PHP is a server-side, cross-platform HTML embedded scripting language.
Package Name: apache2-mod_php5

Configuration File: /etc/apache2/conf.d/php5.conf
More Information: /usr/share/doc/packages/apache2-mod_php5
mod_python
mod_python allows embedding Python within the Apache HTTP server for a considerable
boost in performance and added flexibility in designing Web-based applications.
Package Name: apache2-mod_python

More Information: /usr/share/doc/packages/apache2-mod_python
mod_security
mod_security provides a Web application firewall to protect Web applications from a
range of attacks. It also enables HTTP traffic monitoring and real-time analysis.
Package Name: apache2-mod_security2

Configuration File: /etc/apache2/conf.d/mod_security2.conf
More Information: /usr/share/doc/packages/apache2-mod_security2
444 External Modules SLES 12 SP3

Documentation: http://modsecurity.org/documentation/
31.4.6 Compilation
Apache can be extended by advanced users by writing custom modules. To develop modules
for Apache or compile third-party modules, the package apache2-devel is required along with
the corresponding development tools. apache2-devel also contains the apxs2 tools, which
are necessary for compiling additional modules for Apache.
apxs2 enables the compilation and installation of modules from source code (including the
required changes to the configuration les), which creates dynamic shared objects (DSOs) that
can be loaded into Apache at runtime.
The apxs2 binaries are located under /usr/sbin :
/usr/sbin/apxs2 —suitable for building an extension module that works with any MPM.
The installation location is /usr/lib64/apache2 .
/usr/sbin/apxs2-prefork —suitable for prefork MPM modules. The installation loca-

tion is /usr/lib64/apache2-prefork .
/usr/sbin/apxs2-worker —suitable for worker MPM modules. The installation location

is /usr/lib64/apache2-worker .
Install and activate a module from source code with the following commands:
cd /path/to/module/source
apxs2 -cia MODULE.c
where -c compiles the module, -i installs it, and -a activates it. Other options of apxs2 are
described in the apxs2(1) man page.
31.5 Enabling CGI Scripts

Apache's Common Gateway Interface (CGI) lets you create dynamic content with programs or
scripts usually called CGI scripts. CGI scripts can be written in any programming language.
Usually, script languages such as Perl or PHP are used.
To enable Apache to deliver content created by CGI scripts, mod_cgi needs to be activated.
mod_alias is also needed. Both modules are enabled by default. Refer to Section 31.4.2, “Activation
and Deactivation” for details on activating modules.
445 Compilation SLES 12 SP3

Warning: CGI Security
Allowing the server to execute CGI scripts is a potential security hole. Refer to Section 31.8,
“Avoiding Security Problems” for additional information.
31.5.1 Apache Configuration

In SUSE Linux Enterprise Server, the execution of CGI scripts is only allowed in the directory
/srv/www/cgi-bin/ . This location is already configured to execute CGI scripts. If you have
created a virtual host configuration (see Section 31.2.2.1, “Virtual Host Configuration”) and want to
place your scripts in a host-specific directory, you must unlock and configure this directory.
EXAMPLE 31.5: VIRTUALHOST CGI CONFIGURATION
ScriptAlias /cgi-bin/ "/srv/www/www.example.com/cgi-bin/" 1
<Directory "/srv/www/www.example.com/cgi-bin/">
Options +ExecCGI 2
AddHandler cgi-script .cgi .pl 3
Require all granted 4
</Directory>
1 Tells Apache to handle all les within this directory as CGI scripts.
2 Enables CGI script execution
3 Tells the server to treat les with the extensions .pl and .cgi as CGI scripts. Adjust according
to your needs.
4 The Require directive controls the default access state. In this case, access is granted to
the specified directory without limitation. For more information on authentication and
authorization, see http://httpd.apache.org/docs/2.4/howto/auth.html .
31.5.2 Running an Example Script

CGI programming differs from "regular" programming in that the CGI programs and scripts must
be preceded by a MIME-Type header such as Content-type: text/html . This header is sent
to the client, so it understands what kind of content it receives. Secondly, the script's output
must be something the client, usually a Web browser, understands—HTML usually, or plain text
or images, for example.
446 Apache Configuration SLES 12 SP3

A simple test script available under /usr/share/doc/packages/apache2/test-cgi is part of
the Apache package. It outputs the content of some environment variables as plain text. Copy
this script to either /srv/www/cgi-bin/ or the script directory of your virtual host ( /srv/
www/www.example.com/cgi-bin/ ) and name it test.cgi . Edit the le to have #!/bin/sh as
the rst line.
Files accessible by the Web server should be owned by the user root . For additional information
see Section 31.8, “Avoiding Security Problems”. Because the Web server runs with a different user,
the CGI scripts must be world-executable and world-readable. Change into the CGI directory
and use the command chmod 755 test.cgi to apply the proper permissions.
Now call http://localhost/cgi-bin/test.cgi or http://www.example.com/cgi-bin/
test.cgi . You should see the “CGI/1.0 test script report”.
31.5.3 CGI Troubleshooting

If you do not see the output of the test program but an error message instead, check the following:
CGI TROUBLESHOOTING
Have you reloaded the server after having changed the configuration? If not, reload with sys-
temctl reload apache2
If you have configured your custom CGI directory, is it configured properly? If in doubt, try
the script within the default CGI directory /srv/www/cgi-bin/ and call it with http://
localhost/cgi-bin/test.cgi .
Are the le permissions correct? Change into the CGI directory and execute ls -l test.cgi .
The output should start with
-rwxr-xr-x 1 root root
Make sure that the script does not contain programming errors. If you have not changed
test.cgi , this should not be the case, but if you are using your own programs, always
make sure that they do not contain programming errors.
447 CGI Troubleshooting SLES 12 SP3

31.6 Setting Up a Secure Web Server with SSL
Whenever sensitive data, such as credit card information, is transferred between Web server
and client, it is desirable to have a secure, encrypted connection with authentication. mod_ssl
provides strong encryption using the secure sockets layer (SSL) and transport layer security
(TLS) protocols for HTTP communication between a client and the Web server. Using SSL/TLS,
a private connection between Web server and client is established. Data integrity is ensured and
client and server can authenticate each other.
For this purpose, the server sends an SSL certificate that holds information proving the server's
valid identity before any request to a URL is answered. In turn, this guarantees that the server
is the uniquely correct end point for the communication. Additionally, the certificate generates
an encrypted connection between client and server that can transport information without the
risk of exposing sensitive, plain-text content.
mod_ssl does not implement the SSL/TLS protocols itself, but acts as an interface between
Apache and an SSL library. In SUSE Linux Enterprise Server, the OpenSSL library is used.
OpenSSL is automatically installed with Apache.
The most visible effect of using mod_ssl with Apache is that URLs are prefixed with https://
instead of http:// .
31.6.1 Creating an SSL Certificate

To use SSL/TLS with the Web server, you need to create an SSL certificate. This certificate is
needed for the authorization between Web server and client, so that each party can clearly
identify the other party. To ensure the integrity of the certificate, it must be signed by a party
every user trusts.
There are three types of certificates you can create: a “dummy” certificate for testing purposes
only, a self-signed certificate for a defined circle of users that trust you, and a certificate signed
by an independent, publicly-known certificate authority (CA).
Creating a certificate is a two step process. First, a private key for the certificate authority is
generated then the server certificate is signed with this key.

To learn more about concepts and definitions of SSL/TLS, refer to http://httpd.a-
pache.org/docs/2.4/ssl/ssl_intro.html .
448 Setting Up a Secure Web Server with SSL SLES 12 SP3

31.6.1.1 Creating a “Dummy” Certificate
To generate a dummy certificate, call the script /usr/bin/gensslcert . It creates or overwrites
the les listed below. Use gensslcert 's optional switches to ne-tune the certificate. Call /
usr/bin/gensslcert -h for more information.
/etc/apache2/ssl.crt/ca.crt
/etc/apache2/ssl.crt/server.crt
/etc/apache2/ssl.key/server.key
/etc/apache2/ssl.csr/server.csr
A copy of ca.crt is also placed at /srv/www/htdocs/CA.crt for download.
Important: For Testing Purposes Only

A dummy certificate should never be used on a production system. Only use it for testing
purposes.
31.6.1.2 Creating a Self-Signed Certificate

If you are setting up a secure Web server for an intranet or for a defined circle of users, it is
probably sufficient if you sign a certificate with your own certificate authority (CA). Note that
visitors to such a site will see a warning like “this is an untrusted site”, as Web browsers do not
recognize self-signed certificates.
Important: Self-Signed Certificates

Only use a self-signed certificate on a Web server that is accessed by people who know
and trust you as a certificate authority. It is not recommended to use such a certificate
for a public shop, for example.
First you need to generate a certificate signing request (CSR). You are going to use openssl ,
with PEM as the certificate format. During this step, you will be asked for a passphrase, and to
answer several questions. Remember the passphrase you enter as you will need it in the future.
sudo openssl req -new > new.cert.csr

Generating a 1024 bit RSA private key
..++++++
449 Creating an SSL Certificate SLES 12 SP3

.........++++++
writing new private key to 'privkey.pem'
Enter PEM pass phrase: 1
Verifying - Enter PEM pass phrase: 2
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]: 3
State or Province Name (full name) [Some-State]: 4
Locality Name (eg, city) []: 5
Organization Name (eg, company) [Internet Widgits Pty Ltd]: 6
Organizational Unit Name (eg, section) []: 7
Common Name (for example server FQDN, or YOUR name) []: 8
Email Address []: 9
Please enter the following 'extra' attributes

to be sent with your certificate request
A challenge password []: 10
An optional company name []: 11
1 Fill in your passphrase,

2 ...ll it in once more (and remember it).
3 Fill in your 2 letter country code, such as GB or CZ .
4 Fill in the name of the state where you live.
5 Fill in the city name, such as Prague .
6 Fill in the name of the organization you work for.
7 Fill in your organization unit, or leave blank if you have none.
8 Fill in either the domain name of the server, or your rst and last name.
9 Fill in your work e-mail address.
10 Leave the challenge password empty, otherwise you will need to enter it every time you
restart the Apache Web server.
11 Fill in the optional company name, or leave blank.
Now you can generate the certificate. You are going to use openssl again, and the format of
the certificate is the default PEM .

PROCEDURE 31.3: GENERATING THE CERTIFICATE
1. Export the private part of the key to new.cert.key . You will be prompted for the
passphrase you entered when creating the certificate signing request (CSR).
sudo openssl rsa -in privkey.pem -out new.cert.key
2. Generate the public part of the certificate according to the information you lled out in
the signing request. The -days option specifies the length of time before the certificate
expires. You can revoke a certificate, or replace one before it expires.
sudo openssl x509 -in new.cert.csr -out new.cert.cert -req \

-signkey new.cert.key -days 365
3. Copy the certificate les to the relevant directories, so that the Apache server can read
them. Make sure that the private key /etc/apache2/ssl.key/server.key is not world-
readable, while the public PEM certificate /etc/apache2/ssl.crt/server.crt is.
sudo cp new.cert.cert /etc/apache2/ssl.crt/server.crt

sudo cp new.cert.key /etc/apache2/ssl.key/server.key
Tip: Public Certificate Location

The last step is to copy the public certificate le from /etc/apache2/ssl.crt/serv-
er.crt to a location where your users can access it to incorporate it into the list of known
and trusted CAs in their Web browsers. Otherwise a browser complains that the certificate
was issued by an unknown authority.
31.6.1.3 Getting an Officially Signed Certificate
There are several official certificate authorities that sign your certificates. The certificate is
signed by a trustworthy third party, so can be fully trusted. Publicly operating secure Web servers
usually have an officially signed certificate. A list of the most used Certificate Authorities (CAs)
is available at https://en.wikipedia.org/wiki/Certificate_authority#Providers .
When requesting an officially signed certificate, you do not send a certificate to the CA. Instead,
issue a Certificate Signing Request (CSR). To create a CSR, run the following command:
openssl req -new -newkey rsa:2048 -nodes -keyout newkey.pem -out newreq.pem

You are asked to enter a distinguished name. This requires you to answer a few questions, such
as country name or organization name. Enter valid data—everything you enter here later shows
up in the certificate and is checked. You do not need to answer every question. If one does
not apply to you or you want to leave it blank, use “.”. Common name is the name of the CA
itself—choose a significant name, such as My company CA. Last, a challenge password and an
alternative company name must be entered.
Find the CSR in the directory from which you called the script. The le is named newreq.pem .
31.6.2 Configuring Apache with SSL
The default port for SSL and TLS requests on the Web server side is 443. There is no conflict
between a “regular” Apache listening on port 80 and an SSL/TLS-enabled Apache listening on
port 443. In fact, HTTP and HTTPS can be run with the same Apache instance. Usually separate
virtual hosts are used to dispatch requests to port 80 and port 443 to separate virtual servers.
Important: Firewall Configuration

Do not forget to open the firewall for SSL-enabled Apache on port 443. This can be done
with YaST as described in Book “Security Guide”, Chapter 15 “Masquerading and Firewalls”,
Section 15.4.1 “Configuring the Firewall with YaST”.
The SSL module is enabled by default in the global server configuration. In case it has been
disabled on your host, activate it with the following command: a2enmod ssl . To finally enable
SSL, the server needs to be started with the ag “SSL”. To do so, call a2enflag SSL (case-
sensitive!). If you have chosen to encrypt your server certificate with a password, you should
also increase the value for APACHE_TIMEOUT in /etc/sysconfig/apache2 , so you have enough
time to enter the passphrase when Apache starts. Restart the server to make these changes active.
A reload is not sufficient.
The virtual host configuration directory contains a template /etc/apache2/vhosts.d/vhost-
ssl.template with SSL-specific directives that are extensively documented. Refer to Sec-
tion 31.2.2.1, “Virtual Host Configuration” for the general virtual host configuration.
452 Configuring Apache with SSL SLES 12 SP3

To get started, copy the template to /etc/apache2/vhosts.d/MYSSL-HOST.conf and edit it.
Adjusting the values for the following directives should be sufficient:
DocumentRoot
ServerName
ServerAdmin
ErrorLog
TransferLog
31.6.2.1 Name-Based Virtual Hosts and SSL
By default it is not possible to run multiple SSL-enabled virtual hosts on a server with only one
IP address. Name-based virtual hosting requires that Apache knows which server name has been
requested. The problem with SSL connections is, that such a request can only be read after the
SSL connection has already been established (by using the default virtual host). As a result, users
will receive a warning message stating that the certificate does not match the server name.
SUSE Linux Enterprise Server comes with an extension to the SSL protocol called Server Name
Indication (SNI) addresses this issue by sending the name of the virtual domain as part of the SSL
negotiation. This enables the server to “switch” to the correct virtual domain early and present
the browser the correct certificate.
SNI is enabled by default on SUSE Linux Enterprise Server. To enable Name-Based Virtual Hosts
for SSL, configure the server as described in Section 31.2.2.1.1, “Name-Based Virtual Hosts” (note
that you need to use port 443 rather than port 80 with SSL).
Important: SNI Browser Support

SNI must also be supported on the client side. However, SNI is supported by most
browsers, except for certain older browsers. For more information, see https://en.wikipedi-
a.org/wiki/Server_Name_Indication#Support .
To configure handling of non-SNI capable browsers, use the directive SSLStric-
tSNIVHostCheck . When set to on in the server configuration, non-SNI capable browser
will be rejected for all virtual hosts. When set to on within a VirtualHost directive,
access to this particular host will be rejected.
453 Configuring Apache with SSL SLES 12 SP3

When set to off in the server configuration, the server will behave as if not having SNI
support. SSL requests will be handled by the rst virtual host defined (for port 443).
31.7 Running Multiple Apache Instances on the Same

Server
As of SUSE® Linux Enterprise Server 12 SP1, you can run multiple Apache instances on the
same server. This has several advantages over running multiple virtual hosts (see Section 31.2.2.1,
“Virtual Host Configuration”):
When a virtual host needs to be disabled for some time, you need to change the Web server
configuration and restart it so that the change takes effect.
In case of problems with one virtual host, you need to restart all of them.
You can run the default Apache instance as usual:
sytemctl start apache2
It reads the default /etc/sysconfig/apache2 le. If the le is not present, or it is present but
it does not set the APACHE_HTTPD_CONF variable, it reads /etc/apache2/httpd.conf .
To activate another Apache instance, run:
systemctl start apache2@INSTANCE_NAME
For example:
systemctl start apache2@example_web.org
By default, the instance uses /etc/apache2@example_web.org/httpd.conf as a main con-

figuration le, which can be overwritten by setting APACHE_HTTPD_CONF in /etc/syscon-
fig/apache2@example_web.org .
An example to set up an additional instance of Apache follows. Note that you need to execute
all the commands as root .
454 Running Multiple Apache Instances on the Same Server SLES 12 SP3
PROCEDURE 31.4: CONFIGURING AN ADDITIONAL APACHE INSTANCE
1. Create a new configuration le based on /etc/sysconfig/apache2 , for example /etc/

sysconfig/apache2@example_web.org :
cp /etc/sysconfig/apache2 /etc/sysconfig/apache2@example_web.org
2. Edit the le /etc/sysconfig/apache2@example_web.org and change the line contain-

ing
APACHE_HTTPD_CONF
to
APACHE_HTTPD_CONF="/etc/apache2/httpd@example_web.org.conf"
3. Create the le /etc/apache2/httpd@example_web.org.conf based on /etc/apache2/

httpd.conf .
cp /etc/apache2/httpd.conf /etc/apache2/httpd@example_web.org.conf
4. Edit /etc/apache2/httpd@example_web.org.conf and change
Include /etc/apache2/listen.conf
to
Include /etc/apache2/listen@example_web.org.conf
Review all the directives and change them to t your needs. You will probably want to
change
Include /etc/apache2/global.conf
and create new global@example_web.org.conf for each instance. We suggest to change
ErrorLog /var/log/apache2/error_log
to
ErrorLog /var/log/apache2/error@example_web.org_log
to have separate logs for each instance.
5. Create /etc/apache2/listen@example_web.org.conf based on /etc/apache2/lis-
ten.conf .
cp /etc/apache2/listen.conf /etc/apache2/listen@example_web.org.conf
6. Edit /etc/apache2/listen@example_web.org.conf and change
Listen 80
to the port number you want the new instance to run on, for example 82:
Listen 82
To run the new Apache instance over a secured protocol (see Section 31.6, “Setting Up a
Secure Web Server with SSL”), change also the line
Listen 443
for example to
Listen 445
7. Start the new Apache instance:
systemctl start apache2@example_web.org
8. Check if the server is running by pointing your Web browser at http://server_name:82 .

If you previously changed the name of the error log le for the new instance, you can
check it:
tail -f /var/log/apache2/error@example_web.org_log
Here are several points to consider when setting up more Apache instances on the same server:
The le /etc/sysconfig/apache2@INSTANCE_NAME can include the same variables as /

etc/sysconfig/apache2 , including module loading and MPM setting.
The default Apache instance does not need to be running while other instances run.
The Apache helper utilities a2enmod , a2dismod and apachectl operate on the default
Apache instance if not specified otherwise with the HTTPD_INSTANCE environment vari-
able. The following example
export HTTPD_INSTANCE=example_web.org
a2enmod access_compat
a2enmod status
apachectl start
will add access_compat and status modules to the APACHE_MODULES variable of /etc/
sysconfig/apache2@example_web.org , and then start the example_web.org instance.
31.8 Avoiding Security Problems

A Web server exposed to the public Internet requires an ongoing administrative effort. It is in-
evitable that security issues appear, both related to the software and to accidental misconfigu-
ration. Here are some tips for how to deal with them.
31.8.1 Up-to-Date Software

If there are vulnerabilities found in the Apache software, a security advisory will be issued by
SUSE. It contains instructions for fixing the vulnerabilities, which in turn should be applied
when possible. The SUSE security announcements are available from the following locations:
Web Page. http://www.suse.com/support/security/
Mailing List Archive. http://lists.opensuse.org/opensuse-security-announce/
List of Security Announcements. http://www.suse.com/support/update/
31.8.2 DocumentRoot Permissions

By default in SUSE Linux Enterprise Server, the DocumentRoot directory /srv/www/htdocs
and the CGI directory /srv/www/cgi-bin belong to the user and group root . You should not
change these permissions. If the directories are writable for all, any user can place les into them.
These les might then be executed by Apache with the permissions of wwwrun , which may give
the user unintended access to le system resources. Use subdirectories of /srv/www to place
the DocumentRoot and CGI directories for your virtual hosts and make sure that directories and
les belong to user and group root .
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31.8.3 File System Access
By default, access to the whole le system is denied in /etc/apache2/httpd.conf . You should
never overwrite these directives, but specifically enable access to all directories Apache should
be able to read. For details, see Section 31.2.2.1.3, “Basic Virtual Host Configuration”. In doing so,
ensure that no critical les, such as password or system configuration les, can be read from
the outside.
31.8.4 CGI Scripts

Interactive scripts in Perl, PHP, SSI, or any other programming language can essentially run
arbitrary commands and therefore present a general security issue. Scripts that will be executed
from the server should only be installed from sources the server administrator trusts—allowing
users to run their own scripts is generally not a good idea. It is also recommended to do security
audits for all scripts.
To make the administration of scripts as easy as possible, it is common practice to limit the
execution of CGI scripts to specific directories instead of globally allowing them. The directives
ScriptAlias and Option ExecCGI are used for configuration. The SUSE Linux Enterprise
Server default configuration does not allow execution of CGI scripts from everywhere.
All CGI scripts run as the same user, so different scripts can potentially conflict with each other.
The module suEXEC lets you run CGI scripts under a different user and group.
31.8.5 User Directories

When enabling user directories (with mod_userdir or mod_rewrite ) you should strongly con-
sider not allowing .htaccess les, which would allow users to overwrite security settings.
At least you should limit the user's engagement by using the directive AllowOverRide . In
SUSE Linux Enterprise Server, .htaccess les are enabled by default, but the user is not al-
lowed to overwrite any Option directives when using mod_userdir (see the /etc/apache2/
mod_userdir.conf configuration le).
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If Apache does not start, the Web page is not accessible, or users cannot connect to the Web
server, it is important to nd the cause of the problem. Here are some typical places to look for
error explanations and important things to check:
Output of the apache2.service subcommand:

Instead of starting and stopping the Web server with the binary /usr/sbin/apache2ctl ,
rather use the systemctl commands instead (described in Section 31.3, “Starting and Stop-
ping Apache”). systemctl status apache2 is verbose about errors, and it even provides
tips and hints for fixing configuration errors.
Log Files and Verbosity

In case of both fatal and nonfatal errors, check the Apache log les for causes, mainly the
error log le located at /var/log/apache2/error_log by default. Additionally, you can
control the verbosity of the logged messages with the LogLevel directive if more detail
is needed in the log les.
Tip: A Simple Test

Watch the Apache log messages with the command tail -F /var/log/
apache2/MY_ERROR_LOG . Then run systemctl restart apache2 . Now, try to
connect with a browser and check the output.
Firewall and Ports

A common mistake is to not open the ports for Apache in the firewall configuration of the
server. If you configure Apache with YaST, there is a separate option available to take care
of this specific issue (see Section 31.2.3, “Configuring Apache with YaST”). If you are configuring
Apache manually, open firewall ports for HTTP and HTTPS via YaST's firewall module.
If the error cannot be tracked down with any of these, check the online Apache bug database
at http://httpd.apache.org/bug_report.html . Additionally, the Apache user community can be
reached via a mailing list available at http://httpd.apache.org/userslist.html .

The package apache2-doc contains the complete Apache manual in various localizations for
local installation and reference. It is not installed by default—the quickest way to install it is
to use the command zypper in apache2-doc . having been installed, the Apache manual
is available at http://localhost/manual/ . You may also access it on the Web at http://httpd.a-
pache.org/docs-2.4/ . SUSE-specific configuration hints are available in the directory /usr/
share/doc/packages/apache2/README.* .
31.10.1 Apache 2.4

For a list of new features in Apache 2.4, refer to http://httpd.apache.org/docs/2.4/new_fea-
tures_2_4.html . Information about upgrading from version 2.2 to 2.4 is available at http://
httpd.apache.org/docs-2.4/upgrading.html .
31.10.2 Apache Modules

More information about external Apache modules that are briey described in Section 31.4.5,
“External Modules” is available at the following locations:
mod_apparmor
http://en.opensuse.org/SDB:AppArmor
mod_auth_kerb
http://modauthkerb.sourceforge.net/
mod_perl
http://perl.apache.org/
mod_php5
http://www.php.net/manual/en/install.unix.apache2.php
mod_python
http://www.modpython.org/
mod_security
http://modsecurity.org/

31.10.3 Development
More information about developing Apache modules or about getting involved in the Apache
Web server project are available at the following locations:
Apache Developer Information

http://httpd.apache.org/dev/
Apache Developer Documentation

http://httpd.apache.org/docs/2.4/developer/
Writing Apache Modules with Perl and C

http://www.modperl.com/
31.10.4 Miscellaneous Sources

If you experience difficulties specific to Apache in SUSE Linux Enterprise Server, take a look
at the Technical Information Search at http://www.suse.com/support . The history of Apache
is provided at http://httpd.apache.org/ABOUT_APACHE.html . This page also explains why the
server is called Apache.
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32 Setting Up an FTP Server with YaST
Using the YaST FTP Server module, you can configure your machine to function as
an FTP (File Transfer Protocol) server. Anonymous and/or authenticated users can
connect to your machine and download les using the FTP protocol. Depending
on the configuration, they can also upload les to the FTP server. YaST uses vsftpd
(Very Secure FTP Daemon).
If the YaST FTP Server module is not available in your system, install the yast2-ftp-server
package.
To configure the FTP server using YaST, follow these steps:
1. Open the YaST control center and choose Network Services FTP Server or run the yast2
ftp-server command as root .
2. If there is not any FTP server installed in your system, you will be asked which server
to install when the YaST FTP Server module starts. Choose the vsftpd server and confirm
the dialog.
3. In the Start-Up dialog, configure the options for starting of the FTP server. For more infor-
mation, see Section 32.1, “Starting the FTP Server”.
In the General dialog, configure FTP directories, welcome message, le creation masks and
other parameters. For more information, see Section 32.2, “FTP General Settings”.
In the Performance dialog, set the parameters that affect the load on the FTP server. For
more information, see Section 32.3, “FTP Performance Settings”.
In the Authentication dialog, set whether the FTP server should be available for anonymous
and/or authenticated users. For more information, see Section 32.4, “Authentication”.
In the Expert Settings dialog, configure the operation mode of the FTP server, SSL connec-
tions and firewall settings. For more information, see Section 32.5, “Expert Settings”.
4. Press Finish to save the configurations.
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32.1 Starting the FTP Server
In the Service Start frame of the FTP Start-Up dialog set the way the FTP server is started up.
You can choose between starting the server automatically during the system boot and starting
it manually. If the FTP server should be started only after an FTP connection request, choose
Via xinetd.
The current status of the FTP server is shown in the Switch On and O frame of the FTP Start-Up
dialog. Start the FTP server by clicking Start FTP Now. To stop the server, click Stop FTP Now.
After having changed the settings of the server click Save Settings and Restart FTP Now. Your
configurations will be saved by leaving the configuration module with Finish.
The Selected Service frame of the FTP Start-Up dialog shows which FTP server is used: either
vsftpd or pure-ftpd. If both servers are installed, you can switch between them—the current
configuration will automatically be converted.
FIGURE 32.1: FTP SERVER CONFIGURATION — START-UP
32.2 FTP General Settings

In the General Settings frame of the FTP General Settings dialog you can set the Welcome message
which is shown after connecting to the FTP server.
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If you check the Chroot Everyone option, all local users will be placed in a chroot jail in their
home directory after login. This option has security implications, especially if the users have
upload permission or shell access, so be careful enabling this option.
If you check the Verbose Logging option, all FTP requests and responses are logged.
You can limit permissions of les created by anonymous and/or authenticated users with umask.
Set the le creation mask for anonymous users in Umask for Anonymous and the le creation
mask for authenticated users in Umask for Authenticated Users. The masks should be entered as
octal numbers with a leading zero. For more information about umask, see the umask man page
( man 1p umask ).
In the FTP Directories frame set the directories used for anonymous and authorized users. With
Browse, you can select a directory to be used from the local le system. The default FTP directory
for anonymous users is /srv/ftp . Note that vsftpd does not allow this directory to be writable
for all users. The subdirectory upload with write permissions for anonymous users is created
instead.
Note: Write Permissions in FTP Directory

The pure-ftpd server allows the FTP directory for anonymous users to be writable. When
switching between servers, make sure you remove the write permissions in the directory
that was used with pure-ftpd before switching back to the vsftpd server.
32.3 FTP Performance Settings

In the Performance dialog set the parameters which affect the load on the FTP server. Max Idle
Time is the maximum time (in minutes) the remote client may spend between FTP commands.
In case of longer inactivity, the remote client is disconnected. Max Clients for One IP determines
the maximum number of clients which can be connected from a single IP address. Max Clients
determines the maximum number of clients which may be connected. Any additional clients
will get an error message.
The maximum data transfer rate (in KB/s) is set in Local Max Rate for local authenticated users,
and in Anonymous Max Rate for anonymous clients respectively. The default value for the rate
settings is 0 , which means unlimited data transfer rate.
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32.4 Authentication
In the Enable/Disable Anonymous and Local Users frame of the Authentication dialog, you can
set which users are allowed to access your FTP server. You can choose between the following
options: granting access to anonymous users only, to authenticated users only (with accounts
on the system) or to both types of users.
To allow users to upload les to the FTP server, check Enable Upload in the Uploading frame of the
Authentication dialog. Here you can allow uploading or creating directories even for anonymous
users by checking the respective box.
Note: vsftp—Allowing File Upload for Anonymous Users

If a vsftpd server is used and you want anonymous users to be able to upload les or create
directories, a subdirectory with writing permissions for all users needs to be created in
the anonymous FTP directory.
32.5 Expert Settings

An FTP server can run in active or in passive mode. By default the server runs in passive mode.
To switch into active mode, uncheck Enable Passive Mode option in Expert Settings dialog. You
can also change the range of ports on the server used for the data stream by tweaking the Min
Port for Pas. Mode and Max Port for Pas. Mode options.
If you want encrypted communication between clients and the server, you can Enable SSL. Check
the versions of the protocol to be supported and specify the DSA certificate to be used for SSL
encrypted connections.
If your system is protected by a firewall, check Open Port in Firewall to enable a connection to
the FTP server.

