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Administration Guide
SUSE Linux Enterprise Server 11 SP4

SUSE Linux Enterprise Server 11 SP4
Publication Date: July 24, 2020
SUSE LLC
1800 South Novell Place
Provo, UT 84606
USA
https://documentation.suse.com
Copyright © 2006– 2020 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
Documentation 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
property of their respective owners. A trademark symbol (®, ™ etc.) denotes a SUSE or Novell trademark;
an asterisk (*) denotes a third party trademark.
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 xix

1 Available Documentation xx
2 Feedback xxii
3 Documentation Conventions xxii
I SUPPORT AND COMMON TASKS 1
1 YaST Online Update 2

1.1 The Online Update Dialog 3
KDE Interface (Qt) 3 • GNOME Interface (GTK) 4
1.2 Installing Patches 6
1.3 Automatic Online Update 7
2 Gathering System Information for Support 9

2.1 Collecting System Information with Supportconfig 9
Creating a Service Request Number 9 • Upload Targets 10 • Creating a
Supportconfig Archive with YaST 10 • Creating a Supportconfig Archive from
Command Line 12 • Common Supportconfig Options 12
2.2 Submitting Information to Global Technical Support 13
2.3 Support of Kernel Modules 15

Technical Background 16 • Working with Unsupported Modules 16
2.4 For More Information 17
3 YaST in Text Mode 18

3.1 Navigation in Modules 19
3.2 Restriction of Key Combinations 21
iii Administration Guide

3.3 YaST Command Line Options 21
Starting the Individual Modules 21 • Installing Packages from the Command
Line 22 • Command Line Parameters of the YaST Modules 22
4 Snapshots/Rollback with Snapper 23

4.1 Requirements 23
Snapshots and Disk Space 23
4.2 Using Snapper to Undo System Changes 24

Undoing YaST and Zypper Changes 25 • Using Snapper to Restore
Files from Hourly Backups 30 • Creating and Modifying Snapper
Configurations 31 • Disabling Automatic Snapshots 34
4.3 Manually Creating and Managing Snapshots 35

Snapshot Metadata 35 • Creating Snapshots 37 • Modifying Snapshot
Metadata 38 • Deleting Snapshots 38
4.4 Limitations 39
Data Consistency 39 • Reverting User Additions 39 • No Rollback on /
boot and Boot Loader Changes 40
4.5 Frequently Asked Questions 40
4.6 Using Snapper on Thin-Provisioned LVM Volumes 41
5 Remote Access with VNC 42

5.1 One-time VNC Sessions 42
Initiating a One-time VNC Session 43 • Configuring One-time VNC
Sessions 43
5.2 Persistent VNC Sessions 44

Connecting to a Persistent VNC Session 46 • Configuring Persistent VNC
Sessions 46
6 Managing Software with Command Line Tools 47

6.1 Using Zypper 47
General Usage 47 • Installing and Removing Software with
Zypper 48 • Updating Software with Zypper 51 • Distribution Upgrade
iv Administration Guide
with zypper 54 • Managing Repositories with zypper 58 • Querying
Repositories and Packages with Zypper 60 • Configuring
Zypper 61 • Troubleshooting 62 • Zypper Rollback Feature on btrfs File
System 62
6.2 RPM—the Package Manager 62

Verifying Package Authenticity 63 • Managing Packages: Install,
Update, and Uninstall 63 • RPM and Patches 65 • Delta RPM
Packages 66 • RPM Queries 67 • Installing and Compiling Source
Packages 70 • Compiling RPM Packages with build 72 • Tools for RPM
Archives and the RPM Database 72
7 Bash and Bash Scripts 73

7.1 What is “The Shell”? 73
Knowing The Bash Configuration Files 73 • The Directory Structure 74
7.2 Writing Shell Scripts 78
7.3 Redirecting Command Events 79
7.4 Using Aliases 80
7.5 Using Variables in Bash 81

Using Argument Variables 82 • Using Variable Substitution 82
7.6 Grouping And Combining Commands 83
7.7 Working with Common Flow Constructs 84

The if Control Command 84 • Creating Loops With the For Command 85
8 Using Third-Party Software 87
II SYSTEM 88
9 32-Bit and 64-Bit Applications in a 64-Bit System

Environment 89
9.1 Runtime Support 89
9.2 Software Development 90
v Administration Guide
9.3 Software Compilation on Biarch Platforms 91
9.4 Kernel Specifications 92
10 Booting and Configuring a Linux System 94

10.1 The Linux Boot Process 94
initramfs 95 • init on initramfs 96
10.2 The init Process 98

Runlevels 98 • Init Scripts 101 • Configuring System Services (Runlevel)
with YaST 104
10.3 System Configuration via /etc/sysconfig 106

Changing the System Configuration Using the YaST sysconfig
Editor 107 • Changing the System Configuration Manually 108
11 The Boot Loader GRUB 109

11.1 Booting with GRUB 110
The File /boot/grub/menu.lst 111 • The File device.map 116 • The
File /etc/grub.conf 117 • The File /etc/sysconfig/
bootloader 118 • Setting a Boot Password 119
11.2 Configuring the Boot Loader with YaST 120

Adjusting the Default Boot Entry 121 • Modifying the Boot Loader
Location 122 • Changing the Boot Loader Time-Out 122 • Setting a Boot
Password 123 • Adjusting the Disk Order 123 • Configuring Advanced
Options 124 • Changing Boot Loader Type 125
11.3 Uninstalling the Linux Boot Loader 126
11.4 Creating Boot CDs 126
11.5 The Graphical SUSE Screen 128
11.6 Troubleshooting 128
vi Administration Guide
12 UEFI (Unified Extensible Firmware Interface) 131
12.1 Secure Boot 131
Implementation on SUSE Linux Enterprise 132 • MOK (Machine
Owner Key) 135 • Booting a Custom Kernel 135 • Using Non-Inbox
Drivers 137 • Limitations 138
13 Special System Features 139

13.1 Information about Special Software Packages 139
The bash Package and /etc/profile 139 • The cron Package 140 • Log
Files: Package logrotate 141 • The locate Command 142 • The ulimit
Command 142 • The free Command 143 • Man Pages and Info
Pages 144 • Selecting Man Pages Using the man Command 144 • Settings
for GNU Emacs 144
13.2 Virtual Consoles 145
13.3 Keyboard Mapping 146
13.4 Language and Country-Specific Settings 146

Some Examples 147 • Locale Settings in ~/.i18n 149 • Settings for
Language Support 149 • For More Information 150
14 Printer Operation 151

14.1 The Workflow of the Printing System 152
14.2 Methods and Protocols for Connecting Printers 153
14.3 Installing the Software 153
14.4 Network Printers 154

Configuring CUPS with Command Line Tools 155
14.5 Printing from the Command Line 157
14.6 Special Features in SUSE Linux Enterprise Server 157

CUPS and Firewall 157 • PPD Files in Various Packages 158
vii Administration Guide

Printers without Standard Printer Language Support 159 • No Suitable PPD
File Available for a PostScript Printer 160 • Parallel Ports 160 • Network
Printer Connections 161 • Defective Printouts without Error
Message 164 • Disabled Queues 164 • CUPS Browsing: Deleting Print
Jobs 164 • Defective Print Jobs and Data Transfer Errors 165 • Debugging
the CUPS Print System 165 • For More Information 166
15 Dynamic Kernel Device Management with udev 167

15.1 The /dev Directory 167
15.2 Kernel uevents and udev 167
15.3 Drivers, Kernel Modules and Devices 168
15.4 Booting and Initial Device Setup 168
15.5 Monitoring the Running udev Daemon 169
15.6 Influencing Kernel Device Event Handling with udev Rules 170
Using Operators in udev Rules 172 • Using Substitutions in udev
Rules 173 • Using udev Match Keys 174 • Using udev Assign Keys 175
15.7 Persistent Device Naming 176
15.8 Files used by udev 177
16 The X Window System 179

16.1 Manually Configuring the X Window System 179
Screen Section 183 • Device Section 184 • Monitor and Modes
Section 185
16.2 Installing and Configuring Fonts 186

X11 Core Fonts 187 • Xft 188
17 Accessing File Systems with FUSE 193

17.1 Configuring FUSE 193
viii Administration Guide

17.2 Available FUSE Plug-ins 193
III MOBILE COMPUTERS 195
18 Mobile Computing with Linux 196

18.1 Laptops 196
Power Conservation 196 • Integration in Changing Operating
Environments 197 • Software Options 200 • Data Security 202
18.2 Mobile Hardware 203
18.3 Cellular Phones and PDAs 204
19 Wireless LAN 206

19.1 WLAN Standards 206
19.2 Operating Modes 207
19.3 Authentication 208
19.4 Encryption 209
19.5 Configuration with YaST 210

Deactivating NetworkManager 211 • Configuration for Access
Points 211 • Establishing an Ad-Hoc Network 215 • Setting Additional
Configuration Parameters 216
19.6 Tips and Tricks for Setting Up a WLAN 217

Utilities 217 • Stability and Speed 217 • Security 218

Check the Network Status 219 • Multiple Network Devices 220 • Problems
with Prism2 Cards 220
ix Administration Guide
20 Power Management 222
20.1 Power Saving Functions 222
20.2 Advanced Configuration and Power Interface (ACPI) 223

Controlling the CPU Performance 223 • Troubleshooting 224
20.3 Rest for the Hard Disk 225

ACPI Activated with Hardware Support but Functions Do Not Work 227 • CPU
Frequency Does Not Work 228 • Suspend and Standby Do Not Work 228
21 Using Tablet PCs 229

21.1 Installing Tablet PC Packages 230
21.2 Configuring Your Tablet Device 230
21.3 Using the Virtual Keyboard 230
21.4 Rotating Your Display 231
21.5 Using Gesture Recognition 231

Using CellWriter 232 • Using Xstroke 233
21.6 Taking Notes and Sketching with the Pen 234
IV SERVICES 238
22 Basic Networking 239

22.1 IP Addresses and Routing 242
IP Addresses 243 • Netmasks and Routing 243
22.2 IPv6—The Next Generation Internet 246

Advantages 246 • Address Types and Structure 248 • Coexistence of IPv4
and IPv6 252 • Configuring IPv6 253 • For More Information 254
x Administration Guide
22.3 Name Resolution 255
22.4 Configuring a Network Connection with YaST 256

Configuring the Network Card with
YaST 256 • Modem 267 • ISDN 270 • Cable
Modem 273 • DSL 273 • IBM System z: Configuring Network
Devices 276
22.5 NetworkManager 278

NetworkManager and ifup 278 • NetworkManager Functionality and
Configuration Files 279 • Controlling and Locking Down NetworkManager
Features 279
22.6 Configuring a Network Connection Manually 279

Configuration Files 281 • Testing the Configuration 289 • Start-Up
Scripts 294
22.7 Setting Up Bonding Devices 295

Hotplugging of Bonding Slaves 297
22.8 smpppd as Dial-up Assistant 298

Configuring smpppd 299 • Configuring cinternet for Remote Use 300
23 SLP Services in the Network 301

23.1 Installation 301
23.2 Activating SLP 301
23.3 SLP Front-Ends in SUSE Linux Enterprise Server 302
23.4 Installation over SLP 302
23.5 Providing Services via SLP 302
24 Time Synchronization with NTP 305

24.1 Configuring an NTP Client with YaST 305
Basic Configuration 305 • Changing Basic Configuration 306
24.2 Manually Configuring NTP in the Network 309
xi Administration Guide
24.3 Dynamic Time Synchronization at Runtime 309
24.4 Setting Up a Local Reference Clock 310
24.5 Clock Synchronization to an External Time Reference (ETR) 311
25 The Domain Name System 312

25.1 DNS Terminology 312
25.2 Installation 313
25.3 Configuration with YaST 313

Wizard Configuration 313 • Expert Configuration 316
25.4 Starting the BIND Name Server 322
25.5 The /etc/named.conf Configuration File 323

Important Configuration Options 324 • Logging 326 • Zone Entries 326
25.6 Zone Files 327
25.7 Dynamic Update of Zone Data 331
25.8 Secure Transactions 332
25.9 DNS Security 333
26 DHCP 335
26.1 Configuring a DHCP Server with YaST 336
Initial Configuration (Wizard) 336 • DHCP Server Configuration (Expert) 341
26.2 DHCP Software Packages 346
26.3 The DHCP Server dhcpd 347

Clients with Fixed IP Addresses 349 • The SUSE Linux Enterprise Server
Version 350
27 Using NetworkManager 351

27.1 Use Cases for NetworkManager 351
xii Administration Guide

27.2 Enabling or Disabling NetworkManager 351
27.3 Configuring Network Connections 352
27.4 Using KNetworkManager 355

Managing Wired Network Connections 355 • Managing Wireless
Network Connections 356 • Configuring Your Wireless Card as an Access
Point 357 • Customizing KNetworkManager 358
27.5 Using the GNOME NetworkManager Applet 359

Managing Wired Network Connections 359 • Managing Wireless Network
Connections 360 • Configuring Your Wireless Card as an Access Point 361
27.6 NetworkManager and VPN 362
27.7 NetworkManager and Security 363

User and System Connections 363 • Storing Passwords and Credentials 363
27.8 Frequently Asked Questions 364
28 Samba 368
28.1 Terminology 368
28.2 Starting and Stopping Samba 369
28.3 Configuring a Samba Server 370

Configuring a Samba Server with YaST 370 • Web Administration with
SWAT 372 • Configuring the Server Manually 372
28.4 Configuring Clients 376

Configuring a Samba Client with YaST 377
28.5 Samba as Login Server 377
28.6 Samba Server in the Network with Active Directory 378
xiii Administration Guide

29 Sharing File Systems with NFS 381
29.1 Terminology 381
29.2 Installing NFS Server 382
29.3 Configuring NFS Server 382

Exporting File Systems with YaST 382 • Exporting File Systems
Manually 386 • NFS with Kerberos 389
29.4 Configuring Clients 389

Importing File Systems with YaST 389 • Importing File Systems
Manually 390 • Parallel NFS (pNFS) 391
30 File Synchronization 394

30.1 Available Data Synchronization Software 394
CVS 395 • rsync 395
30.2 Determining Factors for Selecting a Program 395

Client-Server versus Peer-to-Peer 395 • Portability 396 • Interactive
versus Automatic 396 • Conflicts: Incidence and Solution 396 • Selecting
and Adding Files 396 • History 396 • Data Volume and Hard Disk
Requirements 397 • GUI 397 • User Friendliness 397 • Security
against Attacks 397 • Protection against Data Loss 397
30.3 Introduction to CVS 398

Configuring a CVS Server 399 • Using CVS 399
30.4 Introduction to rsync 401

Configuration and Operation 401
31 The Apache HTTP Server 403

31.1 Quick Start 403
Requirements 403 • Installation 404 • Start 404
xiv Administration Guide

31.2 Configuring Apache 405
Apache Configuration Files 405 • Configuring Apache
Manually 408 • Configuring Apache with YaST 413
31.3 Starting and Stopping Apache 419
31.4 Installing, Activating, and Configuring Modules 421

Module Installation 422 • Activation and Deactivation 422 • Base and
Extension Modules 423 • Multiprocessing Modules 426 • External
Modules 427 • Compilation 428
31.5 Getting CGI Scripts to Work 429

Apache Configuration 430 • Running an Example Script 430 • CGI
Troubleshooting 431
31.6 Setting Up a Secure Web Server with SSL 431

Creating an SSL Certificate 432 • Configuring Apache with SSL 436
31.7 Setting Up a Secure Web Server with NSS 438
31.8 Avoiding Security Problems 439

Up-to-Date Software 440 • DocumentRoot Permissions 440 • File System
Access 440 • CGI Scripts 440 • User Directories 441

Apache 2.2 442 • Apache
Modules 443 • Development 443 • Miscellaneous Sources 444
32 Setting up an FTP Server with YaST 445

32.1 Starting the FTP Server 446
32.2 FTP General Settings 447
32.3 FTP Performance Settings 447
32.4 Authentication 448
32.5 Expert Settings 448
xv Administration Guide
33 The Squid Proxy Server 450
33.1 Some Facts about Proxy Caches 450
Squid and Security 451 • Multiple Caches 451 • Caching Internet
Objects 452
33.2 System Requirements 452

Hard Disks 453 • Size of the Disk Cache 453 • RAM 453 • CPU 454
33.3 Starting Squid 454

Commands for Starting and Stopping Squid 454 • Local DNS Server 455
33.4 The /etc/squid/squid.conf Configuration File 456

General Configuration Options (Selection) 457 • Options for Access
Controls 459
33.5 Configuring a Transparent Proxy 461

Configuration Options in /etc/squid/squid.conf 462 • Firewall Configuration
with SuSEfirewall2 462
33.6 cachemgr.cgi 464

Setup 464 • Cache Manager ACLs in /etc/squid/squid.conf 464 • Viewing
the Statistics 465
33.7 squidGuard 465
33.8 Cache Report Generation with Calamaris 467
34 Web Based Enterprise Management Using SFCB 469

34.1 Introduction and Basic Concept 469
34.2 Setting up SFCB 470

Installing Additional Providers 472 • Starting, Stopping and Checking Status
for SFCB 473 • Ensuring Secure Access 473
34.3 SFCB CIMOM Configuration 476

Environment Variables 476 • Command Line Options 477 • SFCB
Configuration File 478
xvi Administration Guide

34.4 Advanced SFCB Tasks 490
Installing CMPI Providers 490 • Testing SFCB 494 • Command Line CIM
Client: wbemcli 496
V TROUBLESHOOTING 499
35 Help and Documentation 500

35.1 Documentation Directory 500
Novell/SUSE Manuals 501 • HOWTOs 501 • Package
Documentation 501
35.2 Man Pages 502
35.3 Info Pages 504
35.4 Online Resources 504
36 Common Problems and Their Solutions 506

36.1 Finding and Gathering Information 506
36.2 Installation Problems 509

Checking Media 509 • Hardware Information 510 • No Bootable DVD
Drive Available 511 • Booting from Installation Media Fails 513 • Fails to
Boot 514 • Fails to Launch Graphical Installer 516 • Only Minimalistic Boot
Screen Started 518
36.3 Boot Problems 518

Fails to Load the GRUB Boot Loader 519 • No Graphical Login 520
36.4 Login Problems 521

Valid Username and Password Combinations Fail 521 • Valid Username
and Password Not Accepted 522 • Login to Encrypted Home Partition
Fails 525 • Login Successful but GNOME Desktop Fails 525 • Login
Successful but KDE Desktop Fails 526
36.5 Network Problems 528

NetworkManager Problems 532
xvii Administration Guide

36.6 Data Problems 532
Managing Partition Images 532 • Backing Up Critical Data 533 • Restoring
a System Backup 534 • Recovering a Corrupted System 535
36.7 IBM System z: Using initrd as a Rescue System 546

IPLing the Rescue System 546 • Configuring Disks 547 • Mounting the
Root Device 548 • Changing to the Mounted File System 549 • Executing
zipl 549 • Exiting the Rescue System 549
A An Example Network 550
B GNU Licenses 551
xviii 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 the purpose of 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 a number of hardware architectures and you can use this to adapt your
own applications to run on SUSE Linux Enterprise. The boot loader and boot procedure
information assists you in understanding how your Linux system works and how your own
custom scripts and applications may blend in with it.
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.
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, and in-
tegrates well into heterogeneous environments including MS Windows clients and servers.
Troubleshooting
xix SUSE Linux Enterp… 11 SP4

Provides an overview of where to nd help and additional documentation in case you
need more information or want to perform specific tasks with your system. Also nd a
compilation of the most frequent problems and annoyances and learn how to solve these
issues on your own.
Many chapters in this manual contain links to additional documentation resources. This includes
additional documentation that is available on the system as well as documentation available
on the Internet.
For an overview of the documentation available for your product and the latest documentation
updates, refer to http://www.suse.com/doc .
1 Available Documentation
We provide HTML and PDF versions of our books in different languages. The following manuals
for users and administrators are available for this product:
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 “Security Guide”

Introduces basic concepts of system security, covering both local and network security as-
pects. Shows how to make use of the product inherent security software like AppArmor
(which lets you specify per program which les the program may read, write, and exe-
cute), and the auditing system that reliably collects information about any security-rele-
vant 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.
xx Available Documentation SUSE Linux Enterp… 11 SP4

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 “Virtualization with Xen”

Offers an introduction to virtualization technology of your product. It features an overview
of the various elds of application and installation types of each of the platforms supported
by SUSE Linux Enterprise Server as well as a short description of the installation procedure.
Book “Virtualization with KVM”

Offers an introduction to setting up and managing virtualization with KVM (Kernel-based
Virtual Machine) on SUSE Linux Enterprise Server. Learn how to manage KVM with libvirt
or QEMU. The guide also contains detailed information about requirements, limitations,
and support status.
Book “AutoYaST”
AutoYaST is a system for installing one or more SUSE Linux Enterprise systems automati-
cally and without user intervention, using an AutoYaST profile that contains installation
and configuration data. The manual guides you through the basic steps of auto-installation:
preparation, installation, and configuration.
Book “Storage Administration Guide”

Provides information about how to manage storage devices on a SUSE Linux Enterprise
Server.
In addition to the comprehensive manuals, several quick start guides are available:
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.
Linux Audit Quick Start

Gives a short overview how to enable and configure the auditing system and how to execute
key tasks such as setting up audit rules, generating reports, and analyzing the log les.
AppArmor Quick Start

Helps you understand the main concepts behind AppArmor®.
Article “Virtualization with Linux Containers (LXC)”
xxi Available Documentation SUSE Linux Enterp… 11 SP4

Gives a short introduction to LXC (a lightweight “virtualization” method) and shows how
to set up an LXC host and LXC containers.
Find HTML versions of most product manuals in your installed system under /usr/share/doc/
manual or in the help centers of your desktop. Find the latest documentation updates at http://
www.suse.com/doc where you can download PDF or HTML versions of the manuals for your
product.
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/ .
To report bugs for a product component, log in to the Novell Customer Center from http://
www.suse.com/support/ and select My Support Service Request.
User Comments
We want to hear your comments about and suggestions for this manual and the other
documentation 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/doc/feedback.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.de . 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 typographical conventions are used in this manual:
/etc/passwd : directory names and filenames
placeholder : replace placeholder with the actual value
xxii Feedback SUSE Linux Enterp… 11 SP4

PATH : the environment variable PATH
ls , --help : commands, options, and parameters
user : users or groups
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
amd64, em64t, ipf This paragraph is only relevant for the architectures amd64 , em64t ,
and ipf . The arrows mark the beginning and the end of the text block.
IBM Z, ipseries This paragraph is only relevant for the architectures System z and
ipseries . 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.
xxiii Documentation Conventions SUSE Linux Enterp… 11 SP4

I Support and Common Tasks
1 YaST Online Update 2
2 Gathering System Information for Support 9
3 YaST in Text Mode 18
4 Snapshots/Rollback with Snapper 23
5 Remote Access with VNC 42
6 Managing Software with Command Line Tools 47
7 Bash and Bash Scripts 73
8 Using Third-Party Software 87

1 YaST Online Update
Novell 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”, Chapter 9
“Installing or Removing Software”, Section 9.4 “Keeping the System Up-to-date” for further information
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 al-
ready configured. If you have not registered SUSE Linux Enterprise Server, you can do so by run-
ning Software Online Update Configuration in YaST and start Advanced Register for Support and
Get Update Repository. 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 9 “Installing or Removing Software”, Section 9.3 “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 due to an expired subscrip-
tion. Normally, SUSE Linux Enterprise Server comes with a one-year or three-year sub-
scription, during which you have access to the update catalog. This access will be denied
once the subscription ends.
In case of an access denial to the update catalog you will see a warning message with a
recommendation to visit the Novell Customer Center and check your subscription. The
Novell Customer Center is available at http://www.novell.com/center/ .
Novell provides updates with different relevance levels:
Security Updates
Fix severe security hazards and should definitely be installed.
Recommended Updates
Fix issues that could compromise your computer.
Optional Updates
Fix non-security relevant issues or provide enhancements.
2 SUSE Linux Enterp… 11 SP4

1.1 The Online Update Dialog
The YaST Online Update dialog is available in two toolkit flavors: GTK (for GNOME) and Qt
(for KDE). Both interfaces differ in look and feel but basically provide the same functions. The
following sections provide a brief description of each. To open the dialog, start YaST and se-
lect Software Online Update. Alternatively, start it from the command line with yast2 on-
line_update .
1.1.1 KDE Interface (Qt)

The Online Update window consists of four sections.
FIGURE 1.1: YAST ONLINE UPDATE—QT INTERFACE
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).
3 The Online Update Dialog SUSE Linux Enterp… 11 SP4

All Patches
All patches available for SUSE Linux Enterprise Server.
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.
1.1.2 GNOME Interface (GTK)

The Online Update window consists of four main sections.
4 GNOME Interface (GTK) SUSE Linux Enterp… 11 SP4

FIGURE 1.2: YAST ONLINE UPDATE—GTK INTERFACE
The upper right section lists the available (or already installed) patches for SUSE Linux Enter-
prise Server. To filter patches according to their security relevance, click the corresponding Pri-
ority entry in the upper right section of the window: Security , Recommended , Optional or
All patches .
If all available patches are already installed, the Package listing in the upper right section will
show no entries. The box in the bottom left-hand section shows the number of both available
and already installed patches and lets you toggle the view to either Available or Installed patches.
Select an entry in the Package listing section to view a patch description and further details at the
bottom right corner of the dialog. As a patch can consist of several packages, click the Applies
to entry in the lower right section to see which packages are included in the respective patch.
Click on a patch entry to open a row with detailed information about the patch in the bottom
of the window. Here you can see a detailed patch description as well as the versions available.
You can also choose to Install optional patches—security and recommended patches are already
preselected for installation.
5 GNOME Interface (GTK) SUSE Linux Enterp… 11 SP4

1.2 Installing Patches
The YaST Online Update dialog allows you to either install all available patches at once or to
manually select the patches that you want to apply to your system. 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.
PROCEDURE 1.1: 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, proceed with Apply or Accept to start the installation of the prese-
lected patches.
3. To rst modify the selection of patches that you want to apply:
a. Use the respective filters and views the GTK and Qt interfaces provide. For details,
refer to Section 1.1.1, “KDE Interface (Qt)” and Section 1.1.2, “GNOME Interface (GTK)”.
b. Select or deselect patches according to your needs and wishes by activating or deac-
tivating the respective check box (GNOME) or by right-clicking the patch and choos-
ing the respective action from the context menu (KDE).
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
(KDE).
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.
6 Installing Patches SUSE Linux Enterp… 11 SP4

Tip: Disabling deltarpms
By default, updates are downloaded as deltarpms. Since rebuilding rpm packages from
deltarpms is a memory and processor consuming task, certain setups or hardware config-
urations might require you to disable the usage of deltarpms for the sake of performance.
To disable the use of deltarpms, edit the le /etc/zypp/zypp.conf and set down-
load.use_deltarpm to false .
1.3 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.
PROCEDURE 1.2: 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.
3. Choose whether to update Daily, Weekly, or Monthly.

Some patches, such as kernel updates or packages requiring license agreements, require
user interaction, which would cause the automatic update procedure to stop.
4. 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
Update from time to time in order to install those patches, too. Otherwise you might
miss important patches.
5. To automatically accept any license agreements, activate Agree with Licenses.
6. To automatically install all packages recommended by updated packages, activate Include

Recommended Packages.
7 Automatic Online Update SUSE Linux Enterp… 11 SP4

7. 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.
8. Confirm your configuration with OK.
8 Automatic Online Update SUSE Linux Enterp… 11 SP4

2 Gathering System Information for Support
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 in-
formation about the system such as: current kernel version, hardware, installed
packages, 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.
The command line tool is provided by the package supportutils which is in-
stalled by default. The YaST Support module is based on the command line tool.
2.1 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.
2.1.1 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 http://www.novell.com/center/eservice and follow the instruc-
tions on the screen. Write down your 11-digit service request number.
Note: Privacy Statement

SUSE and Novell treat system reports as confidential data. For details about our privacy
commitment, see http://www.novell.com/company/legal/privacy/ .
9 Collecting System Information with Supportconfig SUSE Linux Enterp… 11 SP4

2.1.2 Upload Targets
After having created a service request number, you can upload your supportconfig archives to
Global Technical Support as described in Procedure 2.1, “Submitting Information to Support with YaST”
or Procedure 2.2, “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: http://www.novell.com/center/eservice .
2.1.3 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.
10 Upload Targets SUSE Linux Enterp… 11 SP4

3. In the next window, select one of the supportconfig options from the radio button list. Use
Custom (Expert) Settings is pre-selected 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 2.1.2, “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.
11 Creating a Supportconfig Archive with YaST SUSE Linux Enterp… 11 SP4

After the process is finished, continue with Next.
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 2.1.2, “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.
2.1.4 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 2.2, “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
2.1.5 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
12 Creating a Supportconfig Archive from Command Line SUSE Linux Enterp… 11 SP4
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 may want to 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.
2.2 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 2.1.1,
“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 2.1.1, “Creating a
Service Request Number”.
13 Submitting Information to Global Technical Support SUSE Linux Enterp… 11 SP4

PROCEDURE 2.1: 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 2.1.3, “Creating a Supportconfig Archive with YaST”, Step 4.
For instructions on how to generate and submit a supportconfig archive in one go, see
Section 2.1.3, “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 2.1.2, “Upload Targets” for details of which upload servers are available.
Proceed with Next.
5. Click Finish.
PROCEDURE 2.2: 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 2.1.3, “Creating a Supportconfig Archive with YaST”.
14 Submitting Information to Global Technical Support SUSE Linux Enterp… 11 SP4

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
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 2.1.2, “Upload Targets”.
3. After the TAR archive is in the incoming directory of our FTP server, it becomes automat-
ically attached to your service request.
2.3 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”.
15 Support of Kernel Modules SUSE Linux Enterp… 11 SP4

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 ) and will not be loaded by default ( FLAVOR = default | xen |...).
In addition, these unsupported modules are not available in the installer, and the ker-
nel-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 .
2.3.1 Technical Background
Linux Kernel: The value of /proc/sys/kernel/unsupported defaults to 2 on SUSE Linux

Enterprise 11 SP4 ( do not warn in syslog when loading unsupported modules ).
This default is used in the installer as well as in the installed system. See /usr/src/
linux/Documentation/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 2.3.2, “Working with Unsupported Modules”.
Note
SUSE does not generally support the removal of storage modules via modprobe -r .
2.3.2 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/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 mkinitrd to update the initrd.
16 Technical Background SUSE Linux Enterp… 11 SP4

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 module-init-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.
2.4 For More Information

Find more information about gathering system information in the following documents:
man supportconfig —The supportconfig man page.
man supportconfig.conf —The man page of the supportconfig configuration le.
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.
17 For More Information SUSE Linux Enterp… 11 SP4

3 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 3.1: MAIN WINDOW OF YAST IN TEXT MODE
When you start YaST in text mode, the YaST Control Center appears (see Figure 3.1). 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 highlighted. 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 highlighted. Press Enter
to start the active module.

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 Tab .
Exit the YaST Control Center by pressing Alt – Q or by selecting Quit and pressing Enter .
Tip: Refreshing YaST Dialog Window

If a YaST dialog window gets corrupted or distorted (e.g., while resizing the window),
press Ctrl – L to refresh and restore its contents.
3.1 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 3.2, “Restriction of Key Combinations” for information about possible exceptions.
Navigation among Buttons and Selection Lists

Use Tab to navigate among the buttons and frames containing selection lists. To navigate
in reverse order, use Alt – Tab or Shift – Tab 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
19 Navigation in Modules SUSE Linux Enterp… 11 SP4

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 Tab , press Enter to execute the selected
action or activate the respective menu item.
Function Keys
The F keys ( F1 through F12 ) enable quick access to the various buttons. Available F
key shortcuts 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 in order to show the selected dialog. This is an intentional behavior to save
time consuming redraws when browsing through the navigation tree.
FIGURE 3.2: THE SOFTWARE INSTALLATION MODULE
20 Navigation in Modules SUSE Linux Enterp… 11 SP4

3.2 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 F keys 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.
3.3 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
3.3.1 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 .
21 Restriction of Key Combinations SUSE Linux Enterp… 11 SP4

3.3.2 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 , which is installed with
dependency checking, or the full path to an rpm package, which is installed without dependency
checking.
If you need a command-line based software management utility with functionality beyond what
YaST provides, consider using zypper. This new 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”.
3.3.3 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.
22 Installing Packages from the Command Line SUSE Linux Enterp… 11 SP4
4 Snapshots/Rollback 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, in conjunction with the
Btrfs le system 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). Snapper lets
you manage these snapshots. Snapper comes with a command line and a YaST inter-
face.
By default Snapper and Btrfs on SUSE Linux Enterprise Server are set up to serve
as an “undo tool” for system changes made with YaST and zypper. Before and af-
ter running a YaST module or zypper, a snapshot is created. Snapper lets you com-
pare the two snapshots and provides means to revert the differences between the
two snapshots. The tools also provide system backups by creating hourly snapshots
of the system subvolumes.
4.1 Requirements
Since Btrfs is the only le system on SUSE Linux Enterprise Server supporting snapshots, it is
required on all partitions or subvolumes you want to “snapshot”.
4.1.1 Snapshots and Disk Space

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!
23 Requirements SUSE Linux Enterp… 11 SP4

Note: Snapshot Location
Snapshots always reside on the same partition or subvolume that has been “snapshotted”.
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.
Tip: Freeing space / Disk Usage

In order 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.
Since the df does not show the correct disk usage on Btrfs le systems, you need to
use the command btrfs filesystem df MOUNT_POINT . Displaying the amount of disk
space a snapshot allocates is currently not supported by the Btrfs tools.
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 once they are no longer needed is recom-
mended.
Snapper can also be used to create and manage snapshots on thin-provisioned LVM volumes
formatted with ext3 or XFS (see Section 4.6, “Using Snapper on Thin-Provisioned LVM Volumes”).
4.2 Using Snapper to Undo System Changes

Snapper on SUSE Linux Enterprise Server is pre-configured 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 sys-
tem les that have been accidentally deleted or modified. Hourly backups are created for this
purpose.
24 Using Snapper to Undo System Changes SUSE Linux Enterp… 11 SP4

By default, automatic snapshots as described above are configured for the root partition and
its subvolumes. In order to make snapshots available for other partitions such as /home for
example, you can create custom configurations.
4.2.1 Undoing YaST and Zypper Changes

If you set up the root partition with Btrfs during the installation, Snapper—pre-configured 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).
Since Linux is a multitasking system, processes other than YaST or Zypper may modify data in
the time frame between the pre- and the post-snapshot. If this is the case, completely reverting
to the pre-snapshot will also undo these changes by other processes. In most cases this would
be unwanted—therefore it is strongly recommended to closely review the changes between two
snapshots before starting the rollback. If there are changes from other processes you want to
keep, select which les to roll back.
Important: Limitations
Make sure you know about Snapper's limitations before attempting to use its rollback
mechanism. See Section 4.4, “Limitations” for details.
Note: Storage Time of Snapshots

By default, the last 100 YaST and Zypper snapshots are kept. If this number is exceeded,
the oldest snapshot(s) will be deleted.
PROCEDURE 4.1: UNDOING CHANGES USING THE YAST SNAPPER MODULE
1. Start the Snapper module from the Miscellaneous section in YaST or by entering yast2
snapper .
25 Undoing YaST and Zypper Changes SUSE Linux Enterp… 11 SP4

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 yast module_name 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. The fol-
lowing image shows a list of les that have changed after having added the user tester .

5. Review the list of les. To display a “di” between the pre- and post-version of a le, select
it from the list. The following images shows the changes to /etc/passwd after having
added the user tester .
6. To restore a set of les, select the relevant les or directories by ticking the respective
check box. Click Restore Selected and confirm the action by clicking Yes.

To restore a single le, activate its di view by clicking on its name. Click Restore From
First and confirm your choice with Yes.
PROCEDURE 4.2: 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) .
~ # snapper list -t pre-post

Pre # | Post # | Pre Date | Post Date | Description
------+--------+--------------------------+--------------------------+----------------------+
4 | 5 | Tue Jan 10 14:39:14 2012 | Tue Jan 10 14:39:33 2012 | yast system_settings
65 | 66 | Thu Jan 12 17:18:10 2012 | Thu Jan 12 17:18:23 2012 | zypp(zypper)
73 | 74 | Thu Jan 12 17:32:55 2012 | Thu Jan 12 17:33:13 2012 | yast system_settings
75 | 76 | Thu Jan 12 17:33:56 2012 | Thu Jan 12 17:34:42 2012 | yast users
77 | 92 | Thu Jan 12 17:38:36 2012 | Thu Jan 12 23:13:13 2012 | yast snapper
108 | 109 | Fri Jan 13 13:01:06 2012 | Fri Jan 13 13:01:10 2012 | 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 -. The following example shows a snapshot pair for the
installation of the package ncftp .

~ # snapper status 108..109
+... /usr/bin/ncftp
+... /usr/bin/ncftpbatch
+... /usr/bin/ncftpget
+... /usr/bin/ncftpls
[...]
+... /usr/share/man/man1/ncftpspooler.1.gz
c... /var/cache/zypp/solv/@System/cookie
c... /var/cache/zypp/solv/@System/solv
c... /var/lib/rpm/Basenames
c... /var/lib/rpm/Dirnames
c... /var/lib/rpm/Filemd5s
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/Provideversion
c... /var/lib/rpm/Requirename
c... /var/lib/rpm/Requireversion
c... /var/lib/rpm/Sha1header
c... /var/lib/rpm/Sigmd5
c... /var/lib/zypp/SoftLocks
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.
~ # snapper diff 108..109 /var/lib/zypp/SoftLocks

--- /.snapshots/108/snapshot/var/lib/zypp/SoftLocks 2012-01-12
23:15:22.408009164 +0100
+++ /.snapshots/109/snapshot/var/lib/zypp/SoftLocks 2012-01-13
13:01:08.724009131 +0100
@@ -1,4 +1,2 @@
-# zypp::SoftLocksFile generated Thu Jan 12 23:10:46 2012
-#
-ncftp
-#
+# zypp::SoftLocksFile generated Fri Jan 13 13:01:08 2012
+##
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.
~ # snapper -v undochange 108..109

create:0 modify:16 delete:21

undoing change...
deleting /usr/share/man/man1/ncftpspooler.1.gz
deleting /usr/share/man/man1/ncftpput.1.gz
[...]
deleting /usr/bin/ncftpls
deleting /usr/bin/ncftpget
deleting /usr/bin/ncftpbatch
deleting /usr/bin/ncftp
modifying /var/cache/zypp/solv/@System/cookie
modifying /var/cache/zypp/solv/@System/solv
modifying /var/lib/rpm/Basenames
modifying /var/lib/rpm/Dirnames
modifying /var/lib/rpm/Filemd5s
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/Provideversion
modifying /var/lib/rpm/Requirename
modifying /var/lib/rpm/Requireversion
modifying /var/lib/rpm/Sha1header
modifying /var/lib/rpm/Sigmd5
modifying /var/lib/zypp/SoftLocks
undoing change done
4.2.2 Using Snapper to Restore Files from Hourly Backups

Apart from the YaST and Zypper snapshots, Snapper creates hourly snapshots of the system
partition ( / ). You can use these backup snapshots to restore les that have accidentally been
deleted or modified beyond recovery. By making use of Snapper's di feature you can also nd
out which modifications have been made at a certain point of time.
Hourly backup snapshots are of the type Single and are marked with the description time-
line . To restore les from these snapshots proceed as described in Procedure 4.1, “Undoing
changes using the YaST Snapper module” or Procedure 4.2, “Undoing changes using the snapper com-
mand”.
Note: Storage Time of Snapshots

By default, the rst snapshot of the last ten days, months, and years are kept. For details
see Example 4.1, “Example time line configuration”.
30 Using Snapper to Restore Files from Hourly Backups SUSE Linux Enterp… 11 SP4
4.2.3 Creating and Modifying Snapper Configurations
The way Snapper behaves is defined in a config le that is specific for each partition or Btrfs
subvolume. These config les reside under /etc/snapper/configs/ . The default config in-
stalled with Snapper for the / directory is named root . It creates and manages the YaST and
Zypper snapshots as well as the hourly backup snapshot for / .
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 .
You can use either snapper itself or the YaST Snapper module to restore les from these snap-
shots. In YaST you need to select your Current Configuration, while you need to specify your
config for snapper with the global switch -c (e.g. snapper -c myconfig list).
To create a new Snapper configuration, run snapper create-config :
snapper -c www-data 1 create-config

/srv/www 2
1 Name of config le.

2 Mount point of the partition or Btrfs subvolume to snapshot.
This command will create a new config le /etc/snapper/config-templates/www-data with
reasonable default values (taken from /etc/snapper/config-templates/default ).
Tip: Config Defaults

Default values for a new config are taken from /etc/snapper/config-templates/de-
fault . 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-config command:
snapper -c www-data create-config -t my_defaults /srv/www
4.2.3.1 Adjusting the Config File

To adjust the config le, you need to modify it with an editor. It contains key/value pairs in the
form of key=value . You may only change the value .
SUBVOLUME
31 Creating and Modifying Snapper Configurations SUSE Linux Enterp… 11 SP4

Mount point of the partition or subvolume to snapshot. Do not change.
FSTYPE
File system type of the partition. Do not change.
NUMBER_CLEANUP
Defines whether to automatically delete old snapshots when the total snapshot count ex-
ceeds a number specified with NUMBER_LIMIT and an age specified with NUMBER_MIN_AGE .
Valid values: yes , no
Note: Limit and Age

NUMBER_LIMIT and NUMBER_MIN_AGE are always evaluated both. Snapshots are
only deleted when both conditions are met. If you always want to keep a certain
number of snapshots regardless of their age, set NUMBER_MIN_AGE to 0 . On the other
hand, if you do not want to keep snapshots beyond a certain age, set NUMBER_LIMIT
to 0 .
NUMBER_LIMIT
Defines how many snapshots to keep if NUMBER_CLEANUP is set to yes .
NUMBER_MIN_AGE
Defines the minimum age in seconds a snapshot must have before it can automatically
be deleted.
TIMELINE_CREATE
If set to yes , hourly snapshots are created.This is currently the only way to automatically
create snapshots, therefore setting it to yes is strongly recommended. Valid values: yes ,
no
TIMELINE_CLEANUP
Defines whether to automatically delete old snapshots when the snapshot count ex-
ceeds a number specified with the TIMELINE_LIMIT_* options and an age specified with
TIMELINE_MIN_AGE . Valid values: yes , no
TIMELINE_MIN_AGE
Defines the minimum age in seconds a snapshot must have before it can automatically
be deleted.
TIMELINE_LIMIT_HOURLY , TIMELINE_LIMIT_DAILY , TIMELINE_LIMIT_MONTHLY ,

TIMELINE_LIMIT_YEARLY

Number of snapshots to keep for hour, day, month, year.
EXAMPLE 4.1: EXAMPLE TIME LINE CONFIGURATION
TIMELINE_CREATE="yes"
TIMELINE_CLEANUP="yes"
TIMELINE_MIN_AGE="1800"
TIMELINE_LIMIT_HOURLY="10"
TIMELINE_LIMIT_DAILY="10"
TIMELINE_LIMIT_MONTHLY="10"
TIMELINE_LIMIT_YEARLY="10"
This example configuration enables hourly snapshots which are automatically cleaned up.
TIMELINE_MIN_AGE and TIMELINE_LIMIT_* are always evaluated both. 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 ten snapshots that have been made.
Daily: The rst daily snapshot that has been made is kept for the last ten days.
Monthly: The rst snapshot made on the last day of the month is kept for the last
ten months.
Yearly: The rst snapshot made on the last day of the year is kept for the last ten years.
4.2.3.2 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:
a website administrator wants to snapshot /srv/www .
a database administrator wants to snapshot the databases.
a user wants to snapshot her home directory.
For these purposes Snapper configurations that grant permissions to users or/and groups can
be created. In addition to this configuration change, the corresponding .snapshots directory
needs to be readable and accessible by the specified users.

PROCEDURE 4.3: 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 4.2.3, “Creating and Modifying Snapper
Configurations” for instructions. Example:
snapper --config web_data create /srv/www
2. The configuration le is created under /etc/snapper/configs/NAME , where NAME is

the value you specified with -c/--config in the previous step (for example /etc/snap-
per/configs/web_data ). Adjust it according to your needs; see Section 4.2.3.1, “Adjusting
the Config File” 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, enter:
ALLOW_USERS="www_admin"
4. Grant read and access permissions on the snapshot directory PATH /.snapshots. PATH is to
be replaced by the subvolume you specified in the rst step of this procedure. Example:
chmod a+rx /srv/www/.snapshots
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
4.2.4 Disabling Automatic Snapshots

If you have set up the root partition with Btrfs during the installation, Snapper automatically
creates hourly snapshots of the system, as well as pre- and post-snapshots for YaST and zypper
transactions. Each of these tasks can be disabled as follows:
Disabling hourly snapshots

Edit /etc/snapper/configs/root and set TIMELINE_CREATE to no :
TIMELINE_CREATE="no"
34 Disabling Automatic Snapshots SUSE Linux Enterp… 11 SP4

Disabling Zypper snapshots
Uninstall the package snapper-zypp-plugin
Disabling YaST snapshots

Edit /etc/sysconfig/yast2 and set USE_SNAPPER to no :
USE_SNAPPER="no"
4.3 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 4.2.3, “Creating
and Modifying Snapper Configurations” for details). You can only snapshot 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 menu in YaST or specify the -c on the command
line ( snapper -c MYCONFIG COMMAND ).
4.3.1 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. The following metadata is available for each snapshot:
Type: Snapshot type, see Section 4.3.1.1, “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.
35 Manually Creating and Managing Snapshots SUSE Linux Enterp… 11 SP4

Userdata: An extended description where you can specify custom data in the form of a
comma-separated key=value list: reason=testing_stuff, user=tux
Cleanup-Algorithm: Cleanup-algorithm for the snapshot, see Section 4.3.1.2, “Cleanup-algo-

rithms” for details.
4.3.1.1 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 e.g. for the automatic YaST/zypper snapshots.
post
Snapshot of a le system after a modification. Each post snapshot has got a corresponding
pre snapshot. Used e.g. for the automatic YaST/zypper snapshots.
single
Stand-alone snapshot. Used e.g. for the automatic hourly snapshots. This is the default
type when creating snapshots.
4.3.1.2 Cleanup-algorithms
Snapper provides three algorithms to clean up old snapshots. The algorithms are executed in
a daily cron-job. The cleanup-frequency itself is defined in the Snapper configuration for the
partition or subvolume (see Section 4.2.3.1, “Adjusting the Config File” for details).
number
Deletes old snapshots when a certain snapshot count is reached.
time line
Deletes old snapshots having passed a certain age, but keeps a number of hourly, daily,
monthly, and yearly snapshots.
empty-pre-post
Deletes pre/post snapshot pairs with empty dis.
36 Snapshot Metadata SUSE Linux Enterp… 11 SP4

4.3.2 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 in order 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 2013"

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.
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 time line cleanup-algorithm in the configuration.
snapper create --type pre --print-number --description "Before the Apache config
cleanup"
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.
snapper create --type post --pre-number 30 --description "After the Apache con-
fig cleanup"
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.
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.
37 Creating Snapshots SUSE Linux Enterp… 11 SP4

4.3.3 Modifying Snapshot Metadata
Snapper allows you to modify the description, the cleanup algorithm, and the userdata 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 .
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.
4.3.4 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 .
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 .
38 Modifying Snapshot Metadata SUSE Linux Enterp… 11 SP4

Tip: Old Snapshots Occupy More Disk Space
If you delete snapshots in order to free space on your hard disk (see Section 4.1.1, “Snapshots
and Disk Space” for details), 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 4.3.1.2, “Cleanup-
algorithms” for details.
4.4 Limitations
Although being ready for production, Btrfs as well as Snapper are constantly developed fur-
ther. The following limitations exist at the moment. It is planned to solve these issues in future
releases.
4.4.1 Data Consistency

There is no mechanism to ensure data consistency when creating snapshot. Whenever a le is
written (e.g. a database) at the same time the snapshot is created, it will result in a broken
or partly written le. Restoring such a le will cause problems. Therefore it is strongly recom-
mended to always closely review the list of changed les and their dis. Only restore les that
really need to belonging to the action you want to roll back.
4.4.2 Reverting User Additions

Usually /home resides on a separate partition. Such a separate partition is not part of the default
configuration for doing YaST rollbacks. Therefore the user's home partition will not be deleted
when reverting a user addition using Snapper. It is strongly recommended to use the YaST User
and Group Management tool to remove users.
39 Limitations SUSE Linux Enterp… 11 SP4

4.4.3 No Rollback on /boot and Boot Loader Changes
Currently SUSE Linux Enterprise Server cannot boot from Btrfs partitions. Therefore a sep-
arate partition for /boot is created upon the installation when using Btrfs for the system
partition. Since /boot does not support snapshots, the following restrictions apply for YaST/
zypper rollbacks:
no rollback for any configuration changes on the boot loader

The only le that can be rolled back is the boot loader configuration le in /etc . The
main configuration les reside under /boot and cannot be rolled back.
no complete rollback for Kernel installations

The Kernel itself and its initrd are installed in the /boot partition, whereas Kernel mod-
ules or sources are installed in /var/lib and /usr/src , respectively. Furthermore, each
Kernel installation also changes the boot loader configuration les in /boot. So whenever
you do a rollback that involves undoing a Kernel installation, you need to manually remove
the Kernel and its initrd from /boot and adjust the boot loader configuration by removing
the boot entry for the Kernel.
4.5 Frequently Asked Questions

Why does Snapper Never Show Changes in /var/log , /tmp and Other Directories?
For some directories we decided to disable “snapshotting”, e.g. /var/log since reverting
logs makes searching for problems difficult. To exclude a path from “snapshotting” we
create a subvolume for that path. The following mount points are excluded from “snap-
shotting” on SUSE Linux Enterprise Server:
/opt
/srv
/tmp
/var/crash
/var/log
/var/run
/var/spool
/var/tmp
40 No Rollback on /boot and Boot Loader Changes SUSE Linux Enterp… 11 SP4
Can I Boot a Snapshot from the Boot Loader?
This is currently not possible. The boot loader on SUSE Linux Enterprise Server currently
does not support booting from a Btrfs partition.
4.6 Using Snapper on Thin-Provisioned LVM Volumes

Apart from snapshots on Btrfs le systems, snapper also supports “snapshotting” on thin-
provisioned LVM volumes (snapshots on regular LVM volumes are not supported) formatted
with ext3 or XFS. For more information and setup instructions, refer to Book “Deployment Guide”,
Chapter 15 “Advanced Disk Setup”, Section 15.2 “LVM Configuration”.
In order to use Snapper on a thin-provisioned LVM volume you need to create a Snapper configu-
ration for it. On LVM it is required to specify the le system with --fstype=lvm(FILESYSTEM) .
To date ext3 and XFS are supported, so ext3 or xfs are valid values for FILESYSTEM . Example:
snapper -c lvm create-config --fstype="lvm(xfs)" /thin_lvm
You can adjust this configuration according to your needs as described in Section 4.2.3.1, “Adjusting
the Config File”. Now you can use Snapper to create and manage snapshots, to restore les, and
undo changes as described above.
41 Using Snapper on Thin-Provisioned LVM Volumes SUSE Linux Enterp… 11 SP4

5 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.
5.1 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. Once 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 5.1: ENABLING ONE-TIME VNC SESSIONS
1. Start YaST Network Services Remote Administration (VNC).
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.
42 One-time VNC Sessions SUSE Linux Enterp… 11 SP4

Note: Available Configurations
The default configuration on SUSE Linux Enterprise Server serves sessions with a resolu-
tion 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 5.1.2, “Configuring
One-time VNC Sessions”.
VNC display numbers and X display numbers are independent in one-time sessions. A VNC
display number is manually assigned to every configuration that the server supports (:1 in
the example above). Whenever a VNC session is initiated with one of the configurations,
it automatically gets a free X display number.
5.1.1 Initiating a One-time VNC Session

To initiate a one-time VNC session, a VNC viewer must be installed on the client machine. The
standard viewer on SUSE Linux products is vncviewer , provided by the package tightvnc .
You may also view a VNC session using your Web browser and a Java applet.
To start your VNC viewer and initiate a session with the server's default configuration, 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
Alternatively use a Java-capable Web browser to view the VNC session by entering the following
URL: http://jupiter.example.com:5801
5.1.2 Configuring One-time VNC Sessions

You can skip this section, if you do not need or want to modify the default configuration.
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.
43 Initiating a One-time VNC Session SUSE Linux Enterp… 11 SP4

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:
rcxinetd reload
Important: Firewall and VNC Ports

When activating Remote Administration as described in Procedure 5.1, “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.
5.2 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 usecase 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 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.
44 Persistent VNC Sessions SUSE Linux Enterp… 11 SP4

PROCEDURE 5.2: 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
out its choice. See man 1 vncserver for more options.
When running vncviewer 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.
VNC connections are unencrypted, so people who can sni the network(s) between the
two machines can read the password when it gets transferred at the beginning of a session.
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.
45 Persistent VNC Sessions SUSE Linux Enterp… 11 SP4

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
5.2.1 Connecting to a Persistent VNC Session

To connect to a persistent VNC session, a VNC viewer must be installed. The standard viewer
on SUSE Linux products is vncviewer , provided by the package tightvnc . You may also view
a VNC session using your Web browser and a Java applet.
To start your VNC viewer and connect to display :1 of the VNC 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
Alternatively use a Java-capable Web browser to view the VNC session by entering the following
URL: http://jupiter.example.com:5801
5.2.2 Configuring Persistent VNC Sessions

Persistent VNC sessions can be configured by editing $HOME/.vnc/xstartup . By default this
shell script starts an xterm and the twm Window Manager. To start either GNOME or KDE
instead, replace the line starting twm with one of the following:
/usr/bin/gnome # GNOME
/usr/bin/startkde # KDE
Note: One Configuration for Each User

Persistent VNC sessions are configured in a single per-user configuration. Multiple ses-
sions started by a user will all use the same start-up and password les.
46 Connecting to a Persistent VNC Session SUSE Linux Enterp… 11 SP4

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 9 “Installing or
Removing Software”, Section 9.1 “Definition of Terms”.
6.1 Using Zypper

Zypper is a command line package manager for installing, updating and removing packages as
well as for managing repositories. Zypper's syntax is similar to that of rug. In contrast to rug,
Zypper does not require the zmd daemon to run behind the scenes. For more information about
rug compatibility, see man zypper , section “COMPATIBILITY WITH RUG”. 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. 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 type:
zypper patch
Additionally, you can choose from one or more global options by typing them just before the
command. For example, --non-interactive means running the command without asking any-
thing (automatically applying the default answers):
zypper --non-interactive patch
To use the options specific to a particular command, type them right after the command. For ex-
ample, --auto-agree-with-licenses means applying all needed patches to the system with-
out asking to confirm any licenses (they will automatically be accepted):
zypper patch --auto-agree-with-licenses
47 Using Zypper SUSE Linux Enterp… 11 SP4

Some commands require one or more arguments. When using the install command, for example,
you need to specify which package(s) to install:
zypper install mplayer
Some options also require an argument. The following command will list all known patterns:
zypper search -t pattern
You can combine all of the above. For example, the following command will install the mplayer
and amarok packages from the factory repository while being verbose:
zypper -v install --from factory mplayer amarok
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.
zypper remove --dry-run MozillaFirefox
Zypper supports the global --userdata string option for transaction identification purpos-
es. The user-defined string is passed to Zypper history logs in /var/log/zypp/history and
Snapper.
zypper --userdata string patch
6.1.2 Installing and Removing Software with Zypper

To install or remove packages use the following commands:
zypper install package_name

zypper remove package_name
Zypper knows various ways to address packages for the install and remove commands:
by the exact package name (and version number)
zypper install MozillaFirefox
or
48 Installing and Removing Software with Zypper SUSE Linux Enterp… 11 SP4
zypper install MozillaFirefox-3.5.3
by repository alias and package name
zypper install mozilla:MozillaFirefox
Where mozilla is the alias of the repository from which to install.
by package name using wild cards

The following command will install all packages that have names starting with “Moz”. Use
with care, especially when removing packages.
zypper install 'Moz*'
by capability
For example, if you would like to install a perl module without knowing the name of the
package, capabilities come in handy:
zypper install 'perl(Time::ParseDate)'
by capability and/or architecture and/or version

Together with a capability you can specify an architecture (such as i586 or x86_64 ) and/
or a version. The version must be preceded by an operator: < (lesser than), <= (lesser
than or equal), = (equal), >= (greater than or equal), > (greater than).
zypper install 'firefox.x86_64'

zypper install 'firefox>=3.5.3'
zypper install 'firefox.x86_64>=3.5.3'
by path to the RPM file

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

zypper install http://download.opensuse.org/repositories/mozilla/SUSE_Factory/
x86_64/MozillaFirefox-3.5.3-1.3.x86_64.rpm
To install and remove packages simultaneously use the +/- modifiers. To install emacs and
remove vim simultaneously, use:
zypper install emacs -vim
To remove emacs and install vim simultaneously, use:
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 -- :
zypper install -emacs +vim # Wrong

zypper install vim -emacs # Correct
zypper install -- -emacs +vim # same as above
zypper remove emacs +vim # same as above
If (together with a certain package) you automatically want to remove any packages that become
unneeded after removing the specified package, use the --clean-deps option:
rm package_name --clean-deps
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 in
the following:
zypper --non-interactive install package_name
This option allows the use of Zypper in scripts and cron jobs.
Warning: Do not Remove Mandatory System Packages

Do not remove packages such as glibc , zypper , kernel , or similar packages. These
packages are mandatory for the system and, if removed, may cause the system to become
unstable or stop working altogether.
6.1.2.1 Installing or Downloading Source Packages
If you want to install the corresponding source package of a package, use:
zypper source-install package_name
That command will also install the build dependencies of the specified package. If you do not
want this, add the switch -D . To install only the build dependencies use -d .
zypper source-install -D package_name # source package only

zypper source-install -d package_name # build dependencies only
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:
zypper search -t srcpackage
You can also download source packages for all installed packages to a local directory. To down-
load source packages, use:
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.
6.1.2.2 Utilities
To verify whether all dependencies are still fulfilled and to repair missing dependencies, use:
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:
zypper install-new-recommends
This command is very useful after plugging in a webcam or WLAN 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 the zypper dist-upgrade command which is discussed in Section 6.1.4, “Distribution Up-
grade with zypper”.
51 Updating Software with Zypper SUSE Linux Enterp… 11 SP4

6.1.3.1 Installing Patches
To install all officially released patches applying to your system, just run:
zypper patch
In this case, all patches available in your repositories are checked for relevance and installed,
if necessary. After registering your SUSE Linux Enterprise Server installation, an official update
repository containing such patches will be added to your system. The above command is all you
must enter in order to apply them when needed.
Zypper knows three different commands to query for the availability of patches:
zypper patch-check
Lists the number of needed patches (patches, that apply to your system but are not yet
installed)
~ # zypper patch-check
Loading repository data...
Reading installed packages...
5 patches needed (1 security patch)
zypper list-patches
Lists all needed patches (patches, that apply to your system but are not yet installed)
~ # zypper list-patches
Loading repository data...
Reading installed packages...
Repository | Name | Version | Category | Status

------------------------------------+-----------+---------+----------+-------
Updates for openSUSE 11.3 11.3-1.82 | lxsession | 2776 | security | needed
zypper patches
Lists all patches available for SUSE Linux Enterprise Server, regardless of whether they are
already installed or apply to your installation.
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:
--bugzilla[=number]
Lists all needed patches for Bugzilla issues. Optionally, you can specify a bug number if
you only want to list patches for this specific bug.
--cve[=number]

Lists all needed patches for CVE (Common Vulnerabilities and Exposures) issues, or only
patches matching a certain CVE number, if specified. By default, only unapplied patches
are listed. Use -a to list all.
To install a patch for a specific Bugzilla or CVE issue, use the following commands:
zypper patch --bugzilla=number
or
zypper patch --cve=number
For example, to install a security patch with the CVE number CVE-2010-2713 , execute:
zypper patch --cve=CVE-2010-2713
6.1.3.2 Installing Updates

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, use:
zypper update
To update individual packages, specify the package with either the update or install command:
zypper update package_name

zypper install package_name
A list of all new installable packages can be obtained with the command:
zypper list-updates
Note that this command only packages 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:
zypper list-updates --all

To nd out why a new package cannot be installed, just use the zypper install or zypper
update command as described above.
6.1.3.3 Upgrading to a New Product Version

To easily upgrade your installation to a new product version (for example, from SUSE Linux En-
terprise Server 11 to SUSE Linux Enterprise Server 11 SP1, rst adjust your repositories to match
the current SUSE Linux Enterprise Server repositories. For details, refer to Section 6.1.5, “Manag-
ing Repositories with zypper”. Then use the zypper dist-upgrade command with the required
repositories. This command ensures that all packages will be installed from the repositories cur-
rently enabled. For detailed instructions, refer to Section 6.1.4, “Distribution Upgrade with zypper”.
To restrict the distribution upgrade to packages from a certain repository while considering
also the other repositories for satisfying dependencies, use the --from option and specify the
repository by either its alias, its number or URI.
Note: Dierences between zypper update and zypper dist-

upgrade
Choose zypper update to update packages to newer versions available for your product
version while maintaining system integrity. zypper update will honor the following
rules:
no vendor changes
no architecture changes
no downgrades
keep installed packages
When executing zypper dist-upgrade , all packages will be installed from the reposito-
ries currently enabled. This rule is enforced, so packages might change vendor or archi-
tecture or even might get downgraded. All packages that have unfulfilled dependencies
after the upgrade will be uninstalled.
6.1.4 Distribution Upgrade with zypper
With the zypper command line utility you can upgrade to the next version of the distribution.
Most importantly, you can initiate the system upgrade process from within the running system.
54 Distribution Upgrade with zypper SUSE Linux Enterp… 11 SP4

This feature is attractive for advanced users who want to run remote upgrades or upgrades on
many similarly configured systems.
6.1.4.1 Before Starting the Upgrade with zypper

To avoid unexpected errors during the upgrade process using zypper , minimize risky constel-
lations.
Close as many applications and unneeded services as possible and log out all regular users.
Disable third party repositories before starting the upgrade, or lower the priority of these
repositories to make sure packages from the default system repositories will get preference.
Enable them again after the upgrade and edit their version string to match the version
number of the distribution of the upgraded now running system.
Make sure to have the system registered. f this is not done already, it can either be regis-
tered by using the Novell Customer Center Configuration module in YaST or by using the
suse_register commandline tool. This will add update sources to the system.
Warning: Perform Upgrades from Reboot

The upgrade process has to be done completely from beginning to reboot. There is only
a limited chance to revert changes. Furthermore, the server has to be connected online
during the whole process.
6.1.4.2 The Upgrade Procedure
Warning: Check Your System Backup

Before actually starting the upgrade procedure, check that your system backup is up-to-
date and restorable. This is especially important because you must enter many of the
following steps manually.
Note: Registration Key

If add-ons are installed on your system, you might need to enter your registration key in
order to update the system. Be prepared to have the key available.

The program zypper supports long and short command names. For example, you can abbreviate
zypper install as zypper in . In the following text, the short variants are used.
Log in as root and perform the following steps:
1. Refresh all services and repositories:
zypper ref -s
2. Install any package management updates:
zypper up -t patch
For more information, see Chapter 1, YaST Online Update.
3. Repeat Step 2 to install all available updates for your system.

Sidenote: If you want o use the above command in a script for an unattended upgrade,
use the command:
zypper --non-interactive patch --auto-agree-with-licenses --with-interactive
4. Read the migration product informations from /etc/products.d/*.prod . The installed

products contain information about distribution upgrades and which migration products
should be installed to perform the migration. Install them with the following commands:
a. Extract the product information:
zypper se -t product | grep -h -- "-migration" | cut -d\| -f2
A sample output could be as follows:
SUSE_SLES-SP3-migration
sle-sdk-SP3-migration
b. Install these migration products (example):
zypper in -t product sle-sdk-SP3-migration SUSE_SLES-SP3-migration
c. Register the products in order to get the corresponding update repositories:
suse_register -d 2 -L /root/.suse_register.log

Warning: Enable Additional Repository for SLED Users
Some devel packages have been moved from the SLED11-SP2 installation me-
dia to the SLED11-Extras repository. In order to avoid dependency conflicts
during upgrade, enable this repository before performing the actual upgrade.
Execute yast2 repositories and enable SLED11-Extras there. On SLES
this extra step is not needed.
5. Refresh services and repositores:
zypper ref -s
6. Check the repositories using zypper lr . If needed, disable the SP1/SP2 Pool/Core/Up-
dates repositories manually and enable the new SP3 ( SP3-Pool , SP3-Updates ) repos-
itories:
zypper mr --disable REPOALIAS

zypper mr --enable REPOALIAS
7. Perform a dist upgrade by using the following command (example for SLES, adjust catalog
names in case SLED is updated):
zypper dup --from SLES11-SP3-Pool --from SLES11-SP3-Updates
You can add more catalogs here if needed, for example, in case addon products are in-
stalled. Zypper will report that it will delete the migration product and update the main
products. Confirm the message to continue updating the rpm packages.
8. After the upgrade is finished, register the new products again:
suse_register -d 2 -L /root/.suse_register.log
9. Reboot the system:
shutdown -r

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:
zypper repos
The result will look similar to the following output:
EXAMPLE 6.1: ZYPPER—LIST OF KNOWN REPOSITORIES
# | Alias | Name | Enabled |

Refresh
--+-----------------------------------+-----------------------------------+---------
+--------
1 | SUSE-Linux-Enterprise-Server 11-0 | SUSE-Linux-Enterprise-Server 11-0 | Yes |
No
2 | SLES-11-Updates | SLES 11 Online Updates | Yes |
Yes
3 | broadcomdrv | Broadcom Drivers | Yes |
No
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:
zypper repos -d
Sometimes, the list contains a large number of repositories that are not enabled, which might
be confusing. To only show enabled repositories, use the following command:
zypper repos -E
58 Managing Repositories with zypper SUSE Linux Enterp… 11 SP4

6.1.5.1 Adding Repositories
Warning: Possible System Compromise When Adding

Repositories with Zypper
By default, digests and signatures of packages from repositories provided by SUSE are
checked to ensure their integrity and origin. This “GPG check” is enabled in the repository
configuration le on the server that provides the repository.
When adding a repository with the zypper ar command, this configuration le is down-
loaded to /etc/zypp/repos.d . Zypper also informs the user about GPG Check option:
GPG check: Yes
Always make sure that the GPG check output is set to “Yes”. If set to “No” your system
can possibly be compromised by, for example, package downgrades that re-introduce
previously xed vulnerabilities. It is recommended not to trust repositories where this
option is set to “No”. In case you are sure that the GPG check was disabled by mistake, re-
enable the option by adding the following line to the respective repository configuration
le in /etc/zypp/repos.d :
gpgcheck=1
To add a repository, run
zypper addrepo URIalias
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 is has
to be unique. Zypper will issue a warning if you specify an alias that is already in use.
59 Managing Repositories with zypper SUSE Linux Enterp… 11 SP4

6.1.5.2 Removing Repositories
If you want to remove a repository from the list, use the command zypper removerepo to-
gether with the alias or number of the repository you want to delete. For example, to remove
the repository listed as third entry in Example 6.1, “Zypper—List of Known Repositories”, use the
following command:
zypper removerepo 3
6.1.5.3 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:
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 just firefox :
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:
zypper products
zypper patterns
60 Querying Repositories and Packages with Zypper SUSE Linux Enterp… 11 SP4
zypper packages
zypper patches
To query all repositories for certain packages, use search . It works on package names, or,
optionally, on package summaries and descriptions. Using the wild cards * and ? with the
search term is allowed. By default, the search is not case-sensitive.
zypper search firefox # simple search for "firefox"

zypper search "*fire*" # using wild cards
zypper search -d fire # also search in package descriptions and summaries
zypper search -u firefox # only display packages not already installed
To search for packages which provide a special capability, use the command what-provides .
For example, if you would like to know which package provides the perl module SVN::Core ,
use the following command:
zypper what-provides 'perl(SVN::Core)'
To query single packages, use info with an exact package name as an argument. It displays
detailed information about a package. To also show what is required/recommended by the
package, use the options --requires and --recommends :
zypper info --requires MozillaFirefox
The what-provides package is similar to rpm -q --whatprovides package , 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.
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 template: copy it to ~/.zypper.conf and ad-
just it to your liking. Refer to the comments in the le for help about the available options.
61 Configuring Zypper SUSE Linux Enterp… 11 SP4

6.1.8 Troubleshooting
In case you have problems to access packages from configured repositories (for example, Zypper
cannot nd a certain package though you know that it exists in one the repositories), it can help
to refresh the repositories with:
zypper refresh
If that does not help, try
zypper refresh -fdb
This forces a complete refresh and rebuild of the database, including a forced download of raw
metadata.
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 automat-
ically calls snapper (via script installed by snapper ) when committing changes to the le
system to create appropriate le system snapshots. These snapshots can be used for reverting
any changes made by zypper. For more information about snapper , see man snapper .
Zypper (and YaST) currently only make snapshots of the root le system. Other subvolumes
cannot be configured. This feature is not supported on the default le system.
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.
62 Troubleshooting SUSE Linux Enterp… 11 SP4

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 a number of packages, the components needed for software development (libraries,
headers, 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 , gimp-devel , and libkde4-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
Novell/SUSE or from another trustworthy facility. This is especially recommended for update
packages from the Internet.
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
that no conflicts arise—a specific le can only belong to one package. By choosing different
63 Verifying Package Authenticity SUSE Linux Enterp… 11 SP4

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, but -F merely updates previously installed packages.
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 (but 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. Afterwards, be
sure to 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 as 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.
64 Managing Packages: Install, Update, and Uninstall SUSE Linux Enterp… 11 SP4
To remove a package, enter rpm -e package . rpm , which 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 database.
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 RPM and Patches

To guarantee the operational security of a system, update packages must be installed in the
system from time to time. Previously, a bug in a package could only be eliminated by replacing
the entire package. Large packages with bugs in small les could easily result in this scenario.
However the SUSE RPM offers a feature enabling the installation of patches in packages.
The most important considerations are demonstrated using pine as an example:
Is the patch RPM suitable for my system?

To check this, rst query the installed version of the package. For pine , this can be done
with
rpm -q pine
pine-4.44-188
Then check if the patch RPM is suitable for this version of pine :
rpm -qp --basedon pine-4.44-224.i586.patch.rpm

pine = 4.44-188
pine = 4.44-195
pine = 4.44-207
This patch is suitable for three different versions of pine. The installed version in the ex-
ample is also listed, so the patch can be installed.
Which files are replaced by the patch?

The les affected by a patch can easily be seen in the patch RPM. The rpm parameter
-P allows selection of special patch features. Display the list of les with the following
command:
rpm -qpPl pine-4.44-224.i586.patch.rpm

/etc/pine.conf
/etc/pine.conf.fixed
/usr/bin/pine
65 RPM and Patches SUSE Linux Enterp… 11 SP4

or, if the patch is already installed, with the following command:
rpm -qPl pine

/etc/pine.conf
/etc/pine.conf.fixed
/usr/bin/pine
How can a patch RPM be installed in the system?

Patch RPMs are used just like normal RPMs. The only difference is that a suitable RPM
must already be installed.
Which patches are already installed in the system and for which package versions?
A list of all patches installed in the system can be displayed with the command rpm -
qPa . If only one patch is installed in a new system (as in this example), the list appears
as follows:
rpm -qPa
pine-4.44-224
If, at a later date, you want to know which package version was originally installed, this
information is also available in the RPM database. For pine , this information can be
displayed with the following command:
rpm -q --basedon pine

pine = 4.44-188
More information, including information about the patch feature of RPM, is available in the
man pages of rpm and rpmbuild .
Note: Ocial Updates for SUSE Linux Enterprise Server

In order to make the download size of updates as small as possible, official updates for
SUSE Linux Enterprise Server are not provided as Patch RPMs, but as Delta RPM packages.
For details, see Section 6.2.4, “Delta RPM Packages”.
6.2.4 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
66 Delta RPM Packages SUSE Linux Enterp… 11 SP4

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:
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:
applydeltarpm new.delta.rpm new.rpm
To derive it from the old RPM without accessing the le system, use the -r option:
applydeltarpm -r old.rpm new.delta.rpm new.rpm
See /usr/share/doc/packages/deltarpm/README for technical details.
6.2.5 RPM Queries
With the -q option rpm initiates queries, making it possible to inspect an RPM archive (by
adding the option -p ) and also to query the RPM database of installed packages. Several switch-
es are available to specify the type of information required. See Table 6.1, “The Most Important
RPM Query Options”.
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 )
67 RPM Queries SUSE Linux Enterp… 11 SP4

-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 Relocations: (not relocatable)

Version : 1.11.4 Vendor: openSUSE
Release : 1.70 Build Date: Sat 01 Aug 2009 09:49:48 CEST
Install Date: Thu 06 Aug 2009 14:53:24 CEST Build Host: build18
Group : Productivity/Networking/Web/Utilities Source RPM:
wget-1.11.4-1.70.src.rpm
Size : 1525431 License: GPL v3 or later
Signature : RSA/8, Sat 01 Aug 2009 09:50:04 CEST, Key ID b88b2fd43dbdc284
Packager : http://bugs.opensuse.org
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.
[...]
The option -f only works if you specify the complete filename with its full path. Provide as
many filenames as desired. For example, the following command
rpm -q -f /bin/rpm /usr/bin/wget
results in:
rpm-4.8.0-4.3.x86_64

wget-1.11.4-11.18.x86_64
If only part of the filename is known, use a shell script as shown in Example 6.3, “Script to Search
for Packages”. Pass the partial filename 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 rpm displays a detailed list of change information about
a specific package (in this case, the rpm package), sorted by date.
With the help of the installed RPM database, verification checks can be made. Initiate these with
-V , -y 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
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):
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 .
6.2.6 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)
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
70 Installing and Compiling Source Packages SUSE Linux Enterp… 11 SP4

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
Do not experiment with system components ( glibc , rpm , sysvinit , 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 -b X /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.
-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.
71 Installing and Compiling Source Packages SUSE Linux Enterp… 11 SP4

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.
6.2.7 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 :
cd /usr/src/packages/SOURCES/
mv ../SPECS/wget.spec .
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 a number of 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.
6.2.8 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 9 “Installing or Removing Software”.
72 Compiling RPM Packages with build SUSE Linux Enterp… 11 SP4

7 Bash and Bash Scripts
These days many people use computers with a graphical user interface (GUI) like
KDE or 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 chapter gives you an overview of some aspects of shells, in this case Bash.
7.1 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.
7.1.1 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 7.1: 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!
73 What is “The Shell”? SUSE Linux Enterp… 11 SP4

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
TABLE 7.2: 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 7.3: SPECIAL FILES FOR BASH
File Description
~/.bash_history Contains a list of all commands you have

been typing
~/.bash_logout Executed when logging out
7.1.2 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.
74 The Directory Structure SUSE Linux Enterp… 11 SP4

Directory
TABLE 7.4: OVERVIEW OF A STANDARD DIRECTORY TREE Contents
/ Root directory—the starting point of the di-

rectory 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 mod-

ules.
/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.
/usr Secondary hierarchy with read-only data.
The following list provides more detailed information

/var and
Variable gives
data suchsome examples
as log les. of which les
/bin
and subdirectories can be found in the directories:
/windows Only available if you have both Microsoft
Windows* and Linux installed on your sys-
tem. Contains the Windows data.
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 scripts that are 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. KDE users nd the personal configuration data for their desktop in
.kde4 , GNOME users nd it in .gconf .
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, USB sticks and digital
cameras (if they use USB). /media generally holds any type of drive except the hard drive
of your system. As soon as 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.
/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 are not guaranteed to survive a system reboot. It depends, for
example, on settings in /etc/sysconfig/cron .
/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 pro-
grams and establishes a secondary hierarchy in the le system. KDE4 and GNOME are also
located here. /usr holds a number of 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 36.1, “Log Files”.
7.2 Writing Shell Scripts

Shell scripts are a convenient way of doing all sorts of tasks: collecting data, searching for a
word or phrase in a text and many other useful things. The following example shows a small
shell script that prints a text:
EXAMPLE 7.1: 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.
78 Writing Shell Scripts SUSE Linux Enterp… 11 SP4

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 (this is already the case with our example
above.) If a script does not have this line, you have 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 just with hello.sh .
7.3 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
79 Redirecting Command Events SUSE Linux Enterp… 11 SP4

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
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
7.4 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 which outputs a long listing (option -l ),
sorts it by modification time ( -t ) and prints it in reverse order while sorting ( -r ):
alias lt='ls -ltr'
80 Using Aliases SUSE Linux Enterp… 11 SP4

To view all alias definitions, use alias . Remove your alias with unalias and the corresponding
alias name.
7.5 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"
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 7.5: USEFUL ENVIRONMENT VARIABLES
HOME the home directory of the current user
HOST the current hostname
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
81 Using Variables in Bash SUSE Linux Enterp… 11 SP4

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
7.5.1 Using Argument Variables

For example, if you have the script foo.sh you can execute it like this:
foo.sh "Tux Penguin" 2000
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" "" ""
7.5.2 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
82 Using Argument Variables SUSE Linux Enterp… 11 SP4

${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
${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
7.6 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
83 Grouping And Combining Commands SUSE Linux Enterp… 11 SP4

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"; }
You can call this function like this:
hello Tux
which prints:
Hello Tux
7.7 Working with Common Flow Constructs

To control the ow of your script, a shell has while , if , for and case constructs.
7.7.1 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
84 Working with Common Flow Constructs SUSE Linux Enterp… 11 SP4

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 .
7.7.2 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

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
85 Creating Loops With the For Command SUSE Linux Enterp… 11 SP4
http://tldp.org/LDP/abs/html/index.html —Advanced Bash-Scripting Guide
http://www.grymoire.com/Unix/Sh.html —Sh - the Bourne Shell

8 Using Third-Party Software
For information about using third-party software installed on SUSE Linux Enterprise and support
of SUSE products used with third-party software, see the following links:
Partner Software Catalog

https://www.suse.com/susePSC/home
YES Certified Eligible Operating Systems

https://www.suse.com/partners/ihv/yes/yes-certified-eligible-operating-systems.html
SUSE SolidDriver Program

http://drivers.suse.com/doc/SolidDriver/
Independent Software Vendors

https://www.suse.com/partners/isv/
SUSE Technical Support Handbook

https://www.suse.com/support/handbook/
FAQ Support
https://www.suse.com/support/faq.html

II System
9 32-Bit and 64-Bit Applications in a 64-Bit System Environment 89
10 Booting and Configuring a Linux System 94
11 The Boot Loader GRUB 109
12 UEFI (Unified Extensible Firmware Interface) 131
13 Special System Features 139
14 Printer Operation 151
15 Dynamic Kernel Device Management with udev 167
16 The X Window System 179
17 Accessing File Systems with FUSE 193

9 32-Bit and 64-Bit Applications in a 64-Bit System En-
vironment
SUSE® Linux Enterprise Server is available for several 64-bit platforms. This does not necessarily
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 (runtime support)
and how 32-bit applications should be compiled to enable them to run both in 32-bit and 64-bit
system environments. 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 ia64, ppc64, System z and x86_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 x86 for ia64, ppc for ppc64, and x86 for x86_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 ppc64 system runs most applications
in 32-bit mode, but you can run 64-bit applications.
9.1 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.
89 Runtime Support SUSE Linux Enterp… 11 SP4

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 filename 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).
ipf The 64-bit libraries for ia64 are located in the standard lib directories, there is neither a
lib64 directory nor a lib32 directory. ia64 executes 32-bit x86 code under an emulation. A set
of basic libraries is installed in /emul/ia32-linux/lib and /emul/ia32-linux/usr/lib .
9.2 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 tool chain from GCC (GNU Compiler Collection) and binutils, which include the assembler
as and the linker ld :
Biarch Compiler
Both 32-bit and 64-bit objects can be generated with a biarch development tool chain. A
biarch development tool chain allows generation of 32-bit and 64-bit objects. The compi-
lation of 64-bit objects is the default on almost all platforms. 32-bit objects can be gener-
ated 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 tool chain currently exists for amd64 (supports development for x86
and amd64 instructions), for System z and for ppc64. 32-bit objects are normally created
on the ppc64 platform. The -m64 ag must be used to generate 64-bit objects.
No Support
SUSE Linux Enterprise Server does not support the direct development of 32-bit software
on all platforms. To develop applications for x86 under ia64, use the corresponding 32-
bit version of SUSE Linux Enterprise Server.
90 Software Development SUSE Linux Enterp… 11 SP4

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.
9.3 Software Compilation on Biarch Platforms

To develop binaries for the other architecture on a biarch architecture, the respective libraries
for the second architecture must additionally be installed. These packages are called rpm-
name-32bit or rpmname-x86 (for ia64) if the second architecture is a 32-bit architecture or
rpmname-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 whose second architecture is
a 32-bit architecture (x86_64 or System z), 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 ppc64 with ppc as the second architecture would be similar. This example does not apply
to ia64 where you cannot build 32-bit packages.
1. Use the 32-bit compiler:
CC="gcc -m32"
91 Software Compilation on Biarch Platforms SUSE Linux Enterp… 11 SP4

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"
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, ppc64 or System
z could appear as follows:
CC="gcc -m32"
LDFLAGS="-L/usr/lib;"
./configure --prefix=/usr --libdir=/usr/lib --x-libraries=/usr/lib
make
make install
9.4 Kernel Specifications

The 64-bit kernels for x86_64, ppc64 and System z offer both a 64-bit and a 32-bit kernel ABI
(application binary interface). The latter is identical with the ABI for the corresponding 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, a small number of applications,
like lspci , must be compiled on non-ppc64 platforms as 64-bit programs to function properly.
On IBM System z, not all ioctls are available in the 32-bit kernel ABI.
92 Kernel Specifications SUSE Linux Enterp… 11 SP4

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.
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.
93 Kernel Specifications SUSE Linux Enterp… 11 SP4

10 Booting and Configuring a Linux System
Booting a Linux system involves different components. The hardware itself is ini-
tialized by the BIOS, which starts the Kernel by means of a boot loader. After this
point, the boot process with init and the runlevels is completely controlled by the
operating system. The runlevel concept enables you to maintain setups for everyday
usage as well as to perform maintenance tasks on the system.
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. After turning on the computer, the BIOS 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 x86 systems, PXE boot is needed. Other architectures commonly use the
BOOTP protocol to get the boot loader.
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 referred to as 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, the Linux boot loader, can
be found in Chapter 11, The Boot Loader GRUB. For a network boot, the BIOS acts as the
boot loader. It gets the image to start from the boot server and starts the system. This is
completely independent of local hard disks.
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
94 The Linux Boot Process SUSE Linux Enterp… 11 SP4

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 10.1.1, “initramfs”. If the system
does not have a local hard disk, the initramfs must provide the root le system to the
Kernel. This can be done with the help of a network block device like iSCSI or SAN, but
it is also possible to use NFS as the root device.
4. init on initramfs . This program performs all actions needed to mount the proper root
le system, like providing 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
init program on the root le system is executed. For more information about init ,
refer to Section 10.1.2, “init on initramfs”. Find more information about udev in Chapter 15,
Dynamic Kernel Device Management with udev.
5. init . init handles the actual booting of the system through several different levels
providing different functionality. init is described in Section 10.2, “The init Process”.
10.1.1 initramfs
initramfs is a small cpio archive that the Kernel can load to 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 routines and does not
have specific hardware requirements other than sufficient memory. initramfs must always
provide an executable named init that should execute the actual init program 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 drives 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 boot.udev with the command udevtrigger .
If you need to change hardware (for example hard disks) in an installed system and this hardware
requires different drivers to be present in the Kernel at boot time, you must update initramfs .
This is done in the same way as with its predecessor, init —by calling mkinitrd . Calling
95 initramfs SUSE Linux Enterp… 11 SP4

mkinitrd without any argument creates an initramfs . Calling mkinitrd -R creates an
init . In SUSE® Linux Enterprise Server, the modules to load are specified by the variable
INITRD_MODULES in /etc/sysconfig/kernel .
After installation, this variable is automatically set to the correct value. The modules are loaded
in exactly the order in which they appear in INITRD_MODULES . This is only important if you rely
on the correct setting of the device les /dev/sd? . However, in current systems you also may
use the device les below /dev/disk/ that are sorted in several subdirectories, named by-id ,
by-path and by-uuid , and always represent the same disk. This is also possible at install time
by specifying the respective mount option.
Important: Updating initramfs or init

The boot loader loads initramfs or init in the same way as the Kernel. It is not nec-
essary to reinstall GRUB after updating initramfs or init , because GRUB searches the
directory for the right le when booting.
10.1.2 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 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
drive). 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 sets
up LVM or RAID to enable access to the root le system later. Find information about RAID
and LVM in Book “Deployment Guide”, Chapter 15 “Advanced Disk Setup”.
96 init on initramfs SUSE Linux Enterp… 11 SP4

Managing Network Configuration
If you configured your system to use a network-mounted root le system (mounted via
NFS), init 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 networked block device like iSCSI or SAN, the connection to
the storage server is also set up by the initramfs .
When init is called during the initial boot as part of the installation process, its tasks differ
from those mentioned above:
Finding the Installation Medium

As you start the installation process, your machine loads an installation Kernel and a special
init with the YaST installer on the installation medium. The YaST installer, which is
run in a RAM le system, needs to have information about the location of the installation
medium to access it and install the operating system.
Initiating Hardware Recognition and Loading Appropriate Kernel Modules

As mentioned in Section 10.1.1, “initramfs”, the boot process starts with a minimum set
of drivers that can be used with most hardware configurations. init starts an initial
hardware scanning process that determines the set of drivers suitable for your hardware
configuration. The names of the modules needed for the boot process are written to
INITRD_MODULES in /etc/sysconfig/kernel . These names are used to generate a cus-
tom initramfs that is needed to boot the system. If the modules are not needed for boot
but for coldplug, the modules are written to /etc/sysconfig/hardware/hwconfig-* .
All devices that are described with configuration les in this directory are initialized in
the boot process.
Loading the Installation System or Rescue System

As soon as the hardware is properly recognized, the appropriate drivers are loaded, and
udev creates the special device les, init starts the installation system with the actual
YaST installer, or the rescue system.
Starting YaST
Finally, init starts YaST, which starts package installation and system configuration.
97 init on initramfs SUSE Linux Enterp… 11 SP4

10.2 The init Process
The program init is the process with process ID 1. It is responsible for initializing the system in
the required way. init is started directly by the Kernel and resists signal 9, which normally kills
processes. All other programs are either started directly by init or by one of its child processes.
init is centrally configured in the /etc/inittab le where the runlevels are defined (see
Section 10.2.1, “Runlevels”). The le also specifies which services and daemons are available in
each of the runlevels. Depending on the entries in /etc/inittab , several scripts are run by
init . By default, the rst script that is started after booting is /etc/init.d/boot . Once the
system initialization phase is finished, the system changes the runlevel to its default runlevel
with the /etc/init.d/rc script. For reasons of clarity, these scripts, called init scripts, all reside
in the directory /etc/init.d (see Section 10.2.2, “Init Scripts”).
The entire process of starting the system and shutting it down is maintained by init . 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.
10.2.1 Runlevels
In Linux, runlevels define how the system is started and what services are available in the running
system. After booting, the system starts as defined in /etc/inittab in the line initdefault .
Usually this is 3 or 5 . See Table 10.1, “Available Runlevels”. As an alternative, the runlevel can be
specified at boot time (by adding the runlevel number at the boot prompt, for instance). Any
parameters that are not directly evaluated by the Kernel itself are passed to init . To boot into
runlevel 3, just add the single number 3 to the boot prompt.
TABLE 10.1: AVAILABLE RUNLEVELS
Runlevel Description
0 System halt
S or 1 Single user mode
2 Local multiuser mode without remote net-

work (NFS, etc.)
3 Full multiuser mode with network
98 The init Process SUSE Linux Enterp… 11 SP4

Runlevel Description
4 User Defined, this is not used unless the ad-

ministrator configures this runlevel.
5 Full multiuser mode with network and X dis-

play manager—KDM, GDM, or XDM
6 System reboot
Important: Avoid Runlevel 2 with a Partition Mounted via NFS

You should not use runlevel 2 if your system mounts a partition like /usr via NFS. The
system might behave unexpectedly if program les or libraries are missing because the
NFS service is not available in runlevel 2 (local multiuser mode without remote network).
To change runlevels while the system is running, enter telinit and the corresponding number
as an argument. Only the system administrator is allowed to do this. The following list summa-
rizes the most important commands in the runlevel area.
telinit 1 or shutdown now

The system changes to single user mode. This mode is used for system maintenance and
administration tasks.
telinit 3
All essential programs and services (including network) are started and regular users are
allowed to log in and work with the system without a graphical environment.
telinit 5
The graphical environment is enabled. Usually a display manager like XDM, GDM or KDM
is started. If autologin is enabled, the local user is logged in to the preselected window
manager (GNOME or KDE or any other window manager).
telinit 0 or shutdown -h now

The system halts.
telinit 6 or shutdown -r now

The system halts then reboots.
99 Runlevels SUSE Linux Enterp… 11 SP4

Runlevel 5 is the default runlevel in all SUSE Linux Enterprise Server standard installations.
Users are prompted for login with a graphical interface or the default user is logged in auto-
matically.
Warning: Errors in /etc/inittab May Result in a Faulty

System Boot
If /etc/inittab is damaged, the system may not boot properly. Therefore, be extremely
careful while editing /etc/inittab . Always let init reread /etc/inittab with the
command telinit q before rebooting the machine.
Generally, two things happen when you change runlevels. First, stop scripts of the current run-
level are launched, closing down some programs essential for the current runlevel. Then start
scripts of the new runlevel are started. Here, in most cases, a number of programs are started.
For example, the following occurs when changing from runlevel 3 to 5:
1. The administrator ( root ) requests init to change to a different runlevel by entering

telinit 5 .
2. init checks the current runlevel ( runlevel ) and determines it should start /etc/
init.d/rc with the new runlevel as a parameter.
3. Now rc calls the stop scripts of the current runlevel for which there is no start script in the
new runlevel. In this example, these are all the scripts that reside in /etc/init.d/rc3.d
(the old runlevel was 3) and start with a K . The number following K specifies the order to
run the scripts with the stop parameter, because there are some dependencies to consider.
4. The last things to start are the start scripts of the new runlevel. In this example, these
are in /etc/init.d/rc5.d and begin with an S . Again, the number that follows the S
determines the sequence in which the scripts are started.
100 Runlevels SUSE Linux Enterp… 11 SP4

When changing into the same runlevel as the current runlevel, init only checks /etc/init-
tab for changes and starts the appropriate steps, for example, for starting a getty on another
interface. The same functionality may be achieved with the command telinit q .
10.2.2 Init Scripts
There are two types of scripts in /etc/init.d :
Scripts Executed Directly by init

This is the case only during the boot process or if an immediate system shutdown is initiated
(power failure or a user pressing Ctrl – Alt – Del ). For IBM System z systems, this is the
case only during the boot process or if an immediate system shutdown is initiated (power
failure or via “signal quiesce”). The execution of these scripts is defined in /etc/inittab .
Scripts Executed Indirectly by init

These are run when changing the runlevel and always call the master script /etc/init.d/
rc , which guarantees the correct order of the relevant scripts.
All scripts are located in /etc/init.d . Scripts that are run at boot time are called through
symbolic links from /etc/init.d/boot.d . Scripts for changing the runlevel are called through
symbolic links from one of the subdirectories ( /etc/init.d/rc0.d to /etc/init.d/rc6.d ).
This is just for reasons of clarity and avoids duplicate scripts if they are used in several runlevels.
Because every script can be executed as both a start and a stop script, these scripts must un-
derstand the parameters start and stop . The scripts also understand the restart , reload ,
force-reload , and status options. These different options are explained in Table 10.2, “Possi-
ble init Script Options”. Scripts that are run directly by init do not have these links. They are
run independently from the runlevel when needed.
TABLE 10.2: POSSIBLE init SCRIPT OPTIONS
Option Description
start Start service.
stop Stop service.
restart If the service is running, stop it then restart

it. If it is not running, start it.
101 Init Scripts SUSE Linux Enterp… 11 SP4

Option Description
reload Reload the configuration without stopping

and restarting the service.
force-reload Reload the configuration if the service sup-

ports this. Otherwise, do the same as if
restart had been given.
status Show the current status of service.
Links in each runlevel-specific subdirectory make it possible to associate scripts with different
runlevels. When installing or uninstalling packages, these links are added and removed with the
help of the program insserv (or using /usr/lib/lsb/install_initd , which is a script calling
this program). See man 8 insserv for more details.
All of these settings may also be changed with the help of the YaST module. If you need to check
the status on the command line, use the tool chkconfig , described in the man 8 chkconfig
man page.
A short introduction to the boot and stop scripts launched rst or last, respectively, follows as
well as an explanation of the maintaining script.
boot
Executed while starting the system directly using init . It is independent of the chosen
runlevel and is only executed once. Here, the /proc and /dev/pts le systems are mount-
ed and blogd (boot logging daemon) is activated. If the system is booted for the rst time
after an update or an installation, the initial system configuration is started.
The blogd daemon is a service started by boot and rc before any other one. It is stopped
after the actions triggered by these scripts (running a number of subscripts, for example,
making special block les available) are completed. blogd writes any screen output to the
log le /var/log/boot.msg , but only if and when /var is mounted read-write. Other-
wise, blogd buers all screen data until /var becomes available. Get further information
about blogd with man 8 blogd .
The boot script is also responsible for starting all the scripts in /etc/init.d/boot.d
with names that start with S . There, the le systems are checked and loop devices are
configured if needed. The system time is also set. If an error occurs while automatically
checking and repairing the le system, the system administrator can intervene after rst
entering the root password. The last executed script is boot.local .