For more information about the FTP server read the manual pages of vsftpd and vsftpd.conf .
465 Authentication SLES 12 SP3

33 The Proxy Server Squid
Squid is a widely-used proxy cache for Linux and Unix platforms. This means that
it stores requested Internet objects, such as data on a Web or FTP server, on a ma-
chine that is closer to the requesting workstation than the server. It can be set up
in multiple hierarchies to assure optimal response times and low bandwidth usage,
even in modes that are transparent to end users. Additional software like squid-
Guard can be used to filter Web content.
Squid acts as a proxy cache. It redirects object requests from clients (in this case, from Web
browsers) to the server. When the requested objects arrive from the server, it delivers the objects
to the client and keeps a copy of them in the hard disk cache. An advantage of caching is that
several clients requesting the same object can be served from the hard disk cache. This enables
clients to receive the data much faster than from the Internet. This procedure also reduces the
network traffic.
Along with actual caching, Squid offers a wide range of features:
Distributing load over intercommunicating hierarchies of proxy servers
Defining strict access control lists for all clients accessing the proxy
Allowing or denying access to specific Web pages using other applications
Generating statistics about frequently-visited Web pages for the assessment of surfing
habits
Squid is not a generic proxy. It normally proxies only HTTP connections. It supports the protocols
FTP, Gopher, SSL, and WAIS, but it does not support other Internet protocols, such as the news
protocol, or video conferencing protocols. Because Squid only supports the UDP protocol to pro-
vide communication between different caches, many multimedia programs are not supported.
33.1 Some Facts about Proxy Caches

As a proxy cache, Squid can be used in several ways. When combined with a firewall, it can
help with security. Multiple proxies can be used together. It can also determine what types of
objects should be cached and for how long.
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33.1.1 Squid and Security
It is possible to use Squid together with a firewall to secure internal networks from the outside
using a proxy cache. The firewall denies all clients access to external services except Squid. All
Web connections must be established by the proxy. With this configuration, Squid completely
controls Web access.
If the firewall configuration includes a DMZ, the proxy should operate within this zone. Sec-
tion 33.6, “Configuring a Transparent Proxy” describes how to implement a transparent proxy. This
simplifies the configuration of the clients, because in this case, they do not need any information
about the proxy.
33.1.2 Multiple Caches

Several instances of Squid can be configured to exchange objects between them. This reduces
the total system load and increases the chances of retrieving an object from the local network.
It is also possible to configure cache hierarchies, so a cache can forward object requests to
sibling caches or to a parent cache—causing it to request objects from another cache in the local
network or directly from the source.
Choosing the appropriate topology for the cache hierarchy is very important, because it is not
desirable to increase the overall traffic on the network. For a very large network, it would make
sense to configure a proxy server for every subnet and connect them to a parent proxy, which
in turn is connected to the proxy cache of the ISP.
All this communication is handled by ICP (Internet cache protocol) running on top of the UDP
protocol. Data transfers between caches are handled using HTTP (hypertext transmission pro-
tocol) based on TCP.
To nd the most appropriate server from which to request objects, a cache sends an ICP request
to all sibling proxies. The sibling proxies answer these requests via ICP responses. If the object
was detected, they use the code HIT , if not, they use MISS .
If multiple HIT responses were found, the proxy server decides from which server to download,
depending on factors such as which cache sent the fastest answer or which one is closer. If no
satisfactory responses are received, the request is sent to the parent cache.
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Note: How Squid Avoids Duplication of Objects
To avoid duplication of objects in different caches in the network, other ICP protocols are
used, such as CARP (cache array routing protocol) or HTCP (hypertext cache protocol).
The more objects maintained in the network, the greater the possibility of finding the
desired one.
33.1.3 Caching Internet Objects

Many objects available in the network are not static, such as dynamically generated pages and
TLS/SSL-encrypted content. Objects like these are not cached because they change each time
they are accessed.
To determine how long objects should remain in the cache, objects are assigned one of several
states. Web and proxy servers nd out the status of an object by adding headers to these objects,
such as “Last modified” or “Expires” and the corresponding date. Other headers specifying that
objects must not be cached can be used as well.
Objects in the cache are normally replaced, because of a lack of free disk space, using algorithms
such as LRU (last recently used). This means that the proxy expunges those objects that have
not been requested for the longest time.
33.2 System Requirements

System requirements largely depend on the maximum network load that the system must bear.
Therefore, examine load peaks, as during those times, load might be more than four times the
day's average. When in doubt, slightly overestimate the system's requirements. Having Squid
working close to the limit of its capabilities can lead to a severe loss in quality of service. The
following sections point to system factors in order of significance:
1. RAM size
2. CPU speed/physical CPU cores
3. Size of the disk cache
4. Hard disks/SSDs and their architecture
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33.2.1 RAM
The amount of memory (RAM) required by Squid directly correlates with the number of objects
in the cache. Random access memory is much faster than a hard disk/SSD. Therefore, it is
very important to have sufficient memory for the Squid process, because system performance
is dramatically reduced if the swap disk is used.
Squid also stores cache object references and frequently requested objects in the main memory
to speed up retrieval of this data. In addition to that, there is other data that Squid needs to keep
in memory, such as a table with all the IP addresses handled, an exact domain name cache, the
most frequently requested objects, access control lists, buers, and more.
33.2.2 CPU
Squid is tuned to work best with lower processor core counts (4–8 physical cores), with each
providing high performance. Technologies providing virtual cores such as hyperthreading can
hurt performance.
To make the best use of multiple CPU cores, it is necessary to set up multiple worker threads
writing to different caching devices. By default, multi-core support is mostly disabled.
33.2.3 Size of the Disk Cache

In a small cache, the probability of a HIT (finding the requested object already located there) is
small, because the cache is easily lled and less requested objects are replaced by newer ones.
If, for example, 1 GB is available for the cache and the users use up only 10 MB per day surfing,
it would take more than one hundred days to ll the cache.
The easiest way to determine the necessary cache size is to consider the maximum transfer rate
of the connection. With a 1 Mbit/s connection, the maximum transfer rate is 128 KB/s. If all
this traffic ended up in the cache, in one hour it would add up to 460 MB. Assuming that all
this traffic is generated in only eight working hours, it would reach 3.6 GB in one day. Because
the connection is normally not used to its upper volume limit, it can be assumed that the total
data volume handled by the cache is approximately 2 GB. Hence, in this example, 2 GB of disk
space is required for Squid to keep one day's worth of browsing data cached.
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33.2.4 Hard Disk/SSD Architecture
Speed plays an important role in the caching process, so this factor deserves special attention.
For hard disks/SSDs, this parameter is described as random seek time or random read performance,
measured in milliseconds. Because the data blocks that Squid reads from or writes to the hard
disk/SSD tend to be small, the seek time/read performance of the hard disk/SSD is more impor-
tant than its data throughput.
For use as a proxy, hard disks with high rotation speeds or SSDs are the best choice. When using
hard disks, it can be better to use multiple smaller hard disks, each with a single cache directory
to avoid excessive read times.
Using a RAID system allows increasing reliability at expense of speed. However, for performance
reasons, avoid (software) RAID5 and similar settings.
File system choice is usually not decisive. However, using the mount option noatime can im-
prove performance—Squid provides its own time stamps and thus does not need the le system
to track access times.
33.3 Basic Usage of Squid

If not already installed, install the package squid . squid is not among the packages installed
by default on SUSE® Linux Enterprise Server.
Squid is already preconfigured in SUSE Linux Enterprise Server, you can start it directly after the
installation. To ensure a smooth start-up, the network should be configured in a way that at least
one name server and the Internet can be reached. Problems can arise if a dial-up connection is
used with a dynamic DNS configuration. In this case, at least the name server should be specified,
because Squid does not start if it does not detect a DNS server in /etc/resolv.conf .
33.3.1 Starting Squid

To start Squid, use:
tux > sudo systemctl start squid
If you want Squid to start together with the system, enable the service with systemctl enable
squid .
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33.3.2 Checking Whether Squid Is Working
To check whether Squid is running, choose one of the following ways:
Using systemctl :
tux > systemctl status squid
The output of this command should indicate that Squid is loaded and active (running) .
Using Squid itself:
tux > sudo squid -k check | echo $?
The output of this command should be 0 , but may contain additional warnings or mes-
sages.
To test the functionality of Squid on the local system, choose one of the following ways:
To test, you can use squidclient , a command-line tool that can output the response to
a Web request, similar to wget or curl .
Unlike those tools, squidclient will automatically connect to the default proxy setup of
Squid, localhost:3128 . However, if you changed the configuration of Squid, you need
to configure squidclient to use different settings using command line options. For more
information, see squidclient --help .
EXAMPLE 33.1: A REQUEST WITH squidclient
tux > squidclient http://www.example.org

HTTP/1.1 200 OK
Cache-Control: max-age=604800
Content-Type: text/html
Date: Fri, 22 Jun 2016 12:00:00 GMT
Expires: Fri, 29 Jun 2016 12:00:00 GMT
Last-Modified: Fri, 09 Aug 2013 23:54:35 GMT
Server: ECS (iad/182A)
Vary: Accept-Encoding
X-Cache: HIT
x-ec-custom-error: 1
Content-Length: 1270
X-Cache: MISS from moon 1
X-Cache-Lookup: MISS from moon:3128

Via: 1.1 moon (squid/3.5.16) 2
Connection: close
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<!doctype html>
<html>
<head>
<title>Example Domain</title>
[...]
</body>
</html>
The output shown in Example 33.1, “A Request With squidclient” can be split into two
parts:
1. The protocol headers of the response: the lines before the blank line.
2. The actual content of the response: the lines after the blank line.
To verify that Squid is used, refer to the selected header lines:
1 The value of the header X-Cache tells you that the requested document was
not in the Squid cache ( MISS ) of the computer moon .
The example above contains two X-Cache lines. You can ignore the rst X-
Cache header. It is produced by the internal caching software of the originating
Web server.
2 The value of the header Via tells you the HTTP version, the name of the com-
puter, and the version of Squid in use.
Using a browser: Set up localhost as the proxy and 3128 as the port. You can then load
a page and check the response headers in the Network panel of the browser's Inspector or
Developer Tools. The headers should be reproduced similarly to the way shown in Exam-
ple 33.1, “A Request With squidclient”.
To allow users from the local system and other systems to access Squid and the Internet, change
the entry in the configuration les /etc/squid/squid.conf from http_access deny all
to http_access allow all . However, in doing so, consider that Squid is made completely
accessible to anyone by this action. Therefore, define ACLs (access control lists) that control
access to the proxy. After modifying the configuration le, Squid must be reloaded or restarted.
For more information on ACLs, see Section 33.5.2, “Options for Access Controls”.
If Squid quits after a short period of time even though it was started successfully, check whether
there is a faulty name server entry or whether the /etc/resolv.conf le is missing. Squid logs
the cause of a start-up failure in the le /var/log/squid/cache.log .
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33.3.3 Stopping, Reloading, and Restarting Squid
To reload Squid, choose one of the following ways:
Using systemctl :
root # systemctl reload squid
or
root # systemctl restart squid
Using YaST:
In the Squid module, click the Save Settings and Restart Squid Now. button.
To stop Squid, choose one of the following ways:
Using systemctl :
root # systemctl stop squid
Using YaST
In the Squid module click the Stop Squid Now. button.
Shutting down Squid can take a while, because Squid waits up to half a minute before dropping
the connections to the clients and writing its data to the disk (see shutdown_lifetime option
in /etc/squid/squid.conf ),
Warning: Terminating Squid

Terminating Squid with kill or killall can damage the cache. To be able to restart
Squid, damaged caches must be deleted.
33.3.4 Removing Squid

Removing Squid from the system does not remove the cache hierarchy and log les. To remove
these, delete the /var/cache/squid directory manually.
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33.3.5 Local DNS Server
Setting up a local DNS server makes sense even if it does not manage its own domain. It then
simply acts as a caching-only name server and is also able to resolve DNS requests via the
root name servers without requiring any special configuration (see Section 25.4, “Starting the BIND
Name Server”). How this can be done depends on whether you chose dynamic DNS during the
configuration of the Internet connection.
Dynamic DNS
Normally, with dynamic DNS, the DNS server is set by the provider during the establish-
ment of the Internet connection and the local /etc/resolv.conf le is adjusted auto-
matically. This behavior is controlled in the /etc/sysconfig/network/config le with
the NETCONFIG_DNS_POLICY sysconfig variable. Set NETCONFIG_DNS_POLICY to "" with
the YaST sysconfig editor.
Then, add the local DNS server in the /etc/resolv.conf le with the IP address
127.0.0.1 for localhost . This way, Squid can always nd the local name server when
it starts.
To make the provider's name server accessible, specify it in the configuration le /etc/
named.conf under forwarders along with its IP address. With dynamic DNS, this can be
achieved automatically when establishing the connection by setting the sysconfig variable
NETCONFIG_DNS_POLICY to auto .
Static DNS
With static DNS, no automatic DNS adjustments take place while establishing a connection,
so there is no need to change any sysconfig variables. However, you must specify the local
DNS server in the le /etc/resolv.conf as described in Dynamic DNS. Additionally, the
provider's static name server must be specified manually in the /etc/named.conf le
under forwarders along with its IP address.
Tip: DNS and Firewall

If you have a firewall running, make sure DNS requests can pass it.
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33.4 The YaST Squid Module
The YaST Squid module contains the following tabs:
Start-Up
Specifies how Squid is started and which Firewall port is open on which interfaces.
HTTP Ports
Define all ports where Squid will listen for clients' http requests.
Refresh Patterns
Defines how Squid treats objects in the cache.
Cache Settings
Defines settings in regard to cache memory, maximum and minimum object size, and more.
Cache Directory
Defines the top-level directory where Squid stores all cache swap les.
Access Control
Controls the access to the Squid server via ACL groups.
Logging and Timeout

Define paths to access, cache, and cache store log les in addition with connection timeouts
and client lifetime.
Miscellaneous
Sets language and mail address of administrator.
33.5 The Squid Configuration File

All Squid proxy server settings are made in the /etc/squid/squid.conf le. To start Squid
for the rst time, no changes are necessary in this le, but external clients are initially denied
access. The proxy is available for localhost . The default port is 3128 . The preinstalled con-
figuration le /etc/squid/squid.conf provides detailed information about the options and
many examples.
Many entries are commented and therefore begin with the comment character # . The relevant
specifications can be found at the end of the line. The given values usually correlate with the
default values, so removing the comment signs without changing any of the parameters usually
475 The YaST Squid Module SLES 12 SP3

has no effect. If possible, leave the commented lines as they are and insert the options along
with the modified values in the line below. This way, the default values may easily be recovered
and compared with the changes.
Tip: Adapting the Configuration File After an Update

If you have updated from an earlier Squid version, it is recommended to edit the new /
etc/squid/squid.conf and only apply the changes made in the previous le.
Sometimes, Squid options are added, removed, or modified. Therefore, if you try to use
the old squid.conf , Squid might stop working properly.
33.5.1 General Configuration Options

The following is a list of a selection of configuration options for Squid. It is not exhaustive. The
Squid package contains a full, lightly documented list of options in /etc/squid/squid.con-
f.documented .
http_port PORT
This is the port on which Squid listens for client requests. The default port is 3128 , but
8080 is also common.
cache_peer HOST_NAME TYPE PROXY_PORT ICP_PORT

This option allows creating a network of caches that work together. The cache peer is a
computer that also hosts a network cache and stands in a relationship to your own. The
type of relationship is specified as the TYPE . The type can either be parent or sibling .
As the HOST_NAME , specify the name or IP address of the proxy to use. For PROXY_PORT ,
specify the port number for use in a browser (usually 8080 ). Set ICP_PORT to 7 or, if the
ICP port of the parent is not known and its use is irrelevant to the provider, to 0 .
To make Squid behave like a Web browser instead of like a proxy, prohibit the use of the
ICP protocol. You can do so by appending the options default and no-query .
cache_mem SIZE
This option defines the amount of memory Squid can use for very popular replies. The
default is 8 MB . This does not specify the memory usage of Squid and may be exceeded.
476 General Configuration Options SLES 12 SP3

cache_dir STORAGE_TYPE CACHE_DIRECTORY CACHE_SIZE LEVEL_1_DIRECTORIES LEV-
EL_2_DIRECTORIES
The option cache_dir defines the directory for the disk cache. In the default configuration
on SUSE Linux Enterprise Server, Squid does not create a disk cache.
The placeholder STORAGE_TYPE can be one of the following:
Directory-based storage types: ufs , aufs (the default), diskd . All three are varia-
tions of the storage format ufs . However, while ufs runs as part of the core Squid
thread, aufs runs in a separate thread, and diskd uses a separate process. This
means that the latter two types avoid blocking Squid because of disk I/O.
Database-based storage systems: rock . This storage format relies on a single database
le, in which each object takes up one or more memory units of a xed size (“slots”).
In the following, only the parameters for storage types based on ufs will be discussed.
rock has somewhat different parameters.
The CACHE_DIRECTORY is the directory for the disk cache. By default, that is /var/cache/
squid . CACHE_SIZE is the maximum size of that directory in megabytes; by default, this
is set to 100 MB. Set it to between 50% and a maximum of 80% of available disk space.
The final two values, LEVEL_1_DIRECTORIES and LEVEL_2_DIRECTORIES specify how
many subdirectories are created in the CACHE_DIRECTORY . By default, 16 subdirectories
are created at the rst level below CACHE_DIRECTORY and 256 within each of these. These
values should only be increased with caution, because creating too many directories can
lead to performance problems.
If you have several disks that share a cache, specify several cache_dir lines.
cache_access_log LOG_FILE ,
cache_log LOG_FILE ,
cache_store_log LOG_FILE
These three options specify the paths where Squid logs all its actions. Normally, nothing
needs to be changed here. If Squid is burdened by heavy usage, it might make sense to
distribute the cache and the log les over several disks.
client_netmask NETMASK
This option allows masking IP addresses of clients in the log les by applying a subnet
mask. For example, to set the last digit of the IP address to 0 , specify 255.255.255.0 .

ftp_user E-MAIL
This option allows setting the password that Squid should use for anonymous FTP login.
Specify a valid e-mail address here, because some FTP servers check these for validity.
cache_mgr E-MAIL
If it unexpectedly crashes, Squid sends a message to this e-mail address. The default is
webmaster.
logfile_rotate VALUE
If you run squid -k rotate , Squid can rotate log les. The les are numbered in this
process and, after reaching the specified value, the oldest le is overwritten. The default
value is 10 which rotates log les with the numbers 0 to 9.
However, on SUSE Linux Enterprise Server, rotating log les is performed automatically
using logrotate and the configuration le /etc/logrotate.d/squid .
append_domain DOMAIN
Use append_domain to specify which domain to append automatically when none is given.
Usually, your own domain is specified here, so specifying www in the browser accesses
your own Web server.
forwarded_for STATE
If this option is set to on , it adds a line to the header similar to this:
X-Forwarded-For: 192.168.0.1
If you set this option to off , Squid removes the IP address and the system name of the
client from HTTP requests.
negative_ttl TIME ,
negative_dns_ttl TIME
If these options are set, Squid will cache some types of failures, such as 404 responses. It
will then refuse to issue new requests, even if the resource would be available then.
By default, negative_ttl is set to 0 , negative_dns_ttl is set to 1 minutes . This
means that negative responses to Web requests are not cached by default, while negative
responses to DNS requests are cached for 1 minute.

never_direct allow ACL_NAME
To prevent Squid from taking requests directly from the Internet, use the option nev-
er_direct to force connection to another proxy. This must have previously been specified
in cache_peer . If all is specified as the ACL_NAME , all requests are forwarded directly
to the parent . This can be necessary, for example, if you are using a provider that dictates
the use of its proxies or denies its firewall direct Internet access.
33.5.2 Options for Access Controls

Squid provides a detailed system for controlling the access to the proxy. These Access Control
Lists (ACL) are lists with rules that are processed sequentially. ACLs must be defined before they
can be used. Some default ACLs, such as all and localhost , already exist. However, the mere
definition of an ACL does not mean that it is actually applied. This only happens when there
is a corresponding http_access rule.
The syntax for the option acl is as follows:
acl ACL_NAME TYPE DATA
The placeholders within this syntax stand for the following:
The name ACL_NAME can be chosen arbitrarily.
For TYPE , select from a variety of different options which can be found in the ACCESS
CONTROLS section in the /etc/squid/squid.conf le.
The specification for DATA depends on the individual ACL type and can also be read from
a le. For example, “via” host names, IP addresses, or URLs.
To add rules in the YaST squid module, open the module and click the Access Control tab. Click
Add under the ACL Groups list and enter the name of your rule, the type, and its parameters.
For more information on types of ACL rules, see the Squid documentation at http://www.squid-
cache.org/Versions/v3/3.5/cfgman/acl.html .
EXAMPLE 33.2: DEFINING ACL RULES
acl mysurfers srcdomain .example.com 1
acl teachers src 192.168.1.0/255.255.255.0 2
acl students src 192.168.7.0-192.168.9.0/255.255.255.0 3
acl lunch time MTWHF 12:00-15:00 4
479 Options for Access Controls SLES 12 SP3

1 This ACL defines mysurfers to be all users coming from within .example.com (as deter-
mined by a reverse lookup for the IP).
2 This ACL defines teachers to be the users of computers with IP addresses starting with
192.168.1. .
3 This ACL defines students to be the users of the computer with IP addresses starting with
192.168.7. , 192.168.8. , or 192.168.9. .
4 This ACL defines lunch as a time on the days Monday, Tuesday, ... Friday between noon
and 3 p.m.
http_access allow ACL_NAME

http_access defines who is allowed to use the proxy and who can access what on the
Internet. For this, ACLs must be defined. localhost and all have already been defined
above for which you can deny or allow access via deny or allow . A list containing any
number of http_access entries can be created, processed from top to bottom. Depending
on which occurs rst, access is allowed or denied to the respective URL. The last entry
should always be http_access deny all . In the following example, localhost has free
access to everything while all other hosts are denied access completely:
http_access allow localhost

http_access deny all
In another example using these rules, the group teachers always has access to the Inter-
net. The group students only has access between Monday and Friday during lunch time:
http_access deny localhost

http_access allow teachers
http_access allow students lunch time
For readability, within the configuration le /etc/squid/squid.conf , specify all

http_access options as a block.
url_rewrite_program PATH
With this option, specify a URL rewriter. For example, this can be squidGuard ( /usr/
sbin/squidGuard ) which allows blocking unwanted URLs. With it, Internet access can
be individually controlled for various user groups using proxy authentication and the ap-
propriate ACLs.
For more information on squidGuard, see Section 33.8, “squidGuard”.

auth_param basic program PATH
If users must be authenticated on the proxy, set a corresponding program, such as /usr/
sbin/pam_auth . When accessing pam_auth for the rst time, the user sees a login window
in which they need to specify a user name and a password. In addition, you need an ACL,
so only clients with a valid login can use the Internet:
acl password proxy_auth REQUIRED
http_access allow password

In the acl proxy_auth option, using REQUIRED means that all valid user names are
accepted. REQUIRED can also be replaced with a list of permitted user names.
ident_lookup_access allow ACL_NAME

With this option, have an ident request run to nd each user's identity for all clients defined
by an ACL of the type src . Alternatively, use this for all clients, apply the predefined ACL
all as the ACL_NAME .
All clients covered by ident_lookup_access must run an ident daemon. On Linux, you
can use pidentd (package pidentd ) as the ident daemon. For other operating systems,
free software is usually available. To ensure that only clients with a successful ident lookup
are permitted, define a corresponding ACL:
acl identhosts ident REQUIRED
http_access allow identhosts

In the acl identhosts ident option, using REQUIRED means that all valid user names
are accepted. REQUIRED can also be replaced with a list of permitted user names.
Using ident can slow down access time, because ident lookups are repeated for each
request.

33.6 Configuring a Transparent Proxy
The usual way of working with proxy servers is as follows: the Web browser sends requests to a
certain port of the proxy server and the proxy always provides these required objects, regardless
of whether they are in its cache. However, in some cases the transparent proxy mode of Squid
makes sense:
If, for security reasons, it is recommended that all clients use a proxy to surf the Internet.
If all clients must use a proxy, regardless of whether they are aware of it.
If the proxy in a network is moved, but the existing clients need to retain their old con-
figuration.
A transparent proxy intercepts and answers the requests of the Web browser, so the Web brows-
er receives the requested pages without knowing where they are coming from. As the name
indicates, the entire process is transparent to the user.
PROCEDURE 33.1: SQUID AS A TRANSPARENT PROXY (COMMAND LINE)
1. In /etc/squid/squid.conf , on the line of the option http_port add the parameter

transparent :
http_port 3128 transparent
2. Restart Squid:
tux > sudo systemctl restart squid
3. Set up SuSEFirewall2 to redirect HTTP traffic to the port given in http_proxy (in the
example above, that was port 3128). To do so, edit the configuration le /etc/syscon-
fig/SuSEfirewall2 .
This example assumes that you are using the following devices:
Device pointing to the Internet: FW_DEV_EXT="eth1"
Device pointing to the network: FW_DEV_INT="eth0"
Define ports and services (see /etc/services ) on the firewall that are accessed from
untrusted (external) networks such as the Internet. In this example, only Web services are
offered to the outside:
FW_SERVICES_EXT_TCP="www"
482 Configuring a Transparent Proxy SLES 12 SP3

Define ports or services (see /etc/services ) on the firewall that are accessed from the
secure (internal) network, both via TCP and UDP:
FW_SERVICES_INT_TCP="domain www 3128"

FW_SERVICES_INT_UDP="domain"
This allows accessing Web services and Squid (whose default port is 3128 ). The service
“domain” stands for DNS (domain name service). This service is commonly used. Other-
wise, simply remove domain from the above entries and set the following option to no :
FW_SERVICE_DNS="yes"
The option FW_REDIRECT is very important, as it is used for the actual redirection of HTTP
traffic to a specific port. The configuration le explains the syntax in a comment above
the option:
# Format:
# list of <source network>[,<destination network>,<protocol>[,dport[:lport]]
# Where protocol is either tcp or udp. dport is the original
# destination port and lport the port on the local machine to
# redirect the traffic to
#
# An exclamation mark in front of source or destination network
# means everything EXCEPT the specified network
That is:
1. Specify the IP address and the netmask of the internal networks accessing the proxy
firewall.
2. Specify the IP address and the netmask to which these clients send their requests.
In the case of Web browsers, specify the networks 0/0 , a wild card that means “to
everywhere.”
3. Specify the original port to which these requests are sent.
4. Specify the port to which all these requests are redirected. In the example below,
only Web services (port 80 ) are redirected to the proxy port (port 3128 ). If there are
more networks or services to add, separate them with a space in the respective entry.

Because Squid supports protocols other than HTTP, you can also redirect requests
from other ports to the proxy. For example, you can also redirect port 21 (FTP) and
port 443 (HTTPS or SSL).
Therefore, for a Squid configuration, you could use:
FW_REDIRECT="192.168.0.0/16,0/0,tcp,80,3128"
4. In the configuration le /etc/sysconfig/SuSEfirewall2 , make sure that the entry

START_FW is set to "yes" .
5. Restart SuSEFirewall2:
tux > sudo systemctl restart SuSEfirewall2
6. To verify that everything is working properly, check the Squid log les in /var/log/
squid/access.log . To verify that all ports are correctly configured, perform a port scan
on the machine from any computer outside your network. Only the Web services (port
80) should be open. To scan the ports with nmap , use:
nmap -O IP_ADDRESS
PROCEDURE 33.2: SQUID AS A TRANSPARENT PROXY (YAST)
1. Start the YaST Squid module:
a. In the Start-Up tab, enable Open Ports in Firewall. Click Firewall Details to select the
interfaces on which to open the port. This option is available only if the Firewall
is enabled.
b. In the HTTP Ports tab, select the rst line with the port 3128 .
c. Click the Edit button. A small window appear where you can edit the current HTTP
port. Select Transparent.
d. Finish with Ok.
2. Configure the Firewall settings as described in Step 3 of Procedure 33.1, “Squid as a Trans-

parent Proxy (Command Line)”.

33.7 Using the Squid Cache Manager CGI Interface
(cachemgr.cgi)
The Squid cache manager CGI interface ( cachemgr.cgi ) is a CGI utility for displaying statistics
about the memory usage of a running Squid process. It is also a convenient way to manage the
cache and view statistics without logging the server.
PROCEDURE 33.3: SETTING UP cachemgr.cgi
1. Make sure the Apache Web server is running on your system. Configure Apache as de-
scribed in Chapter 31, The Apache HTTP Server. In particular, see Section 31.5, “Enabling CGI
Scripts”. To check whether Apache is already running, use:
tux > sudo systemctl status apache2
If inactive is shown, you can start Apache with the SUSE Linux Enterprise Server default
settings:
tux > sudo systemctl start apache2
2. Now enable cachemgr.cgi in Apache. To do so, create a configuration le for a Scrip-
tAlias .
Create the le in the directory /etc/apache2/conf.d and name it cachemgr.conf . In
it, add the following:
ScriptAlias /squid/cgi-bin/ /usr/lib64/squid/
<Directory "/usr/lib64/squid/">
Options +ExecCGI
AddHandler cgi-script .cgi
Require host HOST_NAME
</Directory>
Replace HOST_NAME with the host name of the computer you want to access cachemgr.c-
gi from. This allows only your computer to access cachemgr.cgi . To allow access from
anywhere, use Require all granted instead.
3. If Squid and your Apache Web server run on the same computer, there should be no
changes that need to be made to /etc/squid/squid.conf . However, verify that /
etc/squid/squid.conf contains the following lines:
http_access allow manager localhost
485 Using the Squid Cache Manager CGI Interface (cachemgr.cgi) SLES 12 SP3
http_access deny manager
These lines allow you to access the manager interface from your own computer ( lo-
calhost ) but not from elsewhere.
If Squid and your Apache Web server run on different computers, you need to add
extra rules to allow access from the CGI script to Squid. Define an ACL for your server
(replace WEB_SERVER_IP with the IP address of your Web server):
acl webserver src WEB_SERVER_IP/255.255.255.255
Make sure the following rules are in the configuration le. Compared to the default
configuration, only the rule in the middle is new. However, the sequence is impor-
tant.
http_access allow manager localhost

http_access allow manager webserver
http_access deny manager
4. (Optional) Optionally, you can configure one or more passwords for cachemgr.cgi . This
also allows access to more actions such as closing the cache remotely or viewing more
information about the cache. For this, configure the options cache_mgr and cachem-
gr_passwd with one or more password for the manager and a list of allowed actions.
For example, to explicitly enable viewing the index page, the menu, 60-minute average
of counters without authentication, to enable toggling offline mode using the password
secretpassword , and to completely disable everything else, use the following configu-
ration:
cache_mgr user
cachemgr_passwd none index menu 60min
cachemgr_passwd secretpassword offline_toggle
cachemgr_passwd disable all
cache_mgr defines a user name. cache_mgr defines which actions are allowed using
which password.
The keywords none and disable are special: none removes the need for a password,
disable disables functionality outright.
The full list of actions can be best seen after logging in to cachemgr.cgi . To nd out
how the operation needs to be referenced in the configuration le, see the string after
&operation= in the URL of the action page. all is a special keyword meaning all actions.
486 Using the Squid Cache Manager CGI Interface (cachemgr.cgi) SLES 12 SP3
5. Reload Squid and Apache after the configuration le changes:
tux > sudo systemctl reload squid
6. To view the statistics, go to the cachemgr.cgi page that you set up before. For example,
it could be http://webserver.example.org/squid/cgi-bin/cachemgr.cgi .
Choose the right server, and, if set, specify user name and password. Then click Continue
and browse through the different statistics.
33.8 squidGuard
This section is not intended to explain an extensive configuration of squidGuard, only to intro-
duce it and give some advice for using it. For more in-depth configuration issues, refer to the
squidGuard Web site at http://www.squidguard.org .
squidGuard is a free (GPL), flexible, and fast filter, redirector, and access controller plug-in for
Squid. It lets you define multiple access rules with different restrictions for different user groups
on a Squid cache. squidGuard uses Squid's standard redirector interface. squidGuard can do the
following:
Limit Web access for some users to a list of accepted or well-known Web servers or URLs.
Block access to some listed or blacklisted Web servers or URLs for some users.
Block access to URLs matching a list of regular expressions or words for some users.
Redirect blocked URLs to an “intelligent” CGI-based information page.
Redirect unregistered users to a registration form.
Redirect banners to an empty GIF.
Use different access rules based on time of day, day of the week, date, etc.
Use different rules for different user groups.
squidGuard and Squid cannot be used to:
Edit, filter, or censor text inside documents.
Edit, filter, or censor HTML-embedded scripts such as JavaScript.
PROCEDURE 33.4: SETTING UP SQUIDGUARD
1. Before it can be used, install squidGuard .
487 squidGuard SLES 12 SP3

2. Provide a minimal configuration le as /etc/squidguard.conf . Find configuration ex-
amples in http://www.squidguard.org/Doc/examples.html . Experiment later with more
complicated configuration settings.
3. Next, create an “access denied” HTML page or CGI page that Squid can redirect to if the
client requests a blacklisted Web site. Using Apache is strongly recommended.
4. Now, configure Squid to use squidGuard. Use the following entry in the /etc/squid/
squid.conf le:
redirect_program /usr/bin/squidGuard
5. Another option called redirect_children configures the number of “redirect” (in this
case squidGuard) processes running on the machine. The more processes you set, the more
RAM is required. Try low numbers rst, for example, 4 :
redirect_children 4
6. Last, have Squid load the new configuration by running systemctl reload squid . Now,
test your settings with a browser.
33.9 Cache Report Generation with Calamaris

Calamaris is a Perl script used to generate reports of cache activity in ASCII or HTML format. It
works with native Squid access log les. The Calamaris home page is located at http://cord.de/
calamaris-english . This tool does not belong to the SUSE Linux Enterprise Server default in-
stallation scope—to use it, install the calamaris package.
Log in as root , then enter:
cat access1.log [access2.log access3.log] | calamaris OPTIONS > reportfile
When using more than one log le, make sure they are chronologically ordered, with older les
listed rst. This can be achieved by either listing the les one after the other as in the example
above, or by using access{1..3}.log .
calamaris takes the following options:
-a
output all available reports
488 Cache Report Generation with Calamaris SLES 12 SP3

-w
output as HTML report
-l
include a message or logo in report header
More information about the various options can be found in the program's manual page with
man calamaris .
A typical example is:
cat access.log.{10..1} access.log | calamaris -a -w \

> /usr/local/httpd/htdocs/Squid/squidreport.html
This puts the report in the directory of the Web server. Apache is required to view the reports.

Visit the home page of Squid at http://www.squid-cache.org/ . Here, nd the “Squid User Guide”
and a very extensive collection of FAQs on Squid.
In addition, mailing lists are available for Squid at http://www.squid-cache.org/Support/mail-
ing-lists.html .

34 Web Based Enterprise Management Using SFCB
34.1 Introduction and Basic Concept

SUSE® Linux Enterprise Server (SLES) provides a collection of open standards based tools for the
unified management of disparate computing systems and environments. Our enterprise solutions
implement the standards proposed by the Distributed Management Task Force. The following
paragraphs describe their basic components.
Distributed Management Task Force, Inc (DMTF) is the industry organization which leads the
development of management standards for enterprise and Internet environments. Their goal is
to unify management standards and initiatives, and to enable more integrated, cost effective and
interoperable management solutions. DMTF standards provide common system management
components for control and communication. Their solutions are independent of platforms and
technologies. Web Based Enterprise Management and Common Information Model are one of their
key technologies.
Web Based Enterprise Management (WBEM) is a set of management and Internet standard tech-
nologies. WBEM is developed to unify the management of enterprise computing environments.
It provides the ability for the industry to deliver a well-integrated collection of management
tools using Web technologies. WBEM consists of the following standards:
A data model: the Common Information Model (CIM) standard
An encoding specification: CIM-XML Encoding Specification
A transport mechanism: CIM operations over HTTP
Common Information Model is a conceptual information model that describes system manage-
ment. It is not bound to a particular implementation and enables the interchange of management
information between management systems, networks, services and applications. There are two
parts to CIM — the CIM Specification and the CIM Schema.
490 Introduction and Basic Concept SLES 12 SP3

The CIM Specification describes the language, naming and meta schema. The meta schema
is a formal definition of the model. It defines the terms used to express the model and
their usage and semantics. The elements of the meta schema are classes, properties, and
methods. The meta schema also supports indications and associations as types of classes, and
references as types of properties.
The CIM Schema provides the actual model descriptions. It supplies a set of classes with
properties and associations that provide a well understood conceptual framework within
which it is possible to organize the available information about the managed environment.
The Common Information Model Object Manager (CIMOM) is a CIM object manager or, more
specifically, an application that manages objects according to the CIM standard. CIMOM man-
ages communication between CIMOM providers and a CIM client, where the administrator man-
ages the system.
CIMOM providers are software performing specific tasks within the CIMOM that are requested
by client applications. Each provider instruments one or more aspects of the CIMOM's schema.
These providers interact directly with the hardware.
Standards Based Linux Instrumentation for Manageability (SBLIM) is a collection of tools designed
to support Web-Based Enterprise Management (WBEM). SUSE® Linux Enterprise Server uses the
open source CIMOM (or CIM server) from the SBLIM project called Small Footprint CIM Broker .
Small Footprint CIM Broker is a CIM server intended for use in resource-limited or embedded envi-
ronments. It is designed to be modular and lightweight at the same time. Its based on open stan-
dards and it supports CMPI providers, CIM-XML encoding, and Managed Object Format (MOF).
It is highly configurable and performs stability even if the provider crashes. It is also easily ac-
cessible as it supports various transport protocols, such as HTTP, HTTPS, Unix domain sockets,
Service Location Protocol (SLP), and Java Database Connectivity (JDBC).
491 Introduction and Basic Concept SLES 12 SP3

34.2 Setting Up SFCB
To set up the Small Footprint CIM Broker (SFCB) environment, make sure the Web-Based Enter-
prise Management pattern in YaST is selected during SUSE Linux Enterprise Server installation.
Alternatively, select it as a component to install on a server that is already running. Make sure
the following packages are installed on your system:
cim-schema, Common Information Model (CIM) Schema

Contains the Common Information Model (CIM). CIM is a model for describing overall
management information in a network or enterprise environments. CIM consists of a spec-
ification and a schema. The specification defines the details for integration with other
management models. The schema provides the actual model descriptions.
cmpi-bindings-pywbem
Contains an adapter to write and run CMPI-type CIM providers in Python.
cmpi-pywbem-base
Contains base system CIM providers.
cmpi-pywbem-power-management
Contains power management providers based on DSP1027.
python-pywbem
Contains a Python module for making CIM operation calls through the WBEM protocol to
query and update managed objects.
cmpi-provider-register, CIMOM neutral provider registration utility

Contains a utility allowing CMPI provider packages to register with whatever CIMOM
happens to be present on the system.
sblim-sfcb, Small Footprint CIM Broker

Contains Small Footprint CIM Broker. It is a CIM server conforming to the CIM Operations
over HTTP protocol. It is robust, with low resource consumption and, therefore, specifical-
ly suited for embedded and resource constrained environments. SFCB supports providers
written against the Common Manageability Programming Interface (CMPI).
sblim-sfcc
Contains Small Footprint CIM Client library runtime libraries.
sblim-wbemcli
Contains WBEM command line interface. It is a stand-alone command line WBEM client
especially suited for basic systems management tasks.
492 Setting Up SFCB SLES 12 SP3

smis-providers
Contains providers to instrument the volumes and snapshots on the Linux le system.
These are based on SNIA's SMI-S volume management profile and Copy Services profile
respectively.
FIGURE 34.1: PACKAGE SELECTION FOR WEB-BASED ENTERPRISE MANAGEMENT PATTERN
34.2.1 Installing Additional Providers

SUSE® Linux Enterprise Server software repository includes additional CIM providers that are
not found in the Web-Based Enterprise Management installation pattern. You can easily get
their list and installation status by searching the pattern sblim-cmpi- in the YaST software
installation module. These providers cover various tasks of system management, such as DHCP,
NFS, or kernel parameters setting. It is useful to install those providers which you are going
to use with SFCB.
493 Installing Additional Providers SLES 12 SP3

FIGURE 34.2: PACKAGE SELECTION OF ADDITIONAL CIM PROVIDERS
34.2.2 Starting, Stopping and Checking Status for SFCB

CIM server sfcbd daemon is installed together with Web-Based Enterprise Management software
and is started by default at system start-up. The following table explains how to start, stop and
check status for sfcbd.
TABLE 34.1: COMMANDS FOR MANAGING SFCBD
Task Linux Command
Start sfcbd Enter systemctl start sfcb as root in

the command line.
Stop sfcbd Enter systemctl stop sfcb as root in the

command line.
Check sfcbd status Enter systemctl status sfcb as root in

the command line.
494 Starting, Stopping and Checking Status for SFCB SLES 12 SP3
34.2.3 Ensuring Secure Access
The default setup of SFCB is relatively secure. However, check that the access to SFCB compo-
nents is as secure as required for your organization.
34.2.3.1 Certificates
Secure Socket Layers (SSL) transports require a certificate for secure communication to occur.
When SFCB is installed, it has a self-signed certificate generated.
You can replace the path to the default certificate with a path to a commercial or self-signed
one by changing the sslCertificateFilePath: PATH_FILENAME setting in /etc/sfcb/
sfcb.cfg . The le must be in PEM format.
The default generated server certificate is in the following location:

/etc/sfcb/server.pem
Note: Paths to SSL Certificates

The default generated certificate les servercert.pem and serverkey.pem are stored
under /etc/ssl/servercerts directory. Files /etc/sfcb/client.pem , /etc/sfcb/
file.pem and /etc/sfcb/server.pem are symbolic links to these les.
To generate a new certificate, enter the following command as root in the command line:
tux > sh /usr/share/sfcb/genSslCert.sh

Generating SSL certificates in .
Generating a 2048 bit RSA private key
...................................................................+++
.+++
writing new private key to '/var/tmp/sfcb.0Bjt69/key.pem'
-----
By default, the script generates certificates client.pem , file.pem and server.pem in the
current working directory. If you want the script to generate the certificates in /etc/sfcb
directory, you need to append it to the command. If these les already exist, a warning message
is displayed and the old certificates are not overwritten.
tux > sh /usr/share/sfcb/genSslCert.sh /etc/sfcb

Generating SSL certificates in .
495 Ensuring Secure Access SLES 12 SP3

WARNING: server.pem SSL Certificate file already exists.
old file will be kept intact.
WARNING: client.pem SSL Certificate trust store already exists.
old file will be kept intact.
You must remove the old certificates from the le system and run the command again.
To change the way SFCB uses certificates, see Section 34.2.3.3, “Authentication”.
34.2.3.2 Ports
By default, SFCB is configured to accept all communications through the secure port 5989. The
following paragraphs explain the communication port setup and recommended configuration.
Port 5989 (secure)

The secure port that SFCB communications use via HTTPS services. This is the default. With
this setting, all communications between the CIMOM and client applications are encrypted
when sent over the Internet between servers and workstations. Users must authenticate
with the client application to reach SFCB server. We recommend that you keep this setting.
For the SFCB CIMOM to communicate with the necessary applications, this port must be
open on routers and firewalls if they are present between the client application and the
nodes being monitored.
Port 5988 (insecure)

The insecure port that SFCB communications use via HTTP services. This setting is disabled
by default. With this setting, all communications between the CIMOM and client applica-
tions are open for review when sent over the Internet between servers and workstations by
anyone, without any authentication. We recommend that you use this setting only when
attempting to debug a problem with the CIMOM. When the problem is resolved, disable
the non-secure port option back. For the SFCB CIMOM to communicate with the necessary
applications that require non-secure access, this port must be open in routers and firewalls
between the client application and the nodes being monitored.
If you want to change the default port assignments, see Section 34.2.3.2, “Ports”.
496 Ensuring Secure Access SLES 12 SP3

34.2.3.3 Authentication
SFCB supports HTTP basic authentication and authentication based on client certificates (HTTP
over SSL connections). Basic HTTP authentication is enabled by specifying doBasicAuth=true
in the SFCB configuration le ( /etc/sfcb/sfcb.cfg by default). SUSE® Linux Enterprise
Server installation of SFCB supports Pluggable Authentication Modules (PAM) approach; there-
fore the local root user can authenticate to the SFCB CIMOM with local root user credentials.
If the sslClientCertificate configuration property is set to accept or require , the SFCB
HTTP adapter will request a certificate from clients when connecting via HTTP over SSL
(HTTPS). If require is specified, the client must provide a valid certificate (according to the
client trust store specified via sslClientTrustStore ). If the client fails to do so, the connec-
tion will be rejected by the CIM server.
The setting sslClientCertificate=accept may not be obvious. It is very useful if both basic
and client certificate authentication are allowed. If the client can provide a valid certificate,
HTTPS connection will be established and the basic authentication procedure will not be ex-
ecuted. If this function cannot verify the certificate, the HTTP basic authentication will take
place instead.
34.3 SFCB CIMOM Configuration

SFCB is a lightweight implementation of the CIM server, but it is also highly configurable. Several
options can control its behavior. You can control the SFCB server in three ways:
by setting appropriate environment variables
by using command line options
by changing its configuration le
34.3.1 Environment Variables

Several environment variables directly affect the behavior of SFCB. You need to restart the SFCB
daemon by systemctl restart sfcb for these changes to take effect.
PATH
Specifies the path to the sfcbd daemon and utilities.
497 SFCB CIMOM Configuration SLES 12 SP3

LD_LIBRARY_PATH
Specifies the path to the sfcb runtime libraries. Alternatively, you can add this path to the
system-wide dynamic loader configuration le /etc/ld.so.conf .
SFCB_PAUSE_PROVIDER
Specifies the provider name. The SFCB server pauses after the provider is loaded for the
rst time. You can then attach a runtime debugger to the provider's process for debugging
purposes.
SFCB_PAUSE_CODEC
Specifies the name of the SFCB codec (currently supports only http . The SFCB server
pauses after the codec is loaded for the rst time. You can then attach a runtime debugger
to the process.
SFCB_TRACE
Specifies the level of debug messages for SFCB. Valid values are 0 (no debug messages),
or 1 (key debug messages) to 4 (all debug messages). Default is 1.
SFCB_TRACE_FILE
By default, SFCB outputs its debug messages to standard error output (STDERR). Setting
this variable causes the debug messages to be written to a specified le instead.
SBLIM_TRACE
Specifies the level of debug messages for SBLIM providers. Valid values are 0 (no debug
messages), or 1 (key debug messages) to 4 (all debug messages).
SBLIM_TRACE_FILE
By default, SBLIM provider outputs its trace messages to STDERR. Setting this variable
causes the trace messages to be written to a specified le instead.
34.3.2 Command Line Options

sfcbd , the SFCB daemon, has several command line options that switch particular runtime
features on or o. Enter these options when SFCB daemon starts.
-c, --config-file = FILE

When SFCB daemon starts, it reads its configuration from /etc/sfcb/sfcb.cfg by de-
fault. With this option, you can specify an alternative configuration le.
498 Command Line Options SLES 12 SP3

-d, --daemon
Forces sfcbd and its child processes to run in the background.
-s, --collect-stats
Turns on runtime statistics collecting. Various sfcbd runtime statistics will be written to
the sfcbStat le in the current working directory. By default, no statistics are collected.
-l, --syslog-level = LOGLEVEL

Specifies the level of verbosity for the system logging facility. LOGLEVEL can be one of
LOG_INFO, LOG_DEBUG, or LOG_ERR, which is the default.
-k, --color-trace = LOGLEVEL

Prints trace output in a different color per process for easier debugging.
-t, --trace-components = NUM

Activates component-level tracing messages, where NUM is an OR-ed bitmask integer that
defines which component to trace. After you specify -t ? , it lists all the components and
their associated integer bitmask:
tux > sfcbd -t ?

--- Traceable Components: Int Hex
--- providerMgr: 1 0x0000001
--- providerDrv: 2 0x0000002
--- cimxmlProc: 4 0x0000004
--- httpDaemon: 8 0x0000008
--- upCalls: 16 0x0000010
--- encCalls: 32 0x0000020
--- ProviderInstMgr: 64 0x0000040
--- providerAssocMgr: 128 0x0000080
--- providers: 256 0x0000100
--- indProvider: 512 0x0000200
--- internalProvider: 1024 0x0000400
--- objectImpl: 2048 0x0000800
--- xmlIn: 4096 0x0001000
--- xmlOut: 8192 0x0002000
--- sockets: 16384 0x0004000
--- memoryMgr: 32768 0x0008000
--- msgQueue: 65536 0x0010000
--- xmlParsing: 131072 0x0020000
--- responseTiming: 262144 0x0040000
--- dbpdaemon: 524288 0x0080000
--- slp: 1048576 0x0100000
A useful value that reveals the internal functions of sfcbd but does not generate too many
messages, is -t 2019 .
499 Command Line Options SLES 12 SP3

34.3.3 SFCB Configuration File
SFCB reads its runtime configuration from configuration le /etc/sfcb/sfcb.cfg after start-
ing up. This behavior can be overridden using -c option at start-up.
The configuration le contains option : VALUE pairs, one per line. When making changes to this
le, you can use any text editor that saves the le in a format that is native to the environment
you are using.
Any setting that has the options commented out with a number sign (#) uses the default setting.
The following list of options may not be complete. See the content of /etc/sfcb/sfcb.cfg
and /usr/share/doc/packages/sblim-sfcb/README for their complete list.
34.3.3.1 httpPort
Purpose
Specifies the local port value that sfcbd should listen to receive HTTP (insecure) requests from
CIM clients. Default is 5988 .
Syntax
httpPort: PORT_NUMBER
34.3.3.2 enableHttp
Purpose
Specifies whether SFCB should accept HTTP client connections. Default is false .
Syntax
enableHttp: OPTION
Option Description
true Enables HTTP connections.
500 SFCB Configuration File SLES 12 SP3

Option Description
false Disables HTTP connections.
34.3.3.3 httpProcs
Purpose
Specifies the maximum number of simultaneous HTTP client connections before new incoming
HTTP requests are blocked. Default is 8 .
Syntax
httpProcs: MAX_NUMBER_OF_CONNECTIONS
34.3.3.4 httpUserSFCB, httpUser
Purpose
These options control what user the HTTP server will run under. If httpUserSFCB is true ,
HTTP will run under the same user as the SFCB main process. If it is false the user name
specified for httpUser will be used. This setting is used for both HTTP and HTTPS servers.
httpUser must be specified if httpUserSFCB is set to false . the default is true .
Syntax
httpUserSFCB: true
34.3.3.5 httpLocalOnly
Purpose
Specifies whether to limit HTTP requests to localhost only. Default is false .

Syntax
httpLocalOnly: false
34.3.3.6 httpsPort
Purpose
Specifies the local port value where sfcbd listens for HTTPS requests from CIM clients. Default
is 5989 .
Syntax
httpsPort: port_number
34.3.3.7 enableHttps
Purpose
Specifies if SFCB will accept HTTPS client connections. Default is true .
Syntax
enableHttps: option
Option Description
true Enables HTTPS connections.
false Disables HTTPS connections.

34.3.3.8 httpsProcs
Purpose
Specifies the maximum number of simultaneous HTTPS client connections before new incoming
HTTPS requests are blocked. Default is 8 .
Syntax
httpsProcs: MAX_NUMBER_OF_CONNECTIONS
34.3.3.9 enableInterOp
Purpose
Specifies if SFCB will provide the interop namespace for indication support. Default is true .
Syntax
enableInterOp: OPTION
Option Description
true Enables interop namespace.
false Disables interop namespace.
34.3.3.10 provProcs
Purpose
Specifies the maximum number of simultaneous provider processes. After this point, if a new
incoming request requires loading a new provider, then one of the existing providers will rst
be automatically unloaded. Default is 32 .

Syntax
provProcs: MAX_NUMBER_OF_PROCS
34.3.3.11 doBasicAuth
Purpose
Switches basic authentication on or o based on the client user identifier before it accepts the
request. Default value is true which means that basic client authentication is performed.
Syntax
doBasicAuth: OPTION
Option Description
true Enables basic authentication.
false Disables basic authentication.
34.3.3.12 basicAuthLib
Purpose
Specifies the local library name. The SFCB server loads the library to authenticate the client user
identifier. Default is sfcBasicPAMAuthentication .
Syntax
provProcs: MAX_NUMBER_OF_PROCS

34.3.3.13 useChunking
Purpose
This option switches the use of HTTP/HTTPS “chunking” on or o. If switched on, the server
will return large volumes of response data to the client in smaller “chunks”, rather than buer
the data and send it back all in one chunk. Default is true .
Syntax
useChunking: OPTION
Option Description
true Enables HTTP/HTTPS data chunking.
false Disables HTTP/HTTPS data chunking.
34.3.3.14 keepaliveTimeout
Purpose
Specifies the maximum time in seconds that SFCB HTTP process waits between two requests on
one connection before it terminates. Setting it to 0 disables HTTP keep-alive. Default is 0 .
Syntax
keepaliveTimeout: SECS
34.3.3.15 keepaliveMaxRequest
Purpose
Specifies the maximum number of consecutive requests on one connection. Setting it to 0 dis-
ables HTTP keep-alive. Default value is 10 .

Syntax
keepaliveMaxRequest: NUMBER_OF_CONNECTIONS
34.3.3.16 registrationDir
Purpose
Specifies the registration directory, which contains the provider registration data, the staging
area, and the static repository. Default is /var/lib/sfcb/registration .
Syntax
registrationDir: DIR
34.3.3.17 providerDirs
Purpose
Specifies a space-separated list of directories where SFCB is searching for provider libraries.
Default is /usr/lib64 /usr/lib64 /usr/lib64/cmpi .
Syntax
providerDirs: DIR
34.3.3.18 providerSampleInterval
Purpose
Specifies the interval in seconds at which the provider manager is checking for idle providers.
Default is 30 .

Syntax
providerSampleInterval: SECS
34.3.3.19 providerTimeoutInterval
Purpose
Specifies the interval in seconds before an idle provider gets unloaded by the provider manager.
Default is 60 .
Syntax
providerTimeoutInterval: SECS
34.3.3.20 providerAutoGroup
Purpose
If the provider registration le does not specify any other group, and the option is set to true ,
all providers in the same shared library are executed in the same process.
Syntax
providerAutoGroup: OPTION
Option Description
true Enables grouping of providers.
false Disables grouping of providers.

34.3.3.21 sslCertificateFilePath
Purpose
Specifies the name of the le that contains the server certificate. The le must be in PEM (Privacy
Enhanced Mail, RFC 1421 and RFC 1424) format. This le is only required if enableHttps is
set to true . Default is /etc/sfcb/server.pem .
Syntax
sslCertificateFilePath: PATH
34.3.3.22 sslKeyFilePath
Purpose
Specifies the name of the le that contains the private key for the server certificate. The le
must be in PEM format and may not be protected by passphrase. This le is only required if
enableHttps is set to true . Default is /etc/sfcb/file.pem .
Syntax
sslKeyFilePath: PATH
34.3.3.23 sslClientTrustStore
Purpose
Specifies the name of the le that contains either the CA or self-signed certificates of the clients.
This le must be in PEM format and is only required if sslClientCertificate is set to accept
or require . Default is /etc/sfcb/client.pem .

Syntax
sslClientTrustStore: PATH
34.3.3.24 sslClientCertificate
Purpose
Specifies the way SFCB handles client certificate based authentication. If set to ignore , it will
not request a certificate from the client. If set to accept it will request a certificate from the
client but will not fail if the client does not present one. If set to require , it will refuse the
client connection if the client does not present a certificate. Default value is ignore .
Syntax
sslClientCertificate: OPTION
Option Description
ignore Disables requesting a client certificate.
accept Disables requesting a client certificate.

Will not fail if no certificate is present.
require Refuses the client connection without a valid

certificate.
34.3.3.25 certificateAuthLib
Purpose
Specifies the name of the local library to request for the user authentication based on client
certificate. This is only requested if sslClientCertificate is not set to ignore . Default value
is sfcCertificateAuthentication .

Syntax
certificateAuthLib: FILE
34.3.3.26 traceLevel
Purpose
Specifies the trace level for SFCB. You can override it by setting environment variable
SFCB_TRACE_LEVEL . Default value is 0 .
Syntax
traceLevel: NUM_LEVEL
34.3.3.27 traceMask
Purpose
Specifies the trace mask for SFCB. you can override it by the command line option --trace-
components . Default value is 0 .
Syntax
traceMask: MASK
34.3.3.28 traceFile
Purpose
Specifies the trace le for SFCB. You can override it by setting environment variable
SFCB_TRACE_FILE . Default value is stderr (standard error output).

Syntax
traceFile: OUTPUT
34.4 Advanced SFCB Tasks

This chapter covers more advanced topics related to SFCB usage. To understand them, you need
to have basic knowledge of the Linux le system and experience with the Linux command line.
This chapter includes the following tasks:
Installing CMPI providers
Testing SFCB
Using wbemcli CIM client
34.4.1 Installing CMPI Providers

To install a CMPI provider, you need to make sure that its shared library is copied into one of the
directories specified by providerDirs configuration option, see Section 34.3.3.17, “providerDirs”.
The provider must also be properly registered using sfcbstage and sfcbrepos commands.
The provider package is usually prepared for SFCB, so that its installation takes care of the
proper registration. Most SBLIM providers are prepared for SFCB.
34.4.1.1 Class Repository

Class repository is a place where SFCB stores information about CIM classes. It usually consists
of a directory tree with namespace components. Typical CIM namespaces are root/cimv2 or
root/interop , which respectively translate to the class repository directory path on the le
system
/var/lib/sfcb/registration/repository/root/cimv2
and
/var/lib/sfcb/registration/repository/root/interop
Each namespace directory contains the le classSchemas . The le has a compiled binary rep-
resentation of all the CIM classes registered under that namespace. It also contains necessary
information about their CIM superclasses.
511 Advanced SFCB Tasks SLES 12 SP3

In addition, each namespace directory may contain a le qualifiers which contains all qual-
ifiers for the namespace. When sfcbd restarts, the class provider will scan the directory /var/
lib/sfcb/registration/repository/ and all its subdirectories to determine the registered
namespaces. Then classSchemas les are decoded and the class hierarchy for each namespace
is built.
34.4.1.2 Adding New Classes

SFCB cannot make live CIM class manipulations. You need to add, change or remove classes
offline and restart SFCB service with systemctl restart sfcb to register the changes.
To store providers class and registration information, SFCB uses a place called staging area. On
SUSE® Linux Enterprise Server systems, it is the directory structure under /var/lib/sfcb/
stage/ .
To add a new provider, you need to:
Copy the provider class definition les to the ./mofs subdirectory of staging area directory
( /var/lib/sfcb/stage/mofs ).
Copy a registration le which contains the name of the class or classes and type of provider,
and the name of the executable library le into the ./regs subdirectory.
There are two default “mof” (class definition) les in the staging directory: indication.mof
and interop.mof . MOF les under the root stage directory /var/lib/sfcb/stage/mofs will
be copied into each namespace after running sfcbrepos command. The interop.mof will
only be compiled into the interop namespace.
The directory layout may look like the following example:
tux > ls /var/lib/sfcb/stage

default.reg mofs regs
tux > ls /var/lib/sfcb/stage/mofs

indication.mof root
tux > ls /var/lib/sfcb/stage/mofs/root

cimv2 interop suse virt
tux > ls -1 /var/lib/sfcb/stage/mofs/root/cimv2 | less

Linux_ABIParameter.mof
Linux_BaseIndication.mof
512 Installing CMPI Providers SLES 12 SP3

Linux_Base.mof
Linux_DHCPElementConformsToProfile.mof
Linux_DHCPEntity.mof
[..]
OMC_StorageSettingWithHints.mof
OMC_StorageVolumeDevice.mof
OMC_StorageVolume.mof
OMC_StorageVolumeStorageSynchronized.mof
OMC_SystemStorageCapabilities.mof
tux > ls -1 /var/lib/sfcb/stage/mofs/root/interop

ComputerSystem.mof
ElementConformsToProfile.mof
HostSystem.mof
interop.mof
Linux_DHCPElementConformsToProfile.mof
[..]
OMC_SMIElementSoftwareIdentity.mof
OMC_SMISubProfileRequiresProfile.mof
OMC_SMIVolumeManagementSoftware.mof
ReferencedProfile.mof
RegisteredProfile.mof
tux > ls -1 /var/lib/sfcb/stage/regs

AllocationCapabilities.reg
Linux_ABIParameter.reg
Linux_BaseIndication.reg
Linux_DHCPGlobal.reg
Linux_DHCPRegisteredProfile.reg
[..]
OMC_Base.sfcb.reg
OMC_CopyServices.sfcb.reg
OMC_PowerManagement.sfcb.reg
OMC_Server.sfcb.reg
RegisteredProfile.reg
tux > cat /var/lib/sfcb/stage/regs/Linux_DHCPRegisteredProfile.reg

[Linux_DHCPRegisteredProfile]
provider: Linux_DHCPRegisteredProfileProvider
location: cmpiLinux_DHCPRegisteredProfile
type: instance
namespace: root/interop
#
[Linux_DHCPElementConformsToProfile]
provider: Linux_DHCPElementConformsToProfileProvider
location: cmpiLinux_DHCPElementConformsToProfile

type: instance association
namespace: root/cimv2
#
[Linux_DHCPElementConformsToProfile]
provider: Linux_DHCPElementConformsToProfileProvider
location: cmpiLinux_DHCPElementConformsToProfile
type: instance association
namespace: root/interop
SFCB uses a custom provider registration le for each provider.
Note: SBLIM Providers Registration Files

All SBLIM providers on the SBLIM Web site already include a registration le that is used
to generate the .reg le for SFCB.
The format of SFCB registration le is:
[<class-name>]
provider: <provide-name>
location: <library-name>
type: [instance] [association] [method] [indication]
group: <group-name>
unload: never
namespace: <namespace-for-class> ...
where:
<class-name>
The CIM class name (required)
<provider-name>
The CMPI provider name (required)
<location-name>
The name of the provider library (required)
type
The type of the provider (required). This can be any combination of: instance , associ-
ation , method or indication .
<group-name>
Multiple providers can be grouped together and run under a single process to further min-
imize runtime resources. All providers registered under the same <group-name> will be
executed under the same process. By default each provider will be run as a separate process.

unload
Specifies the unload policy for the provider. Currently the only supported option is never ,
which specifies that the provider will not be monitored for idle times and will never be
unloaded. By default each provider will be unloaded when its idle times exceed the value
specified in the configuration le.
namespace
List of namespaces for which this provider can be executed. This is required, although for
most providers this will be root/cimv2 .
Once all the class definitions and provider registration les are stored in the staging area, you
need to rebuild the SFCB class repository with the command sfcbrepos -f .
You can add, change or remove classes this way. After rebuilding the class repository, restart
SFCB with command systemctl restart sfcb .
Alternatively, the SFCB package contains a utility that will copy provider class mof les and
registration les to the correct locations in the staging area.
sfcbstage -r [provider.reg] [class1.mof] [class2.mof] ...
After running this command you still need to rebuild the class repository and restart SFCB
service.
34.4.2 Testing SFCB