boot.local
Here enter additional commands to execute at boot before changing into a runlevel. It can
be compared to AUTOEXEC.BAT on DOS systems.
halt
This script is only executed while changing into runlevel 0 or 6. Here, it is executed either
as init or as init . Whether the system shuts down or reboots depends on how halt is
called. If special commands are needed during the shutdown, add these to the init script.
rc
This script calls the appropriate stop scripts of the current runlevel and the start scripts of
the newly selected runlevel. Like the /etc/init.d/boot script, this script is called from
/etc/inittab with the desired runlevel as parameter.
You can create your own scripts and easily integrate them into the scheme described above. For
instructions about formatting, naming and organizing custom scripts, refer to the specifications
of the LSB and to the man pages of init , init.d , chkconfig , and insserv . Additionally
consult the man pages of startproc and killproc .
Warning: Faulty Init Scripts May Halt Your System

Faulty init scripts may hang your machine up. Edit such scripts with great care and, if
possible, subject them to heavy testing in the multiuser environment. Find useful infor-
mation about init scripts in Section 10.2.1, “Runlevels”.
To create a custom init script for a given program or service, use the le /etc/init.d/
skeleton as a template. Save a copy of this le under the new name and edit the relevant
program and filenames, paths and other details as needed. You may also need to enhance the
script with your own parts, so the correct actions are triggered by the init procedure.
The INIT INFO block at the top is a required part of the script and must be edited. See Exam-
ple 10.1, “A Minimal INIT INFO Block”.
EXAMPLE 10.1: A MINIMAL INIT INFO BLOCK
### BEGIN INIT INFO

# Provides: FOO
# Required-Start: $syslog $remote_fs
# Required-Stop: $syslog $remote_fs

# Default-Start: 3 5
# Default-Stop: 0 1 2 6
# Description: Start FOO to allow XY and provide YZ
### END INIT INFO
In the rst line of the INFO block, after Provides: , specify the name of the program or service
controlled by this init script. In the Required-Start: and Required-Stop: lines, specify
all services that need to be still running when the service itself is stopped. This information
is used later to generate the numbering of script names, as found in the runlevel directories.
After Default-Start: and Default-Stop: , specify the runlevels in which the service should
automatically be started or stopped. Finally, for Description: , provide a short description of
the service in question.
To create the links from the runlevel directories ( /etc/init.d/rc?.d/ ) to the corresponding
scripts in /etc/init.d/ , enter the command insserv new-script-name . insserv evaluates
the INIT INFO header to create the necessary links for start and stop scripts in the runlevel
directories ( /etc/init.d/rc?.d/ ). The program also takes care of the correct start and stop
order for each runlevel by including the necessary numbers in the names of these links. If you
prefer a graphical tool to create such links, use the runlevel editor provided by YaST, as described
in Section 10.2.3, “Configuring System Services (Runlevel) with YaST”.
If a script already present in /etc/init.d/ should be integrated into the existing runlevel
scheme, create the links in the runlevel directories right away with insserv or by enabling the
corresponding service in the runlevel editor of YaST. Your changes are applied during the next
reboot—the new service is started automatically.
Do not set these links manually. If something is wrong in the INFO block, problems will arise
when insserv is run later for some other service. The manually added service will be removed
with the next run of insserv for this script.
10.2.3 Configuring System Services (Runlevel) with YaST
After starting this YaST module with YaST System System Services (Runlevel), it displays an
overview listing all the available services and the current status of each service (disabled or
enabled). Decide whether to use the module in Simple Mode or in Expert Mode. The default Simple
Mode should be sufficient for most purposes. The left column shows the name of the service, the
center column indicates its current status and the right column gives a short description. For
the selected service, a more detailed description is provided in the lower part of the window. To
enable a service, select it in the table then select Enable. The same steps apply to disable a service.
104 Configuring System Services (Runlevel) with YaST SUSE Linux Enterp… 11 SP4
For detailed control over the runlevels in which a service is started or stopped or to change
the default runlevel, rst select Expert Mode. The current default runlevel or “initdefault” (the
runlevel into which the system boots by default) is displayed at the top. Normally, the default
runlevel of a SUSE Linux Enterprise Server system is runlevel 5 (full multiuser mode with net-
work and X). A suitable alternative might be runlevel 3 (full multiuser mode with network).
This YaST dialog allows the selection of one of the runlevels (as listed in Table 10.1, “Available Run-
levels”) as the new default. Additionally, use the table in this window to enable or disable indi-
vidual services and daemons. The table lists the services and daemons available, shows whether
they are currently enabled on your system and, if so, for which runlevels. After selecting one of
the rows with the mouse, click the check boxes representing the runlevels (B, 0, 1, 2, 3, 5, 6, and
S) to define the runlevels in which the selected service or daemon should be running. Runlevel 4
is undefined to allow creation of a custom runlevel. A brief description of the currently selected
service or daemon is provided below the table overview.
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.
105 Configuring System Services (Runlevel) with YaST SUSE Linux Enterp… 11 SP4
FIGURE 10.1: SYSTEM SERVICES (RUNLEVEL)
With Start, Stop, or Refresh, decide whether a service should be activated. Refresh status checks
the current status. Set or Reset lets you select whether to apply your changes to the system or
to restore the settings that existed before starting the runlevel editor. Selecting OK saves the
changed settings to disk.
10.3 System Configuration via /etc/sysconfig

The main configuration of SUSE Linux Enterprise Server is controlled by the configuration les
in /etc/sysconfig . The individual les in /etc/sysconfig are only read by the scripts to
which they are relevant. This ensures that network settings, for example, only need to be parsed
by network-related scripts.
There are two ways to edit the system configuration. Either use the YaST sysconfig Editor or
edit the configuration les manually.
106 System Configuration via /etc/sysconfig SUSE Linux Enterp… 11 SP4

10.3.1 Changing the System Configuration Using the YaST
sysconfig Editor
The YaST sysconfig editor provides an easy-to-use front-end for system configuration. Without
any knowledge of the actual location of the configuration variable you need to change, you
can just use the built-in search function of this module, change the value of the configuration
variable as needed and let YaST take care of applying these changes, updating configurations
that depend on the values set in sysconfig and restarting services.
Warning: Modifying /etc/sysconfig/* Files Can Damage Your

Installation
Do not modify the /etc/sysconfig les if you lack previous experience and knowledge.
It can do considerable damage to your system. The les in /etc/sysconfig include a
short comment for each variable to explain what effect they actually have.
FIGURE 10.2: SYSTEM CONFIGURATION USING THE SYSCONFIG EDITOR
The YaST sysconfig dialog is split into three parts. The left part of the dialog shows a tree
view of all configurable variables. When you select a variable, the right part displays both the
current selection and the current setting of this variable. Below, a third window displays a
short description of the variable's purpose, possible values, the default value and the actual
Changing the System Configuration Using the YaST sysconfig Editor SUSE Linux Enterp…
107 11 SP4
configuration le from which this variable originates. The dialog also provides information
about which configuration script is executed after changing the variable and which new service
is started as a result of the change. YaST prompts you to confirm your changes and informs
you which scripts will be executed after you leave the dialog by selecting Finish. Also select
the services and scripts to skip for now, so they are started later. YaST applies all changes
automatically and restarts any services involved for your changes to take an effect.
10.3.2 Changing the System Configuration Manually

To manually change the system configuration, proceed as follows
1. Become root .
2. Bring the system into single user mode (runlevel 1) with telinit 1 .
3. Change the configuration les as needed with an editor of your choice.

If you do not use YaST to change the configuration les in /etc/sysconfig , make sure
that empty variable values are represented by two quotation marks ( KEYTABLE= "" ) and
that values with blanks in them are enclosed in quotation marks. Values consisting of one
word only do not need to be quoted.
4. Execute SuSEconfig to make sure that the changes take effect.
5. Bring your system back to the previous runlevel with a command like telinit de-
fault_runlevel . Replace default_runlevel with the default runlevel of the system.
Choose 5 if you want to return to full multiuser with network and X or choose 3 if you
prefer to work in full multiuser with network.
This procedure is mainly relevant when changing systemwide settings, such as the network
configuration. Small changes should not require going into single user mode, but you may still
do so to make absolutely sure that all the programs concerned are correctly restarted.
Tip: Configuring Automated System Configuration

To disable the automated system configuration by SuSEconfig, set the variable EN-
ABLE_SUSECONFIG in /etc/sysconfig/suseconfig to no . Do not disable SuSEconfig
if you want to use the SUSE installation support. It is also possible to disable the auto-
configuration partially.
108 Changing the System Configuration Manually SUSE Linux Enterp… 11 SP4
11 The Boot Loader GRUB
This chapter describes how to configure GRUB (Grand Unified Bootloader), the boot
loader used in SUSE® Linux Enterprise Server. A special YaST module is available
for configuring all settings. If you are not familiar with the subject of booting in Lin-
ux, read the following sections to acquire some background information. This chap-
ter also describes some of the problems frequently encountered when booting with
GRUB and their solutions.
Note: No GRUB on machines using UEFI

GRUB will routinely be installed on machines equipped with a traditional BIOS and on
UEFI (Unified Extensible Firmware Interface) machines using a Compatibility Support
Module (CSM). On UEFI machines without enabled CSM, eLILO will automatically be
installed (provided DVD1 booted successfully). Refer to the eLILO documentation at /
usr/share/doc/packages/elilo/ on your system for details.
This chapter focuses on boot management and the configuration of the boot loader GRUB. The
boot procedure as a whole is outlined in Chapter 10, Booting and Configuring a Linux System. A boot
loader represents the interface between the machine (BIOS) and the operating system (SUSE
Linux Enterprise Server). The configuration of the boot loader directly impacts the start of the
operating system.
The following terms appear frequently in this chapter and might need some explanation:
MBR (Master Boot Record)

The structure of the MBR is defined by an operating system–independent convention. The
rst 446 bytes are reserved for the program code. They typically hold part of a boot loader
program or an operating system selector. The next 64 bytes provide space for a partition
table of up to four entries. The partition table contains information about the partitioning of
the hard disk and the le system types. The operating system needs this table for handling
the hard disk. With conventional generic code in the MBR, exactly one partition must
be marked active. The last two bytes of the MBR must contain a static “magic number”
( AA55 ). An MBR containing a different value is regarded as invalid by some BIOSes, so
is not considered for booting.

Boot Sectors
Boot sectors are the rst sectors of hard disk partitions with the exception of the extended
partition, which merely serves as a “container” for other partitions. These boot sectors have
512 bytes of space for code used to boot an operating system installed in the respective
partition. This applies to boot sectors of formatted DOS, Windows, and OS/2 partitions,
which also contain some basic important data of the le system. In contrast, the boot
sectors of Linux partitions are initially empty after setting up a le system other than XFS.
Therefore, a Linux partition is not bootable by itself, even if it contains a kernel and a valid
root le system. A boot sector with valid code for booting the system has the same magic
number as the MBR in its last two bytes ( AA55 ).
11.1 Booting with GRUB

GRUB comprises two stages. Stage 1 consists of 512 bytes and its only task is to load the second
stage of the boot loader. Subsequently, stage 2 is loaded. This stage contains the main part of
the boot loader.
In some configurations, an intermediate stage 1.5 can be used, which locates and loads stage 2
from an appropriate le system. If possible, this method is chosen by default on installation or
when initially setting up GRUB with YaST.
Stage 2 is able to access many le systems. Currently, ext2, ext3, ReiserFS, Minix, and the DOS
FAT le system used by Windows are supported. To a certain extent, XFS, and UFS and FFS used
by BSD systems are also supported. Since version 0.95 GRUB is also able to boot from a CD or
DVD containing an ISO 9660 standard le system pursuant to the “El Torito” specification. Even
before the system is booted, GRUB can access le systems of supported BIOS disk devices (floppy
disks or hard disks, CD drives and DVD drives detected by the BIOS). Therefore, changes to the
GRUB configuration le ( menu.lst ) do not require a new installation of the boot manager.
When the system is booted, GRUB reloads the menu le with the valid paths and partition data
of the kernel or the initial RAM disk ( initrd ) and locates these les.
The actual configuration of GRUB is based on four les that are described below:
/boot/grub/menu.lst
This le contains all information about partitions or operating systems that can be booted
with GRUB. Without this information, the GRUB command line prompts the user for how
to proceed (see Section 11.1.1.3, “Editing Menu Entries during the Boot Procedure” for details).
110 Booting with GRUB SUSE Linux Enterp… 11 SP4

/boot/grub/device.map
This le translates device names from the GRUB and BIOS notation to Linux device names.
/etc/grub.conf
This le contains the commands, parameters and options the GRUB shell needs for in-
stalling the boot loader correctly.
/etc/sysconfig/bootloader
This le contains configuration options (such as Kernel parameters) that will be used as
fallback in specific situations, see Section 11.1.4, “The File /etc/sysconfig/bootloader”.
/etc/sysconfig/bootloader is not a GRUB-specific configuration le—the values are
applied to any boot loader installed on SUSE Linux Enterprise Server.
GRUB can be controlled in various ways. Boot entries from an existing configuration can be
selected from the graphical menu (splash screen). The configuration is loaded from the le
menu.lst .
In GRUB, all boot parameters can be changed prior to booting. For example, errors made when
editing the menu le can be corrected in this way. Boot commands can also be entered interac-
tively at a kind of input prompt. For details, see Section 11.1.1.3, “Editing Menu Entries during the
Boot Procedure”. GRUB offers the possibility of determining the location of the kernel and the
initrd prior to booting. In this way, you can even boot an installed operating system for which
no entry exists in the boot loader configuration.
GRUB actually exists in two versions: as a boot loader and as a normal Linux program in /usr/
sbin/grub . The latter is referred to as the GRUB shell. It provides an emulation of GRUB in
the installed system and can be used to install GRUB or test new settings before applying them.
The functionality to install GRUB as the boot loader on a hard disk or floppy disk is integrated
in GRUB in the form of the command setup . This is available in the GRUB shell when Linux
is loaded.
11.1.1 The File /boot/grub/menu.lst

The graphical splash screen with the boot menu is based on the GRUB configuration le /boot/
grub/menu.lst , which contains all information about all partitions or operating systems that
can be booted by the menu.
Every time the system is booted, GRUB loads the menu le from the le system. For this reason,
GRUB does not need to be reinstalled after every change to the le. Use the YaST boot loader to
modify the GRUB configuration as described in Section 11.2, “Configuring the Boot Loader with YaST”.
111 The File /boot/grub/menu.lst SUSE Linux Enterp… 11 SP4

The menu le contains commands. The syntax is very simple. Every line contains a command
followed by optional parameters separated by spaces like in the shell. For historical reasons,
some commands permit an = in front of the rst parameter. Comments are introduced by a
hash ( # ).
To identify the menu items in the menu overview, set a title for every entry. The text (includ-
ing any spaces) following the keyword title is displayed as a selectable option in the menu.
All commands up to the next title are executed when this menu item is selected.
The simplest case is the redirection to boot loaders of other operating systems. The command is
chainloader and the argument is usually the boot block of another partition, in GRUB block
notation. For example:
chainloader (hd0,3)+1
The device names in GRUB are explained in Section 11.1.1.1, “Naming Conventions for Hard Disks
and Partitions”. This example specifies the rst block of the fourth partition of the rst hard disk.
Use the command kernel to specify a kernel image. The rst argument is the path to the kernel
image in a partition. The other arguments are passed to the kernel on its command line.
If the kernel does not have built-in drivers for access to the root partition or a recent Linux
system with advanced hotplug features is used, initrd must be specified with a separate GRUB
command whose only argument is the path to the initrd le. Because the loading address of
the initrd is written into the loaded kernel image, the command initrd must follow after
the kernel command.
The command root simplifies the specification of kernel and initrd les. The only argument of
root is a device or a partition. This device is used for all kernel, initrd , or other le paths
for which no device is explicitly specified until the next root command.
The boot command is implied at the end of every menu entry, so it does not need to be written
into the menu le. However, if you use GRUB interactively for booting, you must enter the boot
command at the end. The command itself has no arguments. It merely boots the loaded kernel
image or the specified chain loader.
After writing all menu entries, define one of them as the default entry. Otherwise, the rst one
(entry 0 ) is used. You can also specify a time-out in seconds after which the default entry should
boot. timeout and default usually precede the menu entries. An example le is described in
Section 11.1.1.2, “An Example Menu File”.

11.1.1.1 Naming Conventions for Hard Disks and Partitions
The naming convention GRUB uses for hard disks and partitions differ from that used for normal
Linux devices. It more closely resembles the simple disk enumeration the BIOS does and the
syntax is similar to that used in some BSD derivatives. In GRUB, the numbering of the partitions
start with zero. This means that ( hd0,0 ) is the rst partition of the rst hard disk. On a common
desktop machine with a hard disk connected as primary master, the corresponding Linux device
name is /dev/sda1 .
The four possible primary partitions are assigned the partition numbers 0 to 3 . The logical
partitions are numbered from 4 :
(hd0,0) first primary partition of the first hard disk

(hd0,1) second primary partition
(hd0,2) third primary partition
(hd0,3) fourth primary partition (usually an extended partition)
(hd0,4) first logical partition
(hd0,5) second logical partition
Being dependent on BIOS devices, GRUB does not distinguish between PATA (IDE), SATA, SCSI,
and hardware RAID devices. All hard disks recognized by the BIOS or other controllers are
numbered according to the boot sequence preset in the BIOS.
Unfortunately, it is often not possible to map the Linux device names to BIOS device names
exactly. It generates this mapping with the help of an algorithm and saves it to the le de-
vice.map , which can be edited if necessary. Information about the le device.map is available
in Section 11.1.2, “The File device.map”.
A complete GRUB path consists of a device name written in parentheses and the path to the
le in the le system in the specified partition. The path begins with a slash. For example, the
bootable kernel could be specified as follows on a system with a single PATA (IDE) hard disk
containing Linux in its rst partition:
(hd0,0)/boot/vmlinuz
11.1.1.2 An Example Menu File

The following example shows the structure of a GRUB menu le. The example installation has
a Linux boot partition under /dev/sda5 , a root partition under /dev/sda7 and a Windows
installation under /dev/sda1 .
gfxmenu (hd0,4)/boot/message 1

color white/blue black/light-gray 2
default 0 3
timeout 8 4
title linux 5
root (hd0,4)
kernel /boot/vmlinuz root=/dev/sda7 vga=791 resume=/dev/sda9
initrd /boot/initrd
title windows 6
rootnoverify (hd0,0)
chainloader +1
title floppy 7
rootnoverify (hd0,0)
chainloader (fd0)+1
title failsafe 8
root (hd0,4)
kernel /boot/vmlinuz.shipped root=/dev/sda7 ide=nodma \
apm=off acpi=off vga=normal nosmp maxcpus=0 3 noresume
initrd /boot/initrd.shipped
The rst block defines the configuration of the splash screen:
1 The background image message is located in the /boot directory of the /dev/sda5 par-
tition.
2 Color scheme: white (foreground), blue (background), black (selection) and light gray
(background of the selection). The color scheme has no effect on the splash screen, only on
the customizable GRUB menu that you can access by exiting the splash screen with Esc .
3 The rst ( 0 ) menu entry title linux is booted by default.
4 After eight seconds without any user input, GRUB automatically boots the default entry.
To deactivate automatic boot, delete the timeout line. If you set timeout 0 , GRUB boots
the default entry immediately.
The second and largest block lists the various bootable operating systems. The sections for the
individual operating systems are introduced by title .
5 The rst entry ( title linux ) is responsible for booting SUSE Linux Enterprise Server.
The kernel ( vmlinuz ) is located in the rst logical partition (the boot partition) of the
rst hard disk. Kernel parameters, such as the root partition and VGA mode, are appended

here. The root partition is specified according to the Linux naming convention ( /dev/
sda7/ ) because this information is read by the kernel and has nothing to do with GRUB.
The initrd is also located in the rst logical partition of the rst hard disk.
6 The second entry is responsible for loading Windows. Windows is booted from the rst
partition of the rst hard disk ( hd0,0 ). The command chainloader +1 causes GRUB to
read and execute the rst sector of the specified partition.
7 The next entry enables booting from floppy disk without modifying the BIOS settings.
8 The boot option failsafe starts Linux with a selection of kernel parameters that enables
Linux to boot even on problematic systems.
The menu le can be changed whenever necessary. GRUB then uses the modified settings during
the next boot. Edit the le permanently using YaST or an editor of your choice. Alternatively,
make temporary changes interactively using the edit function of GRUB. See Section 11.1.1.3,
“Editing Menu Entries during the Boot Procedure”.
11.1.1.3 Editing Menu Entries during the Boot Procedure
In the graphical boot menu, select the operating system to boot with the arrow keys. If you
select a Linux system, you can enter additional boot parameters at the boot prompt. To edit
individual menu entries directly, press Esc to exit the splash screen and get to the GRUB text-
based menu then press E . Changes made in this way only apply to the current boot and are
not adopted permanently.
Important: Keyboard Layout during the Boot Procedure

The US keyboard layout is the only one available when booting. See Figure 36.3, “US Key-
board Layout”.
Editing menu entries facilitates the repair of a defective system that can no longer be booted,
because the faulty configuration le of the boot loader can be circumvented by manually en-
tering parameters. Manually entering parameters during the boot procedure is also useful for
testing new settings without impairing the native system.

After activating the editing mode, use the arrow keys to select the menu entry of the configu-
ration to edit. To make the configuration editable, press E again. In this way, edit incorrect
partitions or path specifications before they have a negative effect on the boot process. Press
Enter to exit the editing mode and return to the menu. Then press B to boot this entry. Fur-
ther possible actions are displayed in the help text at the bottom.
To enter changed boot options permanently and pass them to the kernel, open the le menu.lst
as the user root and append the respective kernel parameters to the existing line, separated
by spaces:
title linux
root(hd0,0)
kernel /vmlinuz root=/dev/sda3 additional parameter
initrd /initrd
GRUB automatically adopts the new parameters the next time the system is booted. Alternative-
ly, this change can also be made with the YaST boot loader module. Append the new parameters
to the existing line, separated by spaces.
11.1.2 The File device.map

The le device.map maps GRUB and BIOS device names to Linux device names. In a mixed
system containing PATA (IDE) and SCSI hard disks, GRUB must try to determine the boot se-
quence by a special procedure, because GRUB may not have access to the BIOS information on
the boot sequence. GRUB saves the result of this analysis in the le /boot/grub/device.map .
Example device.map les for a system on which the boot sequence in the BIOS is set to PATA
before SCSI could look as follows:
(fd0) /dev/fd0
(hd0) /dev/sda
(hd1) /dev/sdb
or
(fd0) /dev/fd0
(hd0) /dev/disk-by-id/DISK1 ID
(hd1) /dev/disk-by-id/DISK2 ID
Because the order of PATA (IDE), SCSI and other hard disks depends on various factors and Linux
is not able to identify the mapping, the sequence in the le device.map can be set manually.
If you encounter problems when booting, check if the sequence in this le corresponds to the
116 The File device.map SUSE Linux Enterp… 11 SP4

sequence in the BIOS and use the GRUB prompt to modify it temporarily, if necessary. After the
Linux system has booted, the le device.map can be edited permanently with the YaST boot
loader module or an editor of your choice.
Note: Maximum Number of Hard Disks

To address a hard disk, GRUB uses BIOS services. This is done via the software interrupt
Int13h. Since Int13h is limited to handling a maximum number of eight disks, GRUB can
only boot from the disks handled by Int13h, even if there are more disks present (which is
often the case on multipath systems). The device.map le created during the installation
will therefore only contain a maximum number of the eight disks handled by Int13h.
After manually changing device.map , execute the following command to reinstall GRUB. This
command causes the le device.map to be reloaded and the commands listed in grub.conf
to be executed:
grub --batch < /etc/grub.conf
11.1.3 The File /etc/grub.conf
The third important GRUB configuration le after menu.lst and device.map is /etc/
grub.conf . This le contains the commands, parameters and options the GRUB shell needs for
installing the boot loader correctly:
setup --stage2=/boot/grub/stage2 --force-lba (hd0,1) (hd0,1)

quit
This command tells GRUB to automatically install the boot loader to the second partition on the
rst hard disk (hd0,1) using the boot images located on the same partition. The --stage2=/
boot/grub/stage2 parameter is needed to install the stage2 image from a mounted le sys-
tem. Some BIOSes have a faulty LBA support implementation, --force-lba provides a solution
to ignore them.
117 The File /etc/grub.conf SUSE Linux Enterp… 11 SP4

11.1.4 The File /etc/sysconfig/bootloader
This le is read by the perl-bootloader library which is used when configuring the boot loader
with YaST. It contains configuration options (such as Kernel parameters) that will be used as
fallback.
Whenever a new kernel is installed, a heuristic tries to nd matching parameters from the pre-
vious kernel. Only if that does not work, for example when the Kernel flavor has changed, the
settings from /etc/sysconfig/boot loader will take effect.
So, changing settings in /etc/ (either manually or with the YaST sysconfig editor) will not
affect the actual boot loader configuration. On the other hand, changing the actual bootloader
configuration le in rare cases may not survive a change of the kernel flavor.
Note: Boot Loader Configuration after a Kernel Update

Every time a new kernel is installed, the perl-bootloader writes a new boot loader config-
uration le (for example, /boot/grub/menu.lst for GRUB). If there is no matching en-
try in /boot/grub/menu.lst , the defaults specified in /etc/sysconfig/bootloader
are used for the boot loader configuration le. Therefore we advise to adjust the relevant
defaults in /etc/sysconfig/bootloader , too—especially if you use a custom kernel.
LOADER_TYPE
Specifies the boot loader installed on the system (e.g. GRUB or LILO). Do not modify—
use YaST to change the boot loader as described in Procedure 11.6, “Changing the Boot Loader
Type”.
DEFAULT_VGA / FAILSAFE_VGA / XEN_VGA

Screen resolution and color depth of the framebuffer used during booting are configured
with the kernel parameter vga . These values define which resolution and color depth to
use for the default boot entry, the failsafe and the XEN entry. The following values are
valid:
TABLE 11.1: SCREEN RESOLUTION AND COLOR DEPTH REFERENCE
640x480 800x600 1024x768 1280x1024 1600x1200
8bit 0x301 0x303 0x305 0x307 0x31C
15bit 0x310 0x313 0x316 0x319 0x31D
118 The File /etc/sysconfig/bootloader SUSE Linux Enterp… 11 SP4

640x480 800x600 1024x768 1280x1024 1600x1200
16bit 0x311 0x314 0x317 0x31A 0x31E
24bit 0x312 0x315 0x318 0x31B 0x31F
DEFAULT_APPEND / FAILSAFE_APPEND / XEN_KERNEL_APPEND

Kernel parameters (other than vga ) that are automatically appended to the default, failsafe
and XEN boot entries in the boot loader configuration le.
CYCLE_DETECTION / CYCLE_NEXT_ENTRY
Configure whether to use boot cycle detection and if so, which alternative entry from /
boot/grub/menu.lst to boot in case of a reboot cycle (e.g. Failsafe ). See /usr/share/
doc/packages/bootcycle/README for detailed information.
11.1.5 Setting a Boot Password
Even before the operating system is booted, GRUB enables access to le systems. Users without
root permissions can access les in your Linux system to which they have no access once the
system is booted. To block this kind of access or to prevent users from booting certain operating
systems, set a boot password.
Important: Boot Password and Splash Screen

If you use a boot password for GRUB, the usual splash screen is not displayed.
As the user root , proceed as follows to set a boot password:
1. At the root prompt, encrypt the password using grub-md5-crypt:
# grub-md5-crypt
Password: ****
Retype password: ****
Encrypted: $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/
2. Paste the encrypted string into the global section of the le menu.lst :
gfxmenu (hd0,4)/message
119 Setting a Boot Password SUSE Linux Enterp… 11 SP4

color white/blue black/light-gray
default 0
timeout 8
password --md5 $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/
Now GRUB commands can only be executed at the boot prompt after pressing P and
entering the password. However, users can still boot all operating systems from the boot
menu.
3. To prevent one or several operating systems from being booted from the boot menu, add
the entry lock to every section in menu.lst that should not be bootable without entering
a password. For example:
title linux
kernel (hd0,4)/vmlinuz root=/dev/sda7 vga=791
initrd (hd0,4)/initrd
lock
After rebooting the system and selecting the Linux entry from the boot menu, the following
error message is displayed:
Error 32: Must be authenticated
Press Enter to enter the menu. Then press P to get a password prompt. After enter-
ing the password and pressing Enter , the selected operating system (Linux in this case)
should boot.
11.2 Configuring the Boot Loader with YaST

The easiest way to configure 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. As in Figure 11.1,
“Boot Loader Settings”, this shows the current boot loader configuration of your system and allows
you to make changes.
120 Configuring the Boot Loader with YaST SUSE Linux Enterp… 11 SP4
FIGURE 11.1: BOOT LOADER SETTINGS
Use the Section Management tab to edit, change and delete boot loader sections for the individual
operating systems. To add an option, click Add. To change the value of an existing option, select
it with the mouse and click Edit. To remove an existing entry, select it and click Delete. If you
are not familiar with boot loader options, read Section 11.1, “Booting with GRUB” rst.
Use the Boot Loader Installation tab to view and change settings related to type, location and
advanced loader settings.
Click Other to access advanced configuration options. The build-in editor lets you change the
GRUB configuration les. For details, see Section 11.1, “Booting with GRUB”. You can also delete
the existing configuration and Start from Scratch or let YaST Propose a New Configuration. It is
also possible to write the configuration to disk or reread the configuration from the disk. To
restore the original Master Boot Record (MBR) that was saved during the installation, choose
Restore MBR of Hard Disk.
11.2.1 Adjusting the Default Boot Entry

To change the system that is booted by default, proceed as follows:
PROCEDURE 11.1: SETTING THE DEFAULT SYSTEM
1. Open the Section Management tab.
121 Adjusting the Default Boot Entry SUSE Linux Enterp… 11 SP4
2. Select the desired entry from the list.
3. Click Set as Default.
4. Click OK to activate these changes.
11.2.2 Modifying the Boot Loader Location

To modify the location of the boot loader, follow these steps:
PROCEDURE 11.2: CHANGING THE BOOT LOADER LOCATION
1. Select the Boot Loader Installation 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 rst disk (according to the boot se-
quence preset in the BIOS).
Boot from Root Partition

This installs the boot loader in the boot sector of the / partition (this is the default).
Boot from Boot Partition

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

This installs the boot loader in the extended partition container.
Custom Boot Partition

Use this option to specify the location of the boot loader manually.
2. Click OK to apply your changes.
11.2.3 Changing the Boot Loader Time-Out

The boot loader does not boot the default system immediately. During the time-out, you can
select the system to boot or write some kernel parameters. To set the boot loader time-out,
proceed as follows:
PROCEDURE 11.3: CHANGING THE BOOT LOADER TIME-OUT
1. Open the Boot Loader Installation tab.
122 Modifying the Boot Loader Location SUSE Linux Enterp… 11 SP4
2. Click Boot Loader Options.
3. Change the value of Time-Out in Seconds by typing in a new value and clicking the appro-
priate arrow key with your mouse, or by using the arrow keys on the keyboard.
4. Click OK twice to save the changes.
Warning: Timeout of 0 Seconds

When setting the timeout to 0 seconds, you will not be able to access GRUB during boot
time. When having set the default boot option to a non-Linux operating system at the
same time, this effectively disables access to the Linux system.
11.2.4 Setting a Boot Password
Using this YaST module, you can also set a password to protect booting. This gives you an
additional level of security.
PROCEDURE 11.4: SETTING A BOOT LOADER PASSWORD
2. Click Boot Loader Options.
3. Activate the Protect Boot Loader with Password option with a click and type in your Password
twice.
4. Click OK twice to save the changes.
11.2.5 Adjusting the Disk Order
If your computer has more than one hard disk, you can specify the boot sequence of the disks to
match the BIOS setup of the machine (see Section 11.1.2, “The File device.map”). To do so, proceed
as follows:
PROCEDURE 11.5: SETTING THE DISK ORDER
2. Click Boot Loader Installation Details.
123 Setting a Boot Password SUSE Linux Enterp… 11 SP4

3. If more than one disk is listed, select a disk and click Up or Down to reorder the displayed
disks.
4. Click OK two times to save the changes.
11.2.6 Configuring Advanced Options
Advanced boot options can be configured via Boot Loader Installation Boot Loader Options. Nor-
mally, it should not be necessary to change the default settings.
Set Active Flag in Partition Table for Boot Partition

Activates the partition that contains the boot loader. Some legacy operating systems (such
as Windows 98) can only boot from an active partition.
Write Generic Boot Code to MBR

Replaces the current MBR with generic, operating system independent code.
Debugging Flag
Sets GRUB in debug mode where it displays messages to show disk activity.
Hide Boot Menu

Hides the boot menu and boots the default entry.
Warning
When hiding the boot menu, you will not be able to access GRUB during boot time.
When having set the default boot option to a non-Linux operation system at the
same time, this effectively disables access to the Linux system.
Use Trusted GRUB

Starts the Trusted GRUB which supports trusted computing functionality.
Graphical Menu File

Path to the graphics le used when displaying the boot screen.
Serial Connection Parameters

If your machine is controlled via a serial console, you can specify which COM port to use at
which speed. Also set Terminal Definition to “serial”. See info grub or http://www.gnu.org/
software/grub/manual/grub.html for details.
124 Configuring Advanced Options SUSE Linux Enterp… 11 SP4

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
11.2.7 Changing Boot Loader Type
Set the boot loader type in Boot Loader Installation. The default boot loader in SUSE Linux En-
terprise Server is GRUB. To use LILO or ELILO, proceed as follows:
Warning: LILO is unsupported

Using LILO is not recommended—it is unsupported on SUSE Linux Enterprise Server.
Only use it in special cases.
PROCEDURE 11.6: CHANGING THE BOOT LOADER TYPE
1. Select the Boot Loader Installation tab.
2. For Boot Loader, select LILO.
3. In the dialog box that opens, select one of the following actions:
Propose New Configuration

Have YaST propose a new configuration.
Convert Current Configuration

Have YaST convert the current configuration. When converting the configuration,
some settings may be lost.
Start New Configuration from Scratch

Write a custom configuration. This action is not available during the installation of
SUSE Linux Enterprise Server.
Read Configuration Saved on Disk

Load your own /etc/lilo.conf . This action is not available during the installation
of SUSE Linux Enterprise Server.
4. Click OK two times to save the changes.
125 Changing Boot Loader Type SUSE Linux Enterp… 11 SP4

During the conversion, the old GRUB configuration is saved to the disk. To use it, simply change
the boot loader type back to GRUB and choose Restore Configuration Saved before Conversion.
This action is available only on an installed system.
Note: Custom Boot Loader

To use a boot loader other than GRUB or LILO, select Do Not Install Any Boot Loader. Read
the documentation of your boot loader carefully before choosing this option.
11.3 Uninstalling the Linux Boot Loader

YaST can be used to uninstall the Linux boot loader and restore the MBR to the state it had prior
to the installation of Linux. During the installation, YaST automatically creates a backup copy
of the original MBR and restores it upon request.
To uninstall GRUB, start YaST and click System Boot Loader to start the boot loader module.
Select Other Restore MBR of Hard Disk and confirm with Yes, Rewrite.
11.4 Creating Boot CDs

If problems occur while booting your system using a boot manager or if the boot manager
cannot be installed on your hard disk disk, it is also possible to create a bootable CD with all
the necessary start-up les for Linux. This requires a CD writer be installed in your system.
Creating a bootable CD-ROM with GRUB merely requires a special form of stage2 called
stage2_eltorito and, optionally, a customized menu.lst . The classic les stage1 and
stage2 are not required.
PROCEDURE 11.7: CREATING BOOT CDS
1. Change into a directory in which to create the ISO image, for example: cd /tmp
2. Create a subdirectory for GRUB and change into the newly created iso directory:
mkdir -p iso/boot/grub && cd iso
126 Uninstalling the Linux Boot Loader SUSE Linux Enterp… 11 SP4
3. Copy the kernel, the les stage2_eltorito , initrd , menu.lst and message to iso/
boot/ :
cp /boot/vmlinuz boot/
cp /boot/initrd boot/
cp /boot/message boot/
cp /usr/lib/grub/stage2_eltorito boot/grub
cp /boot/grub/menu.lst boot/grub
In some cases (when booting multiple operating systems, for example) it may be useful to
also copy /boot/grub/device.map to boot/grub .
4. Replace the root (hdx, y) entries with root (cd) to point to the CD_ROM device.
You may also need to adjust the paths to the message le, the kernel and the initrd—they
need to point to /boot/message , /boot/vmlinuz and /boot/initrd , respectively. Af-
ter having made the adjustments, menu.lst should look similar to the following example:
timeout 8
default 0
gfxmenu (cd)/boot/message
title Linux
root (cd)
kernel /boot/vmlinuz root=/dev/sda5 vga=794 resume=/dev/sda1 \
splash=verbose showopts
initrd /boot/initrd
Use splash=silent instead of splash=verbose to prevent the boot messages from ap-
pearing during the boot procedure.
5. Create the ISO image with the following command:
genisoimage -R -b boot/grub/stage2_eltorito -no-emul-boot \

-boot-load-size 4 -boot-info-table -iso-level 2 -input-charset utf-8 \
-o grub.iso /tmp/iso
6. Write the resulting le grub.iso to a CD using your preferred utility. Do not burn the
ISO image as a data le, but use the option for burning a CD image in your burning utility.
127 Creating Boot CDs SUSE Linux Enterp… 11 SP4

11.5 The Graphical SUSE Screen
The graphical SUSE screen is displayed on the rst console if the option vga=value is used as a
kernel parameter. If you install using YaST, this option is automatically activated in accordance
with the selected resolution and the graphics card. There are three ways to disable the SUSE
screen, if desired:
Disabling the SUSE Screen When Necessary

Enter the command echo 0 >/proc/splash on the command line to disable the graphical
screen. To activate it again, enter echo 1 >/proc/splash .
Disabling the SUSE screen by default.

Add the kernel parameter splash=0 to your boot loader configuration. Chapter 11, The
Boot Loader GRUB provides more information about this. However, if you prefer the text
mode (the default in earlier versions) set vga=normal .
Completely Disabling the SUSE Screen

Compile a new kernel and disable the option Use splash screen instead of boot logo in frame-
buffer support. Disabling framebuffer support in the kernel automatically disables the splash
screen, as well.
Warning: No Support
SUSE cannot provide any support for your system if you run it with a custom kernel.
11.6 Troubleshooting
This section lists some of the problems frequently encountered when booting with GRUB and
a short description of possible solutions. Some of the problems are covered in articles in the
Knowledge base at http://www.suse.com/support . Use the search dialog to search for keywords
like GRUB, boot and boot loader.
GRUB and XFS

XFS leaves no room for stage1 in the partition boot block. Therefore, do not specify an
XFS partition as the location of the boot loader. This problem can be solved by creating a
separate boot partition that is not formatted with XFS.
128 The Graphical SUSE Screen SUSE Linux Enterp… 11 SP4

GRUB Reports GRUB Geom Error
GRUB checks the geometry of connected hard disks when the system is booted. Sometimes,
the BIOS returns inconsistent information and GRUB reports a GRUB Geom Error. In this
case, update the BIOS.
GRUB also returns this error message if Linux was installed on an additional hard disk
that is not registered in the BIOS. stage1 of the boot loader is found and loaded correctly,
but stage2 is not found. This problem can be remedied by registering the new hard disk
in the BIOS.
System Containing Several Hard Disks Does Not Boot

During the installation, YaST may have incorrectly determined the boot sequence of the
hard disks. For example, GRUB may regard the PATA (IDE) disk as hd0 and the SCSI disk
as hd1 , although the boot sequence in the BIOS is reversed (SCSI before PATA).
In this case, correct the hard disks during the boot process with the help of the GRUB
command line. After the system has booted, edit device.map to apply the new mapping
permanently. Then check the GRUB device names in the les /boot/grub/menu.lst and
/boot/grub/device.map and reinstall the boot loader with the following command:
Booting Windows from the Second Hard Disk

Some operating systems, such as Windows, can only boot from the rst hard disk. If such
an operating system is installed on a hard disk other than the rst hard disk, you can effect
a logical change for the respective menu entry.
...
title windows
map (hd0) (hd1)
map (hd1) (hd0)
chainloader(hd1,0)+1
...
In this example, Windows is started from the second hard disk. For this purpose, the logical
order of the hard disks is changed with map . This change does not affect the logic within
the GRUB menu le. Therefore, the second hard disk must be specified for chainloader .

Extensive information about GRUB is available at http://www.gnu.org/software/grub/ . Also re-
fer to the grub info page. You can also search for the keyword “GRUB” in the Technical Infor-
mation Search at http://www.novell.com/support to get information about special issues.

12 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.
Last but not least, 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 just hints about how
some features are implemented in SUSE Linux Enterprise.
12.1 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, the
motherboard and the on-board rmware could be considered the “platform”. Or, put slightly
differently, 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.
131 Secure Boot SUSE Linux Enterp… 11 SP4

Essentially, if you want 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.
12.1.1 Implementation on SUSE Linux Enterprise

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

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 installation, it will try to create a GPT partition .
UEFI expects to nd the EFI programs on a FAT-formatted EFI System Partition (ESP).
Supporting UEFI Secure Boot essentially requires having a boot loader with a digital signature
that the rmware recognizes as a trusted key. In order to be useful to SUSE Linux Enterprise cus-
tomers, 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 (i.e., have it signed with their KEK). By now, SUSE got
the loader signed by UEFI Signing Service (that's Microsoft in this case).
132 Implementation on SUSE Linux Enterprise SUSE Linux Enterp… 11 SP4

FIGURE 12.1: UEFI: SECURE BOOT PROCESS
At the implementation layer, SUSE uses the shim loader—it is a smart solution that avoids legal
issues, and simplifies the certification and signing step considerably. The shim loader’s job is
to load a boot loader such as eLILO or GRUB2 and verify it; this boot loader in turn will load
kernels signed by a SUSE key only. SUSE provides this functionality with 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.
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, but 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 matter that is both
secure and open source friendly, and thus compatible with GPLv3.
SUSE starts with shim —a small and simple EFI boot loader—which was originally developed
by Fedora. It is signed by a certificate signed by the SUSE KEK and a Microsoft-issued certificate,
based on which KEKs are available in the UEFI key database on the system.
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.

12.1.2 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
(e.g., 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
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, once 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 just a single MOK, you can make shim trust keys from several different
vendors, allowing dual- and multi-boot from the boot loader.
12.1.3 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 just 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 .
135 MOK (Machine Owner Key) SUSE Linux Enterp… 11 SP4

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
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.

Alternatively, this is the procedure if you want to launch MOK manually:
a. Reboot
b. In the GRUB menu press the ' c ' key.
c. Type:
chainloader $efibootdir/MokManager.efi
136 Booting a Custom Kernel SUSE Linux Enterp… 11 SP4

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 Signa-
ture Database.
12.1.4 Using Non-Inbox Drivers

There is no support for adding non-inbox drivers (that is, drivers that do not come with SLE)
after having booted into the installation with Secure Boot enabled. The signing key used for
SolidDriver/PLDP is not trusted by default.
However, it ispossible to use third party drivers during installation with Secure Boot enabled
in two different ways:
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 to an empty CD/DVD media.
2. Start the installation by booting from the new CD/DVD media, having the standard SUSE
Linux Enterprise media at hand or a URL to a network installation server.
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 disk of the SUSE Linux Enterprise 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 .
137 Using Non-Inbox Drivers SUSE Linux Enterp… 11 SP4

12.1.5 Limitations
When booting in Secure Boot mode, the following restrictions apply:
Hybridified ISO images are not recognized as bootable on UEFI systems. Thus, UEFI booting
from USB devices is not supported with SP3.
To ensure that Secure Boot cannot be easily circumvented, some kernel features are dis-
abled when running under Secure Boot.
Bootloader, 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.
custom_method in ACPI is not available.
debugfs for asus-wmi module is not available.
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.
138 Limitations SUSE Linux Enterp… 11 SP4

13 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 may
want to change their default behavior, because these components are often closely
coupled with the system. The chapter concludes with a section about language and
country-specific settings (I18N and L10N).
13.1 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.
13.1.1 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
139 Information about Special Software Packages SUSE Linux Enterp… 11 SP4
cp /etc/skel/.bashrc ~/.bashrc
mv ~/.profile ~/.profile.old
cp /etc/skel/.profile ~/.profile
Then copy personal adjustments back from the *.old les.
13.1.2 The cron Package
If you want to run commands regularly and automatically in the background at predefined times,
cron is the tool to use. cron is driven by specially formatted time tables. Some of them come
with the system and users can write their own tables if needed.
The cron tables are located in /var/spool/cron/tabs . /etc/crontab serves as a systemwide
cron table. Enter the username to run the command directly after the time table and before
the command. In Example 13.1, “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 13.1: 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 13.2, “/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 13.2: /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
44 2 1 * * root rm -f /var/spool/cron/lastrun/cron.monthly
140 The cron Package SUSE Linux Enterp… 11 SP4

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 period of 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 .
13.1.3 Log Files: Package logrotate

There are a number of 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.
Configure logrotate with the le
/etc/logrotate.conf . In particular, the include specification primarily configures the ad-
ditional les to read. Programs that produce log les install individual configuration les in
/etc/logrotate.d . For example, such les ship with the packages apache2 ( /etc/logro-
tate.d/apache2 ) and syslogd ( /etc/logrotate.d/syslog ).
EXAMPLE 13.3: EXAMPLE FOR /ETC/LOGROTATE.CONF
# see "man logrotate" for details

# rotate log files weekly
weekly
# keep 4 weeks worth of backlogs

rotate 4
# create new (empty) log files after rotating old ones

create
# uncomment this if you want your log files compressed

#compress
# RPM packages drop log rotation information into this directory

include /etc/logrotate.d
141 Log Files: Package logrotate SUSE Linux Enterp… 11 SP4

# no packages own lastlog or wtmp - we'll rotate them here
#/var/log/wtmp {
# monthly
# create 0664 root utmp
# rotate 1
#}
# system-specific logs may be also be configured here.
logrotate is controlled through cron and is called daily by /etc/cron.daily/logrotate .
Important
The create option reads all settings made by the administrator in /etc/permissions* .
Ensure that no conflicts arise from any personal modifications.
13.1.4 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 findutils-locate . The updatedb process is started
automatically every night or about 15 minutes after booting the system.
13.1.5 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 13.1, “ulimit: Setting Resources for the User”.
TABLE 13.1: 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
142 The locate Command SUSE Linux Enterp… 11 SP4

-c The maximum size of core les created
-a All current limits are reported
Systemwide entries can be made in /etc/profile . There, enable creation of core les (needed
by programmers for debugging). A normal user cannot increase the values specified in /etc/
profile by the system administrator, but can make special entries in ~/.bashrc .
EXAMPLE 13.4: 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
Not all shells support ulimit directives. PAM (for instance, pam_limits ) offers com-
prehensive adjustment possibilities if you depend on encompassing settings for these re-
strictions.
13.1.6 The free Command

The free command displays the total amount of free and used physical memory and swap space
in the system, as well as 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.
Basically, 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 with the help of 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 .
143 The free Command SUSE Linux Enterp… 11 SP4

However, if your goal is to nd out how much RAM is currently being used, nd this information
in /proc/meminfo .
13.1.7 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.
13.1.8 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 don't enter a section number within a few seconds, the rst man page will be displayed.
If you want to change this to the default system behavior, set MAN_POSIXLY_CORRECT=1 in a
shell initialization le such as ~/.bashrc .
13.1.9 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 .
144 Man Pages and Info Pages SUSE Linux Enterp… 11 SP4
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.
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.
13.2 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. More or fewer consoles can be assigned by
modifying the le /etc/inittab .
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 .
145 Virtual Consoles SUSE Linux Enterp… 11 SP4

13.3 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 environments GNOME (gswitchit) and KDE (kxkb).
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).
13.4 Language and Country-Specific Settings

The system is, to a very large extent, internationalized and can be modified for local needs.
Internationalization (I18N) allows specific localizations (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.
146 Keyboard Mapping SUSE Linux Enterp… 11 SP4

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 (see Section 10.3.1, “Changing the System
Configuration Using 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>]]
13.4.1 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 .
147 Some Examples SUSE Linux Enterp… 11 SP4

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 basically 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.
In former releases, it was necessary to run SuSEconfig after doing any changes to /etc/
sysconfig/language . SuSEconfig then wrote the changes to /etc/SuSEconfig/profile and
/etc/SuSEconfig/csh.login . Upon login, these les were read by /etc/profile (for the
Bash) or by /etc/csh.login (for the tcsh) .
In recent releases, /etc/SuSEconfig/profile has been replaced with /etc/pro-
file.d/lang.sh , and /etc/SuSEconfig/csh.login with /etc/profile.de/lang.csh . But
if they exist, both legacy le are still read upon login.
The process chain is now as follows:
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 .
148 Some Examples SUSE Linux Enterp… 11 SP4

This ensures that any changes to /etc/sysconfig/language are available at the next login to
the respective shell, without having to run SuSEconfig rst.
Users can override the system defaults by editing their ~/.bashrc accordingly. For in-
stance, if you do not want to use the systemwide en_US for program messages, include
LC_MESSAGES=es_ES so that messages are displayed in Spanish instead.
13.4.2 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_ namespace prefixes. For ex-
ample, use LANG instead of RC_LANG :
LANG=cs_CZ.UTF-8
LC_COLLATE=C
13.4.3 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.
149 Locale Settings in ~/.i18n SUSE Linux Enterp… 11 SP4

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.
13.4.4 For More Information
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 Software
Development Kit (SDK). The SDK is an add-on product for SUSE Linux Enterprise and is
available for download from http://download.suse.com/ .
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 .

14 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 8 “Setting Up Hardware Components with YaST”, Sec-
tion 8.5 “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 14.7, “Trou-
bleshooting”.
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 (like USB or parallel port) that is
available on your hardware 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.
Standard Printers (Languages Like PCL and ESC/P)

Although these printer languages are quite old, they are still undergoing expansion to
address new features in printers. In the case of known printer languages, the print system
can convert PostScript jobs to the respective printer language with the help of Ghostscript.
This processing stage is referred to as interpreting. 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 developing HPLIP (HP Linux Imaging and Printing), there are currently no printer
manufacturers who develop Linux drivers and make them available to Linux distributors
under an open source license.
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 14.7.1, “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.openprinting.org/printers/
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-library/catalog.devices
List of included drivers.
14.1 The Workflow of the Printing System

The user creates a print job. The print job consists of the data to print plus information for
the spooler, such as 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.
152 The Workflow of the Printing System SUSE Linux Enterp… 11 SP4
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.
14.2 Methods and Protocols for Connecting Printers

There are various possibilities for connecting a printer to the system. The configuration of the
CUPS print system does not distinguish between a local printer and a printer connected to the
system over the network.
IBM Z Printers and similar devices provided by the z/VM that connect locally with the IBM
System z mainframes are not supported by CUPS or LPRng. 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.
14.3 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. During the installation of SUSE
Linux Enterprise Server, many PPD les are pre-installed.
To configure a PostScript printer, the best approach is to get a suitable PPD le. Many PPD
les are available in the package manufacturer-PPDs , which is automatically installed within
the scope of the standard installation. See Section 14.6.2, “PPD Files in Various Packages” and Sec-
tion 14.7.2, “No Suitable PPD File Available for a PostScript Printer”.
153 Methods and Protocols for Connecting Printers SUSE Linux Enterp… 11 SP4
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 8 “Setting Up Hardware Com-
ponents with YaST”, Section 8.5 “Setting Up a Printer”, Section 8.5.1 “Configuring Local Printers”, Sec-
tion 8.5.1.1 “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. First, this
kind of installation may result in the loss of the support provided by SUSE Linux Enterprise
Server and second, 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.
14.4 Network Printers

A network printer can support various protocols, some of them 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 dri-
vers 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 have 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 socket.
Some of the 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 .
154 Network Printers SUSE Linux Enterp… 11 SP4

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 printerIP
14.4.1 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 parallel, and parameters. To determine valid
device URIs on your system use the command lpinfo -v | grep ":/" :
# lpinfo -v | grep ":/"

direct usb://ACME/FunPrinter%20XL
direct parallel:/dev/lp0
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.
155 Configuring CUPS with Command Line Tools SUSE Linux Enterp… 11 SP4
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 parallel:/dev/lp0 -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 .
156 Configuring CUPS with Command Line Tools SUSE Linux Enterp… 11 SP4
14.5 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 .
14.6 Special Features in SUSE Linux Enterprise Server

A number of CUPS features have been adapted for SUSE Linux Enterprise Server. Some of the
most important changes are covered here.
14.6.1 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 .
14.6.1.1 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.
14.6.1.2 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 recommended
to set up a CUPS server in an untrusted network environment unless you take care that it is
protected by special firewall rules and secure settings in the CUPS configuration.
157 Printing from the Command Line SUSE Linux Enterp… 11 SP4
14.6.2 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
only have PostScript printers, normally you do not need the Foomatic PPD les in the cups-
drivers package or the Gutenprint PPD les in the gutenprint package. Instead, the PPD
les for your PostScript printers can be copied directly to /usr/share/cups/model (if they do
not already exist in the manufacturer-PPDs package) to achieve an optimum configuration
for your printers.
14.6.2.1 CUPS PPD Files in the cups Package
The generic PPD les in the cups package have been complemented with adapted Foomatic
PPD les for PostScript level 1 and level 2 printers:
/usr/share/cups/model/Postscript-level1.ppd.gz
/usr/share/cups/model/Postscript-level2.ppd.gz
14.6.2.2 PPD Files in the cups-drivers Package
Normally, the Foomatic printer filter foomatic-rip is used together with Ghostscript for non-
PostScript printers. Suitable Foomatic PPD les have the entries *NickName: ... Foomat-
ic/Ghostscript driver and *cupsFilter: ... foomatic-rip . These PPD les are located
in the cups-drivers package.
YaST generally prefers a manufacturer-PPD le. However, when no suitable manufactur-
er-PPD le exists, a Foomatic PPD le with the entry *NickName: ... Foomatic ... (rec-
ommended) is selected.
158 PPD Files in Various Packages SUSE Linux Enterp… 11 SP4

14.6.2.3 Gutenprint PPD Files in the gutenprint Package
Instead of foomatic-rip , the CUPS filter rastertogutenprint from Gutenprint (formerly
known as GIMP-Print) can be used for many non-PostScript printers. This filter and suitable
Gutenprint PPD les are available in the gutenprint package. The Gutenprint PPD les are
located in /usr/share/cups/model/gutenprint/ and have the entries *NickName: ... CUPS
+Gutenprint and *cupsFilter: ... rastertogutenprint .
14.6.2.4 PPD Files from Printer Manufacturers in the manufacturer-PPDs

Package
The manufacturer-PPDs package contains PPD les from printer manufacturers that are re-
leased under a sufficiently liberal license. PostScript printers should be configured with the suit-
able PPD le of the printer manufacturer, because this le enables the use of all functions of
the PostScript printer. YaST prefers a PPD le from the manufacturer-PPDs . YaST cannot use
a PPD le from the manufacturer-PPDs package if the model name does not match. This may
happen if the manufacturer-PPDs package contains only one PPD le for similar models, like
Funprinter 12xx series. In this case, select the respective PPD le manually in YaST.
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.
14.7.1 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 the fact that these printers can only
be addressed 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 due to new de-
velopments in the print system.
14.7.2 No Suitable PPD File Available for a PostScript Printer

If the manufacturer-PPDs package does not contain a suitable 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.
14.7.3 Parallel Ports

The safest approach is to connect the printer directly to the rst parallel port and to select the
following parallel port settings in the BIOS:
I/O address: 378 (hexadecimal)
Interrupt: irrelevant
160 No Suitable PPD File Available for a PostScript Printer SUSE Linux Enterp… 11 SP4
Mode: Normal , SPP , or Output Only
DMA: disabled
If the printer cannot be addressed on the parallel port despite these settings, enter the I/O ad-
dress explicitly in accordance with the setting in the BIOS in the form 0x378 in /etc/mod-
probe.conf . If there are two parallel ports that are set to the I/O addresses 378 and 278
(hexadecimal), enter these in the form 0x378,0x278 .
If interrupt 7 is free, it can be activated with the entry shown in Example 14.1, “/etc/mod-
probe.conf: Interrupt Mode for the First Parallel Port”. Before activating the interrupt mode, check
the le /proc/interrupts to see which interrupts are already in use. Only the interrupts cur-
rently being used are displayed. This may change depending on which hardware components
are active. The interrupt for the parallel port must not be used by any other device. If you are
not sure, use the polling mode with irq=none .
EXAMPLE 14.1: /etc/modprobe.conf: INTERRUPT MODE FOR THE FIRST PARALLEL PORT
alias parport_lowlevel parport_pc

options parport_pc io=0x378 irq=7
14.7.4 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.
161 Network Printer Connections SUSE Linux Enterp… 11 SP4

As the user root , use the following command to query a (possibly very long) status report
for queue on remote host , provided the respective lpd is active and the host accepts
queries:
echo -e "\004queue" \
| netcat -w 2 -p 722 host 515
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 14.2, “Error Message from lpd”,
the problem is caused by the remote lpd .
EXAMPLE 14.2: 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 14.3,
“Broadcast from the CUPS Network Server”.
EXAMPLE 14.3: BROADCAST FROM THE CUPS NETWORK SERVER
ipp://192.168.2.202:631/printers/queue
IBM Z Take into account that IBM System z 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
Troubleshooting a Network Printer or Print Server Box

Spoolers running in a print server box sometimes cause problems when they have to deal
with multiple print jobs. Since this is caused by the spooler in the print server box, there no
way to resolve this issue. As a work-around, circumvent the spooler in the print server box
by addressing the printer connected to the print server box directly with the TCP socket.
See Section 14.4, “Network Printers”.
In this way, the print server box 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 box. If the printer is connected to the print server
box and turned on, this TCP port can usually be determined with the nmap utility from
the nmap package some time after the print server box is powered up. For example, nmap
IP-address may deliver the following output for a print server box:
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 box can be addressed
via TCP socket on port 9100 . By default, nmap only checks a number of 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.
14.7.5 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 is not able to print the printer-specific data, select a PPD le that is more suitable
for the printer.
14.7.6 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 .
14.7.7 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 as soon as it has been forwarded to the server cupsd .
When it becomes desirable 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, provided the server has
not already completed the print job (that is, sent it completely to the printer). Using this job
number, the print job on the server can be deleted:
cancel -h cups.example.com queue-jobnumber
164 Defective Printouts without Error Message SUSE Linux Enterp… 11 SP4
14.7.8 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 defective or an error occurs in the communication between the host and the
printer, the printer prints numerous sheets of paper with unintelligible characters, because it is
unable to process the data correctly. To rectify this situation, 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.
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. For example, for a printer connected to the parallel port, the command
fuser -k /dev/lp0 can be used to terminate all processes that are still accessing the
printer (more precisely: the parallel port).
4. Reset the printer completely by switching it o for some time. Then insert the paper and
turn on the printer.
14.7.9 Debugging the CUPS Print System

Use the following generic procedure to locate problems in the CUPS print system:
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.
165 Defective Print Jobs and Data Transfer Errors SUSE Linux Enterp… 11 SP4
6. Check the messages in /var/log/cups/error_log* to identify the cause of the problem.

Solutions to many specific problems are presented in the SUSE Knowledgebase (http://
www.suse.com/support/ ). Locate the relevant articles with a text search for CUPS .

15 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 userspace. Devices
need to be configured as soon as 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
processing. This enables you to customize udev device handling by, for example, adding certain
scripts to execute as part of kernel device handling, or request and import additional data to
evaluate during device handling.
15.1 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 present in the /dev directory regardless of the
state of the corresponding kernel device can be placed in the /lib/udev/devices directory.
At system start-up, the contents of that directory is copied to the /dev directory with the same
ownership and permissions as the les in /lib/udev/devices .
15.2 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,
the daemon can reload the in-memory representation of all rules with the command udevadm
167 The /dev Directory SUSE Linux Enterp… 11 SP4

control reload_rules . This is also done when running /etc/init.d/boot.udev reload .
For more details on udev rules and their syntax, refer to Section 15.6, “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 symlinks
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.
15.3 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 .
15.4 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.
168 Drivers, Kernel Modules and Devices SUSE Linux Enterp… 11 SP4
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 possibly
connected devices, udev just requests all device events from the kernel after the root le system
is available, so the event for the USB mouse device just runs again. Now it nds the kernel
module on the mounted root le system and the USB mouse can be initialized.
From userspace, 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.
15.5 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.
169 Monitoring the Running udev Daemon SUSE Linux Enterp… 11 SP4
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
priority of the running daemon can be changed with udevadm control log_priority= lev-
el/number .
15.6 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 symlinks 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 15.1: EXAMPLE udev RULES
# console
170 Influencing Kernel Device Event Handling with udev Rules SUSE Linux Enterp… 11 SP4
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 symlink 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.
171 Influencing Kernel Device Event Handling with udev Rules SUSE Linux Enterp… 11 SP4
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 different op-
erators.
Each given value must be enclosed by quotation marks.
Each line of the rules le represents one rule. If a rule is longer than just one line, use \
to join the different lines just as you would do in shell syntax.
udev rules support a shell-style pattern that matches the * , ? , and [] patterns.
udev rules support substitutions.
15.6.1 Using Operators in udev Rules

Creating keys you can choose from several different operators, depending on the type of key
you want to create. Match keys will normally just 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.
:=
172 Using Operators in udev Rules SUSE Linux Enterp… 11 SP4

Assign a final value. Disallow any later change by later rules.
15.6.2 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} , $attr{variable}
The value of an environment variable (specified by variable ).
%c , $result
The output of PROGRAM .
%%
The % character.
$$
173 Using Substitutions in udev Rules SUSE Linux Enterp… 11 SP4

The $ character.
15.6.3 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}
174 Using udev Match Keys SUSE Linux Enterp… 11 SP4

The value of an environment variable, for example, ENV{ID_BUS}="ieee1394 to search
for all events related to the FireWire bus ID.
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.
15.6.4 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. Once a rule has set a node name, all other
rules with a NAME key for this node are ignored.
SYMLINK
The name of a symlink related to the node to be created. Multiple matching rules can add
symlinks to be created with the device node. You can also specify multiple symlinks for
one node in one rule using the space character to separate the symlink 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.
175 Using udev Assign Keys SUSE Linux Enterp… 11 SP4

LABEL
Add a label where a GOTO can jump to.
GOTO
Tell udev to skip a number of 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 different 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 possible 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.
15.7 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
176 Persistent Device Naming SUSE Linux Enterp… 11 SP4

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
15.8 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 copied at boot time from /lib/udev/
devices/*
The following les and directories contain the crucial elements of the udev infrastructure:
/etc/udev/udev.conf
177 Files used by udev SUSE Linux Enterp… 11 SP4

Main udev configuration le.
/etc/udev/rules.d/*
udev event matching rules.
/lib/udev/devices/*
Static /dev content.
/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.

16 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 describes the setup and
optimization of the X Window System environment, and provides background information about
the use of fonts in SUSE® Linux Enterprise Server.
Tip: IBM System z: Configuring the Graphical User Interface

IBM System z 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 System z can be found in Book “Deployment Guide”, Chapter 4 “Installation
on IBM System z”.
16.1 Manually Configuring the X Window System

By default, the X Window System is configured with the SaX2 interface, described in Book “De-
ployment Guide”, Chapter 8 “Setting Up Hardware Components with YaST”, Section 8.2 “Setting Up Graph-
ics Card and Monitor”. Alternatively it can be configured manually by editing its configuration
les.
Warning: Faulty X Configurations can Damage Your Hardware

Be very careful when configuring your X Window System. Never start the X Window
System until the configuration is finished. A misconfigured system can cause irreparable
damage to your hardware (this applies especially to xed-frequency monitors). The cre-
ators of this book and SUSE Linux Enterprise Server cannot be held responsible for any
resulting damage. This information has been carefully researched, but this does not guar-
antee that all methods presented here are correct and cannot damage your hardware.
179 Manually Configuring the X Window System SUSE Linux Enterp… 11 SP4
The command sax2 creates the /etc/X11/xorg.conf le. This is the primary configuration
le of the X Window System. Find all the settings here concerning your graphics card, mouse
and monitor.
Important: Using X -configure

Use X -configure to configure your X setup if previous tries with SUSE Linux Enterprise
Server's SaX2 have failed. If your setup involves proprietary binary-only drivers, X -
configure does not work.
The following sections describe the structure of the configuration le /etc/X11/xorg.conf . It
consists of several sections, each one dealing with a certain aspect of the configuration. Each
section starts with the keyword Section <designation> and ends with EndSection . The
following convention applies to all sections:
Section "designation"
entry 1
entry 2
entry n
EndSection
The section types available are listed in Table 16.1, “Sections in /etc/X11/xorg.conf”.
TABLE 16.1: SECTIONS IN /ETC/X11/XORG.CONF
Type Meaning
Files The paths used for fonts and the RGB color
table.
ServerFlags General switches for the server behavior.
Module A list of modules the server should load
InputDevice Input devices like keyboards and special in-

put devices (touchpads, joysticks, etc.) are
configured in this section. Important parame-
ters in this section are Driver and the op-
Type Meaning
tions defining the Protocol and Device .
You normally have one InputDevice sec-
tion per device attached to the computer.
Monitor The monitor used. Important elements of this

section are the Identifier , which is re-
ferred to later in the Screen definition, the
refresh rate VertRefresh and the synchro-
nization frequency limits ( HorizSync and
VertRefresh ). Settings are given in MHz,
kHz and Hz. Normally, the server refuses any
modeline that does not correspond with the
specification of the monitor. This prevents
too high frequencies from being sent to the
monitor by accident.
Modes The modeline parameters for the specific

screen resolutions. These parameters can be
calculated by SaX2 on the basis of the values
given by the user and normally do not need
to be changed. Intervene manually at this
point if, for example, you want to connect
a xed frequency monitor. Find details of
the meaning of individual number values in
the HOWTO les in /usr/share/doc/how-
to/en/html/XFree86-Video-Timings-HOW-
TO (available in the howtoenh package).
To calculate VESA modes manually, you can
use the tool cvt . For example, to calculate
a modeline for a 1680x1050@60Hz monitor,
use the command cvt 1680 1050 60 .
Device A specific graphics card. It is referenced by

its descriptive name. The options available
in this section strongly depend on the dri-
Type Meaning
ver used. For example, if you use the i810
driver, nd more information about the
available options in the manual page man 4
i810 .
Screen Combines a Monitor and a Device to form

all the necessary settings for X.Org. In the
Display subsection, specify the size of the
virtual screen ( Virtual ), the ViewPort and
the Modes used with this screen.
Note that some drivers demand that all of
the used configurations must be present in
the Display section at some place. For ex-
ample, if you use a laptop and want to use
an external monitor that is bigger than the
internal LCD, it might be necessary to add a
bigger resolution than supported by the in-
ternal LCD at the end of the Modes line.
ServerLayout The layout of a single or multihead con-

figuration. This section binds the input de-
vices InputDevice and the display devices
Screen .
DRI Provides information for the Direct Render-

ing Infrastructure (DRI).
Monitor , Device and Screen are explained in more detail. Further information about the
other sections can be found in the manual pages of X.Org and xorg.conf .
There can be several different Monitor and Device sections in xorg.conf . Even multiple
Screen sections are possible. The ServerLayout section determines which of these sections
is used.
16.1.1 Screen Section
The screen section combines a monitor with a device section and determines the resolution and
color depth to use. A screen section might resemble Example 16.1, “Screen Section of the File /etc/
X11/xorg.conf”.
EXAMPLE 16.1: SCREEN SECTION OF THE FILE /ETC/X11/XORG.CONF
Section "Screen" 1
DefaultDepth 16 2
SubSection "Display" 3
Depth 16 4
Modes "1152x864" "1024x768" "800x600" 5
Virtual 1152x864 6
EndSubSection
SubSection "Display"
Depth 24
Modes "1280x1024"
EndSubSection
Depth 32
Modes "640x480"
EndSubSection
Depth 8
Modes "1280x1024"
EndSubSection
Device "Device[0]"
Identifier "Screen[0]" 7
Monitor "Monitor[0]"
EndSection
1 Section determines the section type, in this case Screen .
2 DefaultDepth determines the color depth to use by default unless another color depth
is explicitly specified.
3 For each color depth, different Display subsections are specified.
4 Depth determines the color depth to be used with this set of Display settings. Possible
values are 8 , 15 , 16 , 24 and 32 , though not all of these might be supported by all X
server modules or resolutions.
183 Screen Section SUSE Linux Enterp… 11 SP4

5 The Modes section comprises a list of possible screen resolutions. The list is checked by
the X server from left to right. For each resolution, the X server searches for a suitable
Modeline in the Modes section. The Modeline depends on the capability of both the
monitor and the graphics card. The Monitor settings determine the resulting Modeline .
The rst resolution found is the Default mode . With Ctrl – Alt – + (on the number pad)
switch to the next resolution in the list to the right. With Ctrl – Alt – – (on the number
pad) switch to the previous. This enables you to vary the resolution while X is running.
6 The last line of the Display subsection with Depth 16 refers to the size of the virtual
screen. The maximum possible size of a virtual screen depends on the amount of memory
installed on the graphics card and the desired color depth, not on the maximum resolution
of the monitor. If you omit this line, the virtual resolution is just the physical resolution.
Because modern graphics cards have a large amount of video memory, you can create very
large virtual desktops. However, you may no longer be able to use 3D functionality if you
ll most of the video memory with a virtual desktop. If, for example, the card has 16 MB
of video RAM, the virtual screen can take up to 4096x4096 pixels in size at 8-bit color
depth. Especially for accelerated cards, however, it is not recommended to use all your
memory for the virtual screen, because the card's memory is also used for several font and
graphics caches.
7 The Identifier line (here Screen[0] ) gives this section a defined name with which it
can be uniquely referenced in the following ServerLayout section. The lines Device and
Monitor specify the graphics card and the monitor that belong to this definition. These
are just links to the Device and Monitor sections with their corresponding names or
identifiers. These sections are discussed in detail below.
16.1.2 Device Section
A device section describes a specific graphics card. You can have as many device entries in
xorg.conf as you like, provided their names are differentiated using the keyword Identifier .
If you have more than one graphics card installed, the sections are simply numbered in order.
The rst one is called Device[0] , the second one Device[1] , and so on. The following le
shows an excerpt from the Device section of a computer with a Matrox Millennium PCI graphics
card (as configured by SaX2):
Section "Device"
BoardName "MGA2064W"
BusID "0:19:0" 1
184 Device Section SUSE Linux Enterp… 11 SP4

Driver "mga" 2
Identifier "Device[0]"
VendorName "Matrox"
Option "sw_cursor"
EndSection
1 The BusID refers to the PCI or AGP slot in which the graphics card is installed. This matches
the ID displayed by the command lspci . The X server needs details in decimal form, but
lspci displays these in hexadecimal form. The value of BusID is automatically detected
by SaX2.
2 The value of Driver is automatically set by SaX2 and specifies which driver to use for your
graphics card. If the card is a Matrox Millennium, the driver module is called mga . The
X server then searches through the ModulePath defined in the Files section in the dri-
vers subdirectory. In a standard installation, this is the /usr/lib/xorg/modules/dri-
vers directory or the /usr/lib64/xorg/modules/drivers directory for 64-Bit operating
systems directory. _drv.o is added to the name, so, in the case of the mga driver, the
driver le mga_drv.o is loaded.
The behavior of the X server or of the driver can also be influenced through additional options.
An example of this is the option sw_cursor , which is set in the device section. This deactivates
the hardware mouse cursor and depicts the mouse cursor using software. Depending on the
driver module, there are various options available (which can be found in the description les
of the driver modules in the directory /usr/share/doc/packages/package_name ). Generally
valid options can also be found in the manual pages ( man xorg.conf , man 4 <driver mod-
ule> , and man 4 chips ).
If the graphics card has multiple video connectors, it is possible to configure the different devices
of this single card as one single view. Use SaX2 to set up your graphics interface this way.
16.1.3 Monitor and Modes Section
Like the Device sections, the Monitor and Modes sections describe one monitor each. The
configuration le /etc/X11/xorg.conf can contain as many Monitor sections as desired. Each
Monitor section references a Modes section with the line UseModes if available. If no Modes
section is available for the Monitor section, the X server calculates appropriate values from
the general synchronization values. The server layout section specifies which Monitor section
is relevant.
185 Monitor and Modes Section SUSE Linux Enterp… 11 SP4

Monitor definitions should only be set by experienced users. The modelines are an important
part of the Monitor sections. Modelines set horizontal and vertical timings for the respective
resolution. The monitor properties, especially the allowed frequencies, are stored in the Moni-
tor section. Standard VESA modes can be generated with the utility cvt . For more information
read the manual page of cvt man cvt .
Warning
Unless you have in-depth knowledge of monitor and graphics card functions, do not
change the modelines, because this could severely damage your monitor.
Those who try to develop their own monitor descriptions should be very familiar with the docu-
mentation in /usr/share/X11/doc . Install the package xorg-x11-doc to nd PDFs and HTML
pages.
Manual specification of modelines is rarely required today. If you are using a modern multisync
monitor, the allowed frequencies and optimal resolutions can, as a rule, be read directly from
the monitor by the X server via DDC, as described in the SaX2 configuration section. If this is
not possible for some reason, use one of the VESA modes included in the X server. This will
work with most graphics card and monitor combinations.
16.2 Installing and Configuring Fonts

The installation of additional fonts in SUSE Linux Enterprise Server is very easy. Simply copy
the fonts to any directory located in the X11 font path (see Section 16.2.1, “X11 Core Fonts”). To
the enable use of the fonts, the installation directory should be a subdirectory of the directories
configured in /etc/fonts/fonts.conf (see Section 16.2.2, “Xft”) or included into this le with
/etc/fonts/suse-font-dirs.conf .
The following is an excerpt from /etc/fonts/fonts.conf . This le is the standard configura-
tion le that should be appropriate for most configurations. It also defines the included direc-
tory /etc/fonts/conf.d . In this directory, all les or symbolic links starting with a two digit
number are loaded by fontconfig. For a more detailed explanation of this functionality, have a
look at /etc/fonts/conf.d/README .


<dir>/usr/share/fonts</dir>
186 Installing and Configuring Fonts SUSE Linux Enterp… 11 SP4

<dir>/usr/X11R6/lib/X11/fonts</dir>
<dir>/opt/kde3/share/fonts</dir>
<dir>/usr/local/share/fonts</dir>
<dir>~/.fonts</dir>
/etc/fonts/suse-font-dirs.conf is automatically generated to pull in fonts that ship with

(mostly third party) applications like LibreOffice, Java or Adobe Reader. A typical entry would
look like the following:
<dir>/usr/lib/Adobe/Reader9/Resource/Font</dir>
<dir>/usr/lib/Adobe/Reader9/Resource/Font/PFM</dir>
To install additional fonts system-wide, manually copy the font les to a suitable directory (as
root ), such as /usr/share/fonts/truetype . Alternatively, the task can be performed with
the KDE font installer in the KDE Control Center. The result is the same.
Instead of copying the actual fonts, you can also create symbolic links. For example, you may
want to do this if you have licensed fonts on a mounted Windows partition and want to use
them. Subsequently, run SuSEconfig --module fonts .
SuSEconfig --module fonts executes the script /usr/sbin/fonts-config , which handles
the font configuration. For more information on this script, refer to its manual page ( man fonts-
config ).
The procedure is the same for bitmap fonts, TrueType and OpenType fonts, and Type1
(PostScript) fonts. All these font types can be installed into any directory.
X.Org contains two completely different font systems: the old X11 core font system and the newly
designed Xft and fontconfig system. The following sections briey describe these two systems.
16.2.1 X11 Core Fonts
Today, the X11 core font system supports not only bitmap fonts but also scalable fonts, like Type1
fonts, TrueType, and OpenType fonts. Scalable fonts are only supported without anti-aliasing
and subpixel rendering and the loading of large scalable fonts with glyphs for many languages
may take a long time. Unicode fonts are also supported, but their use may be slow and require
more memory.
The X11 core font system has a few inherent weaknesses. It is outdated and can no longer
be extended in any meaningful way. Although it must be retained for reasons of backward
compatibility, the more modern Xft and fontconfig system should be used if at all possible.
187 X11 Core Fonts SUSE Linux Enterp… 11 SP4

For its operation, the X server needs to know which fonts are available and where in the system
it can nd them. This is handled by a FontPath variable, which contains the path to all valid
system font directories. In each of these directories, a le named fonts.dir lists the available
fonts in this directory. The FontPath is generated by the X server at start-up. It searches for
a valid fonts.dir le in each of the FontPath entries in the configuration le /etc/X11/
xorg.conf . These entries are found in the Files section. Display the actual FontPath with
xset q . This path may also be changed at runtime with xset . To add an additional path, use
xset +fp <path> . To remove an unwanted path, use xset -fp <path> .
If the X server is already active, newly installed fonts in mounted directories can be made avail-
able with the command xset fp rehash . This command is executed by SuSEconfig --mod-
ule fonts . Because the command xset needs access to the running X server, this only works
if SuSEconfig --module fonts is started from a shell that has access to the running X server.
The easiest way to achieve this is to acquire root permissions by entering su and the root
password. su transfers the access permissions of the user who started the X server to the root
shell. To check if the fonts were installed correctly and are available by way of the X11 core
font system, use the command xlsfonts to list all available fonts.
By default, SUSE Linux Enterprise Server uses UTF-8 locales. Therefore, Unicode fonts should
be preferred (font names ending with iso10646-1 in xlsfonts output). All available Unicode
fonts can be listed with xlsfonts | grep iso10646-1 . Nearly all Unicode fonts available
in SUSE Linux Enterprise Server contain at least the glyphs needed for European languages
(formerly encoded as iso-8859-* ).
16.2.2 Xft
From the outset, the programmers of Xft made sure that scalable fonts including anti-aliasing are
well supported. If Xft is used, the fonts are rendered by the application using the fonts, not by the
X server as in the X11 core font system. In this way, the respective application has access to the
actual font les and full control of how the glyphs are rendered. This constitutes the basis for the
correct display of text in a number of languages. Direct access to the font les is very useful for
embedding fonts for printing to make sure that the printout looks the same as the screen output.
In SUSE Linux Enterprise Server, the two desktop environments (KDE and GNOME), Mozilla
and many other applications already use Xft by default. Xft is already used by more applications
than the old X11 core font system.
188 Xft SUSE Linux Enterp… 11 SP4

Xft uses the fontconfig library for finding fonts and influencing how they are rendered. The prop-
erties of fontconfig are controlled by the global configuration le /etc/fonts/fonts.conf .
Special configurations should be added to /etc/fonts/local.conf and the user-specific con-
figuration le ~/.fonts.conf . Each of these fontconfig configuration les must begin with
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
and end with
</fontconfig>
To add directories to search for fonts, append lines such as the following:
<dir>/usr/local/share/fonts/</dir>
However, this is usually not necessary. By default, the user-specific directory ~/.fonts is al-
ready entered in /etc/fonts/fonts.conf . Accordingly, all you need to do to install additional
fonts is to copy them to ~/.fonts .
You can also insert rules that influence the appearance of the fonts. For example, enter
<match target="font">
<edit name="antialias" mode="assign">
<bool>false</bool>
</edit>
</match>
to disable anti-aliasing for all fonts or
<match target="font">
<test name="family">
<string>Luxi Mono</string>
<string>Luxi Sans</string>
</test>
<edit name="antialias" mode="assign">
<bool>false</bool>
</edit>
</match>
to disable anti-aliasing for specific fonts.

By default, most applications use the font names sans-serif (or the equivalent sans ), serif ,
or monospace . These are not real fonts but only aliases that are resolved to a suitable font,
depending on the language setting.

Users can easily add rules to ~/.fonts.conf to resolve these aliases to their favorite fonts:
<alias>
<family>sans-serif</family>
<prefer>
<family>FreeSans</family>
</prefer>
</alias>
<alias>
<family>serif</family>
<prefer>
<family>FreeSerif</family>
</prefer>
</alias>
<alias>
<family>monospace</family>
<prefer>
<family>FreeMono</family>
</prefer>
</alias>
Because nearly all applications use these aliases by default, this affects almost the entire system.
Thus, you can easily use your favorite fonts almost everywhere without having to modify the
font settings in the individual applications.
Use the command fc-list to nd out which fonts are installed and available for use. For
instance, the command fc-list returns a list of all fonts. To nd out which of the available
scalable fonts ( :scalable=true ) contain all glyphs required for Hebrew ( :lang=he ), their
font names ( family ), their style ( style ), their weight ( weight ) and the name of the les
containing the fonts, enter the following command:
fc-list ":lang=he:scalable=true" family style weight
The output of this command could look like the following:
Lucida Sans:style=Demibold:weight=200
DejaVu Sans:style=Bold Oblique:weight=200
Lucida Sans Typewriter:style=Bold:weight=200
DejaVu Sans:style=Oblique:weight=80
Lucida Sans Typewriter:style=Regular:weight=80
DejaVu Sans:style=Book:weight=80
DejaVu Sans:style=Bold:weight=200
Lucida Sans:style=Regular:weight=80

Important parameters that can be queried with fc-list :
TABLE 16.2: PARAMETERS OF fc-list
Parameter Meaning and Possible Values
family Name of the font family, for example,

FreeSans .
foundry The manufacturer of the font, for example,

urw .
style The font style, such as Medium , Regular ,

Bold , Italic or Heavy .
lang The language that the font supports, for ex-

ample, de for German, ja for Japanese,
zh-TW for traditional Chinese or zh-CN for
simplified Chinese.
weight The font weight, such as 80 for regular or

200 for bold.
slant The slant, usually 0 for none and 100 for

italic.
file The name of the le containing the font.
outline true for outline fonts or false for other

fonts.
scalable true for scalable fonts or false for other

fonts.
bitmap true for bitmap fonts or false for other

fonts.
pixelsize Font size in pixels. In connection with fc-

list, this option only makes sense for bitmap
fonts.

Install the packages xorg-x11-doc and howtoenh to get more in-depth information about X11.
More information on the X11 development can be found on the project's home page at http://
www.x.org .
Many of the drivers delivered with the package xorg-x11-driver-video are described in detail
in a 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-nvidiaG01 is avail-
able in /usr/share/doc/packages/x11-video-nvidiaG01 after the package was installed.

17 Accessing File Systems with FUSE
FUSE is the acronym for le system in userspace. This means you can configure and
mount a le system as an unprivileged user. Normally, you have 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.
17.1 Configuring FUSE

Before you can use FUSE, you have to install the package fuse . Depending which le system
you want to use, you need additional plug-ins available as separate packages. FUSE plug-ins are
not shipped with SUSE Linux Enterprise.
Generally you do not have to configure FUSE, you just use it. 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.
17.2 Available FUSE Plug-ins

FUSE is dependent on plug-ins. The following table lists common plug-ins. FUSE plug-ins are
not shipped with SUSE Linux Enterprise.
TABLE 17.1: AVAILABLE FUSE PLUG-INS
fuseiso mounts CD-ROM images with ISO9660 le

systems in them
ntfs-3g mount NTFS volumes (with read and write

support)
sshfs le system client based on SSH le transfer

protocol
wdfs mount WebDAV le systems
193 Configuring FUSE SUSE Linux Enterp… 11 SP4

See the home page http://fuse.sourceforge.net of FUSE for more information.

III Mobile Computers
18 Mobile Computing with Linux 196
19 Wireless LAN 206
20 Power Management 222
21 Using Tablet PCs 229

18 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 drives, 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.
18.1 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,
ISDN (and modem cards) and external hard disks.
Tip: SUSE Linux Enterprise Server and Tablet PCs

SUSE Linux Enterprise Server also supports Tablet PCs. Tablet PCs come with a touch-
pad/digitizer that allows you to use a digital pen or even fingertips to edit data right on
the screen instead of using mouse and keyboard. They are installed and configured much
like any other system. For a detailed introduction to the installation and configuration of
Tablet PCs, refer to Chapter 21, Using Tablet PCs.
18.1.1 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 towards
conservation of power is at least as important as that of the operating system. SUSE® Linux
196 Laptops SUSE Linux Enterp… 11 SP4

Enterprise Server supports various methods that influence 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 towards 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, WLAN, etc.).
Spinning down the hard disk when idling.
Detailed background information about power management in SUSE Linux Enterprise Server is
provided in Chapter 20, Power Management.
18.1.2 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.
197 Integration in Changing Operating Environments SUSE Linux Enterp… 11 SP4

Printing ? Mail
? ?
? ?
X configuration ? ?
? Proxy
Network
FIGURE 18.1: INTEGRATING A MOBILE COMPUTER IN AN EXISTING ENVIRONMENT
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 (with smpppd). Both desktop environments (GNOME
and KDE) include a front-end for NetworkManager. For more information about the desk-
top applets, see Section 27.4, “Using KNetworkManager” and Section 27.5, “Using the GNOME Net-
workManager Applet”.
TABLE 18.1: 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)
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
connections, NetworkManager works ne when all DNS addresses are assigned cor-
rectly assigned with DHCP. If some of your connections use static DNS address(es),
add it to the NETCONFIG_DNS_STATIC_SERVERS option in /etc/sysconfig/net-
work/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 23, SLP Services in the Network.
18.1.3 Software Options

There are various special task areas in mobile use that are covered by dedicated software: system
monitoring (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.
18.1.3.1 System Monitoring
Two KDE system monitoring tools are provided by SUSE Linux Enterprise Server:
Power Management
Power Management is an application which lets you adjust energy saving related behavior
of the KDE desktop. You can typically access it via the Battery Monitor tray icon, which
changes according to the type of the current power supply. Other way to open its con-
figuration dialog is through the Kickoff Application Launcher: Applications Configure Desk-
top Advanced Power Management.
Click the Battery Monitor tray icon to access options to configure its behavior. You can
choose one of ve displayed power profiles which best ts your needs. For example, the
Presentation scheme disables the screen saver and the power management in general, so
that your presentation is not interrupted by system events. Click More... to open a more
complex configuration screen. Here you can edit individual profiles and set advanced pow-
er management options and notifications, such as what to do when the laptop lid has been
closed, or when the battery charge is low.
200 Software Options SUSE Linux Enterp… 11 SP4

System Monitor
System Monitor (also called KSysguard) gathers measurable system parameters into one
monitoring environment. It presents the output information in 2 tabs by default. Process
Table gives detailed information about currently running processes, such as CPU load,
memory usage, or process ID number and nice value. The presentation and filtering of the
collected data can be customized — 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. KSysguard can also run as a daemon on
machines without a KDE environment. Find more information about this program in its
integrated help function or in the SUSE help pages.
In the GNOME environment use Power Management Preferences and System Monitor.
18.1.3.2 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 as well as 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 Mozilla
Thunderbird Mail, Evolution, or KMail. 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 synchronization process has com-
pleted. Use an SMTP server implemented in the mail client for sending messages instead of
the system-wide MTA postfix or sendmail to receive reliable 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 )
201 Software Options SUSE Linux Enterp… 11 SP4

18.1.3.3 Wireless Communication
As well as connecting to a home or office network with a cable, a laptop can also use wireless
connection to access other computers, peripherals, cellular phones or PDAs. Linux supports three
types of wireless communication:
WLAN
With the largest range of these wireless technologies, WLAN is the only one suitable for
the operation of large and sometimes even spatially separate networks. Single machines
can connect with each other to form an independent wireless network or access the Inter-
net. Devices called access points act as base stations for WLAN-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 cel-
lular telephony, a large network is available to WLAN users without binding them to a
specific location for accessing it. Find details about WLAN in Chapter 19, Wireless LAN.
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 wireless system components, like a keyboard or a mouse. The range of this
technology is, however, not sufficient to connect remote systems to a network. WLAN is
the technology of choice for communicating through physical obstacles like walls.
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. The long
range transport of the le to the recipient of the le is handled by the mobile network.
Another application of IrDA is the wireless transmission of printing jobs in the office.
18.1.4 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
202 Data Security SUSE Linux Enterp… 11 SP4

Always physically secure your system against theft whenever possible. Various securing
tools (like chains) are available in retail stores.
Strong Authentication
Use biometric authentication in addition to standard authentication via login and pass-
word. SUSE Linux Enterprise Server supports fingerprint authentication. For more details,
see Book “Security Guide”, Chapter 7 “Using the Fingerprint Reader”.
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”. Security measures related to wireless networking are provided in Chapter 19,
Wireless LAN.
18.2 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, USB ash drive, or digital camera. These devices are automatically detected and
configured as soon as they are connected with the system over the corresponding interface. The
le managers of both GNOME and KDE offer flexible handling of mobile hardware items. To
unmount any of these media safely, use the Safely Remove (KDE) or Unmount Volume (GNOME)
feature of either le manager.
203 Mobile Hardware SUSE Linux Enterp… 11 SP4

External Hard Disks (USB and FireWire)
As soon as 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
folders and les here and edit or delete them. To rename a hard disk from the name it had
been given by the system, select the corresponding menu item from the menu that opens
when the icon is right-clicked. This name change is limited to display in the le manager.
The descriptor by which the device is mounted in /media remains unaffected by this.
USB Flash Drives

These devices are handled by the system just like external hard disks. It is similarly possible
to rename the entries in the le manager.
18.3 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
Section 18.1.3.3, “Wireless Communication”. The configuration of these protocols on the cellular
phones themselves is described in their manuals.
The support for synchronizing with handheld devices manufactured by Palm, Inc., is already
built into Evolution and Kontact. Initial connection with the device is easily performed with
the assistance of a wizard. Once the support for Palm Pilots is configured, it is necessary to
determine which type of data should be synchronized (addresses, appointments, etc.).

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.
204 Cellular Phones and PDAs SUSE Linux Enterp… 11 SP4

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.
Information about OpenSync is available on http://opensync.org/ .