The SFCB package includes two testing scripts: wbemcat and xmltest .
wbemcat sends raw CIM-XML data via HTTP protocol to the specified SFCB host (localhost by
default) listening on port 5988. Then it displays the returned results. The following le contains
the CIM-XML representation of a standard EnumerateClasses request:
<?xml version="1.0" encoding="utf-8"?>

<CIM CIMVERSION="2.0" DTDVERSION="2.0">
<MESSAGE ID="4711" PROTOCOLVERSION="1.0">
<SIMPLEREQ>
<IMETHODCALL NAME="EnumerateClasses">
<LOCALNAMESPACEPATH>
<NAMESPACE NAME="root"/>
<NAMESPACE NAME="cimv2"/>
</LOCALNAMESPACEPATH>
<IPARAMVALUE NAME="ClassName">
<CLASSNAME NAME=""/>
</IPARAMVALUE>
515 Testing SFCB SLES 12 SP3

<IPARAMVALUE NAME="DeepInheritance">
<VALUE>TRUE</VALUE>
</IPARAMVALUE>
<IPARAMVALUE NAME="LocalOnly">
<VALUE>FALSE</VALUE>
</IPARAMVALUE>
<IPARAMVALUE NAME="IncludeQualifiers">
<VALUE>FALSE</VALUE>
</IPARAMVALUE>
<IPARAMVALUE NAME="IncludeClassOrigin">
<VALUE>TRUE</VALUE>
</IPARAMVALUE>
</IMETHODCALL>
</SIMPLEREQ>
</MESSAGE>
</CIM>
Sending this request to SFCB CIMOM returns a list of all supported classes for which there is a
registered provider. Suppose you save the le as cim_xml_test.xml .
tux > wbemcat cim_xml_test.xml | less

HTTP/1.1 200 OK
Content-Type: application/xml; charset="utf-8"
Content-Length: 337565
Cache-Control: no-cache
CIMOperation: MethodResponse
<?xml version="1.0" encoding="utf-8" ?>

<SIMPLERSP>
<IMETHODRESPONSE NAME="EnumerateClasses">
[..]
<CLASS NAME="Linux_DHCPParamsForEntity" SUPERCLASS="CIM_Component">
<PROPERTY.REFERENCE NAME="GroupComponent" REFERENCECLASS="Linux_DHCPEntity">
</PROPERTY.REFERENCE>
<PROPERTY.REFERENCE NAME="PartComponent" REFERENCECLASS="Linux_DHCPParams">
</PROPERTY.REFERENCE>
</CLASS>
</IRETURNVALUE>
</IMETHODRESPONSE>
</SIMPLERSP>
</MESSAGE>
</CIM>
The classes listed will vary depending on what providers are installed on your system.
516 Testing SFCB SLES 12 SP3

The second script xmltest is also used to send a raw CIM-XML test le to the SFCB CIMOM. It
then compares the returned results against a previously saved “OK” result le. If there does not
yet exist a corresponding “OK” le, it will be created for later use:
tux > xmltest cim_xml_test.xml

Running test cim_xml_test.xml ... OK
Saving response as cim_xml_test.OK
root # xmltest cim_xml_test.xml
Running test cim_xml_test.xml ... Passed
34.4.3 Command Line CIM Client: wbemcli

In addition to wbemcat and xmltest , the SBLIM project includes a more advanced command
line CIM client wbemcli . The client is used to send CIM requests to SFCB server and display
returned results. It is independent of CIMOM library and can be used with all WBEM compliant
implementations.
For example, if you need to list all the classes implemented by SBLIM providers registered to
your SFCB, send the “EnumerateClasses” (ec) request to SFCB:
tux > wbemcli -dx ec http://localhost/root/cimv2

To server: <?xml version="1.0" encoding="utf-8" ?>
<MESSAGE ID="4711" PROTOCOLVERSION="1.0"><SIMPLEREQ><IMETHODCALL \
NAME="EnumerateClasses"><LOCALNAMESPACEPATH><NAMESPACE NAME="root"> \
</NAMESPACE><NAMESPACE NAME="cimv2"></NAMESPACE> \
</LOCALNAMESPACEPATH>
<IPARAMVALUE NAME="DeepInheritance"><VALUE>TRUE</VALUE> \
</IPARAMVALUE>
<IPARAMVALUE NAME="LocalOnly"><VALUE>FALSE</VALUE></IPARAMVALUE>
<IPARAMVALUE NAME="IncludeQualifiers"><VALUE>FALSE</VALUE> \
</IPARAMVALUE>
<IPARAMVALUE NAME="IncludeClassOrigin"><VALUE>TRUE</VALUE> \
</IPARAMVALUE>
</IMETHODCALL></SIMPLEREQ>
</MESSAGE></CIM>
From server: Content-Type: application/xml; charset="utf-8"
From server: Content-Length: 337565
From server: Cache-Control: no-cache
From server: CIMOperation: MethodResponse
From server: <?xml version="1.0" encoding="utf-8" ?>
517 Command Line CIM Client: wbemcli SLES 12 SP3

<SIMPLERSP>
<IMETHODRESPONSE NAME="EnumerateClasses">
<IRETURNVALUE>
<CLASS NAME="CIM_ResourcePool" SUPERCLASS="CIM_LogicalElement">
<PROPERTY NAME="Generation" TYPE="uint64">
</PROPERTY>
<PROPERTY NAME="ElementName" TYPE="string">
</PROPERTY>
<PROPERTY NAME="Description" TYPE="string">
</PROPERTY>
<PROPERTY NAME="Caption" TYPE="string">
</PROPERTY>
<PROPERTY NAME="InstallDate" TYPE="datetime">
</PROPERTY>
[..]
<CLASS NAME="Linux_ReiserFileSystem" SUPERCLASS="CIM_UnixLocalFileSystem">
<PROPERTY NAME="FSReservedCapacity" TYPE="uint64">
</PROPERTY>
<PROPERTY NAME="TotalInodes" TYPE="uint64">
</PROPERTY>
<PROPERTY NAME="FreeInodes" TYPE="uint64">
</PROPERTY>
<PROPERTY NAME="ResizeIncrement" TYPE="uint64">
<VALUE>0</VALUE>
</PROPERTY>
<PROPERTY NAME="IsFixedSize" TYPE="uint16">
<VALUE>0</VALUE>
</PROPERTY>
[..]
The -dx option shows you the actual XML sent to SFCB by wbemcli and the actual XML re-
ceived. In the above example, the rst of many returned classes was CIM_ResourcePool fol-
lowed by Linux_ReiserFileSystem . Similar entries will appear for all of the other registered
classes.
If you omit the -dx option, wbemcli will display only a compact representation of the returned
data:
tux > wbemcli ec http://localhost/root/cimv2

localhost:5988/root/cimv2:CIM_ResourcePool Generation=,ElementName=, \
Description=,Caption=,InstallDate=,Name=,OperationalStatus=, \
StatusDescriptions=,Status=,HealthState=,PrimaryStatus=, \
DetailedStatus=,OperatingStatus=,CommunicationStatus=,InstanceID=, \
PoolID=,Primordial=,Capacity=,Reserved=,ResourceType=, \
OtherResourceType=,ResourceSubType=, \AllocationUnits=
localhost:5988/root/cimv2:Linux_ReiserFileSystem FSReservedCapacity=, \
TotalInodes=,FreeInodes=,ResizeIncrement=,IsFixedSize=,NumberOfFiles=, \
518 Command Line CIM Client: wbemcli SLES 12 SP3

OtherPersistenceType=,PersistenceType=,FileSystemType=,ClusterSize=, \
MaxFileNameLength=,CodeSet=,CasePreserved=,CaseSensitive=, \
CompressionMethod=,EncryptionMethod=,ReadOnly=,AvailableSpace=, \
FileSystemSize=,BlockSize=,Root=,Name=,CreationClassName=,CSName=, \
CSCreationClassName=,Generation=,ElementName=,Description=,Caption=, \
InstanceID=,InstallDate=,OperationalStatus=,StatusDescriptions=, \
Status=,HealthState=,PrimaryStatus=,DetailedStatus=,OperatingStatus= \
,CommunicationStatus=,EnabledState=,OtherEnabledState=,RequestedState= \
,EnabledDefault=,TimeOfLastStateChange=,AvailableRequestedStates=, \
TransitioningToState=,PercentageSpaceUse=
[..]

FOR MORE DETAILS ABOUT WBEM AND SFCB, SEE THE FOLLOWING SOURCES:
http://www.dmtf.org
Distributed Management Task Force Web site
http://www.dmtf.org/standards/wbem/
Web-Based Enterprise Management (WBEM) Web site
http://www.dmtf.org/standards/cim/
Common Information Model (CIM) Web site
http://sblim.wiki.sourceforge.net/
Standards Based Linux Instrumentation (SBLIM) Web site
http://sblim.sourceforge.net/wiki/index.php/Sfcb
Small Footprint CIM Broker (SFCB) Web site
http://sblim.sourceforge.net/wiki/index.php/Providers
SBLIM providers packages

V Mobile Computers
35 Mobile Computing with Linux 521
36 Using NetworkManager 532
37 Power Management 542

35 Mobile Computing with Linux
Mobile computing is mostly associated with laptops, PDAs and cellular phones (and
the data exchange between them). Mobile hardware components, such as external
hard disks, ash disks, or digital cameras, can be connected to laptops or desktop
systems. A number of software components are involved in mobile computing sce-
narios and some applications are tailor-made for mobile use.
35.1 Laptops
The hardware of laptops differs from that of a normal desktop system. This is because criteria like
exchangeability, space requirements and power consumption must be taken into account. The
manufacturers of mobile hardware have developed standard interfaces like PCMCIA (Personal
Computer Memory Card International Association), Mini PCI and Mini PCIe that can be used to
extend the hardware of laptops. The standards cover memory cards, network interface cards,
and external hard disks.
35.1.1 Power Conservation
The inclusion of energy-optimized system components during laptop manufacturing contributes

to their suitability for use without access to the electrical power grid. Their contribution to
conservation of power is at least as important as that of the operating system. SUSE® Linux
Enterprise Server supports various methods that control the power consumption of a laptop
and have varying effects on the operating time under battery power. The following list is in
descending order of contribution to power conservation:
Throttling the CPU speed.
Switching o the display illumination during pauses.
Manually adjusting the display illumination.
Disconnecting unused, hotplug-enabled accessories (USB CD-ROM, external mouse, unused

PCMCIA cards, Wi-Fi, etc.).
Spinning down the hard disk when idling.
521 Laptops SLES 12 SP3

Detailed background information about power management in SUSE Linux Enterprise Server is
provided in Chapter 37, Power Management.
35.1.2 Integration in Changing Operating Environments
Your system needs to adapt to changing operating environments when used for mobile comput-
ing. Many services depend on the environment and the underlying clients must be reconfigured.
SUSE Linux Enterprise Server handles this task for you.
FIGURE 35.1: INTEGRATING A MOBILE COMPUTER IN AN EXISTING ENVIRONMENT
522 Integration in Changing Operating Environments SLES 12 SP3

The services affected in the case of a laptop commuting back and forth between a small home
network and an office network are:
Network
This includes IP address assignment, name resolution, Internet connectivity and connec-
tivity to other networks.
Printing
A current database of available printers and an available print server must be present,
depending on the network.
E-Mail and Proxies

As with printing, the list of the corresponding servers must be current.
X (Graphical Environment)
If your laptop is temporarily connected to a projector or an external monitor, different
display configurations must be available.
SUSE Linux Enterprise Server offers several ways of integrating laptops into existing operating
environments:
NetworkManager
NetworkManager is especially tailored for mobile networking on laptops. It provides a
means to easily and automatically switch between network environments or different types
of networks such as mobile broadband (such as GPRS, EDGE, or 3G), wireless LAN, and
Ethernet. NetworkManager supports WEP and WPA-PSK encryption in wireless LANs. It
also supports dial-up connections. The GNOME desktop includes a front-end for Network-
Manager. For more information, see Section 36.3, “Configuring Network Connections”.
TABLE 35.1: USE CASES FOR NETWORKMANAGER
My computer… Use NetworkManager
is a laptop Yes
is sometimes attached to different net- Yes

works
provides network services (such as DNS or No

DHCP)
523 Integration in Changing Operating Environments SLES 12 SP3

My computer… Use NetworkManager
only uses a static IP address No
Use the YaST tools to configure networking whenever NetworkManager should not handle
network configuration.
Tip: DNS Configuration and Various Types of Network

Connections
If you travel frequently with your laptop and change different types of network con-
nections, NetworkManager works ne when all DNS addresses are assigned correct-
ly assigned with DHCP. If some connections use static DNS address(es), add it to the
NETCONFIG_DNS_STATIC_SERVERS option in /etc/sysconfig/network/config .
SLP
The service location protocol (SLP) simplifies the connection of a laptop to an existing
network. Without SLP, the administrator of a laptop usually requires detailed knowledge
of the services available in a network. SLP broadcasts the availability of a certain type
of service to all clients in a local network. Applications that support SLP can process the
information dispatched by SLP and be configured automatically. SLP can also be used to
install a system, minimizing the effort of searching for a suitable installation source. Find
detailed information about SLP in Chapter 30, SLP.
35.1.3 Software Options

There are various task areas in mobile use that are covered by dedicated software: system mon-
itoring (especially the battery charge), data synchronization, and wireless communication with
peripherals and the Internet. The following sections cover the most important applications that
SUSE Linux Enterprise Server provides for each task.
524 Software Options SLES 12 SP3

35.1.3.1 System Monitoring
Two system monitoring tools are provided by SUSE Linux Enterprise Server:
Power Management
Power Management is an application that lets you adjust the energy saving related behav-
ior of the GNOME desktop. You can typically access it via Computer Control Center Sys-
tem Power Management.
System Monitor
The System Monitor gathers measurable system parameters into one monitoring environ-
ment. It presents the output information in three tabs by default. Processes gives detailed in-
formation about currently running processes, such as CPU load, memory usage, or process
ID number and priority. The presentation and filtering of the collected data can be cus-
tomized—to add a new type of process information, left-click the process table header and
choose which column to hide or add to the view. It is also possible to monitor different
system parameters in various data pages or collect the data of various machines in parallel
over the network. The Resources tab shows graphs of CPU, memory and network history
and the File System tab lists all partitions and their usage.
35.1.3.2 Synchronizing Data
When switching between working on a mobile machine disconnected from the network and
working at a networked workstation in an office, it is necessary to keep processed data synchro-
nized across all instances. This could include e-mail folders, directories and individual les that
need to be present for work on the road and at the office. The solution in both cases is as follows:
Synchronizing E-Mail
Use an IMAP account for storing your e-mails in the office network. Then access the e-
mails from the workstation using any disconnected IMAP-enabled e-mail client, like Mozil-
la Thunderbird or Evolution as described in Book “GNOME User Guide”. The e-mail client
must be configured so that the same folder is always accessed for Sent messages . This
ensures that all messages are available along with their status information after the syn-
chronization process has completed. Use an SMTP server implemented in the mail client
for sending messages instead of the system-wide MTA postfix or sendmail to receive reli-
able feedback about unsent mail.

Synchronizing Files and Directories
There are several utilities suitable for synchronizing data between a laptop and a worksta-
tion. One of the most widely used is a command-line tool called rsync . For more infor-
mation, see its manual page ( man 1 rsync ).
35.1.3.3 Wireless Communication: Wi-Fi
With the largest range of these wireless technologies, Wi-Fi is the only one suitable for the op-
eration of large and sometimes even spatially separate networks. Single machines can connect
with each other to form an independent wireless network or access the Internet. Devices called
access points act as base stations for Wi-Fi-enabled devices and act as intermediaries for access
to the Internet. A mobile user can switch among access points depending on location and which
access point is offering the best connection. Like in cellular telephony, a large network is avail-
able to Wi-Fi users without binding them to a specific location for accessing it.
Wi-Fi cards communicate using the 802.11 standard, prepared by the IEEE organization. Origi-
nally, this standard provided for a maximum transmission rate of 2 Mbit/s. Meanwhile, several
supplements have been added to increase the data rate. These supplements define details such
as the modulation, transmission output, and transmission rates (see Table 35.2, “Overview of Var-
ious Wi-Fi Standards”). Additionally, many companies implement hardware with proprietary or
draft features.
TABLE 35.2: OVERVIEW OF VARIOUS WI-FI STANDARDS
Name (802.11) Frequency (GHz) Maximum Trans- Note

mission Rate (Mbit/
s)
a 5 54 Less interfer-
ence-prone
b 2.4 11 Less common
g 2.4 54 Widespread, back-

ward-compatible
with 11b
n 2.4 and/or 5 300 Common

Name (802.11) Frequency (GHz) Maximum Trans- Note
mission Rate (Mbit/
s)
ac 5 up to ~865 Expected to be com-

mon in 2015
ad 60 up to appr. 7000 Released 2012, cur-

rently less common;
not supported in
SUSE Linux Enter-
prise Server
802.11 Legacy cards are not supported by SUSE® Linux Enterprise Server. Most cards using
802.11 a/b/g/n are supported. New cards usually comply with the 802.11n standard, but cards
using 802.11g are still available.
35.1.3.3.1 Operating Modes
In wireless networking, various techniques and configurations are used to ensure fast, high-
quality, and secure connections. Usually your Wi-Fi card operates in managed mode. However,
different operating types need different setups. Wireless networks can be classified into four
network modes:
Managed Mode (Infrastructure Mode), via Access Point (default mode)

Managed networks have a managing element: the access point. In this mode (also called
infrastructure or default mode), all connections of the Wi-Fi stations in the network run
through the access point, which may also serve as a connection to an Ethernet. To make
sure only authorized stations can connect, various authentication mechanisms (WPA, etc.)
are used. This is also the main mode that consumes the least amount of energy.
Ad-hoc Mode (Peer-to-Peer Network)

Ad-hoc networks do not have an access point. The stations communicate directly with each
other, therefore an ad-hoc network is usually slower than a managed network. However,
the transmission range and number of participating stations are greatly limited in ad-hoc
networks. They also do not support WPA authentication. Additionally, not all cards support
ad-hoc mode reliably.

Master Mode
In master mode, your Wi-Fi card is used as the access point, assuming your card supports
this mode. Find out the details of your Wi-Fi card at http://linux-wless.passys.nl .
Mesh Mode
Wireless mesh networks are organized in a mesh topology. A wireless mesh network's con-
nection is spread among all wireless mesh nodes. Each node belonging to this network
is connected to other nodes to share the connection, possibly over a large area. (Not sup-
ported in SLE12).
35.1.3.3.2 Authentication
Because a wireless network is much easier to intercept and compromise than a wired network,
the various standards include authentication and encryption methods.
Old Wi-Fi cards support only WEP (Wired Equivalent Privacy). However, because WEP has
proven to be insecure, the Wi-Fi industry has defined an extension called WPA, which is supposed
to eliminate the weaknesses of WEP. WPA, sometimes synonymous with WPA2, should be the
default authentication method.
Usually the user cannot choose the authentication method. For example, when a card operates
in managed mode the authentication is set by the access point. NetworkManager shows the
authentication method.
35.1.3.3.3 Encryption
There are various encryption methods to ensure that no unauthorized person can read the data
packets that are exchanged in a wireless network or gain access to the network:
WEP (defined in IEEE 802.11)

This standard uses the RC4 encryption algorithm, originally with a key length of 40 bits,
later also with 104 bits. Often, the length is declared as 64 bits or 128 bits, depending on
whether the 24 bits of the initialization vector are included. However, this standard has
some weaknesses. Attacks against the keys generated by this system may be successful.
Nevertheless, it is better to use WEP than not to encrypt the network.
Some vendors have implemented the non-standard “Dynamic WEP”. It works exactly as
WEP and shares the same weaknesses, except that the key is periodically changed by a
key management service.

TKIP (defined in WPA/IEEE 802.11i)
This key management protocol defined in the WPA standard uses the same encryption
algorithm as WEP, but eliminates its weakness. Because a new key is generated for every
data packet, attacks against these keys are fruitless. TKIP is used together with WPA-PSK.
CCMP (defined in IEEE 802.11i)

CCMP describes the key management. Usually, it is used in connection with WPA-EAP,
but it can also be used with WPA-PSK. The encryption takes place according to AES and
is stronger than the RC4 encryption of the WEP standard.
35.1.3.4 Wireless Communication: Bluetooth

Bluetooth has the broadest application spectrum of all wireless technologies. It can be used for
communication between computers (laptops) and PDAs or cellular phones, as can IrDA. It can
also be used to connect various computers within range. Bluetooth is also used to connect wire-
less system components, like a keyboard or a mouse. The range of this technology is, however,
not sufficient to connect remote systems to a network. Wi-Fi is the technology of choice for
communicating through physical obstacles like walls.
35.1.3.5 Wireless Communication: IrDA

IrDA is the wireless technology with the shortest range. Both communication parties must be
within viewing distance of each other. Obstacles like walls cannot be overcome. One possible
application of IrDA is the transmission of a le from a laptop to a cellular phone. The short path
from the laptop to the cellular phone is then covered using IrDA. Long-range transmission of
the le to the recipient is handled by the mobile network. Another application of IrDA is the
wireless transmission of printing jobs in the office.
35.1.4 Data Security

Ideally, you protect data on your laptop against unauthorized access in multiple ways. Possible
security measures can be taken in the following areas:
Protection against Theft

Always physically secure your system against theft whenever possible. Various securing
tools (like chains) are available in retail stores.
529 Data Security SLES 12 SP3

Strong Authentication
Use biometric authentication in addition to standard authentication via login and pass-
word. SUSE Linux Enterprise Server supports fingerprint authentication.
Securing Data on the System

Important data should not only be encrypted during transmission, but also on the hard
disk. This ensures its safety in case of theft. The creation of an encrypted partition with
SUSE Linux Enterprise Server is described in Book “Security Guide”, Chapter 11 “Encrypting
Partitions and Files”. Another possibility is to create encrypted home directories when adding
the user with YaST.
Important: Data Security and Suspend to Disk

Encrypted partitions are not unmounted during a suspend to disk event. Thus, all
data on these partitions is available to any party who manages to steal the hardware
and issue a resume of the hard disk.
Network Security
Any transfer of data should be secured, no matter how the transfer is done. Find general
security issues regarding Linux and networks in Book “Security Guide”, Chapter 1 “Security
and Confidentiality”.
35.2 Mobile Hardware

SUSE Linux Enterprise Server supports the automatic detection of mobile storage devices over
FireWire (IEEE 1394) or USB. The term mobile storage device applies to any kind of FireWire
or USB hard disk, ash disk, or digital camera. These devices are automatically detected and
configured when they are connected with the system over the corresponding interface. The le
manager of GNOME offers flexible handling of mobile hardware items. To unmount any of these
media safely, use the Unmount Volume (GNOME) feature of the le manager. For more details
refer to Book “GNOME User Guide”.
External Hard Disks (USB and FireWire)

When an external hard disk is correctly recognized by the system, its icon appears in
the le manager. Clicking the icon displays the contents of the drive. It is possible to
create directories and les here and edit or delete them. To rename a hard disk, select
530 Mobile Hardware SLES 12 SP3

the corresponding menu item from the right-click contextual menu. This name change is
limited to display in the le manager. The descriptor by which the device is mounted in
/media remains unaffected.
USB Flash Disks

These devices are handled by the system like external hard disks. It is similarly possible
to rename the entries in the le manager.
35.3 Cellular Phones and PDAs

A desktop system or a laptop can communicate with a cellular phone via Bluetooth or IrDA.
Some models support both protocols and some only one of the two. The usage areas for the two
protocols and the corresponding extended documentation has already been mentioned in Sec-
tion 35.1.3.3, “Wireless Communication: Wi-Fi”. The configuration of these protocols on the cellular
phones themselves is described in their manuals.

The central point of reference for all questions regarding mobile devices and Linux is http://
tuxmobil.org/ . Various sections of that Web site deal with the hardware and software aspects
of laptops, PDAs, cellular phones and other mobile hardware.
A similar approach to that of http://tuxmobil.org/ is made by http://www.linux-on-laptop-
s.com/ . Information about laptops and handhelds can be found here.
SUSE maintains a mailing list in German dedicated to the subject of laptops. See http://lists.open-
suse.org/opensuse-mobile-de/ . On this list, users and developers discuss all aspects of mobile
computing with SUSE Linux Enterprise Server. Postings in English are answered, but the major-
ity of the archived information is only available in German. Use http://lists.opensuse.org/open-
suse-mobile/ for English postings.
531 Cellular Phones and PDAs SLES 12 SP3

36 Using NetworkManager
NetworkManager is the ideal solution for laptops and other portable computers. It supports
state-of-the-art encryption types and standards for network connections, including connections
to 802.1X protected networks. 802.1X is the “IEEE Standard for Local and Metropolitan Area
Networks—Port-Based Network Access Control”. With NetworkManager, you need not worry
about configuring network interfaces and switching between wired or wireless networks when
you are moving. NetworkManager can automatically connect to known wireless networks or
manage several network connections in parallel—the fastest connection is then used as default.
Furthermore, you can manually switch between available networks and manage your network
connection using an applet in the system tray.
Instead of only one connection being active, multiple connections may be active at once. This
enables you to unplug your laptop from an Ethernet and remain connected via a wireless con-
nection.
36.1 Use Cases for NetworkManager

NetworkManager provides a sophisticated and intuitive user interface, which enables users to
easily switch their network environment. However, NetworkManager is not a suitable solution
in the following cases:
Your computer provides network services for other computers in your network, for exam-
ple, it is a DHCP or DNS server.
Your computer is a Xen server or your system is a virtual system inside Xen.
36.2 Enabling or Disabling NetworkManager

On laptop computers, NetworkManager is enabled by default. However, it can be at any time
enabled or disabled in the YaST Network Settings module.
1. Run YaST and go to System Network Settings.
2. The Network Settings dialog opens. Go to the Global Options tab.
532 Use Cases for NetworkManager SLES 12 SP3

3. To configure and manage your network connections with NetworkManager:
a. In the Network Setup Method eld, select User Controlled with NetworkManager.
b. Click OK and close YaST.
c. Configure your network connections with NetworkManager as described in Sec-

tion 36.3, “Configuring Network Connections”.
4. To deactivate NetworkManager and control the network with your own configuration
a. In the Network Setup Method eld, choose Controlled by wicked.
b. Click OK.
c. Set up your network card with YaST using automatic configuration via DHCP or a
static IP address.
Find a detailed description of the network configuration with YaST in Section 16.4,
“Configuring a Network Connection with YaST”.
36.3 Configuring Network Connections

After having enabled NetworkManager in YaST, configure your network connections with the
NetworkManager front-end available in GNOME. It shows tabs for all types of network connec-
tions, such as wired, wireless, mobile broadband, DSL, and VPN connections.
To open the network configuration dialog in GNOME, open the settings menu via the status
menu and click the Network entry.
Note: Availability of Options

Depending on your system setup, you may not be allowed to configure connections. In a
secured environment, some options may be locked or require root permission. Ask your
system administrator for details.
533 Configuring Network Connections SLES 12 SP3

FIGURE 36.1: GNOME NETWORK CONNECTIONS DIALOG
PROCEDURE 36.1: ADDING AND EDITING CONNECTIONS
1. Open the NetworkManager configuration dialog.
2. To add a Connection:
a. Click the + icon in the lower left corner.
b. Select your preferred connection type and follow the instructions.
c. When you are finished click Add.
d. After having confirmed your changes, the newly configured network connection ap-
pears in the list of available networks you get by opening the Status Menu.
3. To edit a connection:
a. Select the entry to edit.
b. Click the gear icon to open the Connection Settings dialog.
c. Insert your changes and click Apply to save them.
d. To Make your connection available as system connection go to the Identity tab and
set the check box Make available to other users. For more information about User and
System Connections, see Section 36.4.1, “User and System Connections”.
534 Configuring Network Connections SLES 12 SP3

36.3.1 Managing Wired Network Connections
If your computer is connected to a wired network, use the NetworkManager applet to manage
the connection.
1. Open the Status Menu and click Wired to change the connection details or to switch it o.
2. To change the settings click Wired Settings and then click the gear icon.
3. To switch o all network connections, activate the Airplane Mode setting.
36.3.2 Managing Wireless Network Connections

Visible wireless networks are listed in the GNOME NetworkManager applet menu under Wireless
Networks. The signal strength of each network is also shown in the menu. Encrypted wireless
networks are marked with a shield icon.
PROCEDURE 36.2: CONNECTING TO A VISIBLE WIRELESS NETWORK
1. To connect to a visible wireless network, open the Status Menu and click Wi-Fi.
2. Click Turn On to enable it.
3. Click Select Network, select your Wi-Fi Network and click Connect.
4. If the network is encrypted, a configuration dialog opens. It shows the type of encryption
the network uses and text boxes for entering the login credentials.
PROCEDURE 36.3: CONNECTING TO AN INVISIBLE WIRELESS NETWORK
1. To connect to a network that does not broadcast its service set identifier (SSID or ESSID)
and therefore cannot be detected automatically, open the Status Menu and click Wi-Fi.
2. Click Wi-Fi Settings to open the detailed settings menu.
3. Make sure your Wi-Fi is enabled and click Connect to Hidden Network.
4. In the dialog that opens, enter the SSID or ESSID in Network Name and set encryption
parameters if necessary.
A wireless network that has been chosen explicitly will remain connected as long as possible.
If a network cable is plugged in during that time, any connections that have been set to Stay
connected when possible will be connected, while the wireless connection remains up.
535 Managing Wired Network Connections SLES 12 SP3

36.3.3 Configuring Your Wi-Fi/Bluetooth Card as an Access Point
If your Wi-Fi/Bluetooth card supports access point mode, you can use NetworkManager for the
configuration.
1. Open the Status Menu and click Wi-Fi.
2. Click Wi-Fi Settings to open the detailed settings menu.
3. Click Use as Hotspot and follow the instructions.
4. Use the credentials shown in the resulting dialog to connect to the hotspot from a remote
machine.
36.3.4 NetworkManager and VPN
NetworkManager supports several Virtual Private Network (VPN) technologies. For each tech-
nology, SUSE Linux Enterprise Server comes with a base package providing the generic support
for NetworkManager. In addition to that, you also need to install the respective desktop-specific
package for your applet.
OpenVPN
To use this VPN technology, install:
NetworkManager-openvpn
NetworkManager-openvpn-gnome
vpnc (Cisco AnyConnect)

NetworkManager-vpnc
NetworkManager-vpnc-gnome
PPTP (Point-to-Point Tunneling Protocol)

NetworkManager-pptp
NetworkManager-pptp-gnome
536 Configuring Your Wi-Fi/Bluetooth Card as an Access Point SLES 12 SP3

The following procedure describes how to set up your computer as an OpenVPN client using
NetworkManager. Setting up other types of VPNs works analogously.
Before you begin, make sure that the package NetworkManager-openvpn-gnome is installed
and all dependencies have been resolved.
PROCEDURE 36.4: SETTING UP OPENVPN WITH NETWORKMANAGER
1. Open the application Settings by clicking the status icons at the right end of the panel and
clicking the wrench and screwdriver icon. In the window All Settings, choose Network.
2. Click the + icon.
3. Select VPN and then OpenVPN.
4. Choose the Authentication type. Depending on the setup of your OpenVPN server, choose
Certificates (TLS) or Password with Certificates (TLS).
5. Insert the necessary values into the respective text boxes. For our example configuration,
these are:
Gateway The remote endpoint of the VPN server
User name The user (only available when you have selected Password
with Certificates (TLS))
Password The password for the user (only available when you have
selected Password with Certificates (TLS))
User Certificate /etc/openvpn/client1.crt
CA Certificate /etc/openvpn/ca.crt
Private Key /etc/openvpn/client1.key
6. Finish the configuration with Add.
7. To enable the connection, in the Network panel of the Settings application click the switch
button. Alternatively, click the status icons at the right end of the panel, click the name
of your VPN and then Connect.
537 NetworkManager and VPN SLES 12 SP3

36.4 NetworkManager and Security
NetworkManager distinguishes two types of wireless connections, trusted and untrusted. A trust-
ed connection is any network that you explicitly selected in the past. All others are untrusted.
Trusted connections are identified by the name and MAC address of the access point. Using
the MAC address ensures that you cannot use a different access point with the name of your
trusted connection.
NetworkManager periodically scans for available wireless networks. If multiple trusted networks
are found, the most recently used is automatically selected. NetworkManager waits for your
selection in case that all networks are untrusted.
If the encryption setting changes but the name and MAC address remain the same, Network-
Manager attempts to connect, but rst you are asked to confirm the new encryption settings
and provide any updates, such as a new key.
If you switch from using a wireless connection to offline mode, NetworkManager blanks the
SSID or ESSID. This ensures that the card is disconnected.
36.4.1 User and System Connections

NetworkManager knows two types of connections: user and system connections. User con-
nections are connections that become available to NetworkManager when the rst user logs in.
Any required credentials are asked from the user and when the user logs out, the connections
are disconnected and removed from NetworkManager. Connections that are defined as system
connection can be shared by all users and are made available right after NetworkManager is
started—before any users log in. In case of system connections, all credentials must be provided
at the time the connection is created. Such system connections can be used to automatically
connect to networks that require authorization. For information how to configure user or system
connections with NetworkManager, refer to Section 36.3, “Configuring Network Connections”.
36.4.2 Storing Passwords and Credentials

If you do not want to re-enter your credentials each time you want to connect to an encrypted
network, you can use the GNOME Keyring Manager to store your credentials encrypted on the
disk, secured by a master password.
538 NetworkManager and Security SLES 12 SP3

NetworkManager can also retrieve its certificates for secure connections (for example, encrypted
wired, wireless or VPN connections) from the certificate store. For more information, refer to
Book “Security Guide”, Chapter 12 “Certificate Store”.
36.5 Frequently Asked Questions

In the following, nd some frequently asked questions about configuring special network options
with NetworkManager.
36.5.1. How to tie a connection to a specific device?
By default, connections in NetworkManager are device type-specific: they apply to all

physical devices with the same type. If more than one physical device per connection
type is available (for example, your machine is equipped with two Ethernet cards), you
can tie a connection to a certain device.
To do this in GNOME, rst look up the MAC address of your device (use the Connection
Information available from the applet, or use the output of command line tools like nm-
tool or wicked show all ). Then start the dialog for configuring network connections
and choose the connection you want to modify. On the Wired or Wireless tab, enter the
MAC Address of the device and confirm your changes.
36.5.2. How to specify a certain access point in case multiple access points with the same ESSID are de-
tected?
When multiple access points with different wireless bands (a/b/g/n) are available, the
access point with the strongest signal is automatically chosen by default. To override this,
use the BSSID eld when configuring wireless connections.
The Basic Service Set Identifier (BSSID) uniquely identifies each Basic Service Set. In an
infrastructure Basic Service Set, the BSSID is the MAC address of the wireless access point.
In an independent (ad-hoc) Basic Service Set, the BSSID is a locally administered MAC
address generated from a 46-bit random number.
Start the dialog for configuring network connections as described in Section 36.3, “Config-
uring Network Connections”. Choose the wireless connection you want to modify and click
Edit. On the Wireless tab, enter the BSSID.