19 Wireless LAN
Wireless LANs, or Wireless Local Area Network (WLANs), have become an indis-
pensable aspect of mobile computing. Today, most laptops have built-in WLAN
cards. This chapter describes how to set up a WLAN card with YaST, encrypt trans-
missions, and use tips and tricks.
19.1 WLAN Standards

WLAN cards communicate using the 802.11 standard, prepared by the IEEE organization. Orig-
inally, 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 19.1, “Overview of Vari-
ous WLAN Standards”). Additionally, many companies implement hardware with proprietary or
draft features.
TABLE 19.1: OVERVIEW OF VARIOUS WLAN STANDARDS
Name Band (GHz) Maximum Trans- Note

mission Rate (Mbit/
s)
802.11 Legacy 2.4 2 Outdated; virtually

no end devices avail-
able
802.11a 5 54 Less interfer-

ence-prone
802.11b 2.4 11 Less common
802.11g 2.4 54 Widespread, back-

wards-compatible
with 11b
802.11n 2.4 and/or 5 300 Common
206 WLAN Standards SUSE Linux Enterp… 11 SP4

Name Band (GHz) Maximum Trans- Note
mission Rate (Mbit/
s)
802.11 ad 2.4/5/60 up to 7000 Released 2012, cur-

rently less common
802.11 Legacy cards are not supported by SUSE® Linux Enterprise Server. Most cards using
802.11a, 802.11b, 802.11g and 802.11n are supported. New cards usually comply with the
802.11n standard, but cards using 802.11g are still available.
19.2 Operating Modes

In wireless networking, various techniques and configurations are used to ensure fast, high-
quality, and secure connections. Different operating types suit different setups. It can be difficult
to choose the right authentication method. The available encryption methods have different
advantages and pitfalls.
Basically, wireless networks can be classified into three network modes:
Managed Mode (Infrastructure Mode), via Access Point

Managed networks have a managing element: the access point. In this mode (also referred
to as infrastructure mode), all connections of the WLAN 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.
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 faster 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. If you intend to use WPA security,
you should not use Ad-Hoc_Mode.
Master Mode
In master mode your network card is used as the access point. It works only if your
WLAN card supports this mode. Find out the details of your WLAN card on http://lin-
ux-wless.passys.nl .
207 Operating Modes SUSE Linux Enterp… 11 SP4

19.3 Authentication
Because a wireless network is much easier to intercept and compromise than a wired network,
the various standards include authentication and encryption methods. In the original version of
the IEEE 802.11 standard, these are described under the term WEP (Wired Equivalent Privacy).
However, because WEP has proven to be insecure (see Section 19.6.3, “Security”), the WLAN indus-
try (joined under the name Wi-Fi Alliance) has defined an extension called WPA, which is sup-
posed to eliminate the weaknesses of WEP. The later IEEE 802.11i standard includes WPA and
some other authentication and encryption methods. IEEE 802.11i is also referred to as WPA2,
because WPA is based on a draft version of 802.11i.
To make sure that only authorized stations can connect, various authentication mechanisms are
used in managed networks:
None (Open)
An open system is a system that does not require authentication. Any station can join the
network. Nevertheless, WEP encryption can be used, see Section 19.4, “Encryption”.
Shared Key (according to IEEE 802.11)

In this procedure, the WEP key is used for the authentication. However, this procedure
is not recommended, because it makes the WEP key more susceptible to attacks. All an
attacker needs to do is to listen long enough to the communication between the station
and the access point. During the authentication process, both sides exchange the same
information, once in encrypted form and once in unencrypted form. This makes it possible
for the key to be reconstructed with suitable tools. Because this method makes use of the
WEP key for the authentication and for the encryption, it does not enhance the security
of the network. A station that has the correct WEP key can authenticate, encrypt, and
decrypt. A station that does not have the key cannot decrypt received packets. Accordingly,
it cannot communicate, regardless of whether it had to authenticate itself.
WPA-PSK (or WPA-Personal, according to IEEE 802.1x)

WPA-PSK (PSK stands for preshared key) works similarly to the Shared Key procedure. All
participating stations as well as the access point need the same key. The key is 256 bits
in length and is usually entered as a passphrase. This system does not need a complex key
management like WPA-EAP and is more suitable for private use. Therefore, WPA-PSK is
sometimes referred to as WPA “Home”.
WPA-EAP (or WPA-Enterprise, according to IEEE 802.1x)
208 Authentication SUSE Linux Enterp… 11 SP4

Actually, WPA-EAP (Extensible Authentication Protocol) is not an authentication system
but a protocol for transporting authentication information. WPA-EAP is used to protect
wireless networks in enterprises. In private networks, it is scarcely used. For this reason,
WPA-EAP is sometimes referred to as WPA “Enterprise”.
WPA-EAP needs a Radius server to authenticate users. EAP offers three different methods
for connecting and authenticating to the server:
Transport Layer Security (EAP-TLS): TLS authentication relies on the mutual ex-
change of certificates for both server and client. First, the server presents its certifi-
cate to the client where it is evaluated. If the certificate is considered valid, the client
in turn presents its certificate to the server. While TLS is secure, it requires a working
certification management infrastructure in your network. This infrastructure is rarely
found in private networks.
Tunneled Transport Layer Security (EAP-TTSL)
Protected Extensible Authentication Protocol (EAP-PEAP): Both TTLS and PEAP are
two-stage protocols. In the rst stage, a secure connection is established and in the
second the client authentication data is exchanged. They require far less certification
management overhead than TLS, if any.
19.4 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 makes use of 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 to not encrypt the network at all.
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)
209 Encryption SUSE Linux Enterp… 11 SP4

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.
19.5 Configuration with YaST
Important: Security Risks in Wireless Networks

Unencrypted WLAN connections allow third parties to intercept all network data. Be sure
to protect your network traffic by using one of the supported authentication and encryp-
tion methods.
Use the best possible encryption method your hardware allows. However, to use a certain
encryption method, all devices in the network must support this method, otherwise they
cannot communicate with each other. For example, if your router supports both WEP and
WPA but the driver for your WLAN card only supports WEP, WEP is the least common
denominator you can use. But even a weak encryption with WEP is better than none at
all. Refer to Section 19.4, “Encryption” and Section 19.6.3, “Security” for information.
To configure a wireless LAN with YaST, you need to define the following parameters:
IP Address
Use either a static IP address or let a DHCP server dynamically assign an IP address to
the interface.
Operating Mode
Defines how to integrate your machine into a WLAN, depending on the network topology.
For background information, refer to Section 19.2, “Operating Modes”.
Network Name (ESSID)

Unique string identifying a network.
Authentication and Encryption Details
210 Configuration with YaST SUSE Linux Enterp… 11 SP4

Depending on the authentication and encryption method your network uses, you need to
enter one or more keys and/or certificates.
Several input options are available for entering the respective keys: Passphrase, ASCII (only
available for WEP authentication methods), and Hexadecimal.
19.5.1 Deactivating NetworkManager

A WLAN card is usually detected during installation. If your machine is a mobile computer,
NetworkManager is usually activated by default. If instead you want to configure your WLAN
card with YaST, you need to deactivate NetworkManager rst:
1. Start YaST as user root .
2. In the YaST Control Center, select Network Devices Network Settings to open the Network
Settings dialog.
If your network is currently controlled by NetworkManager, you see a warning message
that the network settings cannot be edited by YaST.
3. To enable editing with YaST, leave the message with OK and on the Global Options tab,
activate Traditional Method with ifup.
4. For further configuration, proceed with Section 19.5.2, “Configuration for Access Points” or
Section 19.5.3, “Establishing an Ad-Hoc Network”.
Otherwise confirm your changes with OK to write the network configuration.
19.5.2 Configuration for Access Points

In this section, learn how to configure your WLAN card to connect to an (external) access point
or how to use your WLAN card as access point if your WLAN card supports this. For configuration
of networks without an access point, refer to Section 19.5.3, “Establishing an Ad-Hoc Network”.
PROCEDURE 19.1: CONFIGURING YOUR WLAN CARD FOR USING AN ACCESS POINT
1. Start YaST and open the Network Settings dialog.
2. Switch to the Overview tab where all network cards are listed that have been detected by
the system. If you need more information about general network configuration, refer to
Section 22.4, “Configuring a Network Connection with YaST”.
211 Deactivating NetworkManager SUSE Linux Enterp… 11 SP4

3. Choose your wireless card from the list and click Edit to open the Network Card Setup dialog.
4. On the Address tab, configure whether to use a dynamic or a static IP address for the
machine. Usually Dynamic Address with DHCP is ne.
5. Click Next to proceed to the Wireless Network Card Configuration dialog.
6. To use your WLAN card to connect to an access point, set the Operating Mode to Managed.
If however you want to use your WLAN card as access point, set the Operating Mode to
Master. Note that not all WLAN cards support this mode.
Note: Using WPA-PSK or WPA-EAP

If you want to use WPA-PSK or WPA-EAP authentication modes, the operating mode
must be set to Managed.
7. To connect to a certain network, enter the Network Name (ESSID). Alternatively, click Scan
Network and select a network from the list of available wireless networks.
All stations in a wireless network need the same ESSID for communicating with each other.
If no ESSID is specified, your WLAN card automatically associates with the access point
that has the best signal strength.
Note: WPA Authentication Requires an ESSID

If you select WPA authentication, a network name (ESSID) must be set.
8. Select an Authentication Mode for your network. Which mode is suitable, depends on your
WLAN card's driver and the ability of the other devices in the network.
9. If you have chosen to set the Authentication Mode to No Encryption, finish the configuration
by clicking Next. Confirm the message about this potential security risk and leave the
Overview tab (showing the newly configured WLAN card) with OK.
If you haven chosen any of the other authentication modes, proceed with Procedure 19.2,
“Entering the Encryption Details”.
212 Configuration for Access Points SUSE Linux Enterp… 11 SP4

FIGURE 19.1: YAST: CONFIGURING THE WIRELESS NETWORK CARD
PROCEDURE 19.2: ENTERING THE ENCRYPTION DETAILS
The following authentication methods require an encryption key: WEP - Open, WEP -
Shared Key, and WPA-PSK.
For WEP, usually only key is needed—however, up to 4 different WEP keys can be defined
for your station. One of them needs to be set as the default key and is used for encryption.
The others are used for decryption. Per default, a key length of 128-bit is used, but you
can also choose to set the length to 64-bit.
For higher security, WPA-EAP uses a RADIUS server to authenticate users. For authentica-
tion at the server, three different methods are available: TLS, TTLS and PEAP. The creden-
tials and certificates you need for WPA-EAP depend on the authentication method used
for the RADIUS server. Ask your system administrator to provide the needed information
and credentials. YaST searches for any certificate under /etc/cert . Therefore, save the
certificates given to you to this location and restrict access to these les to 0600 (owner
read and write).
1. To enter the key for WEP - Open or WEP - Shared Key:
a. Set the Key Input Type either to Passphrase, ASCII or Hexadecimal.

b. Enter the respective Encryption Key (usually only one key is used):
If you have selected Passphrase, enter a word or a character string from which a key
is generated according to the specified key length (per default, 128-bit).
ASCII requests an input of 5 characters for a 64-bit key and 13 characters for a 128-
bit key.
For Hexadecimal, enter 10 characters for a 64-bit key or 26 characters for a 128-bit
key in hexadecimal notation.
c. To adjust the key length to a lower bit rate (which might be necessary for older
hardware), click WEP Keys and set the Key Length to 64 bit. The WEP Keys dialog also
shows the WEP keys that have been entered so far. Unless another key is explicitly
set as default, YaST always uses the rst key as default key.
d. To enter more keys for WEP or to modify one of the keys, select the respective entry
and click Edit. Select the Key Input Type and enter the key.
e. Confirm your changes with OK.
2. To enter a key for WPA-PSK:
a. Select the input method Passphrase or Hexadecimal.
b. Enter the respective Encryption Key.

In the Passphrase mode, the input must be 8 to 63 characters. In the Hexadecimal
mode, enter 64 characters.
3. If you have chosen WPA-EAP authentication, click Next to switch to the WPA-EAP dialog,
where you enter the credentials and certificates you have been given by your network
administrator.
a. Select the EAP Mode the RADIUS server uses for authentication. The details you need
to enter in the following depend on the selected EAP Mode.
b. For TLS, provide Identity, Client Certificate, Client Key, and Client Key Password. To
increase security, you can also configure a Server Certificate used to validate the
server's authenticity.
TTLS and PEAP require Identity and Password, whereas Server Certificate and Anony-
mous Identity are optional.
c. To enter the advanced authentication dialog for your WPA-EAP setup, click Details.

d. Select the Authentication Method for the second stage of EAP-TTLS or EAP-PEAP com-
munication (inner authentication). The choice of methods depends on the authenti-
cation method for the RADIUS server you selected in the previous dialog.
e. If the automatically-determined setting does not work for you, choose a specific PEAP
Version to force the use of a certain PEAP implementation.
4. Confirm your changes with OK. The Overview tab shows the details of your newly con-
figured WLAN card.
5. Click OK to finalize the configuration and to leave the dialog.
19.5.3 Establishing an Ad-Hoc Network

In some cases it is useful to connect two computers equipped with a WLAN card. To establish
an ad-hoc network with YaST, do the following:
2. Switch to the Overview tab, choose your wireless card from the list and click Edit to open
the Network Card Setup dialog.
3. Choose Statically assigned IP Address and enter the following data:
IP Address: 192.168.1.1 . Change this address on the second computer to

192.168.1.2 , for example.
Subnet Mask: /24
Hostname: Choose any name you like.
4. Proceed with Next.
5. Set the Operating Mode to Ad-hoc.
6. Choose a Network Name (ESSID). This can be any name, but it has to be used on every
computer in the ad-hoc network.
7. Select an Authentication Mode for your network. Which mode is suitable, depends on your
WLAN card's driver and the ability of the other devices in the network.
215 Establishing an Ad-Hoc Network SUSE Linux Enterp… 11 SP4

8. If you have chosen to set the Authentication Mode to No Encryption, finish the configuration
by clicking Next. Confirm the message about this potential security risk and leave the
Overview tab showing the newly configured WLAN card with OK.
If you haven chosen any of the other authentication modes, proceed with Procedure 19.2,
“Entering the Encryption Details”.
9. If you do not have smpppd installed, YaST asks you to do so.
10. Configure the other WLAN cards in the network accordingly, using the same Network Name
(ESSID), the same Authentication Mode but different IP addresses.
19.5.4 Setting Additional Configuration Parameters

Usually there is no need to change the pre-configured settings when configuring your WLAN
card. However, if you need detailed configuration of your WLAN connection, YaST allows you
to tweak the following settings:
Channel
The specification of a channel on which the WLAN station should work. This is only need-
ed in Ad-hoc and Master modes. In Managed mode, the card automatically searches the
available channels for access points.
Bit Rate
Depending on the performance of your network, you may want to set a certain bit rate for
the transmission from one point to another. In the default setting Auto, the system tries
to use the highest possible data transmission rate. Some WLAN cards do not support the
setting of bit rates.
Access Point
In an environment with several access points, one of them can be preselected by specifying
the MAC address.
Power Management
When you are on the road, power saving technologies can help to maximize the operat-
ing time of your battery. More information about power management is available in Chap-
ter 20, Power Management. Using power management may affect the connection quality and
increase the network latency.
216 Setting Additional Configuration Parameters SUSE Linux Enterp… 11 SP4

To access the advanced options:
2. Switch to the Overview tab, choose your wireless card from the list and click Edit to open
the Network Card Setup dialog.
3. Click Next to proceed to the Wireless Network Card Configuration dialog.
4. Click Expert Settings.
5. In Ad-hoc mode, select one of the offered channels (11 to 14, depending on your country)
for the communication of your station with the other stations. In Master mode, determine
on which Channel your card should offer access point functionality. The default setting
for this option is Auto.
6. Select the Bit Rate to use.
7. Enter the MAC address of the Access Point you want to connect to.
8. Choose if to Use Power Management or not.
9. Confirm your changes with OK and click Next and OK to finish the configuration.
19.6 Tips and Tricks for Setting Up a WLAN

The following tools and tips can help to monitor and improve speed and stability as well as
security aspects of your WLAN.
19.6.1 Utilities
The package wireless-tools contains utilities that allow to set wireless LAN specific para-
meters and get statistics. See http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html
for more information.
19.6.2 Stability and Speed

The performance and reliability of a wireless network mainly depend on whether the partic-
ipating stations receive a clear signal from the other stations. Obstructions like walls greatly
weaken the signal. The more the signal strength sinks, the more the transmission slows down.
217 Tips and Tricks for Setting Up a WLAN SUSE Linux Enterp… 11 SP4
During operation, check the signal strength with the iwconfig utility on the command line
( Link Quality eld) or with the NetworkManager applets provided by KDE or GNOME. If you
have problems with the signal quality, try to set up the devices somewhere else or adjust the
position of the antennas of your access points. Auxiliary antennas that substantially improve
the reception are available for a number of PCMCIA WLAN cards. The rate specified by the
manufacturer, such as 54 Mbit/s, is a nominal value that represents the theoretical maximum.
In practice, the maximum data throughout is no more than half this value.
The iwspy command can displays WLAN statistics:
iwspy wlan0
wlan0 Statistics collected:
00:AA:BB:CC:DD:EE : Quality:0 Signal level:0 Noise level:0
Link/Cell/AP : Quality:60/94 Signal level:-50 dBm Noise level:-140 dBm
(updated)
Typical/Reference : Quality:26/94 Signal level:-60 dBm Noise level:-90 dBm
19.6.3 Security
If you want to set up a wireless network, remember that anybody within the transmission range
can easily access it if no security measures are implemented. Therefore, be sure to activate an
encryption method. All WLAN cards and access points support WEP encryption. Although this
is not entirely safe, it does present an obstacle for a potential attacker.
For private use, use WPA-PSK if available. Although Linux supports WPA on most hardware
components, some drivers do not offer WPA support. It may also not be available on older access
points and routers with WLAN functionality. For such devices, check if WPA can be implemented
by means of a rmware update. If WPA is not available, WEP is better than no encryption. In
enterprises with advanced security requirements, wireless networks should only be operated
with WPA.
Use strong passwords for your authentication method. For example, the Web page https://
www.grc.com/passwords.htm generates random 64 character passwords.
218 Security SUSE Linux Enterp… 11 SP4

If your WLAN card fails to respond, check the following prerequisites:
1. Do you know the device name of the WLAN card? Usually it is wlan0 . Check with the
tool ifconfig .
2. Have you checked your needed rmware? Refer to /usr/share/doc/packages/wire-

less-tools/README.firmware for more information.
3. Is the ESSID of your router broadcasted and visible (not hidden)?
19.7.1 Check the Network Status

The command iwconfig can give you important information about your wireless connection.
For example, the following line displays the ESSID, the wireless mode, frequency, if you signal
is encrypted, the link quality, and much more:
iwconfig wlan0
wlan0 IEEE 802.11abg ESSID:"guest"
Mode:Managed Frequency:5.22GHz Access Point: 00:11:22:33:44:55
Bit Rate:54 Mb/s Tx-Power=13 dBm
Retry min limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality:62/92 Signal level:-48 dBm Noise level:-127 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:10 Invalid misc:0 Missed beacon:0
You can also get the previous information with the iwlist command. For example, the follow-
ing line displays the current bit rate:
iwlist wlan0 rate

wlan0 unknown bit-rate information.
Current Bit Rate=54 Mb/s
If you want an overview how many access points are available, it can also be done with the
iwlist command. It gives you a list of “cells” which looks like this:
iwlist wlan0 scanning

wlan0 Scan completed:
Cell 01 - Address: 00:11:22:33:44:55
Channel:40

Frequency:5.2 GHz (Channel 40)
Quality=67/70 Signal level=-43 dBm
Encryption key: off
ESSID:"Guest"
Bit Rates: 6 Mb/s; 9 Mb/s; 12 Mb/s; 18 Mb/s;
24 Mb/s; 36 Mb/s; 48 Mb/s
Mode: Master
Extra:tsf=0000111122223333
Extra: Last beacon: 179ms ago
IE: Unknown: ...
19.7.2 Multiple Network Devices

Modern laptops usually have a network card and a WLAN card. If you configured both devices
with DHCP (automatic address assignment), you may encounter problems with the name resolu-
tion and the default gateway. This is evident from the fact that you can ping the router but cannot
surf the Internet. The Support Database features an article on this subject at http://old-en.open-
suse.org/SDB:Name_Resolution_Does_Not_Work_with_Several_Concurrent_DHCP_Clients .
19.7.3 Problems with Prism2 Cards

Several drivers are available for devices with Prism2 chips. The various cards work more or
less smoothly with the various drivers. With these cards, WPA is only possible with the hostap
driver. If such a card does not work properly or not at all or you want to use WPA, read /usr/
share/doc/packages/wireless-tools/README.prism2 .

More information can be found on the following pages:
http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wireless.html
The Internet pages of Jean Tourrilhes, who developed the Wireless Tools for Linux, present
a wealth of useful information about wireless networks.
http://tuxmobil.org
Useful hands-on information about mobile computers under Linux.
http://www.linux-on-laptops.com
220 Multiple Network Devices SUSE Linux Enterp… 11 SP4

More information about Linux on laptops.

20 Power Management
IBM Z The features and hardware described in this chapter do not exist on IBM System z,
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.
20.1 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.
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.
222 Power Saving Functions SUSE Linux Enterp… 11 SP4

Automatic Power-O
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.
20.2 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 /var/log/boot.msg . See Section 20.2.2, “Troubleshooting” for
more information about troubleshooting ACPI problems.
20.2.1 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.
223 Advanced Configuration and Power Interface (ACPI) SUSE Linux Enterp… 11 SP4
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”.
20.2.2 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 at all, one of the following boot parameters may be helpful:
pci=noacpi
Do not use ACPI for configuring the PCI devices.
acpi=ht
Only perform a simple resource configuration. Do not use ACPI for other purposes.
acpi=o
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 | 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 Descrip-
tion 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 20.4, “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.
20.2.2.1 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://www.lesswatts.org/projects/acpi/ (the ACPI4Linux project at Sourceforge)
http://acpi.sourceforge.net/dsdt/index.php (DSDT patches by Bruno Ducrot)
20.3 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.
225 Rest for the Hard Disk SUSE Linux Enterp… 11 SP4
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).
/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.
226 Rest for the Hard Disk SUSE Linux Enterp… 11 SP4
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 makes use of 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 le /var/log/messages . The following sections
cover the most common problems.
20.4.1 ACPI Activated with Hardware Support but Functions Do

Not Work
If you experience problems with ACPI, search the output of dmesg for ACPI-specific messages
by using the command dmesg|grep -i acpi .
A BIOS update may be required to resolve the problem. Go to the home page of your laptop
manufacturer, look for an updated BIOS version, and install it. Ask the manufacturer to comply
with the latest ACPI specification. If the errors persist after the BIOS update, proceed as follows
to replace the faulty DSDT table in your BIOS with an updated DSDT:
PROCEDURE 20.1: UPDATING THE DSDT TABLE IN THE BIOS
For the procedure below, make sure the following packages are installed: kernel-source ,
pmtools , and mkinitrd .
1. Download the DSDT for your system from http://acpi.sourceforge.net/dsdt/index.php .

Check if the le is decompressed and compiled as shown by the le extension .aml (ACPI
machine language). If this is the case, continue with step 3.
2. If the le extension of the downloaded table is .asl (ACPI source language) instead,
compile it by executing the following command:
iasl -sa file.asl

3. Copy the (resulting) le DSDT.aml to any location ( /etc/DSDT.aml is recommended).
4. Edit /etc/sysconfig/kernel and adapt the path to the DSDT le accordingly.
5. Start mkinitrd . Whenever you install the kernel and use mkinitrd to create an initrd
le, the modified DSDT is integrated and loaded when the system is booted.
20.4.2 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/* .
20.4.3 Suspend and Standby Do Not Work

ACPI systems may have problems with suspend and standby due to a faulty DSDT implementa-
tion (BIOS). If this is the case, update the BIOS.
When the system tries to unload faulty modules, the system is arrested or the suspend event
is not triggered. The same can also happen if you do not unload modules or stop services that
prevent a successful suspend. In both cases, try to identify the faulty module that prevented the
sleep mode. The log le /var/log/pm-suspend.log contains detailed information about what
is going on and where possible errors are. Modify the SUSPEND_MODULES variable in /usr/lib/
pm-utils/defaults to unload problematic modules prior to a suspend or standby.

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
228 CPU Frequency Does Not Work SUSE Linux Enterp… 11 SP4
21 Using Tablet PCs
SUSE® Linux Enterprise Server comes with support for Tablet PCs. In the following,
learn how to install and configure your Tablet PC and discover some useful Linux*
applications which accept input from digital pens.
The following Tablet PCs are supported:
Tablet PCs with serial and USB Wacom tablet (pen based), touch-screen or multi-touch
devices.
Tablet PCs with FinePoint devices, such as Gateway C210X/M280E/CX2724 or HP Compaq

TC1000.
Tablet PCs with touch screen devices, such as Asus R2H, Clevo TN120R, Fujitsu Siemens
Computers P-Series, LG C1, Samsung Q1/Q1-Ultra.
After you have installed the Tablet PC packages and configured your digitizer correctly, input
with the pen (also called a stylus) can be used for the following actions and applications:
Logging in to KDM or GDM
Unlocking your screen on the KDE and GNOME desktops
Actions that can also be triggered by other pointing devices (such as mouse or touch pad),
for example, moving the cursor on the screen, starting applications, closing, resizing and
moving windows, shifting window focus and dragging and dropping objects
Using gesture recognition in applications of the X Window System
Drawing with GIMP
Taking notes or sketching with applications like Jarnal or Xournal or editing larger
amounts of text with Dasher

21.1 Installing Tablet PC Packages
The packages needed for Tablet PCs are included in the TabletPC installation pattern—if this is
selected during installation, the following packages should already be installed on your system:
cellwriter : a character-based hardwriting input panel
jarnal : a Java-based note taking application
xournal : an application for note taking and sketching
xstroke : a gesture recognition program for the X Window System
xvkbd : a virtual keyboard for the X Window System
x11-input-fujitsu : the X input module for Fujitsu P-Series tablets
x11-input-evtouch : the X input module for some Tablet PCs with touch screens
xorg-x11-driver-input : the X input module for input devices, including the module for
Wacom devices.
If these packages are not installed, manually install the packages you need from command line
or select the TabletPC pattern for installation in YaST.
21.2 Configuring Your Tablet Device

During installation, your tablet or touch device is configured by default. If you have trouble
with the configuration of your Wacom device, you use xsetwacom on the command line to
change the settings.
21.3 Using the Virtual Keyboard

To log in to the KDE or GNOME desktop or to unlock the screen, you can either enter your
username and password as usual or via the virtual keyboard (xvkbd) displayed below the login
eld. To configure the keyboard or to access the integrated help, click the xvkbd eld at the left
lower corner and open the xvkbd main menu.
If your input is not visible (or is not transferred to the window where you need it), redirect
the focus by clicking the Focus key in xvkbd and then clicking into the window that should get
the keyboard events.
230 Installing Tablet PC Packages SUSE Linux Enterp… 11 SP4

FIGURE 21.1: XVKBD VIRTUAL KEYBOARD
If you want to use xvkbd after login, start it from the main menu or with xvkbd from a shell.
21.4 Rotating Your Display

Use KRandRTray (KDE) or gnome-display-properties (GNOME) to rotate or resize your display
manually on the y. Both KRandRTray and gnome-display-properties are applets for the RANDR
extension of the X server.
Start KRandRTray or gnome-display-properties from the main menu, or enter krandrtray or
gnome-display-properties to start the applet from a shell. After you have started the applet,
the applet icon is usually added to your system tray. If the gnome-display-properties icon does
not automatically appear in the system tray, make sure Show Displays in Panel is activated in
the Monitor Resolution Settings dialog.
To rotate your display with KRandRTray, right-click the icon and select Configure Display. Select
the desired orientation from the configuration dialog.
To rotate your display with gnome-display-properties, right-click the icon and select the de-
sired orientation. Your display is immediately tilted to the new direction. The orientation of the
graphics tablet changes also, so it can still interpret the movement of the pen correctly.
If you have problems changing the orientation of your desktop, refer to Section 21.7, “Troubleshoot-
ing” for more information.
21.5 Using Gesture Recognition

SUSE Linux Enterprise Server includes both CellWriter and xstroke for gesture recognition. Both
applications accept gestures executed with the pen or other pointing devices as input for appli-
cations on the X Window System.
231 Rotating Your Display SUSE Linux Enterp… 11 SP4

21.5.1 Using CellWriter
With CellWriter, you can write characters into a grid of cells—the writing is instantly recognized
on a character basis. After you have finished writing, you can send the input to the currently
focused application. Before you can use CellWriter for gesture recognition, the application needs
to be trained to recognize your handwriting: You need to train each character of a certain map
of keys (untrained characters are not activated and thus cannot be used).
PROCEDURE 21.1: TRAINING CELLWRITER
1. Start CellWriter from the main menu or with cellwriter from the command line. On the
rst start, CellWriter automatically starts in the training mode. In training mode it shows
a set of characters of the currently chosen key map.
2. Enter the gesture you would like to use for a character into the respective character's cell.
With the rst input, the background changes its color to white, whereas the character
itself is shown in light gray. Repeat the gesture multiple times until the character changes
its color to black. Untrained characters are shown on a light gray or brown background
(depending on the desktop's color scheme).
3. Repeat this step until you have trained CellWriter for all characters you need.
4. If you want to train CellWriter for another language, click the Setup button and select a
language from the Languages tab. Close the configuration dialog. Click the Train button and
select the key map from the drop-down box at the bottom right corner of the CellWriter
window. Now repeat your training for the new map of keys.
5. After having finished the training for the map of keys, click the Train button to switch
to the normal mode.
In the normal mode, the CellWriter windows shows a couple of empty cells in which to enter
the gestures. The characters are not sent to another application until you click the Enter button,
so you can correct or delete characters before you use them as input. Characters that have been
recognized with a low degree of confidence will appear highlighted. To correct your input, use
the context menu that appears on right-clicking a cell. To delete a character, either use your pen's
eraser, or middle-click with the mouse to clear the cell. After finishing your input in CellWriter,
define which application should receive the input by clicking into the application's window.
Then send the input to the application by clicking Enter.
232 Using CellWriter SUSE Linux Enterp… 11 SP4

FIGURE 21.2: GESTURE RECOGNITION WITH CELLWRITER
If you click the Keys button in CellWriter, you get a virtual keyboard that can be used instead
of the handwriting recognition.
To hide CellWriter, close the CellWriter window. The application now appears as icon in your
system tray. To show the input window again, click the icon in the system tray.
21.5.2 Using Xstroke

With xstroke, you can use gestures with your pen or other pointing devices as input for applica-
tions on the X Window System. The xstroke alphabet is a unistroke alphabet that resembles the
Graffiti* alphabet. When activated, xstroke sends the input to the currently focused window.
1. Start xstroke from the main menu or with xstroke from a shell. This adds a pencil icon
to your system tray.
2. Start the application for which you want to create text input with the pen (for example,
a terminal window, a text editor or an LibreOffice Writer).
3. To activate the gesture recognition mode, click the pencil icon once.
4. Perform some gestures on the graphics tablet with the pen or another pointing device.
xstroke captures the gestures and transfers them to text that appears in the application
window that has the focus.
5. To switch focus to a different window, click the desired window with the pen and hold
for a moment (or use the keyboard shortcut defined in your desktop's control center).
6. To deactivate the gesture recognition mode, click the pencil icon again.
233 Using Xstroke SUSE Linux Enterp… 11 SP4

21.6 Taking Notes and Sketching with the Pen
To create drawings with the pen, you can use a professional graphics editor like GIMP or try one
of the note-taking applications, Xournal or Jarnal. With both Xournal and Jarnal, you can take
notes, create drawings or comment PDF les with the pen. As a Java-based application available
for several platforms, Jarnal also offers basic collaboration features. For more information, re-
fer to http://www.dklevine.com/general/software/tc1000/jarnal-net.htm . When saving your con-
tents, Jarnal stores the data in an archive format (*.jaj) that also contains a le in SVG format.
Start Jarnal or Xournal from the main menu or by entering jarnal or xournal in a shell. To
comment a PDF le in Xournal, for example, select File Annotate PDF and open the PDF le
from your le system. Use the pen or another pointing device to annotate the PDF and save
your changes with File Export to PDF.
FIGURE 21.3: ANNOTATING A PDF WITH XOURNAL
Dasher is another useful application. It was designed for situations where keyboard input is
impractical or unavailable. With a bit of training, you can rapidly enter larger amounts of text
using only the pen (or other input devices—it can even be driven with an eye tracker).
234 Taking Notes and Sketching with the Pen SUSE Linux Enterp… 11 SP4
Start Dasher from the main menu or with dasher from a shell. Move your pen in one direction
and the application starts to zoom into the letters on the right side. From the letters passing
the cross hairs in the middle, the text is created or predicted and is printed to the upper part of
the window. To stop or start writing, click the display once with the pen. Modify the zooming
speed at the bottom of the window.
FIGURE 21.4: EDITING TEXTS WITH DASHER
The Dasher concept works for many languages. For more information, refer to the Dasher Web
site, which offers comprehensive documentation, demonstrations and training texts. Find it at
http://www.inference.phy.cam.ac.uk/dasher/
Virtual Keyboard Does Not Appear on Login Screen

Occasionally, the virtual keyboard is not displayed on the login screen. To solve this, restart
the X server by pressing Ctrl – Alt – <— or press the appropriate key on your Tablet PC
(if you use a slate model without integrated keyboard). If the virtual keyboard still does
not show, connect an external keyboard to your slate model and log in using the hardware
keyboard.
Orientation of the Wacom Graphics Tablets Does Not Change

With the xrandr command, you can change the orientation of your display from within a
shell. Enter xrandr --help to view the options available. To simultaneously change the
orientation of your graphics tablet, the command needs to be modified as described below:
For normal orientation (0° rotation):
xrandr -o normal && xsetwacom --set "Serial Wacom Tablet" Rotate NONE
For 90° rotation (clockwise, portrait):
xrandr -o right && xsetwacom --set "Serial Wacom Tablet" Rotate CW
For 180° rotation (landscape):
xrandr -o inverted && xsetwacom --set "Serial Wacom Tablet" Rotate HALF
For 270° rotation (counterclockwise, portrait):
xrandr -o left && xsetwacom --set "Serial Wacom Tablet" Rotate CCW
Note that the commands above depend on the output of the xsetwacom list command.
Replace "Serial Wacom Tablet" with the output for the stylus or the touch device. If
you have a Wacom device with touch support (you can use your fingers on the tablet to
move the cursor), you need to rotate also the touch device.

Some of the applications mentioned here do not offer integrated online help, but you can nd
some useful information about usage and configuration in your installed system in /usr/
share/doc/package/packagename or on the Web:
For the Xournal manual, refer to http://xournal.sourceforge.net/manual.html
The Jarnal documentation is located at http://jarnal.wikispaces.com/

Find the xstroke man page at http://davesource.com/Projects/xstroke/xstroke.txt
Find more information about the Linux Wacom project at: https://linuxwacom.github.io/
Find a very informative Web site about the Dasher project at http://www.infer-
ence.phy.cam.ac.uk/dasher/
Information on gnome-display-properties can be found at http://old-en.open-

suse.org/GNOME/Multiscreen

IV Services
22 Basic Networking 239
23 SLP Services in the Network 301
24 Time Synchronization with NTP 305
25 The Domain Name System 312
26 DHCP 335
27 Using NetworkManager 351
28 Samba 368
29 Sharing File Systems with NFS 381
30 File Synchronization 394
31 The Apache HTTP Server 403
32 Setting up an FTP Server with YaST 445
33 The Squid Proxy Server 450
34 Web Based Enterprise Management Using SFCB 469

22 Basic Networking
Linux offers the necessary networking tools and features for integration into all
types of network structures. Network access using a network card, modem or other
device can be configured with YaST. Manual configuration is also possible. In this
chapter only the fundamental 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 pro-
tocol, but a family of network protocols that offer various services. The protocols listed in Ta-
ble 22.1, “Several Protocols in the TCP/IP Protocol Family”, are provided for the purpose of exchanging
data between two machines via TCP/IP. Networks combined by TCP/IP, comprising a world-
wide network, are also referred to as “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. To expand your knowledge of any of
the protocols, refer to the appropriate RFC documents. These are available at http://www.iet-
f.org/rfc.html .

TABLE 22.1: SEVERAL PROTOCOLS IN THE TCP/IP PROTOCOL FAMILY
Protocol Description
TCP Transmission Control Protocol: a connec-

tion-oriented secure protocol. The data to
transmit is rst sent by the application as a
stream of data and converted into the ap-
propriate 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 de-
termines whether any data has been lost or
jumbled during the transmission. TCP is im-
plemented wherever the data sequence mat-
ters.
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 da-
ta 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: Essential-

ly, this is not a protocol for the end user, but
a special control protocol that issues error
reports and can control the behavior of ma-
chines participating in TCP/IP data transfer.
In addition, it provides a special echo mode
that can be viewed using the program ping.
IGMP Internet Group Management Protocol: This

As shown in Figure 22.1, “Simplified Layer Model for TCP/IP”, data exchange takes place in different
protocol controls machine behavior when
layers. The actual network layer is the insecure data transfer via IP (Internet protocol). On top
implementing IP multicast.
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.

Host sun Host earth
Application Layer Applications Application Layer
Transport Layer TCP, UDP Transport Layer
Network Layer IP Network Layer
Data Link Layer Ethernet, FDDI, ISDN Data Link Layer
Physical Layer Cable, Fiberglass Physical Layer
Data Transfer
FIGURE 22.1: SIMPLIFIED LAYER MODEL FOR TCP/IP
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 22.2, “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.
Usage Data (maximum 1460 bytes)
TCP (Layer 4) Protocol Header (approx. 20 bytes)
IP (Layer 3) Protocol Header (approx. 20 bytes)
Ethernet (Layer 2) Protocol Header (approx. 14 bytes) + Checksum (2 bytes)
FIGURE 22.2: 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.
22.1 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 22.2, “IPv6—The Next Generation Internet”.
242 IP Addresses and Routing SUSE Linux Enterp… 11 SP4

22.1.1 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 22.1, “Writing IP Addresses”.
EXAMPLE 22.1: 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.
22.1.2 Netmasks and Routing
Netmasks are used to define the address range of a subnetwork. If two hosts are in the same
subnetwork, they can reach each other directly. If they are not in the same subnetwork, they
need the address of a gateway that handles all the traffic for the subnetwork. 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 22.2, “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 subnetwork. This means that the more bits are 1 , the
smaller the subnetwork is. Because the netmask always consists of several successive 1 bits, it is
also possible to just count the number of bits in the netmask. In Example 22.2, “Linking IP Addresses
to the Netmask” the rst net with 24 bits could also be written as 192.168.0.0/24 .
EXAMPLE 22.2: LINKING IP ADDRESSES TO THE NETMASK
IP address (192.168.0.20): 11000000 10101000 00000000 00010100
243 IP Addresses SUSE Linux Enterp… 11 SP4

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
located in the same subnetwork 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.
244 Netmasks and Routing SUSE Linux Enterp… 11 SP4

TABLE 22.2: SPECIFIC ADDRESSES
Address Type Description
Base Network Address This is the netmask AND any address in the
network, as shown in Example 22.2, “Linking IP
Addresses to the Netmask” under Result . This
address cannot be assigned to any hosts.
Broadcast Address This basically says, “Access all hosts in this

subnetwork.” 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 as-
signed to any hosts.
Local Host The address 127.0.0.1 is assigned to the

“loopback device” on each host. A connec-
tion 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 just
one loopback address ( ::1 ).
Because IP addresses must be unique all over the world, you cannot just 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 22.3, “Private
IP Address Domains”.
TABLE 22.3: 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
245 Netmasks and Routing SUSE Linux Enterp… 11 SP4

22.2 IPv6—The Next Generation Internet
Important: IBM System z: IPv6 Support

IPv6 is not supported by the CTC and IUCV network connections of the IBM System z
hardware.
Due to the emergence of the WWW (World Wide Web), 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 due to 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 subnetwork has,
for example, 2, 6, or 14 addresses available. To connect 128 hosts to the Internet, for example,
you need a subnetwork with 256 IP addresses, from which only 254 are usable, because two
IP addresses are needed for the structure of the subnetwork 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
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 a number of 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.
22.2.1 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.
246 IPv6—The Next Generation Internet SUSE Linux Enterp… 11 SP4

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 22.2.2, “Address Types and Structure”.
The following is a list of some 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 advertis-
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 your mobile phone abroad, the phone automatically logs in to a foreign service as
soon as it enters the corresponding area, so you can be reached under the same number
everywhere and are able to place an outgoing call just like 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 are able to 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 through the use of a number of tunnels.
See Section 22.2.3, “Coexistence of IPv4 and IPv6”. Also, systems can rely on a dual stack IP
247 Advantages SUSE Linux Enterp… 11 SP4

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—by addressing a number of hosts as parts of a group
(which 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).
22.2.2 Address Types and Structure

As mentioned, the current IP protocol is lacking in two important aspects: there is an increasing
shortage of IP addresses and configuring the network and maintaining the routing tables is be-
coming a more complex and burdensome task. IPv6 solves the rst problem by expanding the
address space to 128 bits. The second one is countered by introducing a hierarchical address
structure, combined with sophisticated techniques to allocate network addresses, as well as mul-
tihoming (the ability to assign several addresses to one device, giving access to several networks).
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
248 Address Types and Structure SUSE Linux Enterp… 11 SP4

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 22.3,
“Sample IPv6 Address”, where all three lines represent the same address.
EXAMPLE 22.3: 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 22.4,
“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. Just like 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 subnetwork or in another one.
EXAMPLE 22.4: IPV6 ADDRESS SPECIFYING THE PREFIX LENGTH
fe80::10:1000:1a4/64
IPv6 knows about several predefined types of prefixes. Some of these are shown in Table 22.4,
“Various IPv6 Prefixes”.
TABLE 22.4: VARIOUS IPV6 PREFIXES
Prefix (hex) Definition
00 IPv4 addresses and IPv4 over IPv6 compati-

bility addresses. These are used to maintain
compatibility with IPv4. Their use still re-

Prefix (hex) Definition
quires 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 rst digit Aggregatable global unicast addresses. As is

the case with IPv4, an interface can be as-
signed to form part of a certain subnetwork.
Currently, there are the following address
spaces: 2001::/16 (production quality ad-
dress space) and 2002::/16 (6to4 address
space).
fe80::/10 Link-local addresses. Addresses with this pre-

fix should not be routed and should therefore
only be reachable from within the same sub-
network.
fec0::/10 Site-local addresses. These may be routed,

but only within the network of the organi-
zation 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 subnetwork 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 or ISDN.
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—when 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 22.2.3, “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 subnetwork. Packets with a source or
target address of this type should not be routed to the Internet or other subnetworks.
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 subnetwork.
site-local

Packets with this type of address may be routed to other subnetworks, 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 subnetwork 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 as soon as IPv6
is enabled (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.
22.2.3 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
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 22.2.2, “Address Types and Structure”).
252 Coexistence of IPv4 and IPv6 SUSE Linux Enterp… 11 SP4

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) as well as 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
by the fact that 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, a number of
problems 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.
22.2.4 Configuring IPv6

To configure IPv6, you normally do not need to make any changes on the individual worksta-
tions. IPv6 is enabled by default. You can disable it during installation in the network config-
uration step described in Book “Deployment Guide”, Chapter 6 “Installation with YaST”, Section 6.16
“Configuration of the Installed System”, Section 6.16.1 “System Configuration”, Section 6.16.1.3 “Network
Configuration”. To disable or enable IPv6 on an installed system, use the YaST Network Settings
253 Configuring IPv6 SUSE Linux Enterp… 11 SP4

module. On the Global Options tab, check or uncheck the Enable IPv6 option as necessary. If you
want to enable it temporarily until the next reboot, enter modprobe -i ipv6 as root . It is
basically impossible to unload the ipv6 module once 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.
Consult the ifcfg-tunnel (5) man page to get information about how to set up various types of
tunnels using the /etc/sysconfig/network les.

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 2640
The fundamental RFC about IPv6.
IPv6 Essentials
A book describing all the important aspects of the topic is IPv6 Essentials by Silvia Hagen
(ISBN 0-596-00125-8).

22.3 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, referred to as a fully qualified domain name (FQDN), consists of a
hostname 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 hostnames 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 just resolve hostnames. The name server also knows which host is re-
ceiving 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 with the help of YaST. If you have a modem dial-up
connection, you may not need to configure a name server manually at all. The dial-up protocol
provides the name server address as the connection is made. The configuration of name server
access with SUSE® Linux Enterprise Server is described in Section 22.4.1.4, “Configuring Hostname
and DNS”. Setting up your own name server is described in Chapter 25, The Domain Name System.
The protocol whois is closely related to DNS. With this program, quickly nd out who is re-
sponsible for any given domain.
255 Name Resolution SUSE Linux Enterp… 11 SP4

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 .
22.4 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 22.6, “Configuring a Network
Connection Manually”.
On SUSE Linux Enterprise Desktop, where NetworkManager is active by default, all network
cards are configured. If NetworkManager is not active, only the rst interface with link up (with
a network cable connected) is automatically configured. 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 System z: Hotpluggable Network Cards

On IBM System z platforms, hotpluggable network cards are supported, but not their au-
tomatic network integration via DHCP (as is the case on the PC). After detection, manu-
ally configure the interface.
22.4.1 Configuring the Network Card with YaST
To configure your wired or wireless network card in YaST, select Network Devices Network
Settings. After starting the module, YaST displays the Network Settings dialog with four tabs:
Global Options, Overview, Hostname/DNS and Routing.
256 Configuring a Network Connection with YaST SUSE Linux Enterp… 11 SP4
The Global Options tab allows you to set general networking options such as the use of Network-
Manager, IPv6 and general DHCP options. For more information, see Section 22.4.1.1, “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. If you want to manually configure a
card that was not automatically detected, see Section 22.4.1.3, “Configuring an Undetected Network
Card”. If you want to change the configuration of an already configured card, see Section 22.4.1.2,
“Changing the Configuration of a Network Card”.
The Hostname/DNS tab allows to set the hostname of the machine and name the servers to be
used. For more information, see Section 22.4.1.4, “Configuring Hostname and DNS”.
The Routing tab is used for the configuration of routing. See Section 22.4.1.5, “Configuring Routing”
for more information.
FIGURE 22.3: CONFIGURING NETWORK SETTINGS
257 Configuring the Network Card with YaST SUSE Linux Enterp… 11 SP4
22.4.1.1 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.
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 User Con-
trolled with NetworkManager. This option is well suited for switching between multiple wired
and wireless networks. If you do not run a desktop environment (GNOME or KDE), or if your
computer is a Xen server, virtual system, or provides network services such as DHCP or DNS
in your network, use the Traditional Method with ifup. 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
Chapter 27, Using NetworkManager.
In the IPv6 Protocol Settings choose whether you want to use the IPv6 protocol. It is possible
to use IPv6 together with IPv4. By default, IPv6 is activated. However, in networks not using
IPv6 protocol, response times can be faster with IPv6 protocol disabled. If you want to disable
IPv6, uncheck the Enable IPv6 option. This disables autoload of the kernel module for IPv6. This
will be applied after reboot.
In the DHCP Client Options configure options for the DHCP client. If you want the DHCP client
to ask the server to always broadcast its responses, check Request Broadcast Response. It may be
needed if your machine is moving between different networks. 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 hostname option eld when dhcpcd sends
messages to DHCP server. Some DHCP servers update name server zones (forward and reverse
records) according to this hostname (Dynamic DNS). Also, some DHCP servers require the Host-
name to Send option eld to contain a specific string in the DHCP messages from clients. Leave
AUTO to send the current hostname (that is the one defined in /etc/HOSTNAME ). Leave the
option eld empty for not sending any hostname. If yo do not want to change the default route
according to the information from DHCP, uncheck Change Default Route via DHCP.
22.4.1.2 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. For
information about wireless card configuration, see Section 19.5, “Configuration with YaST”.
22.4.1.2.1 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. On SUSE Linux Enterprise Desktop,
where NetworkManager is active by default, all network cards are configured.
Note: IBM System z and DHCP

On IBM System z 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. Specify whether the DHCP client should ask the server to always broadcast its
responses in Request Broadcast Response. This option may be needed if your machine is a mobile
client moving between networks. If you have a virtual host setup where different hosts commu-
nicate 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.
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 22.4.1.4, “Configuring Hostname
and DNS”. To configure a gateway, proceed as described in Section 22.4.1.5, “Configuring Routing”.
22.4.1.2.2 Configuring Aliases
One network device can have multiple IP addresses, called aliases.
Note: Aliases Are a Compatibility Feature

These so-called aliases resp. labels work with IPv4 only. With IPv6 they will be ignored.
Using iproute2 network interfaces can have one or more addresses.
Using YaST to set an alias 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 card
configuration module and click Edit.
2. In the Address Additional Addresses tab, click Add.
3. Enter Alias Name, IP Address, and Netmask. Do not include the interface name in the alias
name.
4. Click OK.
5. Click Next.
22.4.1.2.3 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 ease hot swapping 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
module 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.
5. Click OK and Next.
22.4.1.2.4 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 option = value . If more options are used, they should
be space-separated.
4. Click OK and Next.
22.4.1.2.5 Activating the Network Device
If you use the traditional method with ifup, 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 Network Devices 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 as soon as available. It is similar to the At Boot Time option, and only differs in
the fact 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 at all.
The On NFSroot is similar to At Boot Time, but the interface does not shut down with the
rcnetwork stop command. Use this if you use an nfs or iscsi root le system.
3. Click Next.
Usually, only the system administrator can activate and deactivate network interfaces. If you
want any user to be able to activate this interface via KInternet, select Enable Device Control for
Non-root User via KInternet.
22.4.1.2.6 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 Network Devices Network Settings
and click Edit.
2. In the General tab, select the desired entry from the Set MTU list.
3. Click Next.
22.4.1.2.7 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 “SuSEfirewall2”, Section 15.4.1 “Configuring the Firewall
with YaST”, you can determine the basic firewall setup for your device as part of the device setup.
Proceed as follows:
1. Open the YaST Network Devices 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 at
all. 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.
4. Click Next.
5. Activate the configuration by clicking OK.
22.4.1.3 Configuring an Undetected Network Card

Your card may not be detected correctly. In this case, 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 Network Devices 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. See the
ethtool manual page for available options. If the option string starts with a - (for ex-
ample -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 prepends
-s interface_name .
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 22.4.1.2, “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. Detailed information about wireless device configuration is avail-
able in Chapter 19, Wireless LAN.
6. Click Next.
7. To activate the new network configuration, click OK.
22.4.1.4 Configuring Hostname and DNS
If you did not change the network configuration during installation and the wired card was
already available, a hostname 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 Network Devices 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 hostname is global and applies to all set
network interfaces.
If you are using DHCP to get an IP address, the hostname of your computer will be auto-
matically set by the DHCP. You may want to disable this behavior if you connect to dif-
ferent networks, because they may assign different hostnames and changing the hostname
at runtime may confuse the graphical desktop. To disable using DHCP to get an IP address
uncheck Change Hostname via DHCP.
Assign Hostname to Loopback IP associates your hostname with 127.0.0.2 (loopback)
IP address in /etc/hosts . This is an useful option if you want to have the hostname
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 sufficient in most cases.
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 have 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 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 hostnames. Names specified in the Domain
Search tab are domain names used for resolving hostnames 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 hostname 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 hostname, 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
22.4.1.5 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 any other entry exists that matches the
required address, use this instead of the default route.
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
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 the IP Forwarding option in the Network Settings.
22.4.2 Modem
Tip: IBM System z: Modem

The configuration of this type of hardware is not supported on IBM System z platforms.
In the YaST Control Center, access the modem configuration under Network Devices Modem. If
your modem was not automatically detected, go to the Modem Devices tab and open the dialog
for manual configuration by clicking Add. Enter the interface to which the modem is connected
under Modem Device.
Tip: CDMA and GPRS Modems

Configure supported CDMA and GPRS modems with the YaST Modem module just as you
would configure regular modems.
267 Modem SUSE Linux Enterp… 11 SP4

FIGURE 22.4: MODEM CONFIGURATION
If you are behind a private branch exchange (PBX), you may need to enter a dial prefix. This is
often a zero. Consult the instructions that came with the PBX to nd out. Also select whether
to use tone or pulse dialing, whether the speaker should be on and whether the modem should
wait until it detects a dial tone. The last option should not be enabled if the modem is connected
to an exchange.
Under Details, set the baud rate and the modem initialization strings. Only change these settings
if your modem was not detected automatically or if it requires special settings for data transmis-
sion to work. This is mainly the case with ISDN terminal adapters. Leave this dialog by clicking
OK. To delegate control over the modem to the normal user without root permissions, activate
Enable Device Control for Non-root User via KInternet. In this way, a user without administrator
permissions can activate or deactivate an interface. Under Dial Prefix Regular Expression, specify
a regular expression. The Dial Prefix in KInternet, which can be modified by the normal user,
must match this regular expression. If this eld is left empty, the user cannot set a different Dial
Prefix without administrator permissions.
In the next dialog, select the ISP. To choose from a predefined list of ISPs operating in your
country, select Country. Alternatively, click New to open a dialog in which to provide the data
for your ISP. This includes a name for the dial-up connection and ISP as well as the login and
password provided by your ISP. Enable Always Ask for Password to be prompted for the password
each time you connect.