36.5.3. How to share network connections to other computers?
The primary device (the device which is connected to the Internet) does not need any
special configuration. However, you need to configure the device that is connected to the
local hub or machine as follows:
1. Start the dialog for configuring network connections as described in Section 36.3,

“Configuring Network Connections”. Choose the connection you want to modify and
click Edit. Switch to the IPv4 Settings tab and from the Method drop-down box, ac-
tivate Shared to other computers. That will enable IP traffic forwarding and run a
DHCP server on the device. Confirm your changes in NetworkManager.
2. As the DCHP server uses port 67 , make sure that it is not blocked by the firewall: On
the machine sharing the connections, start YaST and select Security and Users Fire-
wall. Switch to the Allowed Services category. If DCHP Server is not already shown
as Allowed Service, select DCHP Server from Services to Allow and click Add. Confirm
your changes in YaST.
36.5.4. How to provide static DNS information with automatic (DHCP, PPP, VPN) addresses?
In case a DHCP server provides invalid DNS information (and/or routes), you can over-
ride it. Start the dialog for configuring network connections as described in Section 36.3,
“Configuring Network Connections”. Choose the connection you want to modify and click
Edit. Switch to the IPv4 Settings tab, and from the Method drop-down box, activate Auto-
matic (DHCP) addresses only. Enter the DNS information in the DNS Servers and Search
Domains elds. To Ignore automatically obtained routes click Routes and activate the re-
spective check box. Confirm your changes.
36.5.5. How to make NetworkManager connect to password protected networks before a user logs in?
Define a system connection that can be used for such purposes. For more information,
refer to Section 36.4.1, “User and System Connections”.
Connection problems can occur. Some common problems related to NetworkManager include
the applet not starting or a missing VPN option. Methods for resolving and preventing these
problems depend on the tool used.

NetworkManager Desktop Applet Does Not Start
The applets starts automatically if the network is set up for NetworkManager control. If
the applet does not start, check if NetworkManager is enabled in YaST as described in
Section 36.2, “Enabling or Disabling NetworkManager”. Then make sure that the NetworkMan-
ager-gnome package is also installed.
If the desktop applet is installed but is not running for some reason, start it manually. If
the desktop applet is installed but is not running for some reason, start it manually with
the command nm-applet .
NetworkManager Applet Does Not Include the VPN Option

Support for NetworkManager, applets, and VPN for NetworkManager is distributed in sep-
arate packages. If your NetworkManager applet does not include the VPN option, check
if the packages with NetworkManager support for your VPN technology are installed. For
more information, see Section 36.3.4, “NetworkManager and VPN”.
No Network Connection Available

If you have configured your network connection correctly and all other components for
the network connection (router, etc.) are also up and running, it sometimes helps to restart
the network interfaces on your computer. To do so, log in to a command line as root and
run systemctl restart wickeds .

More information about NetworkManager can be found on the following Web sites and direc-
tories:
NetworkManager Project Page

http://projects.gnome.org/NetworkManager/
Package Documentation
Also check out the information in the following directories for the latest information about
NetworkManager and the GNOME applet:
/usr/share/doc/packages/NetworkManager/ ,
/usr/share/doc/packages/NetworkManager-gnome/ .

37 Power Management
System z The features and hardware described in this chapter do not exist on IBM z Systems,
making this chapter irrelevant for these platforms.
Power management is especially important on laptop computers, but is also useful on other sys-
tems. ACPI (Advanced Configuration and Power Interface) is available on all modern computers
(laptops, desktops, and servers). Power management technologies require suitable hardware and
BIOS routines. Most laptops and many modern desktops and servers meet these requirements.
It is also possible to control CPU frequency scaling to save power or decrease noise.
37.1 Power Saving Functions

Power saving functions are not only significant for the mobile use of laptops, but also for desktop
systems. The main functions and their use in ACPI are:
Standby
not supported.
Suspend (to memory)

This mode writes the entire system state to the RAM. Subsequently, the entire system
except the RAM is put to sleep. In this state, the computer consumes very little power.
The advantage of this state is the possibility of resuming work at the same point within
a few seconds without having to boot and restart applications. This function corresponds
to the ACPI state S3 .
Hibernation (suspend to disk)

In this operating mode, the entire system state is written to the hard disk and the system
is powered o. There must be a swap partition at least as big as the RAM to write all the
active data. Reactivation from this state takes about 30 to 90 seconds. The state prior to the
suspend is restored. Some manufacturers offer useful hybrid variants of this mode, such as
RediSafe in IBM Thinkpads. The corresponding ACPI state is S4 . In Linux, suspend to disk
is performed by kernel routines that are independent from ACPI.
542 Power Saving Functions SLES 12 SP3

Note: Changed UUID for Swap Partitions when Formatting via
mkswap
Do not reformat existing swap partitions with mkswap if possible. Reformatting with
mkswap will change the UUID value of the swap partition. Either reformat via YaST
(will update /etc/fstab ) or adjust /etc/fstab manually.
Battery Monitor
ACPI checks the battery charge status and provides information about it. Additionally, it
coordinates actions to perform when a critical charge status is reached.
Automatic Power-Off
Following a shutdown, the computer is powered o. This is especially important when an
automatic shutdown is performed shortly before the battery is empty.
Processor Speed Control

In connection with the CPU, energy can be saved in three different ways: frequency and
voltage scaling (also known as PowerNow! or Speedstep), throttling and putting the proces-
sor to sleep (C-states). Depending on the operating mode of the computer, these methods
can also be combined.
37.2 Advanced Configuration and Power Interface

(ACPI)
ACPI was designed to enable the operating system to set up and control the individual hard-
ware components. ACPI supersedes both Power Management Plug and Play (PnP) and Advanced
Power Management (APM). It delivers information about the battery, AC adapter, temperature,
fan and system events, like “close lid” or “battery low.”
The BIOS provides tables containing information about the individual components and hardware
access methods. The operating system uses this information for tasks like assigning interrupts
or activating and deactivating components. Because the operating system executes commands
stored in the BIOS, the functionality depends on the BIOS implementation. The tables ACPI can
detect and load are reported in journald. See Chapter 15, journalctl: Query the systemd Journal
for more information on viewing the journal log messages. See Section 37.2.2, “Troubleshooting”
for more information about troubleshooting ACPI problems.
543 Advanced Configuration and Power Interface (ACPI) SLES 12 SP3

37.2.1 Controlling the CPU Performance
The CPU can save energy in three ways:
Frequency and Voltage Scaling
Throttling the Clock Frequency (T-states)
Putting the Processor to Sleep (C-states)
Depending on the operating mode of the computer, these methods can be combined. Saving
energy also means that the system heats up less and the fans are activated less frequently.
Frequency scaling and throttling are only relevant if the processor is busy, because the most
economic C-state is applied anyway when the processor is idle. If the CPU is busy, frequency
scaling is the recommended power saving method. Often the processor only works with a partial
load. In this case, it can be run with a lower frequency. Usually, dynamic frequency scaling
controlled by the kernel on-demand governor is the best approach.
Throttling should be used as the last resort, for example, to extend the battery operation time
despite a high system load. However, some systems do not run smoothly when they are throttled
too much. Moreover, CPU throttling does not make sense if the CPU has little to do.
For in-depth information, refer to Book “System Analysis and Tuning Guide”, Chapter 11 “Power
Management”.
37.2.2 Troubleshooting
There are two different types of problems. On one hand, the ACPI code of the kernel may contain
bugs that were not detected in time. In this case, a solution will be made available for download.
More often, the problems are caused by the BIOS. Sometimes, deviations from the ACPI speci-
fication are purposely integrated in the BIOS to circumvent errors in the ACPI implementation
of other widespread operating systems. Hardware components that have serious errors in the
ACPI implementation are recorded in a blacklist that prevents the Linux kernel from using ACPI
for these components.
The rst thing to do when problems are encountered is to update the BIOS. If the computer does
not boot, one of the following boot parameters may be helpful:
pci=noacpi
Do not use ACPI for configuring the PCI devices.
544 Controlling the CPU Performance SLES 12 SP3

acpi=ht
Only perform a simple resource configuration. Do not use ACPI for other purposes.
acpi=off
Disable ACPI.
Warning: Problems Booting without ACPI

Some newer machines (especially SMP systems and AMD64 systems) need ACPI for con-
figuring the hardware correctly. On these machines, disabling ACPI can cause problems.
Sometimes, the machine is confused by hardware that is attached over USB or FireWire. If a
machine refuses to boot, unplug all unneeded hardware and try again.
Monitor the boot messages of the system with the command dmesg -T | grep -2i acpi
(or all messages, because the problem may not be caused by ACPI) after booting. If an error
occurs while parsing an ACPI table, the most important table—the DSDT (Differentiated System
Description Table)—can be replaced with an improved version. In this case, the faulty DSDT of
the BIOS is ignored. The procedure is described in Section 37.4, “Troubleshooting”.
In the kernel configuration, there is a switch for activating ACPI debug messages. If a kernel
with ACPI debugging is compiled and installed, detailed information is issued.
If you experience BIOS or hardware problems, it is always advisable to contact the manufactur-
ers. Especially if they do not always provide assistance for Linux, they should be confronted with
the problems. Manufacturers will only take the issue seriously if they realize that an adequate
number of their customers use Linux.

37.2.2.1 For More Information
http://tldp.org/HOWTO/ACPI-HOWTO/ (detailed ACPI HOWTO, contains DSDT patches)
http://www.acpi.info (Advanced Configuration & Power Interface Specification)
http://acpi.sourceforge.net/dsdt/index.php (DSDT patches by Bruno Ducrot)
37.3 Rest for the Hard Disk

In Linux, the hard disk can be put to sleep entirely if it is not needed or it can be run in a more
economic or quieter mode. On modern laptops, you do not need to switch o the hard disks
manually, because they automatically enter an economic operating mode whenever they are not
needed. However, if you want to maximize power savings, test some of the following methods,
using the hdparm command.
It can be used to modify various hard disk settings. The option -y instantly switches the hard
disk to the standby mode. -Y puts it to sleep. hdparm -S X causes the hard disk to be spun
down after a certain period of inactivity. Replace X as follows: 0 disables this mechanism,
causing the hard disk to run continuously. Values from 1 to 240 are multiplied by 5 seconds.
Values from 241 to 251 correspond to 1 to 11 times 30 minutes.
Internal power saving options of the hard disk can be controlled with the option -B . Select a
value from 0 to 255 for maximum saving to maximum throughput. The result depends on the
hard disk used and is difficult to assess. To make a hard disk quieter, use the option -M . Select
a value from 128 to 254 for quiet to fast.
Often, it is not so easy to put the hard disk to sleep. In Linux, numerous processes write to the
hard disk, waking it up repeatedly. Therefore, it is important to understand how Linux handles
data that needs to be written to the hard disk. First, all data is buered in the RAM. This buer
is monitored by the pdflush daemon. When the data reaches a certain age limit or when the
buer is lled to a certain degree, the buer content is ushed to the hard disk. The buer size
is dynamic and depends on the size of the memory and the system load. By default, pdush is
set to short intervals to achieve maximum data integrity. It checks the buer every 5 seconds
and writes the data to the hard disk. The following variables are interesting:
/proc/sys/vm/dirty_writeback_centisecs
Contains the delay until a pdush thread wakes up (in hundredths of a second).
546 Rest for the Hard Disk SLES 12 SP3

/proc/sys/vm/dirty_expire_centisecs
Defines after which timeframe a dirty page should be written out latest. Default is 3000 ,
which means 30 seconds.
/proc/sys/vm/dirty_background_ratio
Maximum percentage of dirty pages until pdush begins to write them. Default is 5 %.
/proc/sys/vm/dirty_ratio
When the dirty page exceeds this percentage of the total memory, processes are forced to
write dirty buers during their time slice instead of continuing to write.
Warning: Impairment of the Data Integrity

Changes to the pdflush daemon settings endanger the data integrity.
Apart from these processes, journaling le systems, like Btrfs , Ext3 , Ext4 and others write
their metadata independently from pdflush , which also prevents the hard disk from spinning
down.
Another important factor is the way active programs behave. For example, good editors regularly
write hidden backups of the currently modified le to the hard disk, causing the disk to wake
up. Features like this can be disabled at the expense of data integrity.
In this connection, the mail daemon postfix uses the variable POSTFIX_LAPTOP . If this variable
is set to yes , postfix accesses the hard disk far less frequently.
All error messages and alerts are logged in the system journal that can be queried with the
command journalctl (see Chapter 15, journalctl: Query the systemd Journal for more infor-
mation). The following sections cover the most common problems.
37.4.1 CPU Frequency Does Not Work

Refer to the kernel sources to see if your processor is supported. You may need a special kernel
module or module option to activate CPU frequency control. If the kernel-source package is
installed, this information is available in /usr/src/linux/Documentation/cpu-freq/* .

http://en.opensuse.org/SDB:Suspend_to_RAM —How to get Suspend to RAM working
http://old-en.opensuse.org/Pm-utils —How to modify the general suspend framework

VI Troubleshooting
38 Help and Documentation 550
39 Gathering System Information for Support 556
40 Common Problems and Their Solutions 582

38 Help and Documentation
SUSE® Linux Enterprise Server comes with various sources of information and documentation,
many of which are already integrated into your installed system.
Documentation in /usr/share/doc
This traditional help directory holds various documentation les and release notes for your
system. It contains also information of installed packages in the subdirectory packages .
Find more detailed information in Section 38.1, “Documentation Directory”.
Man Pages and Info Pages for Shell Commands

When working with the shell, you do not need to know the options of the commands by
heart. Traditionally, the shell provides integrated help by means of man pages and info
pages. Read more in Section 38.2, “Man Pages” and Section 38.3, “Info Pages”.
Desktop Help Center

The help center of the GNOME desktop (Help) provides central access to the most impor-
tant documentation resources on your system in searchable form. These resources include
online help for installed applications, man pages, info pages, and the SUSE manuals deliv-
ered with your product.
Separate Help Packages for Some Applications

When installing new software with YaST, the software documentation is usually installed
automatically and appears in the help center of your desktop. However, some applications,
such as GIMP, may have different online help packages that can be installed separately
with YaST and do not integrate into the help centers.
38.1 Documentation Directory

The traditional directory to nd documentation on your installed Linux system is /usr/share/
doc . Usually, the directory contains information about the packages installed on your system,
plus release notes, manuals, and more.
550 Documentation Directory SLES 12 SP3

Note: Contents Depends on Installed Packages
In the Linux world, many manuals and other kinds of documentation are available in the
form of packages, like software. How much and which information you nd in /usr/
share/docs also depends on the (documentation) packages installed. If you cannot nd
the subdirectories mentioned here, check if the respective packages are installed on your
system and add them with YaST, if needed.
38.1.1 SUSE Manuals

We provide HTML and PDF versions of our books in different languages. In the manual subdi-
rectory, nd HTML versions of most of the SUSE manuals available for your product. For an
overview of all documentation available for your product refer to the preface of the manuals.
If more than one language is installed, /usr/share/doc/manual may contain different lan-
guage versions of the manuals. The HTML versions of the SUSE manuals are also available in the
help center of both desktops. For information on where to nd the PDF and HTML versions of
the books on your installation media, refer to the SUSE Linux Enterprise Server Release Notes.
They are available on your installed system under /usr/share/doc/release-notes/ or online
at your product-specific Web page at http://www.suse.com/releasenotes// .
38.1.2 Package Documentation

Under packages , nd the documentation that is included in the software packages installed on
your system. For every package, a subdirectory /usr/share/doc/packages/PACKAGENAME is
created. It often contains README les for the package and sometimes examples, configuration
les, or additional scripts. The following list introduces typical les to be found under /usr/
share/doc/packages . None of these entries are mandatory and many packages might only
include a few of them.
AUTHORS
List of the main developers.
BUGS
Known bugs or malfunctions. Might also contain a link to a Bugzilla Web page where you
can search all bugs.
551 SUSE Manuals SLES 12 SP3

CHANGES ,
ChangeLog
Summary of changes from version to version. Usually interesting for developers, because
it is very detailed.
COPYING ,
LICENSE
Licensing information.
FAQ
Question and answers collected from mailing lists or newsgroups.
INSTALL
How to install this package on your system. As the package is already installed by the time
you get to read this le, you can safely ignore the contents of this le.
README , README.*
General information on the software. For example, for what purpose and how to use it.
TODO
Things that are not implemented yet, but probably will be in the future.
MANIFEST
List of les with a brief summary.
NEWS
Description of what is new in this version.
38.2 Man Pages

Man pages are an essential part of any Linux system. They explain the usage of a command
and all available options and parameters. Man pages can be accessed with man followed by the
name of the command, for example, man ls .
Man pages are displayed directly in the shell. To navigate them, move up and down with Page ↑
and Page ↓ . Move between the beginning and the end of a document with Home and End . End
this viewing mode by pressing Q . Learn more about the man command itself with man man .
Man pages are sorted in categories as shown in Table 38.1, “Man Pages—Categories and Descriptions”
(taken from the man page for man itself).
552 Man Pages SLES 12 SP3

TABLE 38.1: MAN PAGES—CATEGORIES AND DESCRIPTIONS
Number Description
1 Executable programs or shell commands
2 System calls (functions provided by the ker-

nel)
3 Library calls (functions within program li-

braries)
4 Special les (usually found in /dev )
5 File formats and conventions ( /etc/fstab )
6 Games
7 Miscellaneous (including macro packages

and conventions), for example, man(7),
gro(7)
8 System administration commands (usually

only for root )
9 Kernel routines (nonstandard)
Each man page consists of several parts labeled NAME , SYNOPSIS , DESCRIPTION , SEE ALSO ,
LICENSING , and AUTHOR . There may be additional sections available depending on the type
of command.
38.3 Info Pages

Info pages are another important source of information on your system. Usually, they are more
detailed than man pages. They consist of more than command line options and contain some-
times whole tutorials or reference documentation. To view the info page for a certain command,
enter info followed by the name of the command, for example, info ls . You can browse an
info page with a viewer directly in the shell and display the different sections, called “nodes”.
Use Space to move forward and <— to move backward. Within a node, you can also browse
553 Info Pages SLES 12 SP3

with Page ↑ and Page ↓ but only Space and <— will take you also to the previous or subse-
quent node. Press Q to end the viewing mode. Not every command comes with an info page
and vice versa.
38.4 Online Resources

In addition to the online versions of the SUSE manuals installed under /usr/share/doc , you
can also access the product-specific manuals and documentation on the Web. For an overview
of all documentation available for SUSE Linux Enterprise Server check out your product-specific
documentation Web page at http://www.suse.com/doc/ .
If you are searching for additional product-related information, you can also refer to the follow-
ing Web sites:
SUSE Technical Support

The SUSE Technical Support can be found at http://www.suse.com/support/ if you have
questions or need solutions for technical problems.
SUSE Forums
There are several forums where you can dive in on discussions about SUSE products. See
http://forums.suse.com/ for a list.
SUSE Conversations
An online community, which offers articles, tips, Q and A, and free tools to download:
http://www.suse.com/communities/conversations/
GNOME Documentation
Documentation for GNOME users, administrators and developers is available at http://
library.gnome.org/ .
The Linux Documentation Project

The Linux Documentation Project (TLDP) is run by a team of volunteers who write Lin-
ux-related documentation (see http://www.tldp.org ). It is probably the most comprehen-
sive documentation resource for Linux. The set of documents contains tutorials for begin-
ners, but is mainly focused on experienced users and professional system administrators.
TLDP publishes HOWTOs, FAQs, and guides (handbooks) under a free license. Parts of the
documentation from TLDP are also available on SUSE Linux Enterprise Server.
554 Online Resources SLES 12 SP3

You can also try general-purpose search engines. For example, use the search terms Linux CD-
RW help or OpenOffice file conversion problem if you have trouble with burning CDs
or LibreOffice le conversion.
555 Online Resources SLES 12 SP3

39 Gathering System Information for Support
For a quick overview of all relevant system information of a machine, SUSE Linux
Enterprise Server offers the hostinfo package. It also helps system administrators
to check for tainted kernels (that are not supported) or any third-party packages in-
stalled on a machine.
In case of problems, a detailed system report may be created with either the sup-
portconfig command line tool or the YaST Support module. Both will collect infor-
mation about the system such as: current kernel version, hardware, installed pack-
ages, partition setup, and much more. The result is a TAR archive of les. After
opening a Service Request (SR), you can upload the TAR archive to Global Techni-
cal Support. It will help to locate the issue you reported and to assist you in solving
the problem.
Additionally, you can analyze the supportconfig output for known issues to help
resolve problems faster. For this purpose, SUSE Linux Enterprise Server provides
both an appliance and a command line tool for Supportconfig Analysis (SCA).
39.1 Displaying Current System Information

For a quick and easy overview of all relevant system information when logging in to a server,
use the package hostinfo . After it has been installed on a machine, the console displays the
following information to any root user that logs in to this machine:
EXAMPLE 39.1: OUTPUT OF hostinfo WHEN LOGGING IN AS root
Hostname: earth
Current As Of: Wed 12 Mar 2014 03:57:05 PM CET
Distribution: SUSE Linux Enterprise Server 12
-Service Pack: 0
Architecture: x86_64
Kernel Version: 3.12.12-3-default
-Installed: Mon 10 Mar 2014 03:15:05 PM CET
-Status: Not Tainted
Last Updated Package: Wed 12 Mar 2014 03:56:43 PM CET
-Patches Needed: 0
556 Displaying Current System Information SLES 12 SP3

-Security: 0
-3rd Party Packages: 0
IPv4 Address: ens3 192.168.1.1
Total/Free/+Cache Memory: 983/95/383 MB (38% Free)
Hard Disk: /dev/sda 10 GB
In case the output shows a tainted kernel status, see Section 39.6, “Support of Kernel Modules”
for more details.
39.2 Collecting System Information with

Supportconfig
To create a TAR archive with detailed system information that you can hand over to Global
Technical Support, use either the supportconfig command line tool directly or the YaST Sup-
port module. The command line tool is provided by the package supportutils which is in-
stalled by default. The YaST Support module is also based on the command line tool.
39.2.1 Creating a Service Request Number

Supportconfig archives can be generated at any time. However, for handing over the support-
config data to Global Technical Support, you need to generate a service request number rst.
You will need it to upload the archive to support.
To create a service request, go to https://scc.suse.com/support/requests and follow the instruc-
tions on the screen. Write down your 12-digit service request number.
Note: Privacy Statement

SUSE and Micro Focus treat system reports as confidential data. For details about our
privacy commitment, see https://www.suse.com/company/policies/privacy/ .
557 Collecting System Information with Supportconfig SLES 12 SP3

39.2.2 Upload Targets
After having created a service request number, you can upload your supportconfig archives to
Global Technical Support as described in Procedure 39.1, “Submitting Information to Support with
YaST” or Procedure 39.2, “Submitting Information to Support from Command Line”. Use one of the
following upload targets:
US customers: ftp://ftp.novell.com/incoming
EMEA, Europe, the Middle East, and Africa: ftp://support-ftp.suse.com/in
Alternatively, you can manually attach the TAR archive to your service request using the service
request URL: https://scc.suse.com/support/requests .
39.2.3 Creating a Supportconfig Archive with YaST

To use YaST to gather your system information, proceed as follows:
1. Start YaST and open the Support module.
2. Click Create report tarball.
558 Upload Targets SLES 12 SP3

3. In the next window, select one of the supportconfig options from the radio button list. Use
Custom (Expert) Settings is preselected by default. If you want to test the report function
rst, use Only gather a minimum amount of info. For some background information on the
other options, refer to the supportconfig man page.
Proceed with Next.
4. Enter your contact information. It will be written to a le called basic-environment.txt

and included in the archive to be created.
5. If you want to submit the archive to Global Technical Support at the end of the information
collection process, Upload Information is required. YaST automatically proposes an upload
server. If you want to modify it, refer to Section 39.2.2, “Upload Targets” for details of which
upload servers are available.
If you want to submit the archive later on, you can leave the Upload Information empty
for now.
6. Proceed with Next.
7. The information gathering begins.
After the process is finished, continue with Next.
559 Creating a Supportconfig Archive with YaST SLES 12 SP3

8. Review the data collection: Select the File Name of a log le to view its contents in YaST. To
remove any les you want excluded from the TAR archive before submitting it to support,
use Remove from Data. Continue with Next.
9. Save the TAR archive. If you started the YaST module as root user, by default YaST
proposes to save the archive to /var/log (otherwise, to your home directory). The le
name format is nts_HOST_DATE_TIME.tbz .
10. If you want to upload the archive to support directly, make sure Upload log les tarball to
URL is activated. The Upload Target shown here is the one that YaST proposes in Step 5. If
you want to modify the upload target, nd detailed information of which upload servers
are available in Section 39.2.2, “Upload Targets”.
11. If you want to skip the upload, deactivate Upload log les tarball to URL.
12. Confirm your changes to close the YaST module.
39.2.4 Creating a Supportconfig Archive from Command Line

The following procedure shows how to create a supportconfig archive, but without submitting
it to support directly. For uploading it, you need to run the command with certain options as
described in Procedure 39.2, “Submitting Information to Support from Command Line”.
1. Open a shell and become root .
2. Run supportconfig without any options. This gathers the default system information.
3. Wait for the tool to complete the operation.
4. The default archive location is /var/log , with the le name format being
nts_HOST_DATE_TIME.tbz
560 Creating a Supportconfig Archive from Command Line SLES 12 SP3

39.2.5 Common Supportconfig Options
The supportconfig utility is usually called without any options. Display a list of all options
with supportconfig -h or refer to the man page. The following list gives a brief overview
of some common use cases:
Reducing the Size of the Information Being Gathered

Use the minimal option ( -m ):
supportconfig -m
Limiting the Information to a Specific Topic

If you have already localized a problem with the default supportconfig output and have
found that it relates to a specific area or feature set only, you should limit the collected
information to the specific area for the next supportconfig run. For example, if you
detected problems with LVM and want to test a recent change that you did to the LVM
configuration, it makes sense to gather the minimum supportconfig information around
LVM only:
supportconfig -i LVM
For a complete list of feature keywords that you can use for limiting the collected infor-
mation to a specific area, run
supportconfig -F
Including Additional Contact Information in the Output:
supportconfig -E tux@example.org -N "Tux Penguin" -O "Penguin Inc." ...
(all in one line)
Collecting Already Rotated Log Files
supportconfig -l
This is especially useful in high logging environments or after a kernel crash when syslog
rotates the log les after a reboot.
561 Common Supportconfig Options SLES 12 SP3

39.3 Submitting Information to Global Technical
Support
Use the YaST Support module or the supportconfig command line utility to submit system
information to the Global Technical Support. When you experience a server issue and want the
support's assistance, you will need to open a service request rst. For details, see Section 39.2.1,
“Creating a Service Request Number”.
The following examples use 12345678901 as a placeholder for your service request number.
Replace 12345678901 with the service request number you created in Section 39.2.1, “Creating
a Service Request Number”.
PROCEDURE 39.1: SUBMITTING INFORMATION TO SUPPORT WITH YAST
The following procedure assumes that you have already created a supportconfig archive,
but have not uploaded it yet. Make sure to have included your contact information in
the archive as described in Section 39.2.3, “Creating a Supportconfig Archive with YaST”, Step 4.
For instructions on how to generate and submit a supportconfig archive in one go, see
Section 39.2.3, “Creating a Supportconfig Archive with YaST”.
1. Start YaST and open the Support module.
2. Click Upload.
3. In Package with log les specify the path to the existing supportconfig archive or Browse
for it.
4. YaST automatically proposes an upload server. If you want to modify it, refer to Sec-
tion 39.2.2, “Upload Targets” for details of which upload servers are available.
562 Submitting Information to Global Technical Support SLES 12 SP3