In the last dialog, specify additional connection options:
Dial on Demand
If you enable Dial on Demand, set at least one name server. Use this feature only if your
Internet connection is inexpensive, because there are programs that periodically request
data from the Internet.
Modify DNS when Connected

This option is enabled by default, with the effect that the name server address is updated
each time you connect to the Internet.
Automatically Retrieve DNS

If the provider does not transmit its domain name server after connecting, disable this
option and enter the DNS data manually.
Automatically Reconnect
If this options is enabled, the connection is automatically reestablished after failure.
Ignore Prompts
This option disables the detection of any prompts from the dial-up server. If the connection
build-up is slow or does not work at all, try this option.
External Firewall Interface

Selecting this option activates the firewall and sets the interface as external. This way, you
are protected from outside attacks for the duration of your Internet connection.
Idle Time-Out (seconds)

With this option, specify a period of network inactivity after which the modem disconnects
automatically.
IP Details
This opens the address configuration dialog. If your ISP does not assign a dynamic IP
address to your host, disable Dynamic IP Address then enter your host's local IP address
and the remote IP address. Ask your ISP for this information. Leave Default Route enabled
and close the dialog by selecting OK.
Selecting Next returns to the original dialog, which displays a summary of the modem configu-
ration. Close this dialog with OK.

22.4.3 ISDN
Tip: IBM System z: ISDN

Use this module to configure one or several ISDN cards for your system. If YaST did not detect
your ISDN card, click on Add in the ISDN Devices tab and manually select your card. Multiple
interfaces are possible, but several ISPs can be configured for one interface. In the subsequent
dialogs, set the ISDN options necessary for the proper functioning of the card.
FIGURE 22.5: ISDN CONFIGURATION
In the next dialog, shown in Figure 22.5, “ISDN Configuration”, select the protocol to use. The default
is Euro-ISDN (EDSS1), but for older or larger exchanges, select 1TR6. If you are in the US, select
NI1. Select your country in the relevant eld. The corresponding country code then appears in
the eld next to it. Finally, provide your Area Code and the Dial Prefix if necessary. If you do
not want to log all your ISDN traffic, uncheck the Start ISDN Log option.
270 ISDN SUSE Linux Enterp… 11 SP4

Activate Device defines how the ISDN interface should be started: At Boot Time causes the ISDN
driver to be initialized each time the system boots. Manually requires you to load the ISDN driver
as root with the command rcisdn start . On Hotplug, used for PCMCIA or USB devices, loads
the driver after the device is plugged in. When finished with these settings, select OK.
In the next dialog, specify the interface type for your ISDN card and add ISPs to an existing
interface. Interfaces may be either the SyncPPP or the RawIP type, but most ISPs operate in
the SyncPPP mode, which is described below.
FIGURE 22.6: ISDN INTERFACE CONFIGURATION
The number to enter for My Phone Number depends on your particular setup:
ISDN Card Directly Connected to Phone Outlet

A standard ISDN line provides three phone numbers (called multiple subscriber numbers,
or MSNs). If the subscriber asked for more, there may be up to 10. One of these MSNs must
be entered here, but without your area code. If you enter the wrong number, your phone
operator automatically falls back to the rst MSN assigned to your ISDN line.
ISDN Card Connected to a Private Branch Exchange

Again, the configuration may vary depending on the equipment installed:
1. Smaller private branch exchanges (PBX) built for home purposes mostly use the Eu-
ro-ISDN (EDSS1) protocol for internal calls. These exchanges have an internal S0 bus
and use internal numbers for the equipment connected to them.

Use one of the internal numbers as your MSN. You should be able to use at least one
of the exchange's MSNs that have been enabled for direct outward dialing. If this
does not work, try a single zero. For further information, consult the documentation
delivered with your phone exchange.
2. Larger phone exchanges designed for businesses normally use the 1TR6 protocol for
internal calls. Their MSN is called EAZ and usually corresponds to the direct-dial
number. For the configuration under Linux, it should be sufficient to enter the last
digit of the EAZ. As a last resort, try each of the digits from 1 to 9.
For the connection to be terminated just before the next charge unit is due, enable ChargeHUP.
However, remember that may not work with every ISP. You can also enable channel bundling
(multilink PPP) by selecting the corresponding option. Finally, you can enable the firewall for
your link by selecting External Firewall Interface and Restart Firewall. To enable the normal user
without administrator permissions to activate or deactivate the interface, select the Enable Device
Control for Non-root User via KInternet.
Details opens a dialog in which to implement more complex connection schemes which are not
relevant for normal home users. Leave the Details dialog by selecting OK.
In the next dialog, configure IP address settings. If you have not been given a static IP by your
provider, select Dynamic IP Address. Otherwise, use the elds provided to enter your host's local
IP address and the remote IP address according to the specifications of your ISP. If the interface
should be the default route to the Internet, select Default Route. Each host can only have one
interface configured as the default route. Leave this dialog by selecting Next.
The following dialog allows you to set your country and select an ISP. The ISPs included in
the list are call-by-call providers only. If your ISP is not in the list, select New. This opens the
Provider Parameters dialog in which to enter all the details for your ISP. When entering the phone
number, do not include any blanks or commas among the digits. Finally, enter your login and
the password as provided by the ISP. When finished, select Next.
To use Dial on Demand on a stand-alone workstation, specify the name server (DNS server) as
well. Most ISPs support dynamic DNS, which means the IP address of a name server is sent by
the ISP each time you connect. For a single workstation, however, you still need to provide a
placeholder address like 192.168.22.99 . If your ISP does not support dynamic DNS, specify
the name server IP addresses of the ISP. If desired, specify a time-out for the connection—the
period of network inactivity (in seconds) after which the connection should be automatically
terminated. Confirm your settings with Next. YaST displays a summary of the configured inter-
faces. To activate these settings, select OK.

22.4.4 Cable Modem
Tip: IBM System z: Cable Modem

In some countries it is quite common to access the Internet through the TV cable network. The
TV cable subscriber usually gets a modem that is connected to the TV cable outlet on one side
and to a computer network card on the other (using a 10Base-TG twisted pair cable). The cable
modem then provides a dedicated Internet connection with a xed IP address.
Depending on the instructions provided by your ISP, when configuring the network card either
select Dynamic Address or Statically Assigned IP Address. Most providers today use DHCP. A static
IP address often comes as part of a special business account.
22.4.5 DSL
Tip: IBM System z: DSL

To configure your DSL device, select the DSL module from the YaST Network Devices section.
This YaST module consists of several dialogs in which to set the parameters of DSL links based
on one of the following protocols:
PPP over Ethernet (PPPoE)
PPP over ATM (PPPoATM)
CAPI for ADSL (Fritz Cards)
Point-to-Point Tunneling Protocol (PPTP)—Austria
In the DSL Devices tab of the DSL Configuration Overview dialog, you will nd a list of installed
DSL devices. To change the configuration of a DSL device, select it in the list and click Edit. If
you click Add, you can manually configure a new DSL device.
273 Cable Modem SUSE Linux Enterp… 11 SP4

The configuration of a DSL connection based on PPPoE or PPTP requires that the corresponding
network card be set up in the correct way. If you have not done so yet, rst configure the card by
selecting Configure Network Cards (see Section 22.4.1, “Configuring the Network Card with YaST”). In
the case of a DSL link, addresses may be assigned automatically but not via DHCP, which is why
you should not enable the option Dynamic Address. Instead, enter a static dummy address for the
interface, such as 192.168.22.1 . In Subnet Mask, enter 255.255.255.0 . If you are configuring
a stand-alone workstation, leave Default Gateway empty.
Tip
Values in IP Address and Subnet Mask are only placeholders. They are only needed to
initialize the network card and do not represent the DSL link as such.
In the rst DSL configuration dialog (see Figure 22.7, “DSL Configuration”), select the PPP Mode and
the Ethernet Card to which the DSL modem is connected (in most cases, this is eth0 ). Then use
Activate Device to specify whether the DSL link should be established during the boot process.
Click Enable Device Control for Non-root User via KInternet to authorize the normal user without
root permissions to activate or deactivate the interface with KInternet.
In the next dialog select your country and choose from a number of ISPs operating in it. The
details of any subsequent dialogs of the DSL configuration depend on the options set so far,
which is why they are only briey mentioned in the following paragraphs. For details on the
available options, read the detailed help available from the dialogs.
274 DSL SUSE Linux Enterp… 11 SP4

FIGURE 22.7: DSL CONFIGURATION
To use Dial on Demand on a stand-alone workstation, also specify the name server (DNS server).
Most ISPs support dynamic DNS—the IP address of a name server is sent by the ISP each time you
connect. For a single workstation, however, provide a placeholder address like 192.168.22.99 .
If your ISP does not support dynamic DNS, enter the name server IP address provided by your
ISP.
275 DSL SUSE Linux Enterp… 11 SP4

Idle Time-Out (seconds) defines a period of network inactivity after which to terminate the con-
nection automatically. A reasonable time-out value is between 60 and 300 seconds. If Dial on
Demand is disabled, it may be useful to set the time-out to zero to prevent automatic hang-up.
The configuration of T-DSL is very similar to the DSL setup. Just select T-Online as your provider
and YaST opens the T-DSL configuration dialog. In this dialog, provide some additional infor-
mation required for T-DSL—the line ID, the T-Online number, the user code and your password.
All of these should be included in the information you received after subscribing to T-DSL.
22.4.6 IBM System z: Configuring Network Devices

SUSE Linux Enterprise Server for IBM System z supports several different types of network
interfaces. YaST can be used to configure all of them.
22.4.6.1 The qeth-hsi Device
To add a qeth-hsi (Hipersockets) interface to the installed system, start the Network De-
vices 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 (example device number format: 0.0.0600 ). 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 pressing Next and OK.
22.4.6.2 The qeth-ethernet Device
To add a qeth-ethernet (IBM OSA Express Ethernet Card) interface to the installed system,
start the Network Devices 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 num-
ber for the read, write and control channels (example device number format: 0.0.0600 ). Enter
the needed port name, port number (if applicable) and some additional options (see the Linux
for IBM System z: Device Drivers, Features, and Commands manual for reference, http://www.ib-
m.com/developerworks/linux/linux390/documentation_novell_suse.html ), your IP address, and
an appropriate netmask. Leave the network configuration with Next and OK.
276 IBM System z: Configuring Network Devices SUSE Linux Enterp… 11 SP4
22.4.6.3 The ctc Device
To add a ctc (IBM parallel CTC Adapter) interface to the installed system, start the Network
Devices Network 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
The use of this interface is deprecated. This interface will not be supported in future
versions of SUSE Linux Enterprise Server.
22.4.6.4 The lcs Device
To add an lcs (IBM OSA-2 Adapter) interface to the installed system, start the Network De-
vices 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
System z: Device Drivers, Features, and Commands manual for reference, http://www.ibm.com/de-
veloperworks/linux/linux390/documentation_novell_suse.html ), your IP address and an appro-
priate netmask. Leave the network configuration with Next and OK.
22.4.6.5 The IUCV Device
To add an iucv (IUCV) interface to the installed system, start the Network Devices 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
The use of this interface is deprecated. This interface will not be supported in future
versions of SUSE Linux Enterprise Server.
277 IBM System z: Configuring Network Devices SUSE Linux Enterp… 11 SP4
22.5 NetworkManager
NetworkManager is the ideal solution for laptops and other portable computers. With Network-
Manager, you do not need to worry about configuring network interfaces and switching between
networks when you are moving.
22.5.1 NetworkManager and ifup

However, NetworkManager is not a suitable solution for all cases, so you can still choose be-
tween the traditional method for managing network connections (ifup) and NetworkManager. If
you want to manage your network connection with NetworkManager, enable NetworkManager
in the YaST Network Settings module as described in Section 27.2, “Enabling or Disabling Network-
Manager” and configure your network connections with NetworkManager. For a list of use cases
and a detailed description of how to configure and use NetworkManager, refer to Chapter 27,
Using NetworkManager.
Some differences between ifup and NetworkManager include:
root Privileges
If you use NetworkManager for network setup, you can easily switch, stop or start your
network connection at any time from within your desktop environment using an applet.
NetworkManager also makes it possible to change and configure wireless card connections
without requiring root privileges. For this reason, NetworkManager is the ideal solution
for a mobile workstation.
Traditional configuration with ifup also provides some ways to switch, stop or start the
connection with or without user intervention, like user-managed devices. However, this
always requires root privileges to change or configure a network device. This is often a
problem for mobile computing, where it is not possible to preconfigure all the connection
possibilities.
Types of Network Connections

Both traditional configuration and NetworkManager can handle network connections with
a wireless network (with WEP, WPA-PSK, and WPA-Enterprise access) and wired networks
using DHCP and static configuration. They also support connection through dial-up, DSL
and VPN. With NetworkManager you can also connect a mobile broadband (3G) modem,
which is not possible with the traditional configuration.
278 NetworkManager SUSE Linux Enterp… 11 SP4

NetworkManager tries to keep your computer connected at all times using the best con-
nection available. If the network cable is accidentally disconnected, it tries to reconnect. It
can nd the network with the best signal strength from the list of your wireless connections
and automatically use it to connect. To get the same functionality with ifup, a great deal
of configuration effort is required.
22.5.2 NetworkManager Functionality and Configuration Files

The individual network connection settings created with NetworkManager are stored in con-
figuration profiles. The system connections configured with either NetworkManager or YaST
are saved in /etc/networkmanager/system-connections/* or in /etc/sysconfig/net-
work/ifcfg-* . Any user-defined connections are stored in GConf for GNOME or $HOME/.kde4/
share/apps/networkmanagement/* for KDE.
In case no profile is configured, NetworkManager automatically creates one and names it Auto
$INTERFACE-NAME . That is made in an attempt to work without any configuration for as many
cases as (securely) possible. If the automatically created profiles do not suit your needs, use
the network connection configuration dialogs provided by KDE or GNOME to modify them as
desired. For more information, refer to Section 27.3, “Configuring Network Connections”.
22.5.3 Controlling and Locking Down NetworkManager Features

On centrally administered machines, certain NetworkManager features can be controlled or dis-
abled with PolicyKit, for example if a user is allowed to modify administrator defined connec-
tions or if a user is allowed to define his own network configurations. To view or change the
respective NetworkManager policies, start the graphical Authorizations tool for PolicyKit. In the
tree on the left side, nd them below the network-manager-settings entry. For an introduction to
PolicyKit and details on how to use it, refer to Book “Security Guide”, Chapter 9 “PolicyKit”.
22.6 Configuring a Network Connection Manually

Manual configuration of the network software should always be the last alternative. Using YaST
is recommended. However, this background information about the network configuration can
also assist your work with YaST.
279 NetworkManager Functionality and Configuration Files SUSE Linux Enterp… 11 SP4
When the Kernel detects a network card and creates a corresponding network interface, it assigns
the device a name depending on the order of device discovery, or order of the loading of the
Kernel modules. The default Kernel device names are only predictable in very simple or tightly
controlled hardware environments. Systems which allow adding or removing hardware during
runtime or support automatic configuration of devices cannot expect stable network device
names assigned by the Kernel across reboots.
However, all system configuration tools rely on persistent interface names. This problem is
solved by udev. The udev persistent net generator ( /lib/udev/rules.d/75-persistent-net-
generator.rules ) generates a rule matching the hardware (using its hardware address by de-
fault) and assigns a persistently unique interface for the hardware. The udev database of network
interfaces is stored in the le /etc/udev/rules.d/70-persistent-net.rules . Every line in
the le describes one network interface and specifies its persistent name. System administrators
can change the assigned names by editing the NAME="" entries. The persistent rules can also
be modified using YaST.
Table 22.5, “Manual Network Configuration Scripts” summarizes the most important scripts involved
in the network configuration.
TABLE 22.5: MANUAL NETWORK CONFIGURATION SCRIPTS
Command Function
ifup, ifdown, ifstatus The if scripts start or stop network inter-

faces, or return the status of the specified in-
terface. For more information, see the ifup
manual page.
rcnetwork The rcnetwork script can be used to start,

stop or restart all network interfaces (or just
a specified one). Use rcnetwork stop to
stop, rcnetwork start to start and rc-
network restart to restart network inter-
faces. If you want to stop, start or restart just
one interface, use the command followed
by the interface name, for example rcnet-
work restart eth0 . The rcnetwork sta-
tus command displays the state of the in-
terfaces, their IP addresses and whether a
280 Configuring a Network Connection Manually SUSE Linux Enterp… 11 SP4

Command Function
DHCP client is running. With rcnetwork
stop-all-dhcp-clients and rcnetwork
restart-all-dhcp-clients you can stop
or restart DHCP clients running on network
interfaces.
For more information about udev and persistent device names, see Chapter 15, Dynamic Kernel
Device Management with udev.
22.6.1 Configuration Files

This section provides an overview of the network configuration les and explains their purpose
and the format used.
22.6.1.1 /etc/sysconfig/network/ifcfg-*
These les contain the configurations for network interfaces. They 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 le can be used in the ifcfg-* les if
a general setting should be used for only one interface. However, most of the /etc/syscon-
fig/network/config variables are global and cannot be overridden in ifcfg-les. For example
NETWORKMANAGER or NETCONFIG_* variables are global.
For ifcfg.template , see Section 22.6.1.2, “/etc/sysconfig/network/config and /etc/

sysconfig/network/dhcp”.
IBM Z IBM System z do not support USB. The names of the interface les and network aliases
contain System z-specific elements like qeth .
22.6.1.2 /etc/sysconfig/network/config and /etc/sysconfig/

network/dhcp
The le config contains general settings for the behavior of ifup , ifdown and ifstatus .
dhcp contains settings for DHCP. The variables in both configuration les are commented.
Some of the variables from /etc/sysconfig/network/config can also be used in ifcfg-*
281 Configuration Files SUSE Linux Enterp… 11 SP4

les, where they are given a higher priority. The /etc/sysconfig/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.
22.6.1.3 /etc/sysconfig/network/routes and /etc/sysconfig/

network/ifroute-*
The static routing of TCP/IP packets is determined here. All the static routes required by the
various system tasks can be entered in the /etc/sysconfig/network/routes le: routes to a
host, routes to a host via a gateway and routes to a network. For each interface that needs in-
dividual routing, define an additional configuration le: /etc/sysconfig/network/ifroute-
* . Replace * with the name of the interface. The entries in the routing configuration les look
like this:
# Destination Dummy/Gateway Netmask Device

#
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
The route's destination is in the rst column. This column may contain the IP address of a net-
work or host or, in the case of reachable name servers, the fully qualified network or hostname.
The second column contains the default gateway or a gateway through which a host or network
can be accessed. The third column contains the netmask for networks or hosts behind a gateway.
For example, the mask is 255.255.255.255 for a host behind a gateway.
The fourth column is only relevant for networks connected to the local host such as loopback,
Ethernet, ISDN, PPP and dummy device. The device name must be entered here.
An (optional) fth column can be used to specify the type of a route. Columns that are not needed
should contain a minus sign - to ensure that the parser correctly interprets the command. For
details, refer to the routes(5) man page.
The unified format for IPv4 and IPv6 now looks as follows:
prefix/lengthgateway - [interface]

And the so-called compatibility format looks accordingly:
prefixgatewaylength [interface]
For IPv4 you still can use the old format with netmask:
ipv4-networkgatewayipv4-netmask [interface]
The following examples are equivalent:
2001:db8:abba:cafe::/64 2001:db8:abba:cafe::dead - eth0

208.77.188.0/24 208.77.188.166 - eth0
2001:db8:abba:cafe:: 2001:db8:abba:cafe::dead 64 eth0

208.77.188.0 208.77.188.166 24 eth0
208.77.188.0 208.77.188.166 255.255.255.0 eth0
22.6.1.4 /etc/resolv.conf
The domain to which the host belongs is specified in this le (keyword search ). Also listed is
the status of the name server address to access (keyword nameserver ). Multiple domain names
can be specified in the le. When resolving a name that is not fully qualified, an attempt is
made to generate one by attaching the individual search entries. Multiple name servers can
be specified in multiple lines, each beginning with nameserver . Comments are preceded by #
signs. Example 22.5, “/etc/resolv.conf” shows what /etc/resolv.conf could look like.
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 hostname lookup
NETCONFIG_DNS_STATIC_SERVERS
list of name server IP addresses to use for hostname lookup
NETCONFIG_DNS_FORWARDER
defines the name of the DNS forwarder that has to be configured
To disable DNS configuration using netconfig, set NETCONFIG_DNS_POLICY='' . For more infor-
mation about netconfig , see man 8 netconfig .

EXAMPLE 22.5: /etc/resolv.conf
# Our domain
search example.com
#
# We use dns.example.com (192.168.1.116) as name server
nameserver 192.168.1.116
22.6.1.5 /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 internally
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 interface is
specified by the -i interface_name parameter. The service is specified by the -s ser-
vice_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 as DHCP or PPP are delivered directly by these tools with the
netconfig modify and netconfig remove actions. NetworkManager also uses netconfig
modify and netconfig remove actions. When NetworkManager is enabled, netconfig (in pol-
icy 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 traditional ifup
method is not supported.
For more information about netconfig , see man 8 netconfig .
22.6.1.6 /etc/hosts
In this le, shown in Example 22.6, “/etc/hosts”, IP addresses are assigned to hostnames. 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 hostname, and
the hostname 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 22.6: /etc/hosts
127.0.0.1 localhost
192.168.2.100 jupiter.example.com jupiter
192.168.2.101 venus.example.com venus
22.6.1.7 /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 22.7, “/etc/networks”.
EXAMPLE 22.7: /etc/networks
loopback 127.0.0.0
localnet 192.168.0.0

22.6.1.8 /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 . A parameter must always stand alone
in its own line. Comments are preceded by a # sign. Table 22.6, “Parameters for /etc/host.conf”
shows the parameters available. A sample /etc/host.conf is shown in Example 22.8, “/etc/
host.conf”.
TABLE 22.6: 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 hostname after hostname resolu-
tion (as long as the hostname includes the
domain 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 22.8: /etc/host.conf
# We have named running

order hosts bind

# Allow multiple address
multi on
22.6.1.9 /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 22.9, “/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 22.9: /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 22.7, “Databases Available via /etc/nss-
witch.conf”.
The configuration options for NSS databases are listed in Table 22.8, “Configuration Options for NSS
“Databases””.
TABLE 22.7: DATABASES AVAILABLE VIA /ETC/NSSWITCH.CONF
aliases Mail aliases implemented by sendmail ; see

man 5 aliases .

ethers Ethernet addresses.
netmasks List of network and their subnet masks. Only

needed, if you use subnetting.
group For user groups used by getgrent . See also

the man page for group .
hosts For hostnames and IP addresses, used by

gethostbyname and similar functions.
netgroup Valid host and user lists in the network for

the purpose of controlling access permis-
sions; see the netgroup(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 22.8: 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
22.6.1.10 /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 and groups 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 or groups. hosts
is not cached by default, because the mechanism in nscd to cache hosts makes the local system
unable to trust forward and reverse lookup checks. Instead of asking nscd to cache names, set
up a caching DNS server.
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 the command
rcnscd restart .
22.6.1.11 /etc/HOSTNAME
This contains the fully qualified hostname with the domain name attached. This le is read
by several scripts while the machine is booting. It must contain only one line (in which the
hostname is set).
22.6.2 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. Older
configuration tools, ifconfig and route , are also available.
289 Testing the Configuration SUSE Linux Enterp… 11 SP4

The commands ip , ifconfig and route change the network configuration directly without
saving it in the configuration le. Unless you enter your configuration in the correct configura-
tion les, the changed network configuration is lost on reboot.
22.6.2.1 Configuring a Network Interface with ip
ip is a tool to show and configure network devices, routing, policy routing, and tunnels.
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 a 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 .
22.6.2.2 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, which
indicates that the network link is basically 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 22.10, “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 hostname 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 22.10: 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
22.6.2.3 Configuring the Network with ifconfig
ifconfig is a network configuration tool.
Note: ifconfig and ip

The ifconfig tool is obsolete. Use ip instead. In contrast to ip , you can use ifconfig
only for interface configuration. It limits interface names to 9 characters.

Without arguments, ifconfig displays the status of the currently active interfaces. As you can
see in Example 22.11, “Output of the ifconfig Command”, ifconfig has very well-arranged and
detailed output. The output also contains information about the MAC address of your device
(the value of HWaddr ) in the rst line.
EXAMPLE 22.11: OUTPUT OF THE ifconfig COMMAND
eth0 Link encap:Ethernet HWaddr 00:08:74:98:ED:51

inet6 addr: fe80::208:74ff:fe98:ed51/64 Scope:Link
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:634735 errors:0 dropped:0 overruns:4 frame:0
TX packets:154779 errors:0 dropped:0 overruns:0 carrier:1
collisions:0 txqueuelen:1000
RX bytes:162531992 (155.0 Mb) TX bytes:49575995 (47.2 Mb)
Interrupt:11 Base address:0xec80
lo Link encap:Local Loopback

inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX bytes:533234 (520.7 Kb) TX bytes:533234 (520.7 Kb)
wlan1 Link encap:Ethernet HWaddr 00:0E:2E:52:3B:1D

inet addr:192.168.2.4 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::20e:2eff:fe52:3b1d/64 Scope:Link
UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
RX bytes:45978185 (43.8 Mb) TX bytes:7526693 (7.1 MB)
For more options and information about using ifconfig , enter ifconfig -h or see the if-
config (8) man page.
22.6.2.4 Configuring Routing with route
route is a program for manipulating the IP routing table. You can use it to view your routing
configuration and to add or remove routes.

Note: route and ip
The program route is obsolete. Use ip instead.
route is especially useful if you need quick and comprehensible information about your routing
configuration to determine problems with routing. To view your current routing configuration,
enter route -n as root .
EXAMPLE 22.12: OUTPUT OF THE route -n COMMAND
route -n
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
10.20.0.0 * 255.255.248.0 U 0 0 0 eth0
link-local * 255.255.0.0 U 0 0 0 eth0
loopback * 255.0.0.0 U 0 0 0 lo
default styx.exam.com 0.0.0.0 UG 0 0 0 eth0
For more options and information about using route, enter route -h or see the route (8)
man page.
22.6.3 Start-Up Scripts
Apart from the configuration les described above, there are also various scripts that load the
network programs while the machine is booting. These are started as soon as the system is
switched to one of the multiuser runlevels. Some of these scripts are described in Table 22.9, “Some
Start-Up Scripts for Network Programs”.
294 Start-Up Scripts SUSE Linux Enterp… 11 SP4

TABLE 22.9: SOME START-UP SCRIPTS FOR NETWORK PROGRAMS
/etc/init.d/network This script handles the configuration of the

network interfaces. If the network service
was not started, no network interfaces are
implemented.
/etc/init.d/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.
/etc/init.d/rpcbind Starts the rpcbind utility that converts RPC

program numbers to universal addresses. It
is needed for RPC services, such as an NFS
server.
/etc/init.d/nfsserver Starts the NFS server.
/etc/init.d/postfix Controls the postfix process.
/etc/init.d/ypserv Starts the NIS server.
/etc/init.d/ypbind Starts the NIS client.
22.7 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.
295 Setting Up Bonding Devices SUSE Linux Enterp… 11 SP4

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 Domain0. 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 Network Devices Network Settings.
2. Use Add and change the Device Type to Bond. Proceed with Next.
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.
296 Setting Up Bonding Devices SUSE Linux Enterp… 11 SP4

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
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 .
22.7.1 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'
297 Hotplugging of Bonding Slaves SUSE Linux Enterp… 11 SP4

but 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.
STARTMODE=hotplug causes the slave interface to join the bond automatically as soon as it is
available.
The udev rules in /etc/udev/rules.d/70-persistent-net.rules have 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 to allow to replacement of defective hardware (a
network card in the same slot but with a different MAC), and to avoid confusion as 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, /etc/init.d/network 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 interfaces
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.
22.8 smpppd as Dial-up Assistant

Some home users do not have a dedicated line connecting them to the Internet. Instead, they
use dial-up connections. Depending on the dial-up method (ISDN or DSL), the connection is
controlled by ipppd or pppd. Basically, all that needs to be done to go online is to start these
programs correctly.
298 smpppd as Dial-up Assistant SUSE Linux Enterp… 11 SP4

If you have a at-rate connection that does not generate any additional costs for the dial-up
connection, simply start the respective daemon. Control the dial-up connection with a desktop
applet or a command-line interface. If the Internet gateway is not the host you are using, you
might want to control the dial-up connection by way of a network host.
This is where smpppd (SUSE Meta PPP Daemon) is involved. It provides a uniform interface for
auxiliary programs and acts in two directions. First, it programs the required pppd or ipppd and
controls its dial-up properties. Second, it makes various providers available to the user programs
and transmits information about the current status of the connection. As smpppd can also be
controlled by way of the network, it is suitable for controlling dial-up connections to the Internet
from a workstation in a private subnetwork.
22.8.1 Configuring smpppd

The connections provided by smpppd are automatically configured by YaST. The actual dial-up
programs KInternet and cinternet are also pre-configured. Manual settings are only required to
configure additional features of smpppd such as remote control.
The configuration le of smpppd is /etc/smpppd.conf . By default, it does not enable remote
control. The most important options of this configuration le are:
open-inet-socket = yes|no
To control smpppd via the network, set this option to yes . smpppd listens on port 3185 . If
this parameter is set to yes , the parameters bind-address , host-range and password
must be set accordingly.
bind-address = ip address
If a host has several IP addresses, use this parameter to determine at which IP address
smpppd should accept connections. The default is to listen at all addresses.
host-range = min ip max ip

The parameter host-range defines a network range. Hosts whose IP addresses are within
this range are granted access to smpppd. All hosts not within this range are denied access.
password = password
By assigning a password, limit the clients to authorized hosts. As this is a plain-text pass-
word, you should not overrate the security it provides. If no password is assigned, all clients
are permitted to access smpppd.
slp-register = yes|no
299 Configuring smpppd SUSE Linux Enterp… 11 SP4

With this parameter, the smpppd service can be announced in the network via SLP.
More information about smpppd is available in the smpppd(8) and smpppd.conf(5) man
pages.
22.8.2 Configuring cinternet for Remote Use
cinternet can be used to control a local or remote smpppd. cinternet is the command-line coun-
terpart to the graphical KInternet. To prepare these utilities for use with a remote smpppd, edit
the configuration le /etc/smpppd-c.conf manually or using cinternet. This le only uses
four options:
sites = list of sites

list of sites where the front-ends search for smpppd. The front-ends test the options
in the order specified here. local orders the establishment of a connection to the local
smpppd. gateway points to an smpppd on the gateway. config-file indicates that the
connection should be established to the smpppd specified in the server and port options
in /etc/smpppd-c.conf . slp orders the front-ends to connect to an smpppd found via
SLP.
server = server
The host on which smpppd runs.
port = port
The port on which smpppd runs.
password = password
The password selected for smpppd.
If smpppd is active, try to access it. For example, with cinternet --verbose --inter-
face-list . In case of difficulties at this point, refer to the smpppd-c.conf(5) and cinter-
net(8) man pages.
300 Configuring cinternet for Remote Use SUSE Linux Enterp… 11 SP4
23 SLP Services in the Network
The service location protocol (SLP) was developed to simplify the configuration of
networked clients within a local network. To configure a network client, including
all required services, the administrator traditionally needs detailed knowledge of
the servers available in the network. SLP makes the availability of selected services
known to all clients in the local network. Applications that support SLP can use the
information distributed and 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. YaST and Konqueror
both have appropriate front-ends 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.
Important: SLP Support in SUSE Linux Enterprise Server

Services that offer SLP support include cupsd, rsyncd, ypserv, openldap2, ksysguardd,
saned, kdm, vnc, login, smpppd, rpasswd , postfix, and sshd (via sh).
23.1 Installation
All packages necessary are installed by default. However, if you want to provide services via
SLP, check that the package openslp-server is installed.
23.2 Activating SLP

slpd must run on your system to offer services with SLP. If the machine should only operate as
client, and does not offer services, it is not necessary to run slpd. Like most system services in
SUSE Linux Enterprise Server, the slpd daemon is controlled by means of a separate init script.
After the installation, the daemon is inactive by default. To activate it temporarily, run rcslpd
start as root or rcslpd stop to stop it. Perform a restart or status check with restart
or status . If slpd should be always active after booting, enable slpd in YaST System System
Services (Runlevel) or run the insserv slpd command as root .
301 Installation SUSE Linux Enterp… 11 SP4

23.3 SLP Front-Ends in SUSE Linux Enterprise Server
To nd services provided via SLP in your network, use an SLP front-end such as slptool
( openslp package) or YaST:
slptool
slptool is a command line program that can be used to announce SLP inquiries in the
network or announce proprietary services. slptool --help lists all available options and
functions. For example, to nd all time servers that announce themselves in the current
network, run the command:
slptool findsrvs service:ntp
YaST
YaST also provides an SLP browser. However, this browser is not available from the YaST
Control Center. To start it, run yast2 slp as root user. Click on a Service Type on the
lefthand side to get more information about a service.
23.4 Installation over SLP

If you have an installation server with SUSE Linux Enterprise Server installation media with-
in your network, this can be registered and offered with SLP. For details, see Book “Deploy-
ment Guide”, Chapter 14 “Remote Installation”, Section 14.2 “Setting Up the Server Holding the Installation
Sources”. If SLP installation is selected, linuxrc starts an SLP inquiry after the system has booted
from the selected boot medium and displays the sources found.
23.5 Providing Services via SLP

Many applications in SUSE Linux Enterprise Server have integrated SLP support through the
use of 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. This is an example for registering
a scanner service:
## Register a saned service on this system
302 SLP Front-Ends in SUSE Linux Enterprise Server SUSE Linux Enterp… 11 SP4
## 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 hostname. 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.
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 deregister an existing
service offering without restarting slpd.

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 nd more information in the Programmers Guide that is included in the openslp-
devel package.

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 the help of 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 facilitates 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.
Now and On Boot

Select Now and On Boot to start ntpd automatically when the system is booted. This setting
is strongly recommended. Then configure the server as described Section 24.1.2, “Changing
Basic Configuration”.
305 Configuring an NTP Client with YaST SUSE Linux Enterp… 11 SP4
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 pull-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
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 .
306 Changing Basic Configuration SUSE Linux Enterp… 11 SP4

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 activated. This 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 disallowing
remote computers to view and modify NTP settings of your computer and to use the trap facility
for remote event logging. Once 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 rcntp start , 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 as soon as 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 Network
Manager with an encrypted WLAN.
If you want ntpd to resolve DNS names at runtime, you must set the dynamic option. Then,
when the network is establish some time 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.
309 Manually Configuring NTP in the Network SUSE Linux Enterp… 11 SP4
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.
310 Setting Up a Local Reference Clock SUSE Linux Enterp… 11 SP4

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 in sync.
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
311 Clock Synchronization to an External Time Reference (ETR) SUSE Linux Enterp… 11 SP4
25 The Domain Name System
DNS (domain name system) is needed to resolve the domain names and hostnames
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 22.3, “Name Resolution”. The following configu-
ration examples refer to BIND.
25.1 DNS Terminology
Zone
The domain namespace is divided into regions called zones. For instance, 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 ).
Record
312 DNS Terminology SUSE Linux Enterp… 11 SP4

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.
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.
25.3.1 Wizard Configuration

The wizard consists of three steps or dialogs. At the appropriate places in the dialogs, you are
given the opportunity to 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 Netconfig DNS Policy decides
which devices should provide forwarders or whether you want to supply your own For-
warder List. For more information about netconfig, see man 8 netconfig .
FIGURE 25.1: DNS SERVER INSTALLATION: FORWARDER SETTINGS
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.
314 Wizard Configuration SUSE Linux Enterp… 11 SP4

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”.
FIGURE 25.3: DNS SERVER INSTALLATION: FINISH WIZARD
315 Wizard Configuration SUSE Linux Enterp… 11 SP4

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 as soon as it is
restarted or prompted to reload its configuration.
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 entry eld. 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 systemwide log le /var/log/messages 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 logfile versions to store.
316 Expert Configuration SUSE Linux Enterp… 11 SP4

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 hostname then select its
type. A-Record represents the main entry. The value for this should be an IP address.
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.
Note: 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 Do-
main) comes pre-configured so it can be started right after installation without any problems. If
you already have a functioning Internet connection and have entered 127.0.0.1 as the name
server address for localhost in /etc/resolv.conf , you normally already have a working
name resolution without needing to know the DNS of the provider. BIND carries out name res-
olution 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 for-
warders to ensure 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 rcnamed start as root . If “done” appears to the
right in green then 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 at all. For the rst test, enter host 127.0.0.1 , which should always work. If you get
322 Starting the BIND Name Server SUSE Linux Enterp… 11 SP4
an error message, use rcnamed status to see whether the server is actually running. If the
name server does not start or behaves unexpectedly, you can usually nd the cause in the log
le /var/log/messages .
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 just ex-
amples. 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;
};
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 rcnamed reload . Achieve
the same by stopping and restarting the name server with rcnamed restart . Stop the server
at any time by entering rcnamed stop .
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 hostnames, 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 {
323 The /etc/named.conf Configuration File SUSE Linux Enterp… 11 SP4

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";
};
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.
324 Important Configuration Options SUSE Linux Enterp… 11 SP4

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 ).
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 /var/log/messages . 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
/var/log/messages 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.
325 Important Configuration Options SUSE Linux Enterp… 11 SP4

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; };
};
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; };
};
326 Logging SUSE Linux Enterp… 11 SP4

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.
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 at all. 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 hostnames and the other does
the reverse: it supplies a hostname for an IP address.
Tip: Using the Dot (Period, Fullstop) in Zone Files

The "." has an important meaning in the zone les. If hostnames are given without a
final . , the zone is appended. Complete hostnames specified with a full domain name
must end with a . 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.
327 Zone Files SUSE Linux Enterp… 11 SP4

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
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 hostname is the preference value. If there are multiple MX entries, the
mail server with the smallest value is taken rst and, if mail delivery to this server fails,
an attempt is made with the next higher value.
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 just 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 pseudodomain in-addr.arpa is used for the reverse lookup of IP addresses into hostnames.
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 hostnames.
Therefore, all hostnames 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.
331 Dynamic Update of Zone Data SUSE Linux Enterp… 11 SP4

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 the help of 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
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"
332 Secure Transactions SUSE Linux Enterp… 11 SP4

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 .
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 gen-
erated with dnssec-keygen , just like 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 .
333 DNS Security SUSE Linux Enterp… 11 SP4

For additional information, refer to the BIND Administrator Reference Manual from package
bind-doc , which is installed under /usr/share/doc/packages/bind/ . Consider additionally
consulting 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.

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 each and
every workstation. A host configured to use DHCP does not have control over its
own static address. It is enabled to configure itself completely and automatically ac-
cording to directions from the server. If you use the NetworkManager on the client
side, you do not need to configure the client at all. This is useful if you have chang-
ing environments and only one interface active at a time. Never use NetworkManag-
er on a machine that runs a DHCP server.
Tip: IBM System z: DHCP Support

On IBM System z 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 .

A DHCP server supplies not only the IP address and the netmask, but also the hostname, domain
name, gateway, and name server addresses for the client to use. In addition to that, DHCP allows
a number of 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. If you want to use LDAP, set up your LDAP environment before configuring the
DHCP server.
For more information about LDAP, see Book “Security Guide”, Chapter 4 “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”.
336 Configuring a DHCP Server with YaST SUSE Linux Enterp… 11 SP4
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 entry elds, 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”.
337 Initial Configuration (Wizard) SUSE Linux Enterp… 11 SP4

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 entry elds pro-
vided 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 up-
per 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 behind bars in the chroot jail,
which prevents him from touching 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.
341 DHCP Server Configuration (Expert) SUSE Linux Enterp… 11 SP4

FIGURE 26.6: DHCP SERVER: CHROOT JAIL AND DECLARATIONS
Selecting the Declaration Type

The Global Options of the DHCP server are made up of a number of 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 subnetwork (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 list to choose 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
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 your product. The DHCP server
available is dhcpd (published by the Internet Systems Consortium). On the client side, choose
between two different DHCP client programs: dhcp-client (also from ISC) and the DHCP client
daemon in the dhcpcd package.
346 DHCP Software Packages SUSE Linux Enterp… 11 SP4

By default, dhcpcd is installed. The program is very easy to handle and is launched automati-
cally on each system boot to watch for a DHCP server. It does not need a configuration le to do
its job and works 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 le /etc/dhclient.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 ).
347 The DHCP Server dhcpd SUSE Linux Enterp… 11 SP4

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 hostnames 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 hostname 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
delivered to a host on the local network (according to the source and target host address
and the subnet mask provided). In most cases, 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 as well as 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 command
rcdhcpd start . It will be ready for use immediately. Use the command rcdhcpd 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
/var/log/messages or on console 10 ( Ctrl – Alt – F10 ).
348 The DHCP Server dhcpd SUSE Linux Enterp… 11 SP4

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 rcdhcpd start 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 hostname 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.
349 Clients with Fixed IP Addresses SUSE Linux Enterp… 11 SP4

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 hostnames 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 hostnames).
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-ng
daemon, there is an additional entry SYSLOGD_ADDITIONAL_SOCKET_DHCP in the le /etc/
sysconfig/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.
350 The SUSE Linux Enterprise Server Version SUSE Linux Enterp… 11 SP4
27 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.
27.1 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.
27.2 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 Network Devices Network Settings.
2. The Network Settings dialog opens. Go to the Global Options tab.
351 Use Cases for NetworkManager SUSE Linux Enterp… 11 SP4

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 27.3, “Configuring Network Connections”.
4. To deactivate NetworkManager and control the network in the traditional way:
a. In the Network Setup Method eld, choose Traditional Method with ifup.
b. Click OK.
c. Set up your network card with YaST using automatic configuration via DHCP or a
static IP address. Alternatively, configure your modem with YaST:
For dial-up connections, use Network Devices Modem.
To configure an internal or USB ISDN modem, select Network Devices ISDN.
To configure an internal or USB DSL modem, select Network Devices DSL.
Find a detailed description of the network configuration with YaST in Section 22.4,

“Configuring a Network Connection with YaST” and Chapter 19, Wireless LAN.
27.3 Configuring Network Connections

After having enabled NetworkManager in YaST, configure your network connections with the
NetworkManager front-ends available in KDE and GNOME. The network configuration dialogs
for both front-ends are very similar. They show tabs for all types of network connections, such
as wired, wireless, mobile broadband, DSL, and VPN connections. On each tab, you can add,
edit or delete connections of that type. In the KDE configuration dialog, the appropriate tabs
are only active if the connection type is available on your system (depending on hardware and
software). By default, KNetworkManager also displays comprehensive tool tips for the input
elds and options available on each tab.
352 Configuring Network Connections SUSE Linux Enterp… 11 SP4

Note: Bluetooth Connections
Currently, Bluetooth connections cannot be configured with NetworkManager.
To open the network configuration dialog in GNOME, open the main menu and click the Network
entry at the right. Alternatively, press Alt – F2 and enter nm-connection-editor or select
System Network Connections in the GNOME Control Center.
FIGURE 27.1: GNOME NETWORK CONNECTIONS DIALOG
If you use KDE, open the main menu and click Configure Desktop. In the Personal Settings, select
Network Settings (on the General tab) to open the network configuration dialog.
FIGURE 27.2: KDE NETWORK CONFIGURATION DIALOG

Alternatively, you can also start the configuration dialogs from the NetworkManager applet in
the system tray. In KDE, left-click the icon and select Manage Connections. In GNOME, right-
click the icon and select Edit Connections.
Note: Availability of Options

Depending on your system set-up, you may not be allowed to configure connections. In
a secured environment, some options might be locked or require root permission. Ask
your system administrator for details.
PROCEDURE 27.1: ADDING OR EDITING CONNECTIONS
When configuring network connections with NetworkManager, you can also define sys-
tem connections that can be shared by all users. In contrast to user connections ,
system connections are made available right after NetworkManager is started—before any
users log in. For more details about both types of connections, refer to Section 27.7.1, “User
and System Connections”.
Currently, the system connection option is not available in KDE. To set up system
connections, you need to use YaST in this case.
Note: Hidden Networks

To connect to a “hidden” network (a network that does not broadcast its service)
you have to know the Service Set Identifier (SSID) or Extended Service Set Identifier
(ESSID) of the network. Hidden networks cannot be detected automatically.
1. In the network configuration dialog, click the tab for the connection type you want to use.
2. Click Add to create a new connection or select an existing connection and click Edit.
3. Enter a Connection Name and your connection details.
4. For a hidden network, enter the ESSID and the encryption parameters.
5. You can tie the connection to a certain device, if more than one physical device per con-
nection type is available (for example, your machine is equipped with two ethernet cards
or two wireless cards).
If you use KDE, do so by using the Restrict to Interface option. If you use GNOME, enter the
MAC address of the device you want to tie the connection to and confirm your settings.