Proceed with Next.
5. Click Finish.
PROCEDURE 39.2: SUBMITTING INFORMATION TO SUPPORT FROM COMMAND LINE
The following procedure assumes that you have already created a supportconfig archive,
but have not uploaded it yet. For instructions on how to generate and submit a support-
config archive in one go, see Section 39.2.3, “Creating a Supportconfig Archive with YaST”.
1. Servers with Internet connectivity:
a. To use the default upload target, run:
supportconfig -ur 12345678901
b. For the secure upload target, use the following:
supportconfig -ar 12345678901
2. Servers without Internet connectivity
a. Run the following:
supportconfig -r 12345678901
563 Submitting Information to Global Technical Support SLES 12 SP3

b. Manually upload the /var/log/nts_SR12345678901*tbz archive to one of our FTP
servers. Which one to use depends on your location in the world. For an overview,
see Section 39.2.2, “Upload Targets”.
3. After the TAR archive arrives in the incoming directory of our FTP server, it becomes
automatically attached to your service request.
39.4 Analyzing System Information

System reports created with supportconfig can be analyzed for known issues to help resolve
problems faster. For this purpose, SUSE Linux Enterprise Server provides both an appliance and
a command line tool for Supportconfig Analysis (SCA). The SCA appliance is a server-side
tool which is non-interactive. The SCA tool ( scatool ) runs on the client-side and is executed
from command line. Both tools analyze supportconfig archives from affected servers. The initial
server analysis takes place on the SCA appliance or the workstation on which scatool is running.
No analysis cycles happen on the production server.
Both the appliance and the command line tool additionally need product-specific patterns that
enable them to analyze the supportconfig output for the associated products. Each pattern is a
script that parses and evaluates a supportconfig archive for one known issue. The patterns are
available as RPM packages.
For example, if you want to analyze supportconfig archives that have been generated on a SUSE
Linux Enterprise 11 machine, you need to install the package sca-patterns-sle11 together
with the SCA tool (or on the machine that you want to use as the SCA appliance server). To
analyze supportconfig archives generated on a SUSE Linux Enterprise 10 machine, you need the
package sca-patterns-sle10 .
You can also develop your own patterns as briey described in Section 39.4.3, “Developing Custom
Analysis Patterns”.
39.4.1 SCA Command Line Tool

The SCA command line tool lets you analyze a local machine using both supportconfig and
the analysis patterns for the specific product that is installed on the local machine. The tool
creates an HTML report showing its analysis results. For an example, see Figure 39.1, “HTML Report
Generated by SCA Tool”.
564 Analyzing System Information SLES 12 SP3

FIGURE 39.1: HTML REPORT GENERATED BY SCA TOOL
The scatool command is provided by the sca-server-report package. It is not installed by

default. Additionally, you need the sca-patterns-base package and any of the product-spe-
cific sca-patterns-* packages that matches the product installed on the machine where you
want to run the scatool command.
Execute the scatool command either as root user or with sudo . When calling the SCA tool,
you can either analyze an existing supportconfig TAR archive or you can let it generate
and analyze a new archive in one go. The tool also provides an interactive console (with tab
completion) and the possibility to run supportconfig on an external machine and to execute
the subsequent analysis on the local machine.
565 SCA Command Line Tool SLES 12 SP3

Find some example commands below:
sudo scatool -s
Calls supportconfig and generates a new supportconfig archive on the local machine.
Analyzes the archive for known issues by applying the SCA analysis patterns that match
the installed product. Displays the path to the HTML report that is generated from the
results of the analysis. It is usually written to the same directory where the supportconfig
archive can be found.
sudo scatool -s -o /opt/sca/reports/

Same as sudo scatool -s , only that the HTML report is written to the path specified
with -o .
sudo scatool -a PATH_TO_TARBALL_OR_DIR

Analyzes the specified supportconfig archive le (or the specified directory to where the
supportconfig archive has been extracted). The generated HTML report is saved in the
same location as the supportconfig archive or directory.
sudo scatool -a SLES_SERVER.COMPANY.COM

Establishes an SSH connection to an external server SLES_SERVER.COMPANY.COM and runs
supportconfig on the server. The supportconfig archive is then copied back to the lo-
cal machine and is analyzed there. The generated HTML report is saved to the default /
var/log directory. (Only the supportconfig archive is created on SLES_SERVER.COMPA-
NY.COM ).
sudo scatool -c
Starts the interactive console for scatool . Press →| twice to see the available commands.
For further options and information, run sudo scatool -h or see the scatool man page.
39.4.2 SCA Appliance

If you decide to use the SCA appliance for analyzing the supportconfig archives, you need to
configure a dedicated server (or virtual machine) as the SCA appliance server. The SCA appliance
server can then be used to analyze supportconfig archives from all machines in your enterprise
running SUSE Linux Enterprise Server or SUSE Linux Enterprise Desktop. You can simply upload
supportconfig archives to the appliance server for analysis. Interaction is not required. In a
MariaDB database, the SCA appliance keeps track of all supportconfig archives that have been
566 SCA Appliance SLES 12 SP3

analyzed . You can read the SCA reports directly from the appliance Web interface. Alternatively,
you can have the appliance send the HTML report to any administrative user via e-mail. For
details, see Section 39.4.2.5.4, “Sending SCA Reports via E-Mail”.
39.4.2.1 Installation Quick Start

To install and set up the SCA appliance in a very fast way from the command line, follow the
instructions here. The procedure is intended for experts and focuses on the bare installation and
setup commands. For more information, refer to the more detailed description in Section 39.4.2.2,
“Prerequisites” to Section 39.4.2.3, “Installation and Basic Setup”.
PREREQUISITES
Web and LAMP Pattern
Web and Scripting Module (you must register the machine to be able to select this module).
Note: root Privileges Required

All commands in the following procedure must be run as root .
PROCEDURE 39.3: INSTALLATION USING ANONYMOUS FTP FOR UPLOAD
After the appliance is set up and running, no more manual interaction is required. This
way of setting up the appliance is therefore ideal for using cron jobs to create and upload
supportconfig archives.
1. On the machine on which to install the appliance, log in to a console and execute the
following commands:
zypper install sca-appliance-* sca-patterns-* vsftpd

systemctl enable apache2
systemctl enable vsftpd
systemctl start vsftpd
yast ftp-server
2. In YaST FTP Server, select Authentication Enable Upload Anonymous Can Upload Fin-
ish Yes to Create /srv/ftp/upload.
systemctl enable mysql

systemctl start mysql
mysql_secure_installation
setup-sca -f
The mysql_secure_installation will create a MariaDB root password.
PROCEDURE 39.4: INSTALLATION USING SCP/TMP FOR UPLOAD
This way of setting up the appliance requires manual interaction when typing the SSH
password.
1. On the machine on which to install the appliance, log in to a console.
zypper install sca-appliance-* sca-patterns-*

systemctl enable apache2
sudo systemctl enable mysql
systemctl start mysql
mysql_secure_installation
setup-sca
39.4.2.2 Prerequisites
To run an SCA appliance server, you need the following prerequisites:
All sca-appliance-* packages.
The sca-patterns-base package. Additionally, any of the product-specific sca-pat-

terns-* for the type of supportconfig archives that you want to analyze with the appli-
ance.
Apache
PHP
MariaDB
anonymous FTP server (optional)

39.4.2.3 Installation and Basic Setup
As listed in Section 39.4.2.2, “Prerequisites”, the SCA appliance has several dependencies on other
packages. Therefore you need do so some preparations before installing and setting up the SCA
appliance server:
1. For Apache and MariaDB, install the Web and LAMP installation patterns.
2. Set up Apache, MariaDB, and optionally an anonymous FTP server. For more information,
see Chapter 31, The Apache HTTP Server and Chapter 32, Setting Up an FTP Server with YaST.
3. Configure Apache and MariaDB to start at boot time:
sudo systemctl enable apache2 mysql
4. Start both services:
sudo systemctl start apache2 mysql
Now you can install the SCA appliance and set it up as described in Procedure 39.5, “Installing
and Configuring the SCA Appliance”.
PROCEDURE 39.5: INSTALLING AND CONFIGURING THE SCA APPLIANCE
After installing the packages, use the setup-sca script for the basic configuration of the
MariaDB administration and report database that is used by the SCA appliance.
It can be used to configure the following options you have for uploading the supportconfig
archives from your machines to the SCA appliance:
scp
anonymous FTP server
1. Install the appliance and the SCA base-pattern library:
sudo zypper install sca-appliance-* sca-patterns-base
2. Additionally, install the pattern packages for the types of supportconfig archives you want
to analyze. For example, if you have SUSE Linux Enterprise Server 11 and SUSE Linux
Enterprise Server 12 servers in your environment, install both the sca-patterns-sle11
and sca-patterns-sle12 packages.
To install all available patterns:
zypper install sca-patterns-*

3. For basic setup of the SCA appliance, use the setup-sca script. How to call it depends
on how you want to upload the supportconfig archives to the SCA appliance server:
If you have configured an anonymous FTP server that uses the /srv/ftp/upload
directory, execute the setup script with the -f option and follow the instructions
on the screen:
setup-sca -f
Note: FTP Server Using Another Directory

If your FTP server uses another directory than /srv/ftp/upload , adjust the
following configuration les rst to make them point to the correct directory:
/etc/sca/sdagent.conf and /etc/sca/sdbroker.conf .
If you want to upload supportconfig les to the /tmp directory of the SCA appliance
server via scp , call the setup script without any parameters and follow the instruc-
tions on the screen:
setup-sca
The setup script runs a few checks regarding its requirements and configures the needed
components. It will prompt you for two passwords: the MySQL root password of the
MariaDB that you have set up, and a Web user password with which to log in to the Web
interface of the SCA appliance.
4. Enter the existing MariaDB root password. It will allow the SCA appliance to connect
to the MariaDB.
5. Define a password for the Web user. It will be written to /srv/www/htdocs/sca/web-

config.php and will be set as the password for the user scdiag . Both user name and
password can be changed at any time later, see Section 39.4.2.5.1, “Password for the Web
Interface”.
After successful installation and setup, the SCA appliance is ready for use, see Section 39.4.2.4,
“Using the SCA Appliance”. However, you should modify some options such as changing the pass-
word for the Web interface, changing the source for the SCA pattern updates, enabling archiving
mode or configuring e-mail notifications. For details on that, see Section 39.4.2.5, “Customizing
the SCA Appliance”.

Warning: Data Protection
As the reports on the SCA appliance server contain security-relevant information of the
machines whose supportconfig archives have been analyzed, make sure to protect the
data on the SCA appliance server against unauthorized access.
39.4.2.4 Using the SCA Appliance
You can upload existing supportconfig archives to the SCA appliance manually or create new
supportconfig archives and upload them to the SCA appliance in one step. Uploading can be
done via FTP or SCP. For both, you need to know the URL where the SCA appliance can be
reached. For upload via FTP, an FTP server needs to be configured for the SCA appliance, see
Procedure 39.5, “Installing and Configuring the SCA Appliance”.
39.4.2.4.1 Uploading Supportconfig Archives to the SCA Appliance
For creating a supportconfig archive and uploading it via (anonymous) FTP:
sudo supportconfig -U “ftp://SCA-APPLIANCE.COMPANY.COM/upload”
For creating a supportconfig archive and uploading it via SCP:
sudo supportconfig -U “scp://SCA-APPLIANCE.COMPANY.COM/tmp”
You will be prompted for the root user password of the server running the SCA appliance.
If you want to manually upload one or multiple archives, copy the existing archive les
(usually located at /var/log/nts_*.tbz ) to the SCA appliance. As target, use either the
appliance server's /tmp directory or the /srv/ftp/upload directory (if FTP is configured
for the SCA appliance server).
39.4.2.4.2 Viewing SCA Reports
SCA reports can be viewed from any machine that has a browser installed and can access the
report index page of the SCA appliance.
1. Start a Web browser and make sure that JavaScript and cookies are enabled.

2. As a URL, enter the report index page of the SCA appliance.
https://sca-appliance.company.com/sca
If in doubt, ask your system administrator.
3. You will be prompted for a user name and a password to log in.
FIGURE 39.2: HTML REPORT GENERATED BY SCA APPLIANCE
4. After logging in, click the date of the report you want to read.
5. Click the Basic Health category rst to expand it.
6. In the Message column, click an individual entry. This opens the corresponding article in
the SUSE Knowledgebase. Read the proposed solution and follow the instructions.
7. If the Solutions column of the Supportconfig Analysis Report shows any additional entries,
click them. Read the proposed solution and follow the instructions.
8. Check the SUSE Knowledgebase (http://www.suse.com/support/kb/ ) for results that di-

rectly relate to the problem identified by SCA. Work at resolving them.
9. Check for results that can be addressed proactively to avoid future problems.

39.4.2.5 Customizing the SCA Appliance
The following sections show how to change the password for the Web interface, how to change
the source for the SCA pattern updates, how to enable archiving mode, and how to configure
e-mail notifications.
39.4.2.5.1 Password for the Web Interface
The SCA Appliance Web interface requires a user name and password for logging in. The default
user name is scdiag and the default password is linux (if not specified otherwise, see Proce-
dure 39.5, “Installing and Configuring the SCA Appliance”). Change the default password to a secure
password at the earliest possibility. You can also modify the user name.
PROCEDURE 39.6: CHANGING USER NAME OR PASSWORD FOR THE WEB INTERFACE
1. Log in as root user at the system console of the SCA appliance server.
2. Open /srv/www/htdocs/sca/web-config.php in an editor.
3. Change the values of $username and $password as desired.
4. Save the le and exit.
39.4.2.5.2 Updates of SCA Patterns
By default, all sca-patterns-* packages are updated regularly by a root cron job that ex-
ecutes the sdagent-patterns script nightly, which in turn runs zypper update sca-pat-
terns-* . A regular system update will update all SCA appliance and pattern packages. To up-
date the SCA appliance and patterns manually, run:
sudo zypper update sca-*
The updates are installed from the SUSE Linux Enterprise 12 SP3 update repository by default.
You can change the source for the updates to an SMT server, if desired. When sdagent-pat-
terns runs zypper update sca-patterns-* , it gets the updates from the currently config-
ured update channel. If that channel is located on an SMT server, the packages will be pulled
from there.
PROCEDURE 39.7: DISABLING AUTOMATIC UPDATES OF SCA PATTERNS

2. Open /etc/sca/sdagent-patterns.conf in an editor.
3. Change the entry
UPDATE_FROM_PATTERN_REPO=1
to
UPDATE_FROM_PATTERN_REPO=0
4. Save the le and exit. The machine does not require any restart to apply the change.
39.4.2.5.3 Archiving Mode
All supportconfig archives are deleted from the SCA appliance after they have been analyzed and
their results have been stored in the MariaDB database. However, for troubleshooting purposes
it can be useful to keep copies of supportconfig archives from a machine. By default, archiving
mode is disabled.
PROCEDURE 39.8: ENABLING ARCHIVING MODE IN THE SCA APPLIANCE
2. Open /etc/sca/sdagent.conf in an editor.
3. Change the entry
ARCHIVE_MODE=0
to
ARCHIVE_MODE=1
4. Save the le and exit. The machine does not require any restart to apply the change.
After having enabled archive mode, the SCA appliance will save the supportconfig les to the
/var/log/archives/saved directory, instead of deleting them.

39.4.2.5.4 Sending SCA Reports via E-Mail
The SCA appliance can e-mail a report HTML le for each supportconfig analyzed. This feature
is disabled by default. When enabling it, you can define a list of e-mail addresses to which the
reports should be sent, and define a level of status messages that trigger the sending of reports
( STATUS_NOTIFY_LEVEL ).
POSSIBLE VALUES FOR STATUS_NOTIFY_LEVEL
$STATUS_OFF
Deactivate sending of HTML reports.
$STATUS_CRITICAL
Send only SCA reports that include a CRITICAL.
$STATUS_WARNING
Send only SCA reports that include a WARNING or CRITICAL.
$STATUS_RECOMMEND
Send only SCA reports that include a RECOMMEND, WARNING or CRITICAL.
$STATUS_SUCCESS
Send SCA reports that include a SUCCESS, RECOMMEND, WARNING or CRITICAL.
PROCEDURE 39.9: CONFIGURING E-MAIL NOTIFICATIONS FOR SCA REPORTS
2. Open /etc/sca/sdagent.conf in an editor.
3. Search for the entry STATUS_NOTIFY_LEVEL . By default, it is set to $STATUS_OFF (e-mail

notifications are disabled).
4. To enable e-mail notifications, change $STATUS_OFF to the level of status messages that
you want to have e-mail reports for, for example:
STATUS_NOTIFY_LEVEL=$STATUS_SUCCESS
For details, see Possible Values for STATUS_NOTIFY_LEVEL.
5. To define the list of recipients to which the reports should be sent:
a. Search for the entry EMAIL_REPORT='root' .

b. Replace root with a list of e-mail addresses to which SCA reports should be sent.
The e-mail addresses must be separated by spaces. For example:
EMAIL_REPORT='tux@my.company.com wilber@your.company.com'
6. Save the le and exit. The machine does not require any restart to apply the changes. All
future SCA reports will be e-mailed to the specified addresses.
39.4.2.6 Backing Up and Restoring the Database
To back up and restore the MariaDB database that stores the SCA reports, use the scadb com-
mand as described below.
PROCEDURE 39.10: BACKING UP THE DATABASE
1. Log in as root user at the system console of the server running the SCA appliance.
2. Put the appliance into maintenance mode by executing:
scadb maint
3. Start the backup with:
scadb backup
The data is saved to a TAR archive: sca-backup-*sql.gz .
4. If you are using the pattern creation database to develop your own patterns (see Sec-
tion 39.4.3, “Developing Custom Analysis Patterns”), back up this data, too:
sdpdb backup
The data is saved to a TAR archive: sdp-backup-*sql.gz .
5. Copy the following data to another machine or an external storage medium:
sca-backup-*sql.gz
sdp-backup-*sql.gz
/usr/lib/sca/patterns/local (only needed if you have created custom patterns)

6. Reactivate the SCA appliance with:
scadb reset agents
PROCEDURE 39.11: RESTORING THE DATABASE
To restore the database from your backup, proceed as follows:
1. Log in as root user at the system console of the server running the SCA appliance.
2. Copy the newest sca-backup-*sql.gz and sdp-backup-*sql.gz TAR archives to the

SCA appliance server.
3. To decompress the les, run:
gzip -d *-backup-*sql.gz
4. To import the data into the database, execute:
scadb import sca-backup-*sql
5. If you are using the pattern creation database to create your own patterns, also import
the following data with:
sdpdb import sdp-backup-*sql
6. If you are using custom patterns, also restore /usr/lib/sca/patterns/local from your
backup data.
7. Reactivate the SCA appliance with:
scadb reset agents
8. Update the pattern modules in the database with:
sdagent-patterns -u
39.4.3 Developing Custom Analysis Patterns

The SCA appliance comes with a complete pattern development environment (the SCA Pattern
Database) that enables you to develop your own, custom patterns. Patterns can be written in
any programming language. To make them available for the supportconfig analysis process,
they need to be saved to /usr/lib/sca/patterns/local and to be made executable. Both the
577 Developing Custom Analysis Patterns SLES 12 SP3

SCA appliance and the SCA tool will then run the custom patterns against new supportconfig
archives as part of the analysis report. For detailed instructions on how to create (and test) your
own patterns, see http://www.suse.com/communities/conversations/sca-pattern-development/ .
39.5 Gathering Information during the Installation

During the installation, supportconfig is not available. However, you can collect log les from
YaST by using save_y2logs . This command will create a .tar.xz archive in the directory
/tmp .
If issues appear very early during installation, you may be able to gather information from the
log le created by linuxrc . linuxrc is a small command that runs before YaST starts. This
log le is available at /var/log/linuxrc.log .
Important: Installation Log Files Not Available in the Installed

System
The log les available during the installation are not available in the installed system
anymore. Properly save the installation log les while the installer is still running.
39.6 Support of Kernel Modules

An important requirement for every enterprise operating system is the level of support you re-
ceive for your environment. Kernel modules are the most relevant connector between hardware
(“controllers”) and the operating system. Every kernel module in SUSE Linux Enterprise has a
supported ag that can take three possible values:
“yes”, thus supported
“external”, thus supported
“” (empty, not set), thus unsupported
The following rules apply:
All modules of a self-recompiled kernel are by default marked as unsupported.
Kernel modules supported by SUSE partners and delivered using SUSE SolidDriver Pro-
gram are marked “external”.
578 Gathering Information during the Installation SLES 12 SP3

If the supported ag is not set, loading this module will taint the kernel. Tainted kernels
are not supported. Unsupported Kernel modules are included in an extra RPM package
( kernel-FLAVOR-extra ) that is only available for SUSE Linux Enterprise Desktop and the
SUSE Linux Enterprise Workstation Extension. Those kernels will not be loaded by default
( FLAVOR = default | xen |...). In addition, these unsupported modules are not available
in the installer, and the kernel-FLAVOR-extra package is not part of the SUSE Linux
Enterprise media.
Kernel modules not provided under a license compatible to the license of the Linux ker-
nel will also taint the kernel. For details, see /usr/src/linux/Documentation/sysctl/
kernel.txt and the state of /proc/sys/kernel/tainted .
39.6.1 Technical Background

Linux kernel: The value of /proc/sys/kernel/unsupported defaults to 2 on SUSE Linux
Enterprise 12 SP3 ( do not warn in syslog when loading unsupported modules ).
This default is used in the installer and in the installed system. See /usr/src/linux/Doc-
umentation/sysctl/kernel.txt for more information.
modprobe : The modprobe utility for checking module dependencies and loading modules
appropriately checks for the value of the supported ag. If the value is “yes” or “external”
the module will be loaded, otherwise it will not. For information on how to override this
behavior, see Section 39.6.2, “Working with Unsupported Modules”.
Note: Support
SUSE does not generally support the removal of storage modules via modprobe -r .
39.6.2 Working with Unsupported Modules

While general supportability is important, situations can occur where loading an unsupported
module is required (for example, for testing or debugging purposes, or if your hardware vendor
provides a hotfix).
To override the default, edit /etc/modprobe.d/10-unsupported-modules.conf and

change the value of the variable allow_unsupported_modules to 1 . If an unsupported
module is needed in the initrd, do not forget to run dracut -f to update the initrd.
579 Technical Background SLES 12 SP3

If you only want to try loading a module once, you can use the --allow-unsupport-
ed-modules option with modprobe . For more information, see the modprobe man page.
During installation, unsupported modules may be added through driver update disks, and
they will be loaded. To enforce loading of unsupported modules during boot and after-
ward, use the kernel command line option oem-modules . While installing and initializ-
ing the suse-module-tools package, the kernel ag TAINT_NO_SUPPORT ( /proc/sys/
kernel/tainted ) will be evaluated. If the kernel is already tainted, allow_unsupport-
ed_modules will be enabled. This will prevent unsupported modules from failing in the
system being installed. If no unsupported modules are present during installation and the
other special kernel command line option ( oem-modules=1 ) is not used, the default still
is to disallow unsupported modules.
Remember that loading and running unsupported modules will make the kernel and the whole
system unsupported by SUSE.

man supportconfig —The supportconfig man page.
man supportconfig.conf —The man page of the supportconfig configuration le.
man scatool —The scatool man page.
man scadb —The scadb man page.
man setup-sca —The setup-sca man page.
https://mariadb.com/kb/en/ —The MariaDB documentation.
http://httpd.apache.org/docs/ and Chapter 31, The Apache HTTP Server—Documentation

about the Apache Web server.
Chapter 32, Setting Up an FTP Server with YaST—Documentation of how to set up an FTP server.
http://www.suse.com/communities/conversations/sca-pattern-development/ —
Instructions on how to create (and test) your own SCA patterns.
http://www.suse.com/communities/conversations/basic-server-health-check-
supportconfig/ —A Basic Server Health Check with Supportconfig.

https://www.novell.com/communities/coolsolutions/cool_tools/create-your-own-
supportconfig-plugin/ —Create Your Own Supportconfig Plugin.
http://www.suse.com/communities/conversations/creating-a-
central-supportconfig-repository/ —Creating a Central Supportconfig Repository.

40 Common Problems and Their Solutions
This chapter describes a range of potential problems and their solutions. Even if your situation
is not precisely listed here, there may be one similar enough to offer hints to the solution of
your problem.
40.1 Finding and Gathering Information

Linux reports things in a very detailed way. There are several places to look when you encounter
problems with your system, most of which are standard to Linux systems in general, and some
are relevant to SUSE Linux Enterprise Server systems. Most log les can be viewed with YaST
(Miscellaneous Start-Up Log).
YaST offers the possibility to collect all system information needed by the support team. Use
Other Support and select the problem category. When all information is gathered, attach it to
your support request.
A list of the most frequently checked log les follows with the description of their typical pur-
pose. Paths containing ~ refer to the current user's home directory.
TABLE 40.1: LOG FILES
Log File Description
~/.xsession-errors Messages from the desktop applications cur-

rently running.
/var/log/apparmor/ Log les from AppArmor, see Book “Security

Guide” for detailed information.
/var/log/audit/audit.log Log le from Audit to track any access to

les, directories, or resources of your sys-
tem, and trace system calls. See Book “Securi-
ty Guide” for detailed information.
/var/log/mail.* Messages from the mail system.
/var/log/NetworkManager Log le from NetworkManager to collect

problems with network connectivity
582 Finding and Gathering Information SLES 12 SP3

Log File Description
/var/log/samba/ Directory containing Samba server and client

log messages.
/var/log/warn All messages from the kernel and system log

daemon with the “warning” level or higher.
/var/log/wtmp Binary le containing user login records for

the current machine session. View it with
last .
/var/log/Xorg.*.log Various start-up and runtime log les from

the X Window System. It is useful for debug-
ging failed X start-ups.
/var/log/YaST2/ Directory containing YaST's actions and their

results.
/var/log/zypper.log Log le of Zypper.
Apart from log les, your machine also supplies you with information about the running system.
See Table 40.2: System Information With the /proc File System
TABLE 40.2: SYSTEM INFORMATION WITH THE /proc FILE SYSTEM
File Description
/proc/cpuinfo Contains processor information, including its

type, make, model, and performance.
/proc/dma Shows which DMA channels are currently

being used.
/proc/interrupts Shows which interrupts are in use, and how

many of each have been in use.
/proc/iomem Displays the status of I/O (input/output)

memory.

File Description
/proc/ioports Shows which I/O ports are in use at the mo-

ment.
/proc/meminfo Displays memory status.
/proc/modules Displays the individual modules.
/proc/mounts Displays devices currently mounted.
/proc/partitions Shows the partitioning of all hard disks.
/proc/version Displays the current version of Linux.
Apart from the /proc le system, the Linux kernel exports information with the sysfs module,
an in-memory le system. This module represents kernel objects, their attributes and relation-
ships. For more information about sysfs , see the context of udev in Chapter 21, Dynamic Kernel
Device Management with udev. Table 40.3 contains an overview of the most common directories
under /sys .
TABLE 40.3: SYSTEM INFORMATION WITH THE /sys FILE SYSTEM
File Description
/sys/block Contains subdirectories for each block device

discovered in the system. Generally, these
are mostly disk type devices.
/sys/bus Contains subdirectories for each physical bus

type.
/sys/class Contains subdirectories grouped together as

a functional types of devices (like graphics,
net, printer, etc.)
/sys/device Contains the global device hierarchy.
Linux comes with several tools for system analysis and monitoring. See Book “System Analysis
and Tuning Guide”, Chapter 2 “System Monitoring Utilities” for a selection of the most important ones
used in system diagnostics.

Each of the following scenarios begins with a header describing the problem followed by a
paragraph or two offering suggested solutions, available references for more detailed solutions,
and cross-references to other scenarios that are related.
40.2 Installation Problems

Installation problems are situations when a machine fails to install. It may fail entirely or it may
not be able to start the graphical installer. This section highlights some typical problems you
may run into, and offers possible solutions or workarounds for these kinds of situations.
40.2.1 Checking Media
If you encounter any problems using the SUSE Linux Enterprise Server installation media, check
the integrity of your installation media. Boot from the media and choose Check Installation Media
from the boot menu. In a running system, start YaST and choose Software Media Check. To
check the SUSE Linux Enterprise Server medium, insert it into the drive and click Start Check in
the Media Check screen of YaST. This may take several minutes. If errors are detected, do not
use this medium for installation. Media problems may occur when having burned the medium
yourself. Burning the media at a low speed (4x) helps to avoid problems.
585 Installation Problems SLES 12 SP3

FIGURE 40.1: CHECKING MEDIA
40.2.2 No Bootable DVD Drive Available

If your computer does not contain a bootable DVD-ROM drive or if the one you have is not
supported by Linux, there are several options you can install your machine without a built-in
DVD drive:
Using an External Boot Device

If it is supported by your BIOS and the installation kernel, boot from external DVD drives
or USB storage devices. Refer to Book “Deployment Guide”, Chapter 6 “Installation with YaST”,
Section 6.2.2 “PC (AMD64/Intel 64/ARM AArch64): System Start-up” for instructions on how to
create a bootable USB storage device.
Network Boot via PXE

If a machine lacks a DVD drive, but provides a working Ethernet connection, perform a
completely network-based installation. See Book “Deployment Guide”, Chapter 10 “Remote
Installation”, Section 10.1.3 “Remote Installation via VNC—PXE Boot and Wake on LAN” and Book
“Deployment Guide”, Chapter 10 “Remote Installation”, Section 10.1.6 “Remote Installation via SSH
—PXE Boot and Wake on LAN” for details.
586 No Bootable DVD Drive Available SLES 12 SP3

40.2.2.1 External Boot Devices
Linux supports most existing DVD drives. If the system has no DVD drive, it is still possible
that an external DVD drive, connected through USB, FireWire, or SCSI, can be used to boot the
system. This depends mainly on the interaction of the BIOS and the hardware used. Sometimes
a BIOS update may help if you encounter problems.
When installing from a Live CD, you can also create a “Live ash disk” to boot from.
40.2.3 Booting from Installation Media Fails
One reason a machine does not boot the installation media can be an incorrect boot sequence
setting in BIOS. The BIOS boot sequence must have DVD drive set as the rst entry for booting.
Otherwise the machine would try to boot from another medium, typically the hard disk. Guid-
ance for changing the BIOS boot sequence can be found the documentation provided with your
mainboard, or in the following paragraphs.
The BIOS is the software that enables the very basic functions of a computer. Motherboard
vendors provide a BIOS specifically made for their hardware. Normally, the BIOS setup can only
be accessed at a specific time—when the machine is booting. During this initialization phase, the
machine performs several diagnostic hardware tests. One of them is a memory check, indicated
by a memory counter. When the counter appears, look for a line, usually below the counter or
somewhere at the bottom, mentioning the key to press to access the BIOS setup. Usually the key
to press is one of Del , F1 , or Esc . Press this key until the BIOS setup screen appears.
PROCEDURE 40.1: CHANGING THE BIOS BOOT SEQUENCE
1. Enter the BIOS using the proper key as announced by the boot routines and wait for the
BIOS screen to appear.
2. To change the boot sequence in an AWARD BIOS, look for the BIOS FEATURES SETUP
entry. Other manufacturers may have a different name for this, such as ADVANCED CMOS
SETUP. When you have found the entry, select it and confirm with Enter .
3. In the screen that opens, look for a subentry called BOOT SEQUENCE or BOOT ORDER.
Change the settings by pressing Page ↑ or Page ↓ until the DVD drive is listed rst.
4. Leave the BIOS setup screen by pressing Esc . To save the changes, select SAVE & EXIT
SETUP, or press F10 . To confirm that your settings should be saved, press Y .
587 Booting from Installation Media Fails SLES 12 SP3

PROCEDURE 40.2: CHANGING THE BOOT SEQUENCE IN AN SCSI BIOS (ADAPTEC HOST ADAPTER)
1. Open the setup by pressing Ctrl –A .
2. Select Disk Utilities. The connected hardware components are now displayed.
Make note of the SCSI ID of your DVD drive.
3. Exit the menu with Esc .
4. Open Configure Adapter Settings. Under Additional Options, select Boot Device Options and
press Enter .
5. Enter the ID of the DVD drive and press Enter again.
6. Press Esc twice to return to the start screen of the SCSI BIOS.
7. Exit this screen and confirm with Yes to boot the computer.
Regardless of what language and keyboard layout your final installation will be using, most
BIOS configurations use the US keyboard layout as shown in the following figure:
FIGURE 40.2: US KEYBOARD LAYOUT
40.2.4 Fails to Boot

Some hardware types, mainly very old or very recent ones, fail to install. Often this may happen
because support for this type of hardware is missing in the installation kernel, or because of
certain functionality included in this kernel, such as ACPI, that can still cause problems on some
hardware.
588 Fails to Boot SLES 12 SP3

If your system fails to install using the standard Installation mode from the rst installation boot
screen, try the following:
1. With the DVD still in the drive, reboot the machine with Ctrl – Alt – Del or using the
hardware reset button.
2. When the boot screen appears, press F5 , use the arrow keys of your keyboard to navigate
to No ACPI and press Enter to launch the boot and installation process. This option
disables the support for ACPI power management techniques.
3. Proceed with the installation as described in Book “Deployment Guide”, Chapter 6 “Installation
with YaST”.
If this fails, proceed as above, but choose Safe Settings instead. This option disables ACPI and
DMA support. Most hardware will boot with this option.
If both of these options fail, use the boot options prompt to pass any additional parameters
needed to support this type of hardware to the installation kernel. For more information about
the parameters available as boot options, refer to the kernel documentation located in /usr/
src/linux/Documentation/kernel-parameters.txt .
Tip: Obtaining Kernel Documentation

Install the kernel-source package to view the kernel documentation.
There are other ACPI-related kernel parameters that can be entered at the boot prompt prior
to booting for installation:
acpi=off
This parameter disables the complete ACPI subsystem on your computer. This may be
useful if your computer cannot handle ACPI or if you think ACPI in your computer causes
trouble.
acpi=force
Always enable ACPI even if your computer has an old BIOS dated before the year 2000.
This parameter also enables ACPI if it is set in addition to acpi=off .
acpi=noirq
Do not use ACPI for IRQ routing.
589 Fails to Boot SLES 12 SP3

acpi=ht
Run only enough ACPI to enable hyper-threading.
acpi=strict
Be less tolerant of platforms that are not strictly ACPI specification compliant.
pci=noacpi
Disable PCI IRQ routing of the new ACPI system.
pnpacpi=off
This option is for serial or parallel problems when your BIOS setup contains wrong inter-
rupts or ports.
notsc
Disable the time stamp counter. This option can be used to work around timing problems
on your systems. It is a recent feature, if you see regressions on your machine, especially
time related or even total hangs, this option is worth a try.
nohz=off
Disable the nohz feature. If your machine hangs, this option may help. Otherwise it is of
no use.
Once you have determined the right parameter combination, YaST automatically writes them
to the boot loader configuration to make sure that the system boots properly next time.
If unexplainable errors occur when the kernel is loaded or during the installation, select Memory
Test in the boot menu to check the memory. If Memory Test returns an error, it is usually a
hardware error.
40.2.5 Fails to Launch Graphical Installer

After you insert the medium into your drive and reboot your machine, the installation screen
comes up, but after you select Installation, the graphical installer does not start.
There are several ways to deal with this situation:
Try to select another screen resolution for the installation dialogs.
Select Text Mode for installation.
Do a remote installation via VNC using the graphical installer.
590 Fails to Launch Graphical Installer SLES 12 SP3

PROCEDURE 40.3: CHANGE SCREEN RESOLUTION FOR INSTALLATION
1. Boot for installation.
2. Press F3 to open a menu from which to select a lower resolution for installation purposes.
3. Select Installation and proceed with the installation as described in Book “Deployment
Guide”, Chapter 6 “Installation with YaST”.
PROCEDURE 40.4: INSTALLATION IN TEXT MODE
2. Press F3 and select Text Mode.
3. Select Installation and proceed with the installation as described in Book “Deployment
Guide”, Chapter 6 “Installation with YaST”.
PROCEDURE 40.5: VNC INSTALLATION
2. Enter the following text at the boot options prompt:
vnc=1 vncpassword=SOME_PASSWORD
Replace SOME_PASSWORD with the password to use for VNC installation.
3. Select Installation then press Enter to start the installation.

Instead of starting right into the graphical installation routine, the system continues to run
in a text mode, then halts, displaying a message containing the IP address and port number
at which the installer can be reached via a browser interface or a VNC viewer application.
4. If using a browser to access the installer, launch the browser and enter the address infor-
mation provided by the installation routines on the future SUSE Linux Enterprise Server
machine and press Enter :
http://IP_ADDRESS_OF_MACHINE:5801
A dialog opens in the browser window prompting you for the VNC password. Enter it and
proceed with the installation as described in Book “Deployment Guide”, Chapter 6 “Installation
with YaST”.
591 Fails to Launch Graphical Installer SLES 12 SP3

Important: Cross-platform Support
Installation via VNC works with any browser under any operating system, provided
Java support is enabled.
Provide the IP address and password to your VNC viewer when prompted. A window
opens, displaying the installation dialogs. Proceed with the installation as usual.
40.2.6 Only Minimalistic Boot Screen Started

You inserted the medium into the drive, the BIOS routines are finished, but the system does not
start with the graphical boot screen. Instead it launches a very minimalistic text-based interface.
This may happen on any machine not providing sufficient graphics memory for rendering a
graphical boot screen.
Although the text boot screen looks minimalistic, it provides nearly the same functionality as
the graphical one:
Boot Options
Unlike the graphical interface, the different boot options cannot be selected using the
cursor keys of your keyboard. The boot menu of the text mode boot screen offers some
keywords to enter at the boot prompt. These keywords map to the options offered in the
graphical version. Enter your choice and press Enter to launch the boot process.
Custom Boot Options

After selecting a boot option, enter the appropriate keyword at the boot prompt or enter
some custom boot options as described in Section 40.2.4, “Fails to Boot”. To launch the instal-
lation process, press Enter .
Screen Resolutions
Use the function keys ( F1 ... F12 ) to determine the screen resolution for installation. If
you need to boot in text mode, choose F3 .
40.2.7 Log Files

For more information about log les that are created during installation, see Section 39.5, “Gath-
ering Information during the Installation”.
592 Only Minimalistic Boot Screen Started SLES 12 SP3

40.3 Boot Problems
Boot problems are situations when your system does not boot properly (does not boot to the
expected target and login screen).
40.3.1 The GRUB 2 Boot Loader Fails to Load

If the hardware is functioning properly, it is possible that the boot loader is corrupted and Linux
cannot start on the machine. In this case, it is necessary to repair the boot loader. To do so, you
need to start the Rescue System as described in Section 40.6.2, “Using the Rescue System” and follow
the instructions in Section 40.6.2.4, “Modifying and Re-installing the Boot Loader”.
Alternatively, you can use the Rescue System to x the boot loader as follows. Boot your machine
from the installation media. In the boot screen, choose More Boot Linux System. Select the disk
containing the installed system and kernel with the default kernel options.
When the system is booted, start YaST and switch to System Boot Loader. Make sure that the
Write generic Boot Code to MRB option is enabled, and press OK. This fixes the corrupted boot
loader by overwriting it, or installs the boot loader if it is missing.
Other reasons for the machine not booting may be BIOS-related:
BIOS Settings
Check your BIOS for references to your hard disk. GRUB 2 may simply not be started if
the hard disk itself cannot be found with the current BIOS settings.
BIOS Boot Order

Check whether your system's boot order includes the hard disk. If the hard disk option
was not enabled, your system may install properly, but fails to boot when access to the
hard disk is required.
40.3.2 No Graphical Login

If the machine starts, but does not boot into the graphical login manager, anticipate problems
either with the choice of the default systemd target or the configuration of the X Window System.
To check the current systemd default target run the command sudo systemctl get-default .
If the value returned is not graphical.target , run the command sudo systemctl isolate
593 Boot Problems SLES 12 SP3

graphical.target . If the graphical login screen starts, log in and start YaST System Services
Manager and set the Default System Target to Graphical Interface. From now on the system should
boot into the graphical login screen.
If the graphical login screen does not start even if having booted or switched to the graphical
target, your desktop or X Window software is probably misconfigured or corrupted. Examine
the log les at /var/log/Xorg.*.log for detailed messages from the X server as it attempted
to start. If the desktop fails during start, it may log error messages to the system journal that
can be queried with the command journalctl (see Chapter 15, journalctl: Query the systemd
Journal for more information). If these error messages hint at a configuration problem in the X
server, try to x these issues. If the graphical system still does not come up, consider reinstalling
the graphical desktop.
40.3.3 Root Btrfs Partition Cannot Be Mounted

If a btrfs root partition becomes corrupted, try the following options:
Mount the partition with the -o recovery option.
If that fails, run btrfs-zero-log on your root partition.
40.3.4 Force Checking Root Partitions

If the root partition becomes corrupted, use the parameter forcefsck on the boot prompt. This
passes the option -f (force) to the fsck command.
40.4 Login Problems

Login problems occur when your machine does boot to the expected welcome screen or login
prompt, but refuses to accept the user name and password, or accepts them but then does not
behave properly (fails to start the graphic desktop, produces errors, drops to a command line,
etc.).
594 Root Btrfs Partition Cannot Be Mounted SLES 12 SP3

40.4.1 Valid User Name and Password Combinations Fail
This usually occurs when the system is configured to use network authentication or directory
services and, for some reason, cannot retrieve results from its configured servers. The root
user, as the only local user, is the only user that can still log in to these machines. The following
are some common reasons a machine appears functional but cannot process logins correctly:
The network is not working. For further directions on this, turn to Section 40.5, “Network
Problems”.
DNS is not working at the moment (which prevents GNOME from working and the system
from making validated requests to secure servers). One indication that this is the case
is that the machine takes an extremely long time to respond to any action. Find more
information about this topic in Section 40.5, “Network Problems”.
If the system is configured to use Kerberos, the system's local time may have drifted past
the accepted variance with the Kerberos server time (this is typically 300 seconds). If NTP
(network time protocol) is not working properly or local NTP servers are not working,
Kerberos authentication ceases to function because it depends on common clock synchro-
nization across the network.
The system's authentication configuration is misconfigured. Check the PAM configuration

les involved for any typographical errors or misordering of directives. For additional
background information about PAM and the syntax of the configuration les involved,
refer to Book “Security Guide”, Chapter 2 “Authentication with PAM”.
The home partition is encrypted. Find more information about this topic in Section 40.4.3,
“Login to Encrypted Home Partition Fails”.
In all cases that do not involve external network problems, the solution is to reboot the system
into single-user mode and repair the configuration before booting again into operating mode
and attempting to log in again. To boot into single-user mode:
1. Reboot the system. The boot screen appears, offering a prompt.
2. Press Esc to exit the splash screen and get to the GRUB 2 text-based menu.
3. Press B to enter the GRUB 2 editor.
4. Add the following parameter to the line containing the kernel parameters:
systemd.unit=rescue.target
595 Valid User Name and Password Combinations Fail SLES 12 SP3
5. Press F10 .
6. Enter the user name and password for root .
7. Make all the necessary changes.
8. Boot into the full multiuser and network mode by entering systemctl isolate graph-
ical.target at the command line.
40.4.2 Valid User Name and Password Not Accepted

This is by far the most common problem users encounter, because there are many reasons this
can occur. Depending on whether you use local user management and authentication or network
authentication, login failures occur for different reasons.
Local user management can fail for the following reasons:
The user may have entered the wrong password.
The user's home directory containing the desktop configuration les is corrupted or write
protected.
There may be problems with the X Window System authenticating this particular user,
especially if the user's home directory has been used with another Linux distribution prior
to installing the current one.
To locate the reason for a local login failure, proceed as follows:
1. Check whether the user remembered his password correctly before you start debugging the
whole authentication mechanism. If the user may not remember his password correctly,
use the YaST User Management module to change the user's password. Pay attention to
the Caps Lock key and unlock it, if necessary.
2. Log in as root and check the system journal with journalctl -e for error messages
of the login process and of PAM.
3. Try to log in from a console (using Ctrl – Alt – F1 ). If this is successful, the blame cannot
be put on PAM, because it is possible to authenticate this user on this machine. Try to locate
any problems with the X Window System or the GNOME desktop. For more information,
refer to Section 40.4.4, “Login Successful but GNOME Desktop Fails”.
596 Valid User Name and Password Not Accepted SLES 12 SP3
4. If the user's home directory has been used with another Linux distribution, remove the
Xauthority le in the user's home. Use a console login via Ctrl – Alt – F1 and run
rm .Xauthority as this user. This should eliminate X authentication problems for this
user. Try graphical login again.
5. If the desktop could not start because of corrupt configuration les, proceed with Sec-
tion 40.4.4, “Login Successful but GNOME Desktop Fails”.
In the following, common reasons a network authentication for a particular user may fail on a
specific machine are listed:
The user may have entered the wrong password.
The user name exists in the machine's local authentication les and is also provided by a
network authentication system, causing conflicts.
The home directory exists but is corrupt or unavailable. Perhaps it is write protected or is
on a server that is inaccessible at the moment.
The user does not have permission to log in to that particular host in the authentication
system.
The machine has changed host names, for whatever reason, and the user does not have
permission to log in to that host.
The machine cannot reach the authentication server or directory server that contains that
user's information.
There may be problems with the X Window System authenticating this particular user, es-
pecially if the user's home has been used with another Linux distribution prior to installing
the current one.
To locate the cause of the login failures with network authentication, proceed as follows:
1. Check whether the user remembered their password correctly before you start debugging
the whole authentication mechanism.
2. Determine the directory server which the machine relies on for authentication and make
sure that it is up and running and properly communicating with the other machines.
3. Determine that the user's user name and password work on other machines to make sure
that his authentication data exists and is properly distributed.
597 Valid User Name and Password Not Accepted SLES 12 SP3
4. See if another user can log in to the misbehaving machine. If another user can log in with-
out difficulty or if root can log in, log in and examine the system journal with jour-
nalctl -e > le. Locate the time stamps that correspond to the login attempts and de-
termine if PAM has produced any error messages.
5. Try to log in from a console (using Ctrl – Alt – F1 ). If this is successful, the problem is
not with PAM or the directory server on which the user's home is hosted, because it is
possible to authenticate this user on this machine. Try to locate any problems with the
X Window System or the GNOME desktop. For more information, refer to Section 40.4.4,
“Login Successful but GNOME Desktop Fails”.
6. If the user's home directory has been used with another Linux distribution, remove the
Xauthority le in the user's home. Use a console login via Ctrl – Alt – F1 and run
rm .Xauthority as this user. This should eliminate X authentication problems for this
user. Try graphical login again.
7. If the desktop could not start because of corrupt configuration les, proceed with Sec-
tion 40.4.4, “Login Successful but GNOME Desktop Fails”.
40.4.3 Login to Encrypted Home Partition Fails
It is recommended to use an encrypted home partition for laptops. If you cannot log in to your
laptop, the reason is usually simple: your partition could not be unlocked.
During the boot time, you need to enter the passphrase to unlock your encrypted partition. If
you do not enter it, the boot process continues, leaving the partition locked.
To unlock your encrypted partition, proceed as follows:
1. Switch to the text console with Ctrl – Alt – F1 .
2. Become root .
3. Restart the unlocking process again with:
systemctl restart home.mount
4. Enter your passphrase to unlock your encrypted partition.
5. Exit the text console and switch back to the login screen with Alt – F7 .
598 Login to Encrypted Home Partition Fails SLES 12 SP3

6. Log in as usual.
40.4.4 Login Successful but GNOME Desktop Fails

If this is the case, it is likely that your GNOME configuration les have become corrupted. Some
symptoms may include the keyboard failing to work, the screen geometry becoming distorted, or
even the screen coming up as a bare gray eld. The important distinction is that if another user
logs in, the machine works normally. It is then likely that the problem can be xed relatively
quickly by simply moving the user's GNOME configuration directory to a new location, which
causes GNOME to initialize a new one. Although the user is forced to reconfigure GNOME, no
data is lost.
1. Switch to a text console by pressing Ctrl – Alt – F1 .
2. Log in with your user name.
3. Move the user's GNOME configuration directories to a temporary location:
mv .gconf .gconf-ORIG-RECOVER
mv .gnome2 .gnome2-ORIG-RECOVER
4. Log out.
5. Log in again, but do not run any applications.
6. Recover your individual application configuration data (including the Evolution e-mail
client data) by copying the ~/.gconf-ORIG-RECOVER/apps/ directory back into the new
~/.gconf directory as follows:
cp -a .gconf-ORIG-RECOVER/apps .gconf/
If this causes the login problems, attempt to recover only the critical application data and
reconfigure the remainder of the applications.
40.5 Network Problems

Many problems of your system may be network-related, even though they do not seem to be
at rst. For example, the reason for a system not allowing users to log in may be a network
problem of some kind. This section introduces a simple checklist you can apply to identify the
cause of any network problem encountered.
599 Login Successful but GNOME Desktop Fails SLES 12 SP3

PROCEDURE 40.6: HOW TO IDENTIFY NETWORK PROBLEMS
When checking the network connection of your machine, proceed as follows:
1. If you use an Ethernet connection, check the hardware rst. Make sure that your network
cable is properly plugged into your computer and router (or hub, etc.). The control lights
next to your Ethernet connector are normally both be active.
If the connection fails, check whether your network cable works with another machine.
If it does, your network card causes the failure. If hubs or switches are included in your
network setup, they may be faulty, as well.
2. If using a wireless connection, check whether the wireless link can be established by other
machines. If not, contact the wireless network's administrator.
3. Once you have checked your basic network connectivity, try to nd out which service
is not responding. Gather the address information of all network servers needed in your
setup. Either look them up in the appropriate YaST module or ask your system adminis-
trator. The following list gives some typical network servers involved in a setup together
with the symptoms of an outage.
DNS (Name Service)

A broken or malfunctioning name service affects the network's functionality in many
ways. If the local machine relies on any network servers for authentication and these
servers cannot be found because of name resolution issues, users would not even be
able to log in. Machines in the network managed by a broken name server would
not be able to “see” each other and communicate.
NTP (Time Service)

A malfunctioning or completely broken NTP service could affect Kerberos authenti-
cation and X server functionality.
NFS (File Service)

If any application needs data stored in an NFS mounted directory, it cannot start
or function properly if this service was down or misconfigured. In the worst case
scenario, a user's personal desktop configuration would not come up if their home
directory containing the .gconf subdirectory could not be found because of a faulty
NFS server.
Samba (File Service)

If any application needs data stored in a directory on a faulty Samba server, it cannot
start or function properly.
600 Network Problems SLES 12 SP3

NIS (User Management)
If your SUSE Linux Enterprise Server system relies on a faulty NIS server to provide
the user data, users cannot log in to this machine.
LDAP (User Management)

If your SUSE Linux Enterprise Server system relies on a faulty LDAP server to provide
the user data, users cannot log in to this machine.
Kerberos (Authentication)
Authentication will not work and login to any machine fails.
CUPS (Network Printing)

Users cannot print.
4. Check whether the network servers are running and whether your network setup allows
you to establish a connection:
Important: Limitations
The debugging procedure described below only applies to a simple network serv-
er/client setup that does not involve any internal routing. It assumes both server
and client are members of the same subnet without the need for additional routing.
a. Use ping IP_ADDRESS/HOSTNAME (replace with the host name or IP address of the
server) to check whether each one of them is up and responding to the network. If
this command is successful, it tells you that the host you were looking for is up and
running and that the name service for your network is configured correctly.
If ping fails with destination host unreachable , either your system or the desired
server is not properly configured or down. Check whether your system is reachable
by running ping IP address or YOUR_HOSTNAME from another machine. If you
can reach your machine from another machine, it is the server that is not running
or not configured correctly.
If ping fails with unknown host , the name service is not configured correctly or
the host name used was incorrect. For further checks on this matter, refer to Step
4.b. If ping still fails, either your network card is not configured correctly or your
network hardware is faulty.

b. Use host HOSTNAME to check whether the host name of the server you are trying to
connect to is properly translated into an IP address and vice versa. If this command
returns the IP address of this host, the name service is up and running. If the host
command fails, check all network configuration les relating to name and address
resolution on your host:
/etc/resolv.conf
This le is used to keep track of the name server and domain you are currently
using. It can be modified manually or automatically adjusted by YaST or DHCP.
Automatic adjustment is preferable. However, make sure that this le has the
following structure and all network addresses and domain names are correct:
search FULLY_QUALIFIED_DOMAIN_NAME
nameserver IPADDRESS_OF_NAMESERVER
This le can contain more than one name server address, but at least one of
them must be correct to provide name resolution to your host. If needed, adjust
this le using the YaST Network Settings module (Hostname/DNS tab).
If your network connection is handled via DHCP, enable DHCP to change host
name and name service information by selecting Set Hostname via DHCP (can
be set globally for any interface or per interface) and Update Name Servers and
Search List via DHCP in the YaST Network Settings module (Hostname/DNS
tab).
/etc/nsswitch.conf
This le tells Linux where to look for name service information. It should look
like this:
...
hosts: files dns
networks: files dns
...
The dns entry is vital. It tells Linux to use an external name server. Normally,
these entries are automatically managed by YaST, but it would be prudent to
check.
If all the relevant entries on the host are correct, let your system administra-
tor check the DNS server configuration for the correct zone information. For
detailed information about DNS, refer to Chapter 25, The Domain Name System.

If you have made sure that the DNS configuration of your host and the DNS
server are correct, proceed with checking the configuration of your network
and network device.
c. If your system cannot establish a connection to a network server and you have ex-
cluded name service problems from the list of possible culprits, check the configu-
ration of your network card.
Use the command ip addr show NETWORK_DEVICE to check whether this device was
properly configured. Make sure that the inet address with the netmask ( /MASK )
is configured correctly. An error in the IP address or a missing bit in your network
mask would render your network configuration unusable. If necessary, perform this
check on the server as well.
d. If the name service and network hardware are properly configured and running,
but some external network connections still get long time-outs or fail entirely, use
traceroute FULLY_QUALIFIED_DOMAIN_NAME (executed as root ) to track the net-
work route these requests are taking. This command lists any gateway (hop) that a
request from your machine passes on its way to its destination. It lists the response
time of each hop and whether this hop is reachable. Use a combination of traceroute
and ping to track down the culprit and let the administrators know.
Once you have identified the cause of your network trouble, you can resolve it yourself (if the
problem is located on your machine) or let the system administrators of your network know
about your findings so they can reconfigure the services or repair the necessary systems.
40.5.1 NetworkManager Problems

If you have a problem with network connectivity, narrow it down as described in Procedure 40.6,
“How to Identify Network Problems”. If NetworkManager seems to be the culprit, proceed as follows
to get logs providing hints on why NetworkManager fails:
1. Open a shell and log in as root .
2. Restart the NetworkManager:
systemctl restart Network.Manager
3. Open a Web page, for example, http://www.opensuse.org as normal user to see, if you
can connect.
603 NetworkManager Problems SLES 12 SP3

4. Collect any information about the state of NetworkManager in /var/log/NetworkMan-
ager .
For more information about NetworkManager, refer to Chapter 36, Using NetworkManager.
40.6 Data Problems

Data problems are when the machine may or may not boot properly but, in either case, it is
clear that there is data corruption on the system and that the system needs to be recovered.
These situations call for a backup of your critical data, enabling you to recover the system state
from before your system failed.
40.6.1 Managing Partition Images

Sometimes you need to perform a backup from an entire partition or even hard disk. Linux
comes with the dd tool which can create an exact copy of your disk. Combined with gzip you
save some space.
PROCEDURE 40.7: BACKING UP AND RESTORING HARD DISKS
1. Start a Shell as user root .
2. Select your source device. Typically this is something like /dev/sda (labeled as SOURCE ).
3. Decide where you want to store your image (labeled as BACKUP_PATH ). It must be different
from your source device. In other words: if you make a backup from /dev/sda , your
image le must not to be stored under /dev/sda .
4. Run the commands to create a compressed image le:
dd if=/dev/SOURCE | gzip > /BACKUP_PATH/image.gz
5. Restore the hard disk with the following commands:
gzip -dc /BACKUP_PATH/image.gz | dd of=/dev/SOURCE
If you only need to back up a partition, replace the SOURCE placeholder with your respective
partition. In this case, your image le can lie on the same hard disk, but on a different partition.
604 Data Problems SLES 12 SP3

40.6.2 Using the Rescue System
There are several reasons a system could fail to come up and run properly. A corrupted le
system following a system crash, corrupted configuration les, or a corrupted boot loader con-
figuration are the most common ones.
To help you to resolve these situations, SUSE Linux Enterprise Server contains a rescue system
that you can boot. The rescue system is a small Linux system that can be loaded into a RAM disk
and mounted as root le system, allowing you to access your Linux partitions from the outside.
Using the rescue system, you can recover or modify any important aspect of your system.
Manipulate any type of configuration le.
Check the le system for defects and start automatic repair processes.
Access the installed system in a “change root” environment.
Check, modify, and re-install the boot loader configuration.
Recover from a badly installed device driver or unusable kernel.
Resize partitions using the parted command. Find more information about this tool at the
GNU Parted Web site http://www.gnu.org/software/parted/parted.html .
The rescue system can be loaded from various sources and locations. The simplest option is to
boot the rescue system from the original installation medium.
Note: IBM z Systems Starting the Rescue System

On IBM z Systems the installation system can be used for rescue purposes. To start the
rescue system follow the instructions in Section 40.7, “IBM z Systems: Using initrd as a Rescue
System”.
1. Insert the installation medium into your DVD drive.
2. Reboot the system.
3. At the boot screen, press F4 and choose DVD-ROM. Then choose Rescue System from the
main menu.
605 Using the Rescue System SLES 12 SP3

4. Enter root at the Rescue: prompt. A password is not required.
If your hardware setup does not include a DVD drive, you can boot the rescue system
from a network source. The following example applies to a remote boot scenario—if using
another boot medium, such as a DVD, modify the info le accordingly and boot as you
would for a normal installation.
1. Enter the configuration of your PXE boot setup and add the lines install=PROTO-
COL://INSTSOURCE and rescue=1 . If you need to start the repair system, use repair=1
instead. As with a normal installation, PROTOCOL stands for any of the supported network
protocols (NFS, HTTP, FTP, etc.) and INSTSOURCE for the path to your network installa-
tion source.
2. Boot the system using “Wake on LAN”, as described in Book “Deployment Guide”, Chapter 9
“Preparing the Boot of the Target System”, Section 9.7 “Wake on LAN”.
Once you have entered the rescue system, you can use the virtual consoles that can be reached
with Alt – F1 to Alt – F6 .
A shell and other useful utilities, such as the mount program, are available in the /bin directo-
ry. The /sbin directory contains important le and network utilities for reviewing and repair-
ing the le system. This directory also contains the most important binaries for system mainte-
nance, such as fdisk , mkfs , mkswap , mount , and shutdown , ip and ss for maintaining the
network. The directory /usr/bin contains the vi editor, nd, less, and SSH.
To see the system messages, either use the command dmesg or view the system log with jour-
nalctl .
40.6.2.1 Checking and Manipulating Configuration Files
As an example for a configuration that might be xed using the rescue system, imagine you
have a broken configuration le that prevents the system from booting properly. You can x
this using the rescue system.
To manipulate a configuration le, proceed as follows:
1. Start the rescue system using one of the methods described above.

2. To mount a root le system located under /dev/sda6 to the rescue system, use the fol-
lowing command:
mount /dev/sda6 /mnt
All directories of the system are now located under /mnt
3. Change the directory to the mounted root le system:
cd /mnt
4. Open the problematic configuration le in the vi editor. Adjust and save the configuration.
5. Unmount the root le system from the rescue system:
umount /mnt
6. Reboot the machine.
40.6.2.2 Repairing and Checking File Systems
Generally, le systems cannot be repaired on a running system. If you encounter serious prob-
lems, you may not even be able to mount your root le system and the system boot may end
with a “kernel panic”. In this case, the only way is to repair the system from the outside. The
system contains the utilities to check and repair the btrfs , ext2 , ext3 , ext4 , reiserfs ,
xfs , dosfs , and vfat le systems. Look for the command fsck. FILESYSTEM , for example,
if you need a le system check for btrfs , use fsck.btrfs .
40.6.2.3 Accessing the Installed System
If you need to access the installed system from the rescue system, you need to do this in a
change root environment. For example, to modify the boot loader configuration, or to execute
a hardware configuration utility.

To set up a change root environment based on the installed system, proceed as follows:
1.
Tip: Import LVM Volume Groups
If you are using a LVM setup (refer to Book “Storage Administration Guide” for more
general details), import all existing volume groups in order to be able to nd and
mount the device(s):
rootvgimport -a
Run lsblk to check which node corresponds to the root partition. It is /dev/sda2 in
our example:
lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 149,1G 0 disk
├─sda1 8:1 0 2G 0 part [SWAP]
├─sda2 8:2 0 20G 0 part /
└─sda3 8:3 0 127G 0 part
└─cr_home 254:0 0 127G 0 crypt /home
2. Mount the root partition from the installed system:
mount /dev/sda2 /mnt
3. Mount /proc , /dev , and /sys partitions:
mount -t proc none /mnt/proc

mount --rbind /dev /mnt/dev
mount --rbind /sys /mnt/sys
4. Now you can “change root” into the new environment, keeping the bash shell:
chroot /mnt /bin/bash
5. Finally, mount the remaining partitions from the installed system:
mount -a
6. Now you have access to the installed system. Before rebooting the system, unmount the
partitions with umount -a and leave the “change root” environment with exit .