6. For NetworkManager to automatically use a certain connection, activate the following
option for this connection: Connect Automatically (KDE) or Stay connected when possible
(GNOME).
7. To turn a connection into a system connection activate Available to all users (GNOME).
To create and edit system connections, root permission is required.
After having confirmed your changes, the newly configured network connection appears in the
list of available networks you get by left-clicking the NetworkManager applet.
FIGURE 27.3: KNETWORKMANAGER—CONFIGURED AND AVAILABLE CONNECTIONS
27.4 Using KNetworkManager

The KDE front-end for NetworkManager is the KNetworkManager applet. If the network has been
set up for NetworkManager control, the applet usually starts automatically with the desktop
environment and is shown as an icon in the system tray.
If your system tray does not show any network connection icon, the applet is probably not
started. Press Alt – F2 and enter knetworkmanager to start it manually.
KNetworkManager only shows wireless networks that you have configured a connection for. It
hides connections when you are out of range of a wireless network, or when the network cable
is disconnected, thus always giving you a clear view of which connections may be used.
27.4.1 Managing Wired Network Connections

If your computer is connected to an existing network with a network cable, use KNetworkMan-
ager to choose the network connection.
1. Left-click the applet icon to show a menu with available networks. The connection cur-
rently being used is selected in the menu and marked as Active.
355 Using KNetworkManager SUSE Linux Enterp… 11 SP4

2. If you want to use a different configuration with the wired network, click Manage Connec-
tions and add another wired connection as described in Procedure 27.1, “Adding or Editing
Connections”.
3. Click the KNetworkManager icon and select the newly configured connection to activate it.
27.4.2 Managing Wireless Network Connections

By default, KNetworkManager only shows wireless networks that you have configured a con-
nection for—provided they are both available and visible. To connect to a wireless network for
the rst time, proceed as follows:
PROCEDURE 27.2: CONNECTING TO A WIRELESS NETWORK
1. Left-click the applet icon and select Create Network Connection. KNetworkManager shows
a list of available visible wireless networks, including details about signal strength and
security.
2. To connect to a visible network, select the network from the list and click Connect. If the
network is encrypted, a dialog opens. Choose the type of Security the network uses and
enter the appropriate credentials.
3. To connect to a network that does not broadcast its service set identifier (SSID or ESSID)
and therefore cannot be detected automatically, select Connect to Other Network with WLAN
interface.
4. In the dialog that opens, enter the SSID or ESSID and set encryption parameters, if nec-
essary.
5. Confirm your changes and click OK. NetworkManager now activates the new connection.
6. To terminate a connection and to disable wireless networking, click the applet icon and
uncheck Enable Wireless. This can be useful if you are on a plane or in any other environ-
ment where wireless networking is not allowed.
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 Connect
Automatically will be connected, while the wireless connection remains up.
356 Managing Wireless Network Connections SUSE Linux Enterp… 11 SP4

27.4.3 Configuring Your Wireless Card as an Access Point
If your wireless card supports access point mode, you can use NetworkManager for configura-
tion.

Depending on your system setup, you may not be allowed to configure connections. In
1. Click the KNetworkManager applet and select Create Network Connection New Ad-Hoc
Network.
2. In the following configuration dialog, enter a name for your network in the SSID eld.
3. Set the encryption on the Wireless Security tab.
357 Configuring Your Wireless Card as an Access Point SUSE Linux Enterp… 11 SP4
Important: Unprotected Wireless Networks Are a Security
Risk
If you set Security to None , everybody can connect to your network, reuse your
connectivity and intercept your network connection. To restrict access to your ac-
cess point and to secure your connection, use encryption. You can choose between
various WEP and WPA–based encryptions. If you are not sure which technology is
best for you, read Section 19.3, “Authentication”.
4. On the IP Address tab, make sure the Configure option is set to Shared (which is the default
option for ad-hoc networks).
5. Confirm your configuration with OK.
27.4.4 Customizing KNetworkManager

You can customize some aspects of KNetworkManager: the number of icons displayed in the
system tray, which tool tips to show and how to store your password and credentials for network
connections. For more information about the last aspect, refer to Section 27.7.2, “Storing Passwords
and Credentials”.
To explore the options available, right-click the NetworkManager system tray icon, select Man-
age Connections and click Other on the left-hand side of the configuration dialog.
PROCEDURE 27.3: CONFIGURING MULTIPLE TRAY ICONS FOR KNETWORKMANAGER
As KNetworkManager can keep multiple connections active at once, you might wish to
be informed about the connection status for several connections at one glance. You can
do so by using multiple NetworkManager icons in your system tray, each representing a
different group of connection types (for example, one icon for wired connections, another
icon for wireless connections).
1. In the configuration dialog, switch to the Tray Icon tab.
2. Click More Icons. A new icon entry appears in the list.
3. Select the network connection types you want to be represented by this icon and group
them under the respective icon.
358 Customizing KNetworkManager SUSE Linux Enterp… 11 SP4

4. Confirm your changes.
Now the system tray shows multiple NetworkManager icons from which you then can access
the connection types tied to that icon.
When configuring a network connection as described in Procedure 27.1, “Adding or Editing Connec-
tions”, KNetworkManager also allows you to customize the icon displayed for this connection.
To change the icon, click the icon button next to Connection Name and in the following dialog,
select the icon of your choice. After confirming your changes, the new icon is displayed in the
list of available connections you get by clicking the KNetworkManager icon in the system tray.
27.5 Using the GNOME NetworkManager Applet

In GNOME, NetworkManager can be controlled with the GNOME NetworkManager applet. If
the network is set up for NetworkManager control, the applet usually starts automatically with
the desktop environment and is shown as an icon in the system tray.
If your system tray does not show any network connection icon, the applet is probably not
started. Press Alt – F2 and enter nm-applet to start it manually.
27.5.1 Managing Wired Network Connections

If your computer is connected to an existing network with a network cable, use the Network-
Manager applet to choose the network connection.
359 Using the GNOME NetworkManager Applet SUSE Linux Enterp… 11 SP4
1. Left-click the applet icon to show a menu with available networks. The currently used
connection is selected in the menu.
2. To switch to another network, choose it from the list.
3. To switch o all network connections, both wired and wireless, right-click the applet icon
and uncheck Enable Networking.
27.5.2 Managing Wireless Network Connections

Available visible wireless networks are listed in the GNOME NetworkManager applet menu un-
der Wireless Networks. The signal strength of each network is also shown in the menu. Encrypted
wireless networks are marked with a shield icon.
PROCEDURE 27.4: CONNECTING TO A WIRELESS NETWORK
1. To connect to a wireless network, left-click the applet icon and choose an entry from the
list of available wireless networks.
2. If the network is encrypted, a dialog opens. It shows the type of encryption the network
uses (Wireless Security) and holds a number of input elds according to the respective
encryption and authentication settings. Enter the appropriate credentials.
3. To connect to a network that does not broadcast its service set identifier (SSID or ESSID)
and therefore cannot be detected automatically, left-click the NetworkManager icon and
choose Connect to Hidden Wireless Network.
4. In the dialog that opens, enter the SSID or ESSID in Network Name and set encryption
parameters if necessary.
5. To disable wireless networking, right-click the applet icon and uncheck Enable Wireless.
This can be useful if you are on a plane or in any other environment where wireless
networking is not allowed.
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.
360 Managing Wireless Network Connections SUSE Linux Enterp… 11 SP4

27.5.3 Configuring Your Wireless Card as an Access Point
If your wireless card supports access point mode, you can use NetworkManager for configura-
tion.

Depending on your system setup, you may not be allowed to configure connections. In
1. Click the NetworkManager applet and select Create New Wireless Network.
2. Enter a Network Name and set the encryption to use with the Wireless Security drop-down
list.
Important: Unprotected Wireless Networks Are a Security

Risk
If you set Wireless Security to None , everybody can connect to your network, reuse
your connectivity and intercept your network connection. To restrict access to your
access point and to secure your connection, use encryption. You can choose between
various WEP and WPA–based encryptions. If you are not sure which technology is
best for you, read Section 19.3, “Authentication”.
361 Configuring Your Wireless Card as an Access Point SUSE Linux Enterp… 11 SP4
27.6 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.
NovellVPN
To use this VPN technology, install
NetworkManager-novellvpn and
NetworkManager-novellvpn-kde4 or NetworkManager-novellvpn-gnome .
NovellVPN support for KDE is not available yet, but is currently being worked on.
OpenVPN
NetworkManager-openvpn and
NetworkManager-openvpn-kde4 or NetworkManager-openvpn-gnome .
vpnc (Cisco)
NetworkManager-vpnc and
NetworkManager-vpnc-kde4 or NetworkManager-vpnc-gnome .
PPTP (Point-to-Point Tunneling Protocol)

NetworkManager-pptp and
NetworkManager-pptp-kde4 or NetworkManager-pptp-gnome .
After you have installed the packages, configure your VPN connection as described in Section 27.3,
“Configuring Network Connections”.
362 NetworkManager and VPN SUSE Linux Enterp… 11 SP4

27.7 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.
27.7.1 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 27.3, “Configuring Network Connections”.
For KDE, configuring system connections with NetworkManager are currently not supported
(use YaST instead).
27.7.2 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 desktop-specific tools GNOME Keyring Manager or KWalletManager
to store your credentials encrypted on the disk, secured by a master password.
363 NetworkManager and Security SUSE Linux Enterp… 11 SP4

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”.
27.8 Frequently Asked Questions

In the following, nd some frequently asked questions about configuring special network options
with NetworkManager.
How to tie a connection to a specific device?

By default, connections in NetworkManager are device type-specific: they apply to all phys-
ical 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 so 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 ifconfig ). 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.
If you are using KDE, start the dialog for configuring network connections and choose the
connection you want to modify. On the Ethernet or Wireless tab, use the Restrict to Interface
option to select the network interface to which to tie the connection.
How to specify a certain access point in case multiple access points with the same ESSID are
detected?
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 27.3, “Configur-
ing Network Connections”. Choose the wireless connection you want to modify and click Edit.
On the Wireless tab, enter the BSSID.
How to share network connections to other computers?
364 Frequently Asked Questions SUSE Linux Enterp… 11 SP4

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 27.3, “Con-
figuring Network Connections”. Choose the connection you want to modify and click
Edit. If you are using GNOME, switch to the IPv4 Settings tab and from the Method
drop-down list, choose Shared to other computers. If you are using KDE, switch to the
IP Address tab and from the Configure drop-down list, choose Shared. 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.
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 override
it. Start the dialog for configuring network connections as described in Section 27.3, “Con-
figuring Network Connections”. Choose the connection you want to modify and click Edit. If
you are using GNOME, switch to the IPv4 Settings tab, and from the Method drop-down
list, choose Automatic (DHCP) addresses only. If you are using KDE, switch to the IP Address
tab, and from the Configure drop-down list, choose Automatic (DHCP) addresses only. Enter
the DNS information in the DNS Servers and Search Domains elds. To Ignore automatically
obtained routes click Routes (GNOME) and activate the respective check box, or from the
drop-down list at the bottom of the tab (KDE), select Routes and activate the respective
check box. Confirm your changes.
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 27.7, “NetworkManager and Security”.
365 Frequently Asked Questions SUSE Linux Enterp… 11 SP4

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 GNOME and KDE NetworkManager applets start 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 27.2, “Enabling or Disabling NetworkManager”. Then
make sure that the appropriate package for your desktop environment is also installed.
If you are using KDE 4, the package is NetworkManager-kde4 . For GNOME users the
package is NetworkManager-gnome .
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 (GNOME) or knetworkmanager (KDE).
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 27.6, “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 rcnetwork restart .

More information about NetworkManager can be found on the following Web sites and direc-
tories:
NetworkManager Project Page

http://projects.gnome.org/NetworkManager/
KDE NetworkManager Front-End

http://userbase.kde.org/NetworkManagement
Package Documentation
Also check out the information in the following directories for the latest information about
NetworkManager and the GNOME and KDE NetworkManager applets:
/usr/share/doc/packages/NetworkManager/ ,
/usr/share/doc/packages/NetworkManager-kde4/ , and
/usr/share/doc/packages/NetworkManager-gnome/ .

28 Samba
Using Samba, a Unix machine can be configured as a le and print server for Mac
OS X, Windows, and OS/2 machines. Samba has developed into a fully-edged and
rather complex product. Configure Samba with YaST, SWAT (a Web interface), or
by editing the configuration 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 System z: NetBIOS Support

IBM System z 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
368 Terminology SUSE Linux Enterp… 11 SP4

closely with network hardware is called NetBEUI, but this is often referred to as NetBIOS.
Network 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
hostnames 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. All common operating systems, such as Mac OS X, Windows, and OS/2, support
the SMB protocol. 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 have 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 domain. For data replication,
additional domain controllers are available in one domain.
28.2 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 28.3.1,
“Configuring a Samba Server with YaST”.
369 Starting and Stopping Samba SUSE Linux Enterp… 11 SP4

To stop or start running Samba services with YaST, use System System Services (Runlevel) and
check winbind, smb, and nmb. From a command line, stop services required for Samba with
rcsmb stop && rcnmb stop and start them with rcnmb start && rcsmb start ; rcsmb
cares about winbind if needed.
28.3 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.
28.3.1 Configuring a Samba Server with YaST

To configure a Samba server, start YaST and select Network Services Samba Server.
28.3.1.1 Initial Samba Configuration
When starting the module for the rst time, the Samba Installation dialog starts, prompting you
to make just a few basic decisions concerning administration of the server. At the end of the
configuration 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.
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 to act as a domain controller at all. By
default, the server is not configured 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.
370 Configuring a Samba Server SUSE Linux Enterp… 11 SP4

28.3.1.2 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 28.3.1.1, “Initial Samba Configuration”. Use it to adjust
your Samba server configuration.
After editing your configuration, click OK to save your settings.
28.3.1.2.1 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 28.2, “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.
28.3.1.2.2 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.
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.
28.3.1.2.3 Identity
In the Identity tab, you can determine the domain with which the host is associated (Base Set-
tings) and whether to use an alternative hostname 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 in-
stead of TDB database, click Advanced Settings.
371 Configuring a Samba Server with YaST SUSE Linux Enterp… 11 SP4
28.3.1.2.4 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.
28.3.1.2.5 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 4 “LDAP—A
Directory Service”.
28.3.2 Web Administration with SWAT

An alternative tool for Samba server administration is SWAT (Samba Web Administration Tool).
It provides a simple Web interface with which to configure the Samba server. To use SWAT,
open http://localhost:901 in a Web browser and log in as user root . If you do not have a
special Samba root account, use the system root account.
Note: Activating SWAT

After Samba server installation, SWAT is not activated. To activate it, open Network Ser-
vices Network Services (xinetd) in YaST, enable the network services configuration, select
swat from the table, and click Toggle Status (On or O).
28.3.3 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 [share] sections contain the individual le and
printer shares. By means of this approach, details regarding the shares can be set differently
or globally in the [global] section, which enhances the structural transparency of the config-
uration le.
372 Web Administration with SWAT SUSE Linux Enterp… 11 SP4

28.3.3.1 The global Section
The following parameters of the [global] section need some adjustment to match the require-
ments of your network setup so other machines can access your Samba server via SMB in a
Windows environment.
workgroup = TUX-NET
This line assigns the Samba server to a workgroup. Replace TUX-NET with an appropriate
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. With the Samba 3 release series, it is seldom necessary to
override the default setting ( 20 ). Choose a very low value such as 2 to spare the existing
Windows network from any disturbances caused by a misconfigured Samba server. More
information about this important topic can be found in the Network Browsing chapter of
the Samba 3 Howto; for more information on the Samba 3 Howto, see Section 28.7, “For
More Information”.
If no other SMB server is present 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 need 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.
373 Configuring the Server Manually SUSE Linux Enterp… 11 SP4

28.3.3.2 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 (DEACTIVATED)
;[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 > create mask = 0640
directory mask = 0750

[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 username.
valid users = %S
%S is replaced with the concrete name of the share as soon as a connection has
been successfully established. For a [homes] share, this is always the username. 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 para-
meter create mask defines the access permissions assigned to newly created les.
This only 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 .
28.3.3.3 Security Levels
To improve security, each share access can be protected with a password. SMB offers the fol-
lowing ways of checking permissions:
Share Level Security ( security = share )

A password is firmly assigned to a share. Everyone who knows this password has access
to that share.
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 usernames.
Server Level Security ( security = server )

To its clients, Samba pretends to be working in user level mode. However, it passes all
password queries to another user level mode server, which takes care of authentication.
This setting requires the additional password server parameter.
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 username 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 .
28.4 Configuring Clients

Clients can only access the Samba server via TCP/IP. NetBEUI and NetBIOS via IPX cannot be
used with Samba.
376 Configuring Clients SUSE Linux Enterp… 11 SP4

28.4.1 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 will be able to access their home directories when hosted on CIFS. For details, see
the the pam_mount man page.
After completing all settings, confirm the dialog to finish the configuration.
28.5 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]
workgroup = TUX-NET
domain logons = Yes
domain master = Yes
If encrypted passwords are used for verification purposes the Samba server must be able to
handle these. The entry encrypt passwords = yes in the [global] section enables this (with
Samba version 3, this is now the default). In addition, 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\$
377 Configuring a Samba Client with YaST SUSE Linux Enterp… 11 SP4
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
For more information about this topic, see Chapter 12 of the Samba 3 HOWTO, found in /usr/
share/doc/packages/samba/Samba3-HOWTO.pdf .
28.6 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).
Join an existing AD domain during installation or by later activating SMB user authentication
with YaST in the installed system. Domain join during installation is covered in Book “Deploy-
ment Guide”, Chapter 6 “Installation with YaST”, Section 6.16 “Configuration of the Installed System”, Sec-
tion 6.16.1 “System Configuration”, Section 6.16.1.7 “User Authentication Method”.
To join an AD domain in a running system, proceed as follows:
1. Log in as root and start YaST.
2. Start Network Services Windows Domain Membership.
3. Enter the domain to join at Domain or Workgroup in the Windows Domain Membership
screen.
378 Samba Server in the Network with Active Directory SUSE Linux Enterp… 11 SP4
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 SUSE Linux Enterprise 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
In an environment with more than one Samba server, UIDs and GIDs will not be created
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
make use of idnetity mapping. See https://www.samba.org/samba/docs/man/Samba-HOW-
TO-Collection/idmapper.html for more details
379 Samba Server in the Network with Active Directory SUSE Linux Enterp… 11 SP4
Detailed Samba information is available in the digital documentation. Enter apropos samba
at the command line to display some manual pages or just browse the /usr/share/doc/pack-
ages/samba directory if Samba documentation is installed for more online documentation and
examples. Find a commented example configuration ( smb.conf.SUSE ) in the examples sub-
directory.
The Samba 3 HOWTO provided by the Samba team includes a section about troubleshooting.
In addition to that, Part V of the document provides a step-by-step guide to checking your con-
figuration. You can nd Samba 3 HOWTO in /usr/share/doc/packages/samba/Samba3-HOW-
TO.pdf after installing the package samba-doc .

29 Sharing File Systems with NFS
Distributing and sharing le systems over a network is a common task in corpo-
rate environments. The well-proven network le system (NFS) works together with
NIS, the yellow pages protocol. For a more secure protocol that works together with
LDAP and may also use Kerberos, check NFSv4. Combined with pNFS, you can elim-
inate performance bottlenecks.
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.
29.1 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 (user and group name mappings to IDs and vice versa),
statd (le locking), and mountd (mount requests).
381 Terminology SUSE Linux Enterp… 11 SP4

pNFS
Parallel NFS, a protocol extension of NFSv4. Any pNFS clients can directly access the data
on an NFS server.
29.2 Installing NFS Server

The NFS server software is not part of the default installation. If you configure an NFS server as
described in Section 29.3, “Configuring NFS Server” you will automatically be prompted to install the
required packages. Alternatively, install the package nfs-kernel-server with YaST or zypper.
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).
29.3 Configuring NFS Server

Configuring an NFS server can be done either through YaST or manually. For authentication,
NFS can also be combined with Kerberos.
29.3.1 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. The server can also provide applications to all members
of a group without installing the applications locally on each and every host.
To set up such a server, proceed as follows:
PROCEDURE 29.1: SETTING UP AN NFSV3 SERVER
1. Start YaST and select Network Services NFS Server; see Figure 29.1, “NFS Server Configuration
Tool”. You may be prompted to install additional software.
382 Installing NFS Server SUSE Linux Enterp… 11 SP4

FIGURE 29.1: 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. Leave the Enable NFSv4 check box disabled.
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.
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.
8. Click Finish to complete the configuration.
383 Exporting File Systems with YaST SUSE Linux Enterp… 11 SP4
29.3.1.1 Exporting for NFSv4 Clients
For a xed set of NFSv4 clients, there are two types of directories that can be exported—direc-
tories that act as pseudo root le systems and those that are bound to some subdirectory of the
pseudo le system. This pseudo le system acts as a base point under which all le systems
exported for the same client set take their place. For a client or set of clients, only one directory
on the server can be configured as pseudo root for export. For this client, export multiple direc-
tories by binding them to some existing subdirectory in the pseudo root.
For example, suppose that the directory /exports is chosen as the pseudo root directory for all
the clients that can access the server. Then add this into the list of exported directories and make
sure that the options entered for this directory include fsid=0 . If there is another directory, /
data , that also needs to be NFSv4 exported, add this directory also to the list. While entering
options for this, make sure that bind=/exports/data is in the list and that /exports/data is
an already existing subdirectory of /exports . Any change in the option bind=/target/path ,
whether addition, deletion, or change in value, is reflected in Bindmount Targets.
In order to set up the server to export directories for NFSv4 clients, use the the general guideline
in Procedure 29.1, “Setting Up an NFSv3 Server”, but change the following steps:
1. Check Enable NFSv4 in the rst dialog.
2. Enter the appropriate NFSv4 domain name in the rst dialog.

Make sure the name is the same as the one in the /etc/idmapd.conf le of any NFSv4
client that accesses this particular server. This parameter is for the idmapd daemon that
is required for NFSv4 support (on both server and client). Leave it as localdomain (the
default) if you do not have any special requirements.
After clicking Next, the dialog that follows has two sections. The upper half consists of
two columns named Directories and Bindmount Targets. The service will become available
immediately.
3. Click Add Directory in the upper half of the dialog to export your directory and confirm
with Ok.
4. Enter your hostnames in the Host Wild Card texteld and options.
In Options texteld, include fsid=0 in the comma-separated list of options to configure
the directory as pseudo root. If this directory needs to be bound to another directory under
an already configured pseudo root, make sure that a target bind path is given in the option
list with bind=/target/path .
The Bindmount Targets column is not a directly editable column, but instead summarizes
directories and their nature.
5. Click Finish to complete the configuration.
29.3.1.2 NFSv3 and NFSv2 Exports
Make sure that Enable NFSv4 is not checked in the initial dialog before clicking Next.
The next dialog has two parts. In the upper text eld, enter the directories to export. Below,
enter the hosts that should have access to them. There are four 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.
This dialog is shown in Figure 29.2, “Exporting Directories with NFSv2 and v3”. Find a more thorough
explanation of these options in man exports . Click Finish to complete the configuration.
FIGURE 29.2: EXPORTING DIRECTORIES WITH NFSV2 AND V3
29.3.1.3 Coexisting v3 and v4 Exports
NFSv3 and NFSv4 exports can coexist on a server. After enabling the support for NFSv4 in the
initial configuration dialog, those exports for which fsid=0 and bind=/target/path are not
included in the option list are considered v3 exports.
Consider the example in Section 29.3.1.1, “Exporting for NFSv4 Clients”. If you add another directory,
such as /data2 , using Add Directory then in the corresponding options list do not mention either
fsid=0 or bind=/target/path , this export acts as a v3 export.
Important
Automatic Firewall Configuration
If SuSEfirewall2 is active on your system, YaST adapts its configuration for the NFS server
by enabling the nfs service when Open Ports in Firewall is selected.
29.3.2 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 configu-
ration. To start or restart the services, run the command rcnfsserver restart . This also starts
the rpc.idmapd if NFSv4 is configured in /etc/sysconfig/nfs . The NFS server depends on
a running RPC portmapper. Therefore, also start or restart the portmapper service with rcr-
pcbind restart .
29.3.2.1 Exporting File Systems with NFSv4
NFSv4 is the latest version of NFS protocol available on SUSE Linux Enterprise Server. Config-
uring directories for export with NFSv4 differs slightly from previous NFS versions.
29.3.2.1.1 /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)
386 Exporting File Systems Manually SUSE Linux Enterp… 11 SP4

For example:
/export 192.168.1.2(rw,fsid=0,sync,crossmnt)
/export/data 192.168.1.2(rw,bind=/data,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 ).
The directory which specifies fsid=0 is special. It is the root of the le system that is exported,
sometimes referred to as the pseudo root le system. This directory must also have the crossmnt
for correct operation with NFSv4. All other directories exported via NFSv4 must be mounted
below this point. If you want to export a directory that is not within the exported root, it needs
to be bound into the exported tree. This can be done using the bind= syntax.
In the example above, /data is not within /export , so we export /export/data , and specify
that the /data directory should be bound to that name. The directory /export/data must
exist and should normally be empty.
When clients mount from this server, they just mount servername:/ rather than server-
name:/export . It is not necessary to mount servername:/data , because it will automatically
appear beneath wherever servername:/ was mounted.
29.3.2.1.2 /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 . NFS4_SUPPORT deter-
mines whether the NFS server supports NFSv4 exports and clients.
29.3.2.1.3 /etc/idmapd.conf
Every user on a Linux machine has a name and ID. idmapd does the name-to-ID mapping for
NFSv4 requests to the server and replies to the client. It must be running on both server and
client for NFSv4, because NFSv4 uses only names for its communication.
Make sure that there is a uniform way in which usernames 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
For further reference, read the man page of idmapd and idmapd.conf ; man idmapd , man
idmapd.conf .
29.3.2.1.4 Starting and Stopping Services
After changing /etc/exports or /etc/sysconfig/nfs , start or restart the NFS server service
with rcnfsserver restart . After changing /etc/idmapd.conf , reload the configuration le
with the command killall -HUP rpc.idmapd .
If the NFS service needs to start at boot time, run the command chkconfig nfsserver on .
29.3.2.2 Exporting File Systems with NFSv2 and NFSv3

This section is specific to NFSv3 and NFSv2 exports. Refer to Section 29.3.1.1, “Exporting for NFSv4
Clients” for exporting with NFSv4.
Exporting le systems with NFS involves two configuration les: /etc/exports and /etc/
sysconfig/nfs . A typical /etc/exports le entry is in the format:
/shared/directory host(list_of_options)
For example:
/export 192.168.1.2(rw,sync)
Here, the directory /export is shared with the host 192.168.1.2 with the option list rw,sync .
This IP address can be replaced with a client name or set of clients using a wild card (such as
*.abc.com ) or even netgroups.

For a detailed explanation of all options and their meaning, refer to the man page of exports
( man exports ).
After changing /etc/exports or /etc/sysconfig/nfs , start or restart the NFS server using
the command rcnfsserver restart .
29.3.3 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 just 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 rcgssd start .
3. Start the svcgssd service on the server with rcsvcgssd start .
For more information about configuring kerberized NFS, refer to the links in Section 29.5, “For
More Information”.
29.4 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.
29.4.1 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 29.2: IMPORTING NFS DIRECTORIES
1. Start the YaST NFS client module.
389 NFS with Kerberos SUSE Linux Enterp… 11 SP4

2. Click on Add in the NFS Shares tab. Enter the hostname of the NFS server, the directory to
import, and the mount point at which to mount this directory locally.
3. 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.
4. When using NFSv4, make sure that the check box Enable NFSv4 is selected and that the
NFSv4 Domain Name contains the same value as used by the NFSv4 server. The default
domain is localdomain .
5. 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.
29.4.2 Importing File Systems Manually

The prerequisite for importing le systems manually from an NFS server is a running RPC port
mapper. Start it by entering rcrpcbind start as root . Then remote le systems can be mount-
ed in the le system like local partitions using mount :
mount host:remote-pathlocal-path
To import user directories from the nfs.example.com machine, for example, use:
mount nfs.example.com:/home /home
29.4.2.1 Using the Automount Service

The autofs daemon can be used to mount remote le systems automatically. Add the following
entry in the your /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
390 Importing File Systems Manually SUSE Linux Enterp… 11 SP4

nfs4mount -fstype=nfs4 server2:/
Activate the settings with rcautofs start as root . In this example, /nfsmounts/localda-
ta , the /data directory of server1 , is mounted with NFS and /nfsmounts/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 rcautofs restart .
29.4.2.2 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
NFSv4 mounts may also be added to the /etc/fstab le. For these mounts, use nfs4 instead
of nfs in the third column and make sure that the remote le system is given as / after the
nfs.example.com: in the rst column. A sample line for an NFSv4 mount in /etc/fstab
looks like this:
nfs.example.com:/ /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:
mount /local/path
Note, that if you do not enter the noauto option, the initialization scripts of the system will
handle the mount of those le systems at start up.
29.4.3 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 significantly impacts on
the system performance. This is due to les quickly getting bigger, whereas the relative speed
of your Ethernet just has not fully kept up.
391 Parallel NFS (pNFS) SUSE Linux Enterp… 11 SP4

When you request a le from a “normal” 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 transfering 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 which handels all the non-data traffic
One or more storage server(s) which 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 supports pNFS on the client side only.
29.4.3.1 Configuring pNFS Client With YaST
Proceed as described in Procedure 29.2, “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 .
29.4.3.2 Configuring pNFS Client Manually
Refer to Section 29.4.2, “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:
mount -t nfs4 -o minorversion=1 MDS_SERVER MOUNTPOINT
To help with debugging, change the value in the /proc le system:
echo 32767 > /proc/sys/sunrpc/nfsd_debug

echo 32767 > /proc/sys/sunrpc/nfs_debug
392 Parallel NFS (pNFS) SUSE Linux Enterp… 11 SP4

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/) .

30 File Synchronization
These days, many people use several computers—one computer at home, one or
several computers at the workplace, and possibly a laptop, tablet, or a smartphone
on the road. Many les are needed on all these computers. You may want to be able
to work with all computers and modify the les so that you have the latest version
of the data available on all computers.
30.1 Available Data Synchronization Software

Data synchronization is no problem for computers that are permanently linked by means of a
fast network. In this case, use a network le system, like NFS, and store the les on a server,
enabling all hosts to access the same data via the network. This approach is impossible if the
network connection is poor or not permanent. When you are on the road with a laptop, copies
of all needed les must be on the local hard disk. However, it is then necessary to synchronize
modified les. When you modify a le on one computer, make sure a copy of the le is updated
on all other computers. For occasional copies, this can be done manually with scp or rsync.
However, if many les are involved, the procedure can be complicated and requires great care
to avoid errors, such as overwriting a new le with an old le.
Warning: Risk of Data Loss

Before you start managing your data with a synchronization system, you should be well
acquainted with the program used and test its functionality. A backup is indispensable
for important les.
The time-consuming and error-prone task of manually synchronizing data can be avoided by
using one of the programs that use various methods to automate this job. The following sum-
maries are merely intended to convey a general understanding of how these programs work and
how they can be used. If you plan to use them, read the program documentation.
394 Available Data Synchronization Software SUSE Linux Enterp… 11 SP4

30.1.1 CVS
CVS, which is mostly used for managing program source versions, offers the possibility of keep-
ing copies of the les on multiple computers. Accordingly, it is also suitable for data synchro-
nization. CVS maintains a central repository on the server in which the les and changes to
les are saved. Changes that are performed locally are committed to the repository and can be
retrieved from other computers by means of an update. Both procedures must be initiated by
the user.
CVS is very resilient to errors when changes occur on several computers. The changes are merged
and (if changes took place in the same lines) a conflict is reported. When a conflict occurs, the
database remains in a consistent state. The conflict is only visible for resolution on the client
host.
30.1.2 rsync
When no version control is needed but large directory structures need to be synchronized over
slow network connections, the tool rsync offers well-developed mechanisms for transmitting
only changes within les. This not only applies to text les, but also binary les. To detect the
differences between les, rsync subdivides the les into blocks and computes checksums over
them.
The effort put into the detection of the changes comes at a price. The systems to synchronize
should be scaled generously for the usage of rsync. RAM is especially important.
30.2 Determining Factors for Selecting a Program

There are some important factors to consider when deciding which program to use.
30.2.1 Client-Server versus Peer-to-Peer

Two different models are commonly used for distributing data. In the rst model, all clients
synchronize their les with a central server. The server must be accessible by all clients at least
occasionally. This model is used by CVS.
The other possibility is to let all networked hosts synchronize their data between each other as
peers. rsync actually works in client mode, but any client can also act as a server.
395 CVS SUSE Linux Enterp… 11 SP4

30.2.2 Portability
CVS and rsync are also available for many other operating systems, including various Unix and
Windows systems.
30.2.3 Interactive versus Automatic

In CVS, the data synchronization is started manually by the user. This allows ne control over
the data to synchronize and easy conflict handling. However, if the synchronization intervals
are too long, conflicts are more likely to occur.
30.2.4 Conflicts: Incidence and Solution

Conflicts only rarely occur in CVS, even when several people work on one large program project.
This is because the documents are merged on the basis of individual lines. When a conflict
occurs, only one client is affected. Usually conflicts in CVS can easily be resolved.
There is no conflict handling in rsync. The user is responsible for not accidentally overwriting
les and manually resolving all possible conflicts. To be on the safe side, a versioning system
like RCS can additionally be employed.
30.2.5 Selecting and Adding Files

In CVS, new directories and les must be added explicitly using the command cvs add . This
results in greater user control over the les to synchronize. On the other hand, new les are
often overlooked, especially when the question marks in the output of cvs update are ignored
due to the large number of les.
30.2.6 History
An additional feature of CVS is that old le versions can be reconstructed. A brief editing remark
can be inserted for each change and the development of the les can easily be traced later based
on the content and the remarks. This is a valuable aid for theses and program texts.
396 Portability SUSE Linux Enterp… 11 SP4

30.2.7 Data Volume and Hard Disk Requirements
A sufficient amount of free space for all distributed data is required on the hard disks of all
involved hosts. CVS require additional space for the repository database on the server. The
le history is also stored on the server, requiring even more space. When les in text format
are changed, only the modified lines need to be saved. Binary les require additional space
amounting to the size of the le every time the le is changed.
30.2.8 GUI
Experienced users normally run CVS from the command line. However, graphical user interfaces
are available for Linux (such as cervisia) and other operating systems (like wincvs). Many de-
velopment tools (such as kdevelop) and text editors (such as Emacs) provide support for CVS.
The resolution of conflicts is often much easier to perform with these front-ends.
30.2.9 User Friendliness

rsync is rather easy to use and is also suitable for newcomers. CVS is somewhat more difficult to
operate. Users should understand the interaction between the repository and local data. Changes
to the data should rst be merged locally with the repository. This is done with the command
cvs update . Then the data must be sent back to the repository with the command cvs commit .
Once this procedure has been understood, newcomers are also able to use CVS with ease.
30.2.10 Security against Attacks

During transmission, the data should ideally be protected against interception and manipulation.
CVS and rsync can easily be used via ssh (secure shell), providing security against attacks of
this kind. Running CVS via rsh (remote shell) should be avoided. Accessing CVS with the pserver
mechanism in insecure networks is likewise not advisable.
30.2.11 Protection against Data Loss

CVS has been used by developers for a long time to manage program projects and is extremely
stable. Because the development history is saved, CVS even provides protection against certain
user errors, such as unintentional deletion of a le.
397 Data Volume and Hard Disk Requirements SUSE Linux Enterp… 11 SP4
TABLE 30.1: FEATURES OF THE FILE SYNCHRONIZATION TOOLS: -- = VERY POOR, - = POOR OR NOT AVAILABLE, O =
MEDIUM, + = GOOD, ++ = EXCELLENT, X = AVAILABLE
CVS rsync
Client/Server C-S C-S
Portability Lin,Un*x,Win Lin,Un*x,Win
Interactivity x x
Speed o +
Conflicts ++ o
File Sel. Sel./le, dir. Dir.
History x -
Hard Disk Space -- o
GUI o -
Difficulty o +
Attacks + (ssh) +(ssh)
Data Loss ++ +
30.3 Introduction to CVS

CVS is suitable for synchronization purposes if individual les are edited frequently and are
stored in a le format, such as ASCII text or program source text. The use of CVS for synchro-
nizing data in other formats (such as JPEG les) is possible, but leads to large amounts of data,
because all variants of a le are stored permanently on the CVS server. In such cases, most of
the capabilities of CVS cannot be used. The use of CVS for synchronizing les is only possible
if all workstations can access the same server.
398 Introduction to CVS SUSE Linux Enterp… 11 SP4

30.3.1 Configuring a CVS Server
The server is the host on which all valid les are located, including the latest versions of all les.
Any stationary workstation can be used as a server. If possible, the data of the CVS repository
should be included in regular backups.
When configuring a CVS server, it might be a good idea to grant users access to the server via
SSH. If the user is known to the server as tux and the CVS software is installed on the server
as well as on the client, the following environment variables must be set on the client side:
CVS_RSH=ssh CVSROOT=tux@server:/serverdir
The command cvs init can be used to initialize the CVS server from the client side. This
needs to be done only once.
Finally, the synchronization must be assigned a name. Select or create a directory on the client to
contain les to manage with CVS (the directory can also be empty). The name of the directory is
also the name of the synchronization. In this example, the directory is called synchome . Change
to this directory and enter the following command to set the synchronization name to synchome :
cvs import synchome tux wilber
Many CVS commands require a comment. For this purpose, CVS starts an editor (the editor
defined in the environment variable $EDITOR or vi if no editor was defined). The editor call
can be circumvented by entering the comment in advance on the command line, such as in the
following example:
cvs import -m 'this is a test' synchome tux wilber
30.3.2 Using CVS

The synchronization repository can now be checked out from all hosts with cvs co synchome .
This creates a new subdirectory synchome on the client. To commit your changes to the server,
change to the directory synchome (or one of its subdirectories) and enter cvs commit .
By default, all les (including subdirectories) are committed to the server. To commit only in-
dividual les or directories, specify them as in cvs commit file1 directory1 . New les and
directories must be added to the repository with a command like cvs add file1 directo-
ry1 before they are committed to the server. Subsequently, commit the newly added les and
directories with cvs commit file1 directory1 .
399 Configuring a CVS Server SUSE Linux Enterp… 11 SP4

If you change to another workstation, check out the synchronization repository if this has not
been done during an earlier session at the same workstation.
Start the synchronization with the server with cvs update . Update individual les or directo-
ries as in cvs update file1 directory1 . To see the difference between the current les and
the versions stored on the server, use the command cvs diff or cvs diff file1 directo-
ry1 . Use cvs -nq update to see which les would be affected by an update.
Here are some of the status symbols displayed during an update:
U
The local version was updated. This affects all les that are provided by the server and
missing on the local system.
M
The local version was modified. If there were changes on the server, it was possible to
merge the differences in the local copy.
P
The local version was patched with the version on the server.
C
The local le conflicts with current version in the repository.
?
This le does not exist in CVS.
The status M indicates a locally modified le. Either commit the local copy to the server or
remove the local le and run the update again. In this case, the missing le is retrieved from
the server. If you commit a locally modified le and the le was changed in the same line and
committed, you might get a conflict, indicated with C .
400 Using CVS SUSE Linux Enterp… 11 SP4

In this case, look at the conflict marks (“ >> ” and “ << ”) in the le and decide between the two
versions. As this can be a rather unpleasant job, you might decide to abandon your changes,
delete the local le, and enter cvs up to retrieve the current version from the server.
30.4 Introduction to rsync

rsync is useful when large amounts of data need to be transmitted regularly while not changing
too much. This is, for example, often the case when creating backups. Another application con-
cerns staging servers. These are servers that store complete directory trees of Web servers that
are regularly mirrored onto a Web server in a DMZ.
30.4.1 Configuration and Operation

rsync can be operated in two different modes. It can be used to archive or copy data. To accom-
plish this, only a remote shell, like ssh, is required on the target system. However, rsync can
also be used as a daemon to provide directories to the network.
The basic mode of operation of rsync does not require any special configuration. rsync directly
allows mirroring complete directories onto another system. As an example, the following com-
mand creates a backup of the home directory of tux on a backup server named sun:
rsync -baz -e ssh /home/tux/ tux@sun:backup
The following command is used to play the directory back:
rsync -az -e ssh tux@sun:backup /home/tux/
Up to this point, the handling does not differ much from that of a regular copying tool, like scp.
rsync should be operated in “rsync” mode to make all its features fully available. This is done by
starting the rsyncd daemon on one of the systems. Configure it in the le /etc/rsyncd.conf .
For example, to make the directory /srv/ftp available with rsync, use the following config-
uration:
gid = nobody
uid = nobody
read >use chroot = no
transfer logging = true
401 Introduction to rsync SUSE Linux Enterp… 11 SP4

log format = %h %o %f %l %b
log file = /var/log/rsyncd.log
[FTP]
path = /srv/ftp
comment = An Example
Then start rsyncd with rcrsyncd start . rsyncd can also be started automatically during the
boot process. Set this up by activating this service in the runlevel editor provided by YaST or
by manually entering the command insserv rsyncd . rsyncd can alternatively be started by
xinetd. This is, however, only recommended for servers that rarely use rsyncd.
The example also creates a log le listing all connections. This le is stored in /var/log/
rsyncd.log .
It is then possible to test the transfer from a client system. Do this with the following command:
rsync -avz sun::FTP
This command lists all les present in the directory /srv/ftp of the server. This request is
also logged in the log le /var/log/rsyncd.log . To start an actual transfer, provide a target
directory. Use . for the current directory. For example:
rsync -avz sun::FTP .
By default, no les are deleted while synchronizing with rsync. If this should be forced, 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.

CVS
Important information about CVS can be found in the home page http://
www.cvshome.org .
rsync
Important information about rsync is provided in the man pages man rsync and
man rsyncd.conf . A technical reference about the operating principles of rsync is fea-
tured in /usr/share/doc/packages/rsync/tech_report.ps . Find the latest news about
rsync on the project Web site at http://rsync.samba.org/ .

31 The Apache HTTP Server
With a share of more than 50%, the Apache HTTP Server (Apache) is the world's
most widely-used Web server according to the Survey from http://www.net-
craft.com/ . Apache, developed by the Apache Software Foundation (http://www.a-
pache.org/ ), is available for most operating systems. SUSE® Linux Enterprise
Server includes Apache version 2.2. In this chapter, 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 the help of 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 22, 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 “SuSE-
firewall2”, Section 15.4.1 “Configuring the Firewall with YaST” for details.
403 Quick Start SUSE Linux Enterp… 11 SP4

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 Filter Patterns and select Web and LAMP Server int Server Functions.
3. Confirm the installation of the dependent packages to finish the installation process.
The installation includes the multiprocessing module apache2-prefork as well as the PHP5
module. Refer to Section 31.4, “Installing, Activating, and Configuring Modules” for more information
about modules.
31.1.3 Start
You can start Apache automatically at boot time or start it manually.
PROCEDURE 31.2: STARTING APACHE AUTOMATICALLY
1. To make sure that Apache is automatically started during boot in runlevels 3 and 5 ,
execute the following command:
chkconfig -a apache2
2. Alternatively, start YaST and select System System Services (Runlevel).
3. Search for apache2 and Enable the service.

The Web server starts immediately.
4. Save your changes with Finish.

The system is configured to automatically start Apache in runlevels 3 and 5 during boot.
For more information about the runlevels in SUSE Linux Enterprise Server and a description of
the YaST runlevel editor, refer to Section 10.2.3, “Configuring System Services (Runlevel) with YaST”.
To manually start Apache using the shell, run rcapache2 start .