Warning: Limitations
Although you have full access to the les and applications of the installed system, there
are some limitations. The kernel that is running is the one that was booted with the res-
cue system, not with the change root environment. It only supports essential hardware
and it is not possible to add kernel modules from the installed system unless the kernel
versions are identical. Always check the version of the currently running (rescue) kernel
with uname -r and then nd out if a matching subdirectory exists in the /lib/modules
directory in the change root environment. If yes, you can use the installed modules, oth-
erwise you need to supply their correct versions on other media, such as a ash disk. Most
often the rescue kernel version differs from the installed one — then you cannot simply
access a sound card, for example. It is also not possible to start a graphical user interface.
Also note that you leave the “change root” environment when you switch the console
with Alt – F1 to Alt – F6 .
40.6.2.4 Modifying and Re-installing the Boot Loader
Sometimes a system cannot boot because the boot loader configuration is corrupted. The start-
up routines cannot, for example, translate physical drives to the actual locations in the Linux
le system without a working boot loader.
To check the boot loader configuration and re-install the boot loader, proceed as follows:
1. Perform the necessary steps to access the installed system as described in Section 40.6.2.3,
“Accessing the Installed System”.
2. Check that the GRUB 2 boot loader is installed on the system. If not, install the package
grub2 and run
grub2-install /dev/sda
3. Check whether the following les are correctly configured according to the GRUB 2 con-
figuration principles outlined in Chapter 12, The Boot Loader GRUB 2 and apply fixes if nec-
essary.
/etc/default/grub
/boot/grub2/device.map (optional le, only present if created manually)

/boot/grub2/grub.cfg (this le is generated, do not edit)
/etc/sysconfig/bootloader
4. Re-install the boot loader using the following command sequence:
grub2-mkconfig -o /boot/grub2/grub.cfg
5. Unmount the partitions, log out from the “change root” environment, and reboot the sys-
tem:
umount -a
exit
reboot
40.6.2.5 Fixing Kernel Installation
A kernel update may introduce a new bug which can impact the operation of your system. For
example a driver for a piece of hardware in your system may be faulty, which prevents you from
accessing and using it. In this case, revert to the last working kernel (if available on the system)
or install the original kernel from the installation media.
Tip: How to Keep Last Kernels after Update

To prevent failures to boot after a faulty kernel update, use the kernel multiversion feature
and tell libzypp which kernels you want to keep after the update.
For example to always keep the last two kernels and the currently running one, add
multiversion.kernels = latest,latest-1,running
to the /etc/zypp/zypp.conf le. See Book “Deployment Guide”, Chapter 15 “Installing Mul-
tiple Kernel Versions” for more information.
A similar case is when you need to re-install or update a broken driver for a device not sup-
ported by SUSE Linux Enterprise Server. For example when a hardware vendor uses a specific
device, such as a hardware RAID controller, which needs a binary driver to be recognized by
the operating system. The vendor typically releases a Driver Update Disk (DUD) with the xed
or updated version of the required driver.

In both cases you need to access the installed system in the rescue mode and x the kernel
related problem, otherwise the system may fail to boot correctly:
1. Boot from the SUSE Linux Enterprise Server installation media.
2. If you are recovering after a faulty kernel update, skip this step. If you need to use a driver
update disk (DUD), press F6 to load the driver update after the boot menu appears, and
choose the path or URL to the driver update and confirm with Yes.
3. Choose Rescue System from the boot menu and press Enter . If you chose to use DUD, you
will be asked to specify where the driver update is stored.
5. Manually mount the target system and “change root” into the new environment. For more
information, see Section 40.6.2.3, “Accessing the Installed System”.
6. If using DUD, install/re-install/update the faulty device driver package. Always make sure
the installed kernel version exactly matches the version of the driver you are installing.
If fixing faulty kernel update installation, you can install the original kernel from the
installation media with the following procedure.
a. Identify your DVD device with hwinfo --cdrom and mount it with mount /dev/
sr0 /mnt .
b. Navigate to the directory where your kernel les are stored on the DVD, for example
cd /mnt/suse/x86_64/ .
c. Install required kernel-* , kernel-*-base , and kernel-*-extra packages of

your flavor with the rpm -i command.
7. Update configuration les and reinitialize the boot loader if needed. For more information,
see Section 40.6.2.4, “Modifying and Re-installing the Boot Loader”.
8. Remove any bootable media from the system drive and reboot.

40.7 IBM z Systems: Using initrd as a Rescue System
If the kernel of the SUSE® Linux Enterprise Server for IBM z Systems is upgraded or modified,
it is possible to reboot the system accidentally in an inconsistent state, so standard procedures
of IPLing the installed system fail. In such a case, you may use the installation system for rescue
purposes.
IPL the SUSE Linux Enterprise Server for IBM z Systems installation system as described in Book
“Deployment Guide”, Chapter 4 “Installation on IBM z Systems”, Section 4.2 “Preparing for Installation”.
Choose Start Installation and enter all required parameters. After the installation system has
loaded and you are asked which display type to use to control the installation, select SSH . Now
you can log in to the system with SSH as root without a password.
In this state, no disks are configured. You need to configure them before you can proceed.
PROCEDURE 40.8: CONFIGURING DASDS
1. Configure DASDs with the following command:
dasd_configure 0.0.0150 1 0
0.0.0150 is the channel to which the DASD is connected. The 1 means activate the disk
(a 0 at this place would deactivate the disk). The 0 stands for “no DIAG mode” for the
disk (a 1 here would enable DAIG access to the disk).
2. Now the DASD is online (check with cat /proc/partitions ) and can used for subse-
quent commands.
PROCEDURE 40.9: CONFIGURING A ZFCP DISK
1. To configure a zFCP disk, it is necessary to rst configure the zFCP adapter. Do this with
zfcp_host_configure 0.0.4000 1
0.0.4000 is the channel to which the adapter is attached and 1 stands for activate (a
0 here would deactivate the adapter).
2. After the adapter is activated, a disk can be configured. Do this with the following com-
mand:
zfcp_disk_configure 0.0.4000 1234567887654321 8765432100000000 1
612 IBM z Systems: Using initrd as a Rescue System SLES 12 SP3

0.0.4000 is the previously-used channel ID, 1234567887654321 is the WWPN (World
wide Port Number), and 8765432100000000 is the LUN (logical unit number). The 1
stands for activating the disk (a 0 here would deactivate the disk).
3. Now the zFCP disk is online (check with cat /proc/partitions ) and can used for sub-
sequent commands.
Now the rescue system is fully set up and you can start repairing the installed system. See
Section 40.6.2, “Using the Rescue System” for instructions on how to repair the most common issues.
613 IBM z Systems: Using initrd as a Rescue System SLES 12 SP3

A Documentation Updates
This chapter lists content changes for this document.

This manual was updated on the following dates:
Section A.1, “January 2018 (Maintenance Release of SUSE Linux Enterprise Server 12 SP3)”
Section A.2, “December 2017 (Maintenance Release of SUSE Linux Enterprise Server 12 SP3)”
Section A.3, “September 2017 (Initial Release of SUSE Linux Enterprise Server 12 SP3)”
Section A.4, “November 2016 (Initial Release of SUSE Linux Enterprise Server 12 SP2)”
Section A.5, “March 2016 (Maintenance Release of SUSE Linux Enterprise Server 12 SP1)”
Section A.6, “December 2015 (Initial Release of SUSE Linux Enterprise Server 12 SP1)”
Section A.7, “February 2015 (Documentation Maintenance Update)”
Section A.8, “October 2014 (Initial Release of SUSE Linux Enterprise Server 12)”
614 SLES 12 SP3

A.1 January 2018 (Maintenance Release of SUSE Linux
Enterprise Server 12 SP3)
Chapter 12, The Boot Loader GRUB 2
List video modes in grub with videoinfo , vbeinfo is outdated. See Sec-
tion 12.2.2, “The File /etc/default/grub”. (https://bugzilla.opensuse.com/show_bug.c-
gi?id=1074026 )
Chapter 22, Live Patching the Linux Kernel Using kGraft
POWER is supported for kGraft live patching, see Chapter 22, Live Patching the Linux
Kernel Using kGraft. (https://bugzilla.opensuse.com/show_bug.cgi?id=1074844 )
Replace grub2-reboot with grub2-once to set the default boot entry for the next
boot only, see Section 12.2.2, “The File /etc/default/grub”. (https://bugzilla.open-
suse.com/show_bug.cgi?id=1071210 )
A.2 December 2017 (Maintenance Release of SUSE

Linux Enterprise Server 12 SP3)
General
Numerous small fixes and additions to the documentation, based on technical feed-
back.
Removed all references to the faillog package, which is no longer shipped (https://
bugzilla.suse.com/show_bug.cgi?id=710788 ).

kGraft patches are available for CVSS 7+ vulnerabilities, Section 22.9, “Scope of SLE Live
Patching”. (https://bugzilla.suse.com/show_bug.cgi?id=1068181 )
615 January 2018 (Maintenance Release of SUSE Linux Enterprise Server 12 SP3) SLES 12 SP3
Bugfixes
Removed a note referencing YaST for *DEFAULT options in Section 12.2.2, “The File /
etc/default/grub” (https://bugzilla.suse.com/show_bug.cgi?id=1017728 ).
Aligned sections + gave more details in Section 12.3.1, “Boot Loader Location and Boot
Code Options” (https://bugzilla.suse.com/show_bug.cgi?id=1017737 ).
Added ~/.alias in Section 1.1.1, “Knowing the Bash Configuration Files”. (https://bugzil-

la.suse.com/show_bug.cgi?id=1062209 ).
Added hint on importing volume groups in Section 40.6.2.3, “Accessing the Installed Sys-
tem” (https://bugzilla.suse.com/show_bug.cgi?id=1051369 ).
Described boot disk order in Section 12.3.2, “Adjusting the Disk Order” (https://bugzil-
Replaced VGA mode in Figure 12.5, “Kernel Parameters” (https://bugzil-

Updated and simplified Section 12.2.3, “Scripts in /etc/grub.d” (https://bugzil-

A.3 September 2017 (Initial Release of SUSE Linux

General
back.
Removed all references to the faillog package, which is no longer shipped (https://
616 September 2017 (Initial Release of SUSE Linux Enterprise Server 12 SP3) SLES 12 SP3
Chapter 4, YaST
Added a new chapter about the YaST GUI and mentioned advanced key combinations
(https://bugzilla.suse.com/show_bug.cgi?id=1010039 ).
Chapter 5, YaST in Text Mode
Added Section 5.2, “Advanced Key Combinations” (https://bugzilla.suse.com/show_bug.c-

gi?id=1010039 ).
Chapter 6, Managing Software with Command Line Tools
Added Section 6.1.5.2, “Refreshing Repositories” (Fate #319486).
Updated Section 6.1.3.1, “Installing All Needed Patches” (Fate #320653).
Added Section 6.1.6.3, “zypper info Usage” (Fate #321104).
Chapter 7, System Recovery and Snapshot Management with Snapper
Mentioned that snapper rollback snapshots are automatically deleted. See Section 7.3,
“System Rollback by Booting from Snapshots” and Section 7.3.1, “Snapshots after Rollback”
(Fate #321773).
In Section 7.4, “Creating and Modifying Snapper Configurations”, added in-depth informa-

tion on how the minimum root le system size for enabling snapshots is calculated
Mentioned Btrfs default subvolume and its restrictions (https://bugzil-

Chapter 8, Remote Access with VNC
Fixed information about encrypted communication and added Section 8.4, “Encrypt-

ed VNC Communication” on how to set it up (https://bugzilla.suse.com/show_bug.c-
gi?id=1029117 ).
Chapter 9, File Copying with RSync
Completely revised former File Synchronization chapter and focused on Rsync.
Chapter 13, The systemd Daemon
Added the System V init command chkconfig to the comparison table in Sec-
tion 13.2.2.1, “Enabling/Disabling Services on the Command Line” (Doc Comment #30251).
Chapter 16, Basic Networking
Fixed several doc comments in Section 16.8, “Setting Up Team Devices for Network Team-
ing”.
Chapter 21, Dynamic Kernel Device Management with udev
Fixed udevadm commands.

Updated Section 22.4, “Patch Lifecycle” (Fate #322212).
Chapter 23, Special System Features
Removed duplicate content from Section 23.1.4, “Log Files: Package logrotate”.
Part II, “Booting a Linux System”
Reordered included chapters so that they follow the boot process order.
Chapter 33, The Proxy Server Squid
Explained the YaST Squid module.
Bugfixes
Replaced the command to start Apache2, httpd2 , with apache2ctl (https://bugzil-

In Section 16.2.5, “For More Information”, corrected a typo in a referenced RFC document

In Section 40.6, “Data Problems”, removed a reference to a YaST module that is no

longer shipped (https://bugzilla.suse.com/show_bug.cgi?id=1052675 ).
A.4 November 2016 (Initial Release of SUSE Linux

General
The e-mail address for documentation feedback has changed to doc-

team@suse.com .
The documentation for Docker has been enhanced and renamed to Docker Guide.
619 November 2016 (Initial Release of SUSE Linux Enterprise Server 12 SP2) SLES 12 SP3
Chapter 3, YaST Online Update
Mentioned in Section 3.3, “Automatic Online Update” that the automatic online update
does not automatically restart the system afterward (Doc Comment #30116).
zypper patch no longer installs optional patches by default. To install optional

patches, use the --with-optional parameter (FATE#320447).
Added /var/cache and /var/lib/libvirt/images to Section 7.1.2, “Directories That

Are Excluded from Snapshots” (Fate #320834).
Added Section 7.6, “Automatic Snapshot Clean-Up”, which also includes documentation

on Snapper's new quota support (Fate #312751).
Added Q: (Fate #318799).
Chapter 10, Introduction to the Booting Process
Advised users to repair le system in case root le system fails on boot time
(FATE#320443).
Added a hint on grub-once support of /boot/grub2/custom.cfg to Section 12.2,

“Configuration File Structure” (Fate #319632).
Added Section 7.3.2, “Accessing and Identifying Snapshot Boot Entries” (Fate #317972 and
#318101).
Added information about trusted boot support to Section 12.3.1, “Boot Loader Location
and Boot Code Options” (Fate #316553).
Added section about Network Teaming (FATE#320468), see Section 16.8, “Setting Up

Team Devices for Network Teaming”.
Mentioned TUNNEL_DEVICE for Wicked (FATE#317977, Section 16.5.1.5, “Using Tun-

nels with Wicked”).
620 November 2016 (Initial Release of SUSE Linux Enterprise Server 12 SP2) SLES 12 SP3
Chapter 24, Time Synchronization with NTP
Added information on the Synchronize without Daemon start-up option. Chroot jail is
no longer the default (FATE #320392).
Note: NFSv2
Added a note about enabling NFSv2 (https://bugzilla.suse.com/show_bug.c-

gi?id=919708 ).
Chapter 33, The Proxy Server Squid
Updated chapter for Squid 3.5 (FATE#319674).
Section 39.5, “Gathering Information during the Installation”
Added section about log les created during installation (FATE#320015).
Bugfixes
Wrong service names for NFS with Kerberos (https://bugzilla.suse.com/show_bug.c-

gi?id=983230 ).
Live patches are released based on the SUSE CVSS score (https://bugzil-
A.5 March 2016 (Maintenance Release of SUSE Linux

Added a note about initramfs migration from swap to LVM (https://bugzil-
la.suse.com/show_bug.cgi?id= ).
621 March 2016 (Maintenance Release of SUSE Linux Enterprise Server 12 SP1) SLES 12 SP3
A.6 December 2015 (Initial Release of SUSE Linux
General
Book “Subscription Management Tool for SLES 12 SP3” is now part of the documentation
for SUSE Linux Enterprise Server.
Add-ons provided by SUSE have been renamed as modules and extensions. The man-
uals have been updated to reflect this change.
back.
The registration service has been changed from Novell Customer Center to SUSE
Customer Center.
In YaST, you will now reach Network Settings via the System group. Network Devices
is gone (https://bugzilla.suse.com/show_bug.cgi?id=867809 ).
Added information about the new --sync switch for snapper delete to Sec-
tion 7.5.4, “Deleting Snapshots” (Fate #317066).
Added Section 7.3.2, “Accessing and Identifying Snapshot Boot Entries” (Fate #317972 and
Fate #318101).
Added a tip to Section 7.3, “System Rollback by Booting from Snapshots” on how to do

a rollback to the initial installation state or the state before a system update (Fate
#317973 and Fate #317900).
Added Section 7.1.3.3, “Creating and Mounting New Subvolumes” (Fate #318805, https://
622 December 2015 (Initial Release of SUSE Linux Enterprise Server 12 SP1) SLES 12 SP3
Turned a note into a section, added information about VNC using secured protocol by
default (Fate #318936), and removed tightvnc as it is fully replaced by tigervnc .
All in Section 8.2.1, “Available Configurations”.
Added Section 6.1.4, “Identifying Processes and Services Using Deleted Files” (Fate
#318827).
Added more examples of zypper list-patches --cve in Section 6.1.3.1, “Installing

All Needed Patches” (Fate #319053).
Added Section 6.1.2.6, “Installing Packages from Disabled Repositories” and a tip on remov-
ing all debuginfo packages in Section 6.1.2, “Installing and Removing Software with Zyp-
per” (Fate #316287).
Added a sentence on announcing the need for the system reboot after specific patch
is applied. (Fate #317872).
Chapter 15, journalctl: Query the systemd Journal
Added section Section 15.6, “Using YaST to Filter the systemd Journal” (Fate #318486).
Updated/simplified the whole chapter to match the latest GRUB version, both com-
mand line and YaST version.
Chapter 11, UEFI (Unified Extensible Firmware Interface)
Added Section 11.1.4, “Using Non-Inbox Drivers” (Fate #317593).
Nanny is now on by default in Section 16.5.1.3, “Nanny” (Fate #318977).
Added Section 16.6, “Basic Router Setup” (Fate #317121, https://bugzil-

Added Section 16.9, “Software-Defined Networking with Open vSwitch” (Fate #318497).
Chapter 25, The Domain Name System
Added Section 25.3.2.9.1, “Adding Reverse Zones” (Doc Comment #1356).
Chapter 27, Sharing File Systems with NFS
Added tip saying that --bind mount is no longer necessary for NFSv4 mounts in
Section 27.3.2, “Exporting File Systems Manually” (Fate #316311).
Available Data Synchronization Software
Mentioned cloud computing for le synchronization.
Chapter 31, The Apache HTTP Server
Replaced CA.sh with the explicit openssl command in Section 31.6.1.3, “Getting an

Officially Signed Certificate” (Doc Comment #28367).
Added Section 31.7, “Running Multiple Apache Instances on the Same Server” (Fate
#317786).
Updated the chapter to match the latest Apache version 2.4 (Fate #319012).
Chapter 40, Common Problems and Their Solutions
Improved GRUB 2 re-installation procedure in Section 40.6.2.4, “Modifying and Re-in-

stalling the Boot Loader”.
Part III, “System”
Added Chapter 22, Live Patching the Linux Kernel Using kGraft (Fate #313296 and Fate
#313438).
Bugfixes
Removed obsolete acpid.service (https://bugzilla.suse.com/show_bug.c-

gi?id=918655 ).
Fixed wrong title in Chapter 22, Live Patching the Linux Kernel Using kGraft (https://bugzil-
Fixed wrong path name in Chapter 31, The Apache HTTP Server (https://bugzil-
Added a paragraph on secure boot enabled by default in Section 11.1.1, “Implementation
on SUSE Linux Enterprise Server” (https://bugzilla.suse.com/show_bug.cgi?id=879486 ).
Removed documentation about VNC view-only passwords in Section 8.3, “Persistent

VNC Sessions” because they are not available in SUSE Linux Enterprise Server (https://
Fixed procedure to access the installed system in a rescue mode in Section 40.6.2.3,

“Accessing the Installed System” (https://bugzilla.suse.com/show_bug.cgi?id=918217 ).
Added a new tip on updating the initramfs le after changing the default sysctl
configuration in Section 10.2, “initramfs” (https://bugzilla.suse.com/show_bug.c-
gi?id=927506 ).
Added a tip on preventing wicked from deactivating the network device on NFS roots
in Section 27.4.1, “Importing File Systems with YaST” and Section 16.4.1.2.5, “Activating the
Network Device” (https://bugzilla.suse.com/show_bug.cgi?id=938152 ).
Fixed misleading statement about kernel-FLAVOR-extra in Section 39.6, “Support of

Kernel Modules” (http://bugzilla.suse.com/show_bug.cgi?id=922976 ).
Btrfs/Snapper: Snapshots with new Subvolumes will not be Deleted ( https://bugzil-

Btrfs Documentation on Separate Subvolume on /var/lib and Supportability ( https://

A.7 February 2015 (Documentation Maintenance

Update)
A typo in a command has been xed (https://bugzilla.suse.com/show_bug.cgi?id=900219 ).
625 February 2015 (Documentation Maintenance Update) SLES 12 SP3

A.8 October 2014 (Initial Release of SUSE Linux
Enterprise Server 12)
General
Removed all KDE documentation and references because KDE is no longer shipped.
Removed all references to SuSEconfig, which is no longer supported (Fate #100011).
Move from System V init to systemd (Fate #310421). Updated affected parts of the
documentation.
YaST Runlevel Editor has changed to Services Manager (Fate #312568). Updated
affected parts of the documentation.
Removed all references to ISDN support, as ISDN support has been removed (Fate
#314594).
Removed all references to the YaST DSL module as it is no longer shipped (Fate
#316264).
Removed all references to the YaST Modem module as it is no longer shipped (Fate
#316264).
Btrfs has become the default le system for the root partition (Fate #315901). Up-
dated affected parts of the documentation.
The dmesg now provides human-readable time stamps in ctime() -like format (Fate
#316056). Updated affected parts of the documentation.
syslog and syslog-ng have been replaced by rsyslog (Fate #316175). Updated affected
parts of the documentation.
MariaDB is now shipped as the relational database instead of MySQL (Fate #313595).
Updated affected parts of the documentation.
SUSE-related products are no longer available from http://download.novell.com but

from http://download.suse.com . Adjusted links accordingly.
Novell Customer Center has been replaced with SUSE Customer Center. Updated
affected parts of the documentation.
626 October 2014 (Initial Release of SUSE Linux Enterprise Server 12) SLES 12 SP3
/var/run is mounted as tmpfs (Fate #303793). Updated affected parts of the doc-
umentation.
The following architectures are no longer supported: IA64 and x86. Updated affected
parts of the documentation.
The traditional method for setting up the network with ifconfig has been replaced
by wicked . Updated affected parts of the documentation.
A lot of networking commands are deprecated and have been replaced by newer
commands (usually ip ). Updated affected parts of the documentation.
arp : ip neighbor
ifconfig : ip addr , ip link
iptunnel : ip tunnel
iwconfig : iw
nameif : ip link , ifrename
netstat : ss , ip route , ip -s link , ip maddr
route : ip route
back.
Chapter 3, YaST Online Update
YaST provides an option to enable or disable the use of delta RPMs (Fate #314867).
Before installing patches that require a reboot, you are notified by YaST and can
choose how to proceed.
Chapter 39, Gathering System Information for Support
Added the section Section 39.1, “Displaying Current System Information” (Fate #315869).
Added a section about the Supportconfig Analysis (SCA) tool and appliance: Sec-
tion 39.4, “Analyzing System Information” (Fate #315699).
Added the section Section 39.6, “Support of Kernel Modules” (http://bugzil-

Updated and restructured the chapter.
Chapter 5, YaST in Text Mode
Added information on how to filter and select packages in the software installation
module.
Removed documentation about Zypper's rug compatibility mode (Fate #317708).
Rewrote Section 6.1.6, “Querying Repositories and Packages with Zypper”.
Updated the chapter and added new features (Fate #312751, Fate #316238, Fate
#316233, Fate #316232, Fate #316222, Fate #316203, Fate #316222).
Added the section Section 7.3, “System Rollback by Booting from Snapshots” (Fate
#316231, Fate #316221, Fate #316541, Fate #316522).
The default VNC viewer is now tigervnc .
Added corrections on window manager start-up in persistent VNC sessions.
Significantly shortened the chapter, because System V init has been replaced by sys-
temd. systemd is now described in a separate chapter: Chapter 13, The systemd Dae-
mon.
Added a new chapter on systemd and the YaST Services Manager (Fate #316631,
Fate #312568).
New section on loading kernel modules (http://bugzilla.suse.com/show_bug.c-

gi?id=892349 ).
Chapter 15, journalctl: Query the systemd Journal

Added a new chapter (http://bugzilla.suse.com/show_bug.cgi?id=878352 ).
Replaced the GRUB Legacy documentation with a new chapter on GRUB 2.
Support for LILO has been dropped.
Added new section Section 12.4, “Differences in Terminal Usage on z Systems”.
Chapter 11, UEFI (Unified Extensible Firmware Interface)
Updated the chapter and added new features (Fate #314510, Fate #316365).
Added instructions on where to nd the SUSE Key certificate (Doc Comment
#25080).
Chapter 17, Printer Operation

Updated chapter and section according to new CUPS version and with PDF now being a
common printing data format (Fate #314630).
Chapter 18, The X Window System
Updated the chapter to reflect dynamic configuration during each start-up.
Updated Section 18.1, “Installing and Configuring Fonts”.
NetworkManager is now part of the Workstation Extension: Section 16.4.1.1, “Config-

uring Global Networking Options” (Fate #316888).
Added section about new wicked framework for network configuration: Section 16.5,
“Configuring a Network Connection Manually” (Fate #316649).
Mentioned additional options that can be added to /etc/resolv.conf : Sec-

tion 16.5.2, “Configuration Files” (Fate #316048).
Chapter 30, SLP
Re-wrote chapter to provide significantly more information on the slptool com-

mand.
Chapter 25, The Domain Name System
The YaST DNS module now supports configuring forwarders (Fate #309036).
Chapter 26, DHCP
Removed dhcpcd as it is no longer shipped (Fate #316111).
Chapter 28, Samba
Added section Section 28.8, “Advanced Topics”.
Added section Section 28.8.1, “Transparent File Compression on Btrfs”.
Added section Section 28.8.2, “Snapshots”.
Chapter 27, Sharing File Systems with NFS
Configuring NFSv4 shares is now mostly similar to NFSv3, especially the previously
required bind mount setting is now deprecated (Fate #315589).
Mounting NFS volumes locally on the exporting server is not supported.
Chapter 29, On-Demand Mounting with Autofs
Added a chapter on autofs (Fate #316185).
Chapter 31, The Apache HTTP Server
Removed references to mono and mod_mono as it was removed from the distribution.
Updated the chapter to Apache version 2.4 (Fate #316067).
Removed deprecated directive NameVirtualHost and updated Section 31.2.2.1, “Vir-

tual Host Configuration” accordingly.
Updated Order , Allow , and Deny directives with standard Require .
Removed virtual "Snake Oil" company from Section 31.6, “Setting Up a Secure Web Server
with SSL”.
Chapter 32, Setting Up an FTP Server with YaST
pure-ftpd was dropped (Fate #315176, Fate #316308).
Chapter 37, Power Management
Removed obsolete references to the pm-utils package.
Chapter 40, Common Problems and Their Solutions
Added new section Section 40.3.3, “Root Btrfs Partition Cannot Be Mounted” (Fate
#308679, Fate #315126).
Removed section about deprecated YaST Repair module (Fate #308679).
Wi-Fi Configuration
Removed chapter about Wi-Fi configuration with YaST as Wi-Fi configuration can be
done with NetworkManager: Chapter 36, Using NetworkManager.
Tablet PCs
Removed deprecated chapter about tablet PCs.
Bugfixes
Added the section Section 39.6, “Support of Kernel Modules” (http://bugzil-

Added a new chapter Chapter 15, journalctl: Query the systemd Journal (http://bugzil-
B An Example Network
This example network is used across all network-related chapters of the SUSE® Linux Enterprise
Server documentation.
632 SLES 12 SP3

C GNU Licenses
formats that can be read and edited only by proprietary word processors, SGML or XML for
This appendix contains the GNU Free Docu- which the DTD and/or processing tools are not generally available, and the machine-generat-
ed HTML, PostScript or PDF produced by some word processors for output purposes only.
mentation License version 1.2. The "Title Page" means, for a printed book, the title page itself, plus such following pages as
are needed to hold, legibly, the material this License requires to appear in the title page. For
works in formats which do not have any title page as such, "Title Page" means the text near the
GNU Free Documentation License most prominent appearance of the work's title, preceding the beginning of the body of the text.
A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely
Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc. 51 Franklin St, Fifth Floor, XYZ or contains XYZ in parentheses following text that translates XYZ in another language.
Boston, MA 02110-1301 USA. Everyone is permitted to copy and distribute verbatim copies (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements",
of this license document, but changing it is not allowed. "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when
you modify the Document means that it remains a section "Entitled XYZ" according to this
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0. PREAMBLE
The Document may include Warranty Disclaimers next to the notice which states that this
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add other material on the covers in addition. Copying with changes limited to the covers, as
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Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.
It is requested, but not required, that you contact the authors of the Document well before
A "Transparent" copy of the Document means a machine-readable copy, represented in a for-
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paint programs or (for drawings) some widely available drawing editor, and that is suitable
for input to text formatters or for automatic translation to a variety of formats suitable for
input to text formatters. A copy made in an otherwise Transparent le format whose markup,
or absence of markup, has been arranged to thwart or discourage subsequent modification
by readers is not Transparent. An image format is not Transparent if used for any substantial
amount of text. A copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain ASCII without markup, Tex-
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of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary
633 SLES 12 SP3

The author(s) and publisher(s) of the Document do not by this License give permission to use
4. MODIFICATIONS
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must do these things in the Modified Version: the terms defined in section 4 above for modified versions, provided that you include in the
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list them all as Invariant Sections of your combined work in its license notice, and that you
Document, and from those of previous versions (which should, if there were any,
preserve all their Warranty Disclaimers.
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previous version if the original publisher of that version gives permission. The combined work need only contain one copy of this License, and multiple identical Invari-
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634 SLES 12 SP3

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Administration Guide

SUSE Linux Enterprise Server 12 SP3

Covers system administration tasks like maintaining, monitoring and customizing

Publication Date: February 09, 2018

About This Guide xxi

1 Bash and Bash Scripts 2

1.2 Writing Shell Scripts 8

1.3 Redirecting Command Events 9

1.4 Using Aliases 10

1.5 Using Variables in Bash 10

1.6 Grouping and Combining Commands 13

1.7 Working with Common Flow Constructs 14

1.8 For More Information 15

2.2 Configuring sudo 18

2.3 Common Use Cases 22

iii Administration Guide

3 YaST Online Update 25

3.2 Installing Patches 27

3.3 Automatic Online Update 28

5 YaST in Text Mode 32

5.2 Advanced Key Combinations 35

5.3 Restriction of Key Combinations 35

5.4 YaST Command Line Options 36

6 Managing Software with Command Line Tools 38

6.2 RPM—the Package Manager 54

7.2 Using Snapper to Undo Changes 71

7.3 System Rollback by Booting from Snapshots 79

7.4 Creating and Modifying Snapper Configurations 85

7.5 Manually Creating and Managing Snapshots 90

7.6 Automatic Snapshot Clean-Up 95

7.7 Frequently Asked Questions 101

8 Remote Access with VNC 103

8.2 One-time VNC Sessions 104

8.4 Encrypted VNC Communication 108

9 File Copying with RSync 111

9.2 Basic Syntax 111

9.3 Copying Files and Directories Locally 112

9.4 Copying Files and Directories Remotely 113

9.5 Configuring and Using an Rsync Server 113

9.6 For More Information 116

II BOOTING A LINUX SYSTEM 117

10 Introduction to the Booting Process 118

10.2 initramfs 120

10.3 Init on initramfs 121

11 UEFI (Unified Extensible Firmware Interface) 124

11.2 For More Information 132

12 The Boot Loader GRUB 2 133

12.3 Configuring the Boot Loader with YaST 142

12.4 Differences in Terminal Usage on z Systems 148

12.5 Helpful GRUB 2 Commands 151

12.6 More Information 152

13 The systemd Daemon 153

13.2 Basic Usage 155

13.3 System Start and Target Management 159

13.4 Managing Services with YaST 166

13.5 Customization of systemd 167

13.6 Advanced Usage 169

vii Administration Guide

13.7 More Information 175