PROCEDURE 31.3: 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 rcapache2 reload 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.
405 Configuring Apache SUSE Linux Enterp… 11 SP4

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.
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 referred to as 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
406 Apache Configuration Files SUSE Linux Enterp… 11 SP4

| |
| |- 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.
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
407 Apache Configuration Files SUSE Linux Enterp… 11 SP4

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, “Multiprocess-
ing Modules”) as well as 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.
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 .
408 Configuring Apache Manually SUSE Linux Enterp… 11 SP4

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 httpd2 -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).
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 filename, start the filename 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/2.2/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 directive NameVirtualHost tells Apache on which IP address and, optionally, which port
it should listen to for requests by clients containing the domain name in the HTTP header. This
option is configured in the configuration le /etc/apache2/listen.conf .
The rst argument can be a fully qualified domain name, but it is recommended to use the IP
address. The second argument is the port and is optional. By default, port 80 is used and is
configured via the Listen directive.
The wild card * can be used for both the IP address and the port number to receive requests
on all interfaces. IPv6 addresses must be enclosed in square brackets.
EXAMPLE 31.1: VARIATIONS OF NAME-BASED VirtualHost ENTRIES
# NameVirtualHost IP-address[:Port]
NameVirtualHost 192.168.3.100:80
NameVirtualHost 192.168.3.100
NameVirtualHost *:80
NameVirtualHost *
NameVirtualHost [2002:c0a8:364::]:80
The opening VirtualHost tag takes the IP address (or fully qualified domain name) previously
declared with the NameVirtualHost as an argument in a name-based virtual host configuration.
A port number previously declared with the NameVirtualHost directive is optional.
The wild card * is also allowed as a substitute for the IP address. This syntax is only valid in
combination with the wild card usage in NameVirtualHost * . 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 present in each virtual host configuration in order 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">
Order allow,deny
Allow from all
</Directory>
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">
Order allow,deny
Allow from all
</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 are given the
opportunity to 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.
413 Configuring Apache with YaST SUSE Linux Enterp… 11 SP4

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.
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 referred to as the default host. Each
virtual host inherits the default host's configuration.
To edit the host settings (also called directives), choose 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
With the help of 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 pre-configured: /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
filenames (space-separated) if you want 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.example.com/~user .
Important: Creating Virtual Hosts

It is not possible to add virtual hosts at will. If using name-based virtual hosts, each
hostname 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. If you want 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 or the error log. 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 runlevels 3 and 5 and stopped in runlevels 0, 1, 2, and 6. You can change
this behavior using YaST's runlevel editor or the command line tool chkconfig .
To start, stop, or manipulate Apache on a running system, use the init script /usr/sbin/rca-
pache2 . For general information about init scripts, refer to Section 10.2.2, “Init Scripts”. The rca-
pache2 command takes the following parameters:
status
Checks if Apache is started.
start
419 Starting and Stopping Apache SUSE Linux Enterp… 11 SP4

Starts Apache if it is not already running.
startssl
Starts Apache with SSL support if it is not already running. For more information about
SSL support, refer to Section 31.6, “Setting Up a Secure Web Server with SSL”.
stop
Stops Apache by terminating the parent process.
restart
Stops and then restarts Apache. Starts the Web server if it was not running before.
try-restart
Stops then restarts Apache only if it is already running.
reload or graceful
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

To activate changes in the Apache configuration without causing connection break-
os, use the rcapache2 reload command.
restart-graceful
Starts a second Web server that immediately serves all incoming requests. The previous
instance of the Web server continues to handle all existing requests for a defined period
of time configured with GracefulShutdownTimeout .
rcapache2 restart-graceful is either useful when upgrading to a new version or when
having changed configuration options that require a restart. Using this option ensures a
minimum server downtime.
GracefulShutdownTimeout needs to be set, otherwise restart-graceful will result in
a regular restart. If set to zero, the server will wait indefinitely until all remaining requests
have been fully served.
A graceful restart can fail if the original Apache instance is not able to clear all necessary
resources. In this case, the command will result in a graceful stop.
stop-graceful
420 Starting and Stopping Apache SUSE Linux Enterp… 11 SP4

Stops the Web server after a defined period of time configured with GracefulShutdown-
Timeout in order to ensure that existing requests can be finished.
GracefulShutdownTimeout needs to be set, otherwise stop-graceful will result in a
regular restart. If set to zero, the server will wait indefinitely until all remaining requests
have been fully served.
configtest or extreme-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). The extreme-configtest options start the
Web server as user nobody and actually load the configuration, so more errors can be
detected. Note that although the configuration is loaded, it is not possible to test the SSL
setup because the SSL certificates cannot be read by nobody .
probe
Probes for the necessity of a reload (checks whether the configuration has changed) and
suggests the required arguments for the rcapache2 command.
server-status and full-server-status

Dumps a short or full status screen, respectively. Requires either lynx or w3m installed as
well as the module mod_status enabled. In addition to that, status must be added to
APACHE_SERVER_FLAGS in the le /etc/sysconfig/apache2 .
Tip: Additional Flags

If you specify additional ags to the rcapache2 , 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 dynamically loaded
at runtime. Refer to Section 31.4.2, “Activation and Deactivation” for details of how to load modules
dynamically.
421 Installing, Activating, and Configuring Modules SUSE Linux Enterp… 11 SP4
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.
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 modules mod_php5 and mod_python .
You can install additional external modules by starting YaST and choosing Software Software
Management. Now choose Filter 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”.
422 Module Installation SUSE Linux Enterp… 11 SP4

If you prefer to activate or deactivate the modules manually, use the commands a2enmod
mod_foo or a2dismod mod_foo , respectively. a2enmod -l outputs a list of all currently active
modules.
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 locat-
ed under /etc/apache2/conf.d/ and are not loaded by default. If you need the same
modules on each virtual host, you can include *.conf from this directory. Otherwise
include individual les. See /etc/apache2/vhost.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/2.2/mod/ to learn details about each module.
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 . Digest au-
thentication in Apache 2.2 is considered experimental.
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).
423 Base and Extension Modules SUSE Linux Enterp… 11 SP4

More information about this topic is available in the Authentication HOWTO at http://
httpd.apache.org/docs/2.2/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.
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_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 makes certain that a le is delivered with the correct MIME header
based on the filename'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/2.2/content-negotia-
tion.html for more information. This module is enabled by default.
mod_nss
Enables encrypted connections between Web server and clients via TLS 1.1 and TLS 1.2
protocols using the Mozilla Network Security Services library. See Section 31.7, “Setting Up
a Secure Web Server with NSS” for details.
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.
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_speling
mod_speling 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
Section 31.4.4.2, “Worker MPM”
31.4.4.1 Prefork MPM

The prefork MPM implements a nonthreaded, 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.
426 Multiprocessing Modules SUSE Linux Enterp… 11 SP4

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 due to 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 in conjunction 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.
31.4.5 External Modules

Find a list of all external modules shipped with SUSE Linux Enterprise Server here.
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_mono
mod_auth_kerb provides Kerberos authentication to the Apache Web server.
Package Name: apache2-mod_auth_kerb

More Information: http://modauthkerb.sourceforge.net/configure.html
mod_mono
Using mod_mono allows you to run ASP.NET pages in your server.
Package Name: apache2-mod_mono

Configuration File: /etc/apache2/conf.d/mod_mono.conf
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.
427 External Modules SUSE Linux Enterp… 11 SP4

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
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.
428 Compilation SUSE Linux Enterp… 11 SP4

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/lib/apache2 .
/usr/sbin/apxs2-prefork —suitable for prefork MPM modules. The installation loca-

tion is /usr/lib/apache2-prefork .
/usr/sbin/apxs2-worker —suitable for worker MPM modules. The installation location

is /usr/lib/apache2-worker .
Install and activate a module from source code with the following commands:
cd /path/to/module/source; apxs2 -cia

mod_foo.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 Getting CGI Scripts to Work

Apache's Common Gateway Interface (CGI) lets you create dynamic content with programs or
scripts usually referred to as CGI scripts. CGI scripts can be written in any programming lan-
guage. 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.
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.
429 Getting CGI Scripts to Work SUSE Linux Enterp… 11 SP4

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
Order allow,deny 4
Allow from all

</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 Order and Allow directives control the default access state and the order in which
allow and deny directives are evaluated. In this case “allow” statements are evaluated
before “deny” statements and universal access is enabled.
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 in most cases or plain text
or images, for example.
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 .
430 Apache Configuration SUSE Linux Enterp… 11 SP4

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? Check with rca-
pache2 probe .
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.c-
gi . Its 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.
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/TSL,
a private connection between Web server and client is established. Data integrity is ensured and
client and server are able to authenticate each other.
431 CGI Troubleshooting SUSE Linux Enterp… 11 SP4

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/TSL 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.
Note: TLS Versions Higher Than TLS 1.0

The openssl library supports TLS version up to and including TLS 1.0. Support for newer
TLS versions like 1.1 or 1.2 is missing. mod_nss from the apache2-mod_nss package
provides TLS 1.1 and 1.2 using the Mozilla Network Security Services library. See Sec-
tion 31.7, “Setting Up a Secure Web Server with NSS” for details.
The most visible effect of using mod_ssl with Apache is that URLs are prefixed with https://
instead of http:// .
Tip: Example Certificate

An example certificate for a hypothetical company “Snake Oil” is available when in-
stalling the package apache2-example-certificates .
31.6.1 Creating an SSL Certificate

In order to use SSL/TSL 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 basically a two step process. First, a private key for the certificate au-
thority is generated then the server certificate is signed with this key.
432 Creating an SSL Certificate SUSE Linux Enterp… 11 SP4

Tip: For More Information
To learn more about concepts and definitions of SSL/TSL, refer to http://httpd.a-
pache.org/docs/2.2/ssl/ssl_intro.html .
31.6.1.1 Creating a “Dummy” Certificate
Generating a dummy certificate is simple. Just call the script /usr/bin/gensslcert . It creates
or overwrites the les listed below. Make use of 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
/root/.mkcert.cfg
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 might
be sufficient if you sign a certificate with your own certificate authority (CA).
Creating a self-signed certificate is an interactive nine-step process. Change into the directory
/usr/share/doc/packages/apache2 and run the following command: ./mkcert.sh make
--no-print-directory /usr/bin/openssl /usr/sbin/ custom . Do not attempt to run this
command from outside this directory. The program provides a series of prompts, some of which
require user input.

PROCEDURE 31.4: CREATING A SELF-SIGNED CERTIFICATE WITH mkcert.sh
1. Decide the signature algorithm used for certificates

Choose RSA ( R , the default), because some older browsers have problems with DSA.
2. Generating RSA private key for CA (1024 bit)

No interaction needed.
3. Generating X.509 certificate signing request for CA

Create the CA's distinguished name here. This requires you to answer a few questions, such
as country name or organization name. Enter valid data, because everything you enter
here later shows up in the certificate. 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.
Important: Common Name of the CA

The common name of the CA must be different from the server's common name, so
do not choose the fully qualified hostname in this step.
4. Generating X.509 certificate for CA signed by itself

Choose certificate version 3 (the default).
5. Generating RSA private key for SERVER (1024 bit)

No interaction needed.
6. Generating X.509 certificate signing request for SERVER

Create the distinguished name for the server key here. Questions are almost identical to the
ones already answered for the CA's distinguished name. The data entered here applies to
the Web server and does not necessarily need to be identical to the CA's data (for example,
if the server is located elsewhere).
Important: Selecting a Common Name

The common name you enter here must be the fully qualified hostname of your
secure server (for example, www.example.com). Otherwise the browser issues a
warning that the certificate does not match the server when accessing the Web
server.
7. Generating X.509 certificate signed by own CA

Choose certificate version 3 (the default).
8. Encrypting RSA private key of CA with a passphrase for security

It is strongly recommended to encrypt the private key of the CA with a password, so choose
Y and enter a password.
9. Encrypting RSA private key of SERVER with a passphrase for security

Encrypting the server key with a password requires you to enter this password every time
you start the Web server. This makes it difficult to automatically start the server on boot
or to restart the Web server. Therefore, it is common sense to say N to this question.
Keep in mind that your key is unprotected when not encrypted with a password and make
sure that only authorized persons have access to the key.
Important: Encrypting the Server Key

If you choose to encrypt the server key with a password, increase the value
for APACHE_TIMEOUT in /etc/sysconfig/apache2 . Otherwise you do not have
enough time to enter the passphrase before the attempt to start the server is stopped
unsuccessfully.
The script's result page presents a list of certificates and keys it has generated. Contrary to what
the script outputs, the les have not been generated in the local directory conf , but to the
correct locations under /etc/apache2/ .
The last step is to copy the CA certificate le from /etc/apache2/ssl.crt/ca.crt to a location
where your users can access it in order 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. The certificate is valid for one year.
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.

31.6.1.3 Getting an Ocially Signed Certificate
There are a number of 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 got an officially signed certificate.
The best-known official CAs are Thawte (http://www.thawte.com/ ) or Verisign (http://
www.verisign.com ). These and other CAs are already compiled into all browsers, so certificates
signed by these certificate authorities are automatically accepted by the browser.
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, call the script /usr/share/ssl/
misc/CA.sh -newreq .
First the script asks for a password with which the CSR should be encrypted. Then 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 “SuSEfirewall2”, 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 . If you
436 Configuring Apache with SSL SUSE Linux Enterp… 11 SP4

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.
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. In order 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).
437 Configuring Apache with SSL SUSE Linux Enterp… 11 SP4

Important: SNI Browser Support
SNI must also be supported on the client side. Although SNI is supported by most
browsers, some browsers for mobile hardware as well as Internet Explorer and Safari on
Windows* XP lack SNI support. See http://en.wikipedia.org/wiki/Server_Name_Indication
for details.
Configure how to handle non-SNI capable browser with 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.
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 Setting Up a Secure Web Server with NSS

The mod_nss module provides strong encryption using the transport layer security (TLS) pro-
tocols version 1.1 and 1.2 that are not available when using Apache with mod_ssl .
SSL/TLS support in the apache2 package is normally provided by mod_ssl , the apache module
that provides SSL/TLS using the the openssl cryptographic library. The version of the openssl
library used in SUSE Linux Enterprise Server 11 SP4 supports TLS of version 1.0 only. TLS 1.1
and 1.2 support can only be provided by versions that are not compatible with the large variety
of packages contained in SLE 11 SP4. The alternative is to make use of the Mozilla Network
Security Services library provided by the mozilla-nss package.
Note: Support for SSLv2

The SSLv2 support is not provided by mod_nss . If you require the SSLv2 protocol, you
need to use mod_ssl .
Both mod_ssl and mod_nss can be initialized at the same time, but the protocol handlers
( SSLEngine on for mod_ssl and NSSEngine on for mod_nss ) cannot be active simultaneous-
ly, at a global scope, or in the context of a VirtualHost configuration directive block.
438 Setting Up a Secure Web Server with NSS SUSE Linux Enterp… 11 SP4
If only one VirtualHost section has the directive NSSEngine set to on , it will have precedence
over all other VirtualHost declarations (that may have SSLEngine set to on in their context),
for a port that Apache listens on. A simultaneaous operation of both modules for different Vir-
tualHosts on the same IP address and port is not possible. If you need support for encrypted
connections using both mod_nss and mod_ssl , you should consider using more than one IP
address and configuring the server's cryptographic modules to be bound to their IP addresses.
If you do not need both cryptographic modules simultaneaously, it is recommended to decide
on one and deactivate the other.
Because mmod_nss uses a database format for the server and CA certificates and the private
key, existing mod_ssl-based certificates need to be converted for the use with mmod_nss . The
package apache2-mod_nss contains the perl script /usr/sbin/mod_nss_migrate.pl for this
task. The script creates a new database.
To list the certificates contained in the NSS database, use the following command:
certutil -d /etc/apache2/mod_nss.d -L
For more information about the certutil NSS database management utility, use certutil
--help .
The default configuration le that comes with the mod_nss package is /etc/apache2/con-
f.d/mod_nss.conf . Read the comments in the le for more information.
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.
439 Avoiding Security Problems SUSE Linux Enterp… 11 SP4

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 as
soon as possible. The SUSE security announcements are available from the following locations:
Web Page. http://www.novell.com/linux/security/securitysupport.html
Mailing List Archive. http://lists.opensuse.org/opensuse-security-announce/
RSS Feed. http://www.novell.com/linux/security/suse_security.xml
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 .
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.
440 Up-to-Date Software SUSE Linux Enterp… 11 SP4

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).
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 rcapache2
Instead of starting and stopping the Web server with the binary /usr/sbin/httpd2 , rather
use the rcapache2 script instead (described in Section 31.3, “Starting and Stopping Apache”).
It 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.
441 User Directories SUSE Linux Enterp… 11 SP4

Tip: A Simple Test
Watch the Apache log messages with the command tail -F /var/log/apache2/
my_error_log . Then run rcapache2 restart . 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 the help of any these, check the online Apache bug
database at http://httpd.apache.org/bug_report.html . Additionally, the Apache user communi-
ty can be reached via a mailing list available at http://httpd.apache.org/userslist.html . A rec-
ommended newsgroup is comp.infosystems.www.servers.unix .

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 . Once 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-2.2/ . SUSE-specific configuration hints are available in the directory /usr/
share/doc/packages/apache2/README.* .
31.10.1 Apache 2.2

For a list of new features in Apache 2.2, refer to http://httpd.apache.org/docs/2.2/new_fea-
tures_2_2.html . Information about upgrading from version 2.0 to 2.2 is available at http://
httpd.apache.org/docs-2.2/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_mono
http://www.mono-project.com/Mod_mono
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/2.2/developer/
Writing Apache Modules with Perl and C

http://www.modperl.com/
443 Apache Modules SUSE Linux Enterp… 11 SP4

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.novell.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.
444 Miscellaneous Sources SUSE Linux Enterp… 11 SP4

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 provides a uni-
fied configuration interface for various FTP server daemons installed on your sys-
tem.
You can use the YaST FTP Server configuration module to configure two different FTP server
daemons:
vsftpd (Very Secure FTP Daemon) and
pure-ftpd
Only installed servers can be configured.

The vsftpd and pure-ftpd servers have slightly different configuration options, especially in the
Experts Settings dialog. This chapter describes the settings of the vsftpd server .
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 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 a server and confirm the dialog.
If there are two servers installed, choose the preferred server and click OK.
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
various 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.
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
446 Starting the FTP Server SUSE Linux Enterp… 11 SP4

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.
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.
447 FTP General Settings SUSE Linux Enterp… 11 SP4

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.
32.4 Authentication
In the Enable/Disable Anonymous and Local Users frame of the Authentication dialog, you are able
to 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.
If you want to allow users to upload les to the FTP server, check Enable Upload in the Uploading
frame of the Authentication dialog. Here you are able to 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 has 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, just 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.
448 Authentication SUSE Linux Enterp… 11 SP4

For more information about FTP servers read the manual pages of pure-ftpd , vsftpd and
vsftpd.conf .

33 The Squid Proxy Server
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 may be set up
in multiple hierarchies to assure optimal response times and low bandwidth usage,
even in modes that are transparent for the end user. Additional software like squid-
Guard may be used to filter Web contents.
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 ob-
jects to the client and keeps a copy of them in the hard disk cache. One of the advantages 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 the actual caching, Squid offers a wide range of features such as distributing the
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 with the
help of other applications, and generating statistics about frequently-visited Web pages for the
assessment of the users' 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 Real Audio, news, or video conferencing. Because Squid only
supports the UDP protocol to provide communication between different caches, many other
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.
450 Some Facts about Proxy Caches SUSE Linux Enterp… 11 SP4
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 33.5, “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 finding an object already existing in the local
network. It is also possible to configure cache hierarchies, so a cache is able to forward object
requests to sibling caches or to a parent cache—causing it to get 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 subnetwork 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 get the objects, one cache sends an ICP
request to all sibling proxies. These answer the requests via ICP responses with a HIT code if
the object was detected or a MISS if it was not. 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.
451 Squid and Security SUSE Linux Enterp… 11 SP4

Tip
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
Not all objects available in the network are static. There are a lot of dynamically generated CGI
pages, visitor counters, and encrypted SSL content documents. Objects like this are not cached
because they change each time they are accessed.
The question remains as to how long all the other objects stored in the cache should stay there.
To determine this, all objects in the cache are assigned one of various possible 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 are used as well.
Objects in the cache are normally replaced, due to a lack of free hard disk space, using algorithms
such as LRU (last recently used). Basically this means that the proxy expunges the objects that
have not been requested for the longest time.
33.2 System Requirements

The most important thing is to determine the maximum network load the system must bear.
Therefore, it is important to pay more attention to the load peaks, because these might be more
than four times the day's average. When in doubt, it would be better to overestimate the system's
requirements, because having Squid working close to the limit of its capabilities could lead to
a severe loss in the quality of the service. The following sections point to the system factors in
order of significance.
452 Caching Internet Objects SUSE Linux Enterp… 11 SP4

33.2.1 Hard Disks
Speed plays an important role in the caching process, so this factor deserves special attention. For
hard disks, this parameter is described as random seek time, measured in milliseconds. Because
the data blocks that Squid reads from or writes to the hard disk tend to be rather small, the
seek time of the hard disk is more important than its data throughput. For the purposes of a
proxy, hard disks with high rotation speeds are probably the better choice, because they allow
the read-write head to be positioned in the required spot more quickly. One possibility to speed
up the system is to use a number of disks concurrently or to employ striping RAID arrays.
33.2.2 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 the less requested objects are replaced by newer
ones. If, for example, one GB is available for the cache and the users only surf ten MB per day,
it would take more than one hundred days to ll the cache.
The easiest way to determine the needed cache size is to consider the maximum transfer rate of
the connection. With a 1 Mbit/s connection, the maximum transfer rate is 125 KB/s. If all this
traffic ends up in the cache, in one hour it would add up to 450 MB and, 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. This is why 2 GB of disk space is required
in the example for Squid to keep one day's worth of browsed data cached.
33.2.3 RAM
The amount of memory (RAM) required by Squid directly correlates to the number of objects
in the cache. Squid also stores cache object references and frequently requested objects in the
main memory to speed up retrieval of this data. Random access memory is much faster than
a hard disk.
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.
453 Hard Disks SUSE Linux Enterp… 11 SP4

It is very important to have sufficient memory for the Squid process, because system performance
is dramatically reduced if it must be swapped to disk. The cachemgr.cgi tool can be used for the
cache memory management. This tool is introduced in Section 33.6, “cachemgr.cgi”.
33.2.4 CPU
Squid is not a program that requires intensive CPU usage. The load of the processor is only
increased while the contents of the cache are loaded or checked. Using a multiprocessor machine
does not increase the performance of the system. To increase efficiency, it is better to buy faster
disks or add more memory.
33.3 Starting Squid

If not already installed, install the squid package. squid does not belong to the default SUSE
Linux Enterprise Server installation scope.
Squid is already pre-configured in SUSE® Linux Enterprise Server, you can start it right 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 entered,
because Squid does not start if it does not detect a DNS server in /etc/resolv.conf .
33.3.1 Commands for Starting and Stopping Squid
To start Squid, enter rcsquid start at the command line as root . In the initial start-up, the
directory structure of the cache must rst be defined in /var/cache/squid . This is done auto-
matically by the start script /etc/init.d/squid and can take a few seconds or even minutes. If
done appears to the right in green, Squid has been successfully loaded. To test the functionality
of Squid on the local system, enter localhost as the proxy and 3128 as the port in the browser.
454 CPU SUSE Linux Enterp… 11 SP4

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 that control access to the proxy.
More information about this is available in Section 33.4.2, “Options for Access Controls”.
After modifying the configuration le /etc/squid/squid.conf , Squid must reload the con-
figuration le. Do this with rcsquid reload . Alternatively, completely restart Squid with
rcsquid restart .
The command rcsquid status can be used to check if the proxy is running. The command
rcsquid stop causes Squid to shut down. This can take a while, because Squid waits up to
half a minute ( shutdown_lifetime option in /etc/squid/squid.conf ) before dropping the
connections to the clients and writing its data to the disk.
Warning: Terminating Squid

Terminating Squid with kill or killall can damage the cache. To be able to restart
Squid, a damaged cache must be deleted.
If Squid dies 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 . If Squid should be
loaded automatically when the system boots, use the YaST runlevel editor to activate Squid for
the desired runlevels. See Section 10.2.3, “Configuring System Services (Runlevel) with YaST”.
An uninstall of Squid does not remove the cache hierarchy or the log les. To remove these,
delete the /var/cache/squid directory manually.
33.3.2 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 or not you chose dynamic DNS during the
configuration of the Internet connection.
Dynamic DNS
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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 (see Section 10.3.1, “Changing the System Configuration Using the YaST
sysconfig Editor”). Then enter 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, enter it in the configuration le /etc/
named.conf under forwarders along with its IP address. With dynamic DNS, this can be
achieved automatically during connection establishment 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. You must, however, enter the local
DNS server in the le /etc/resolv.conf as described above. Additionally, the providers
static name server must be entered manually in the /etc/named.conf le under for-
warders along with its IP address.
Tip: DNS and Firewall

If you have a firewall running, make sure DNS requests can pass it.
33.4 The /etc/squid/squid.conf 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 pre-installed con-
figuration le /etc/squid/squid.conf provides detailed information about the options and
many examples. Nearly all entries begin with # (the lines are commented) and the relevant
specifications can be found at the end of the line. The given values almost always correlate
with the default values, so removing the comment signs without changing any of the parameters
actually has little effect in most cases. If possible, leave the sample as it is and insert the options
along with the modified parameters in the line below. This way, the default values may easily
be recovered and compared with the changes.
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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. If you
try to use the old squid.conf , you risk that the configuration no longer works, because
options are sometimes modified and new changes added.
33.4.1 General Configuration Options (Selection)
http_port 3128
This is the port on which Squid listens for client requests. The default port is 3128 , but
8080 is also common. If desired, specify several port numbers separated by blank spaces.
cache_peer hostname type proxy-port icp-port

Here, enter a parent proxy, for example, if you want to use the proxy of your ISP. As
hostname , enter the name or IP address of the proxy to use and, as type , enter parent .
For proxy-port , enter the port number that is also given by the operator of the parent
for use in the browser (usually 8080 ). Set the icp-port to 7 or 0 if the ICP port of the
parent is not known and its use is irrelevant to the provider. In addition, default and
no-query may be specified after the port numbers to prohibit the use of the ICP protocol.
Squid then behaves like a normal browser as far as the provider's proxy is concerned.
cache_mem 8 MB
This entry 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.
cache_dir ufs /var/cache/squid/ 100 16 256

The entry cache_dir defines the directory where all the objects are stored on disk. The
numbers at the end indicate the maximum disk space in MB to use and the number of
directories in the rst and second level. The ufs parameter should be left alone. The
default is 100 MB occupied disk space in the /var/cache/squid directory and creation
of 16 subdirectories inside it, each containing 256 more subdirectories. When specifying
the disk space to use, leave sufficient reserve disk space. Values from a minimum of 50%
to a maximum of 80% of the available disk space make the most sense here. The last
two numbers for the directories should only be increased with caution, because too many
directories can also lead to performance problems. If you have several disks that share the
cache, enter several cache_dir lines.
457 General Configuration Options (Selection) SUSE Linux Enterp… 11 SP4

cache_access_log /var/log/squid/access.log,
cache_log /var/log/squid/cache.log,
cache_store_log /var/log/squid/store.log
These three entries specify the paths where Squid logs all its actions. Normally, nothing
is changed here. If Squid is experiencing a heavy usage burden, it might make sense to
distribute the cache and the log les over several disks.
emulate_httpd_log o
If the entry is set to on, obtain readable log les. Some evaluation programs cannot inter-
pret this, however.
client_netmask 255.255.255.255
With this entry, mask IP addresses of clients in the log les. The last digit of the IP address
is set to zero if you enter 255.255.255.0 here. You may protect the privacy of your clients
this way.
ftp_user Squid@
With this, set the password Squid should use for the anonymous FTP login. It can make
sense to specify a valid e-mail address here, because some FTP servers check these for
validity.
cache_mgr webmaster
An e-mail address to which Squid sends a message if it unexpectedly crashes. The default
is webmaster.
logfile_rotate 0
If you run squid -k rotate , Squid can rotate secured log les. The les are numbered
in this process and, after reaching the specified value, the oldest le is overwritten. The
default value is 0 because archiving and deleting log les in SUSE Linux Enterprise Server
is carried out by a cron job set in the configuration le /etc/logrotate/squid .
append_domain <domain>
With append_domain, specify which domain to append automatically when none is given.
Usually, your own domain is entered here, so entering www in the browser accesses your
own Web server.
forwarded_for on
If you set the entry to o, Squid removes the IP address and the system name of the client
from HTTP requests. Otherwise it adds a line to the header like
458 General Configuration Options (Selection) SUSE Linux Enterp… 11 SP4

X-Forwarded-For: 192.168.0.1
negative_ttl 5 minutes; negative_dns_ttl 5 minutes

Normally, you do not need to change these values. If you have a dial-up connection, how-
ever, the Internet may, at times, not be accessible. Squid makes a note of the failed requests
then refuses to issue new ones, although the Internet connection has been reestablished.
In a case such as this, change the minutes to seconds. Then, after clicking Reload in the
browser, the dial-up process should be reengaged after a few seconds.
never_direct allow acl_name

To prevent Squid from taking requests directly from the Internet, use the above command
to force connection to another proxy. This must have previously been entered in cache_peer.
If all is specified as the acl_name , force all requests to be forwarded directly to the par-
ent. This might be necessary, for example, if you are using a provider that strictly stipulates
the use of its proxies or denies its firewall direct Internet access.
33.4.2 Options for Access Controls
Squid provides a detailed system for controlling the access to the proxy. By implementing ACLs,
it can be configured easily and comprehensively. This involves 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 in conjunction with http_access rules.
acl <acl_name> <type> <data>

An ACL requires at least three specifications to define it. 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 specifi-
cation for <data> depends on the individual ACL type and can also be read from a le, for
example, via hostnames, IP addresses, or URLs. The following are some simple examples:
acl mysurfers srcdomain .my-domain.com

acl teachers src 192.168.1.0/255.255.255.0
acl students src 192.168.7.0-192.168.9.0/255.255.255.0
acl lunch time MTWHF 12:00-15:00
http_access allow <acl_name>
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http_access defines who is allowed to use the proxy and who can access what on the Internet.
For this, ACLs must be given. localhost and all have already been defined above, which 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, and, 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, the 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 gets access Monday to Friday during lunch time.
http_access deny localhost

http_access allow teachers
http_access allow students lunch time
The list with the http_access entries should only be entered, for the sake of readability, at
the designated position in the /etc/squid/squid.conf le. That is, between the text
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR

# CLIENTS
and the last
redirect_program /usr/bin/squidGuard
With this option, specify a redirector such as squidGuard, which allows the blocking of
unwanted URLs. Internet access can be individually controlled for various user groups
with the help of proxy authentication and the appropriate ACLs. squidGuard is a separate
package that can be installed and configured.
auth_param basic program /usr/sbin/pam_auth

If users must be authenticated on the proxy, set a corresponding program, such as
pam_auth. When accessing pam_auth for the rst time, the user sees a login window in
which to enter the username and password. In addition, an ACL is still required, so only
clients with a valid login can use the Internet:
acl password proxy_auth REQUIRED
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http_access allow password
The REQUIRED after proxy_auth can be replaced with a list of permitted usernames or with
the path to such a list.
ident_lookup_access allow <acl_name>

With this, have an ident request run for all ACL-defined clients to nd each user's identity.
If you apply all to the <acl_name>, this is valid for all clients. Also, an ident daemon
must be running on all clients. For Linux, install the pidentd package for this purpose. For
Microsoft Windows, free software is available for download from the Internet. To ensure
that only clients with a successful ident lookup are permitted, define a corresponding ACL
here:
acl identhosts ident REQUIRED
http_access allow identhosts

Here, too, replace REQUIRED with a list of permitted usernames. Using ident can slow
down the access time quite a bit, because ident lookups are repeated for each request.
33.5 Configuring a Transparent Proxy

The usual way of working with proxy servers is the following: the Web browser sends requests
to a certain port in the proxy server and the proxy provides these required objects, whether they
are in its cache or not. When working in a network, several situations may arise:
For security reasons, it is recommended that all clients use a proxy to surf the Internet.
All clients must use a proxy, regardless of whether they are aware of it.
The proxy in a network is moved, but the existing clients need to retain their old config-
uration.
In all these cases, a transparent proxy may be used. The principle is very easy: the proxy inter-
cepts and answers the requests of the Web browser, so the Web browser receives the requested
pages without knowing from where they are coming. As the name indicates, the entire process
is done transparently.
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33.5.1 Configuration Options in /etc/squid/squid.conf
To inform squid that it should act as a transparent proxy, use the option transparent at the
tag http_port in the main configuration le /etc/squid/squid.conf . After restarting squid,
the only other thing that must be done is to reconfigure the firewall to redirect the http port to
the port given in http_port . In the following squid config line, this would be the port 3128.
http_port 3128 transparent
33.5.2 Firewall Configuration with SuSEfirewall2
Now redirect all incoming requests via the firewall with help of a port forwarding rule to the
Squid port. To do this, use the enclosed tool SuSEFirewall2, described in Book “Security Guide”,
Chapter 15 “Masquerading and Firewalls”, Section 15.4 “SuSEfirewall2”, Section 15.4.1 “Configuring the
Firewall with YaST”. Its configuration le can be found in /etc/sysconfig/SuSEfirewall2 . The
configuration le consists of well-documented entries. To set a transparent proxy, you must
configure several firewall options:
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"
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 “do-
main” stands for DNS (domain name service). This service is commonly used. Otherwise, simply
take it out of the above entries and set the following option to no :
FW_SERVICE_DNS="yes"
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The most important option is option number 15 :
EXAMPLE 33.1: FIREWALL CONFIGURATION: OPTION 15
# 15.)
# Which accesses to services should be redirected to a local port on
# the firewall machine?
#
# This option can be used to force all internal users to surf via
# your squid proxy, or transparently redirect incoming webtraffic to
# a secure webserver.
#
# 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
#
# Example: "10.0.0.0/8,0/0,tcp,80,3128 0/0,172.20.1.1,tcp,80,8080"
The comments above show the syntax to follow. First, enter the IP address and the netmask of
the internal networks accessing the proxy firewall. Second, enter 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.” After that, enter the original port to which these
requests are sent and, finally, the port to which all these requests are redirected. Because Squid
supports protocols other than HTTP, redirect requests from other ports to the proxy, such as
FTP (port 21), HTTPS, or SSL (port 443). In this example, Web services (port 80 ) are redirected
to the proxy port (port 3128 ). If there are more networks or services to add, they must be
separated by a blank space in the respective entry.
FW_REDIRECT="192.168.0.0/16,0/0,tcp,80,3128"
To start the firewall and the new configuration with it, change an entry in the /etc/syscon-
fig/SuSEfirewall2 le. The entry START_FW must be set to "yes" .
Start Squid as shown in Section 33.3, “Starting Squid”. To verify that everything is working properly,
check the Squid logs 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, the command syntax is nmap -O IP_address .
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33.6 cachemgr.cgi
The cache manager (cachemgr.cgi) is a CGI utility for displaying statistics about the memory
usage of a running Squid process. It is also a more convenient way to manage the cache and
view statistics without logging the server.
33.6.1 Setup
First, a running Web server on your system is required. Configure Apache as described in Chap-
ter 31, The Apache HTTP Server. To check if Apache is already running, as root enter the command
rcapache status . If a message like this appears:
Checking for service httpd: OK

Server uptime: 1 day 18 hours 29 minutes 39 seconds
Apache is running on the machine. Otherwise, enter rcapache start to start Apache with
the SUSE Linux Enterprise Server default settings. The last step to set it up is to copy the le
cachemgr.cgi to the Apache directory cgi-bin . For 32-bit, this works as follows:
cp /usr/lib/squid/cachemgr.cgi /srv/www/cgi-bin/
In a 64-bit environment, the le cachemgr.cgi is located below /usr/lib64/squid/ and the
command to copy it to the Apache directory is the following:
cp /usr/lib64/squid/cachemgr.cgi /srv/www/cgi-bin/
33.6.2 Cache Manager ACLs in /etc/squid/squid.conf

There are some default settings in the original le required for the cache manager. First, two
ACLs are defined, then http_access options use these ACLs to grant access from the CGI script
to Squid. The rst ACL is the most important, because the cache manager tries to communicate
with Squid over the cache_object protocol.
acl manager proto cache_object

acl localhost src 127.0.0.1/255.255.255.255
The following rules give Apache the access rights to Squid:
http_access allow manager localhost
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http_access deny manager
These rules assume that the Web server and Squid are running on the same machine. If the
communication between the cache manager and Squid originates at the Web server on another
computer, include an extra ACL as in Example 33.2, “Access Rules”.
EXAMPLE 33.2: ACCESS RULES
acl manager proto cache_object

acl localhost src 127.0.0.1/255.255.255.255
acl webserver src 192.168.1.7/255.255.255.255 # webserver IP
Then add the rules in Example 33.3, “Access Rules” to permit access from the Web server.
EXAMPLE 33.3: ACCESS RULES
http_access allow manager localhost

http_access allow manager webserver
http_access deny manager
Configure a password for the manager for access to more options, like closing the cache remotely
or viewing more information about the cache. For this, configure the entry cachemgr_passwd
with a password for the manager and the list of options to view. This list appears as a part of
the entry comments in /etc/squid/squid.conf .
Restart Squid every time the configuration le is changed. Do this easily with rcsquid reload .
33.6.3 Viewing the Statistics

Go to the corresponding Web site—http://webserver.example.org/cgi-bin/cachemgr.cgi . Press
continue and browse through the different statistics.
33.7 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 .
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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 script languages, such as JavaScript or VBscript.
Before it can be used, install squidGuard . Provide a minimal configuration le as /etc/squid-
guard.conf . Find configuration examples in http://www.squidguard.org/Doc/examples.html .
Experiment later with more complicated configuration settings.
Next, create a dummy “access denied” page or a more or less complex CGI page to redirect Squid
if the client requests a blacklisted Web site. Using Apache is strongly recommended.
Now, configure Squid to use squidGuard. Use the following entry in the /etc/squid/
squid.conf le:
redirect_program /usr/bin/squidGuard
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 (e.g. 4) rst.
redirect_children 4
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Last, have Squid load the new configuration by running rcsquid reload . Now, test your set-
tings with a browser.
33.8 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://Cala-
maris.Cord.de/ . This tool does not belong to the SUSE Linux Enterprise Server default instal-
lation scope—to use it, install the calamaris package.
Log in as root then enter cat access.log | calamaris options > reportfile. It is important
when piping more than one log le that the log les are chronologically ordered with older les
rst. These are some options of the program:
Tip: Shell and File Sequences

If you have multiple similar les like access.log.1 , access.log.2 and so on, the
default shell Bash would sort those les not in the number sequence when listing ac-
cess.log.* . To solve this issue, you may use the syntax access.log.{1..42} which
generates a list of les extended with numbers from 1 to 42.
-a
output all available reports
-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.
467 Cache Report Generation with Calamaris SUSE Linux Enterp… 11 SP4
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.
Following the installation, a small HOWTO about transparent proxies is available in how-
toenh as /usr/share/doc/howto/en/txt/TransparentProxy.gz . In addition, mailing lists
are available for Squid at squid-users@squid-cache.org . The archive for this is located at http://
www.squid-cache.org/mail-archive/squid-users/ .

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.
469 Introduction and Basic Concept SUSE Linux Enterp… 11 SP4

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).
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
470 Setting up SFCB SUSE Linux Enterp… 11 SP4

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 standalone command line WBEM client
especially suited for basic systems management tasks.
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.
471 Setting up SFCB SUSE Linux Enterp… 11 SP4

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.
472 Installing Additional Providers SUSE Linux Enterp… 11 SP4

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 startup. 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 rcsfcb start as root in the com-

mand line.
Stop sfcbd Enter rcsfcb stop as root in the com-

mand line.
Check sfcbd status Enter rcsfcb status as root in the com-

mand line.
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.
473 Starting, Stopping and Checking Status for SFCB SUSE Linux Enterp… 11 SP4
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.
If you want to generate a new certificate, enter the following command as root in the command
line:
tux@mercury:~> 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@mercury:~> sh /usr/share/sfcb/genSslCert.sh /etc/sfcb

Generating SSL certificates in .
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.
474 Ensuring Secure Access SUSE Linux Enterp… 11 SP4

If you want 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.
In order 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. As soon as the problem is resolved, dis-
able the non-secure port option back. In order 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”.
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 Enter-
prise Server installation of SFCB supports Pluggable Authentication Modules (PAM) approach;
therefore the local root user can authenticate to the SFCB CIMOM with local root user creden-
tials.
475 Ensuring Secure Access SUSE Linux Enterp… 11 SP4

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 is able to provide a valid
certificate, HTTPS connection will be established and the basic authentication procedure will
not be executed. 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. Basically, 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 rcsfcb restart for these changes to take effect.
PATH
Specifies the path to the sfcbd daemon and utilities.
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.
476 SFCB CIMOM Configuration SUSE Linux Enterp… 11 SP4

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.
-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 syslog. LOGLEVEL can be one of LOG_INFO, LOG_DEBUG,
or LOG_ERR, which is the default.
477 Command Line Options SUSE Linux Enterp… 11 SP4

-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@mercury:~> 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 .
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.
478 SFCB Configuration File SUSE Linux Enterp… 11 SP4

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.
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 username 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 to
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 comprised of 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.
490 Advanced SFCB Tasks SUSE Linux Enterp… 11 SP4

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 rcsfcb restart 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@mercury:~> ls /var/lib/sfcb/stage
default.reg mofs regs
tux@mercury:~> ls /var/lib/sfcb/stage/mofs
indication.mof root
tux@mercury:~> ls /var/lib/sfcb/stage/mofs/root
cimv2 interop suse virt
tux@mercury:~> ls -1 /var/lib/sfcb/stage/mofs/root/cimv2 | less

Linux_ABIParameter.mof
Linux_BaseIndication.mof
491 Installing CMPI Providers SUSE Linux Enterp… 11 SP4

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@mercury:~> 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@mercury:~> 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@mercury:~> 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 rcsfcb restart .
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"/>
494 Testing SFCB SUSE Linux Enterp… 11 SP4

<NAMESPACE NAME="cimv2"/>
</LOCALNAMESPACEPATH>
<IPARAMVALUE NAME="ClassName">
<CLASSNAME NAME=""/>
</IPARAMVALUE>
<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@mercury:~> 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>
495 Testing SFCB SUSE Linux Enterp… 11 SP4

</MESSAGE>
</CIM>
The classes listed will vary depending on what providers are installed on your system.
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@mercury:~> xmltest cim_xml_test.xml

Running test cim_xml_test.xml ... OK
Saving response as cim_xml_test.OK
tux@mercury:~> 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@mercury:~> 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
496 Command Line CIM Client: wbemcli SUSE Linux Enterp… 11 SP4
From server: CIMOperation: MethodResponse
From server: <?xml version="1.0" encoding="utf-8" ?>
<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 send to SFCB by wbemcli as well as the actual
XML received. In the above example, the rst of many returned classes was CIM_ResourcePool
followed 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@mercury:~> 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=, \
497 Command Line CIM Client: wbemcli SUSE Linux Enterp… 11 SP4
PoolID=,Primordial=,Capacity=,Reserved=,ResourceType=, \
OtherResourceType=,ResourceSubType=, \AllocationUnits=
localhost:5988/root/cimv2:Linux_ReiserFileSystem FSReservedCapacity=, \
TotalInodes=,FreeInodes=,ResizeIncrement=,IsFixedSize=,NumberOfFiles=, \
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

V Troubleshooting
35 Help and Documentation 500
36 Common Problems and Their Solutions 506

35 Help and Documentation
SUSE® Linux Enterprise Server comes with various sources of information and doc-
umentation, 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 35.1, “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 35.2, “Man Pages” and Section 35.3, “Info Pages”.
Desktop Help Centers

The help centers of both the KDE desktop (KDE help center) and the GNOME desktop (Yelp)
provide central access to the most important documentation resources on your system in
searchable form. These resources include online help for installed applications, man pages,
info pages, and the Novell/SUSE manuals delivered with your product.
Separate Help Packages for Some Applications

When installing new software with YaST, the software documentation is installed auto-
matically (in most cases) and usually 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.
35.1 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.
500 Documentation Directory SUSE Linux Enterp… 11 SP4

Note: Contents Depends on Installed Packages
In the Linux world, many manuals and other kinds of documentation are available in the
form of packages, just 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.
35.1.1 Novell/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 Novell/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 Novell/SUSE manuals are also avail-
able in the help center of both desktops. For information on where to nd the PDF and HTML ver-
sions 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/doc/ .
35.1.2 HOWTOs
If the howto package is installed on your system, /usr/share/doc also holds the howto sub-
directory, where you nd additional documentation for many tasks relating to the setup and
operation of Linux software.
35.1.3 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, configura-
tion 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 just
include a few of them.
501 Novell/SUSE Manuals SUSE Linux Enterp… 11 SP4

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.
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.
35.2 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 .
502 Man Pages SUSE Linux Enterp… 11 SP4

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 35.1, “Man Pages—Categories and Descriptions”
(taken from the man page for man itself).
TABLE 35.1: 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.
503 Man Pages SUSE Linux Enterp… 11 SP4

35.3 Info Pages
Info pages are another important source of information on your system. Usually, they are more
detailed than man pages. 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 backwards. Within a node, you can also browse with Page ↑
and Page ↓ but only Space and <— will take you also to the previous or subsequent node.
Press Q to end the viewing mode. Not every man page comes with an info page and vice versa.
35.4 Online Resources

In addition to the online versions of the Novell 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:
Novell Technical Support Knowledgebase

The Novell Technical Support Knowledgebase can be found at http://www.novell.com/sup-
port/ . It features articles written as solutions for technical problems with SUSE Linux
Enterprise Server.
Novell Forums
There are several forums where you can dive in on discussions about Novell products. See
http://forums.novell.com/ for a list.
Cool Solutions
An online community, which offers articles, tips, Q and A, and free tools to download:
http://www.novell.com/communities/coolsolutions
KDE Documentation
Find documentation for many aspects of KDE suitable for users and administrators at http://
www.kde.org/documentation/ .
GNOME Documentation
504 Info Pages SUSE Linux Enterp… 11 SP4

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's 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 is also available on SUSE Linux Enterprise Server
You may also want to try general-purpose search engines. For example, use search terms Linux
CD-RW help or OpenOffice file conversion problem if you have trouble with burning CDs
or LibreOffice le conversion.
505 Online Resources SUSE Linux Enterp… 11 SP4

36 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.
36.1 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
of which 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 36.1: 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 system,
and trace system calls.
/var/log/boot.msg Messages from the kernel reported during

the boot process.
/var/log/mail.* Messages from the mail system.
506 Finding and Gathering Information SUSE Linux Enterp… 11 SP4

Log File Description
/var/log/messages Ongoing messages from the kernel and sys-

tem log daemon (when running).
/var/log/NetworkManager Log le from NetworkManager to collect

problems with network connectivity
/var/log/samba/ Directory containing Samba server and client

log messages.
/var/log/SaX.log Hardware messages from the SaX display and

KVM system.
/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 logs from the

X Window system. It is useful for debugging
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 36.2: System Information With the /proc File System
TABLE 36.2: SYSTEM INFORMATION WITH THE /proc FILE SYSTEM
File Description
/proc/cpuinfo Contains processor information, including its

type, make, model, and performance.

File Description
/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.
/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 15, Dynamic Kernel
Device Management with udev. Table 36.3 contains an overview of the most common directories
under /sys .
TABLE 36.3: 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.

File Description
/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 a number of tools for system analysis and monitoring. See Book “System Analy-
sis 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.
36.2 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 of the typical problems
you may run into, and offers possible solutions or workarounds for these kinds of situations.
36.2.1 Checking Media
If you encounter any problems using the SUSE Linux Enterprise Server installation media, check
the integrity of your installation media with Software Media Check. Media problems are more
probable with the media you burn yourself. 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.
509 Installation Problems SUSE Linux Enterp… 11 SP4

FIGURE 36.1: CHECKING MEDIA
36.2.2 Hardware Information
Display detected hardware and technical data using Hardware Hardware Information. Click any
node of the tree for more information about a device. This module is especially useful, when
submitting a support request for which you need information about your hardware.
Save the displayed hardware information to a le by clicking Save to File. Select the desired
directory and filename then click Save to create the le.
510 Hardware Information SUSE Linux Enterp… 11 SP4

FIGURE 36.2: DISPLAYING HARDWARE INFORMATION
36.2.3 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:
Booting from a Floppy Disk

Create a boot floppy and boot from floppy disk instead of DVD.
Using an External Boot Device

If it is supported by your BIOS and the installation kernel, boot from external DVD drives.
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 14 “Remote
Installation”, Section 14.1 “Installation Scenarios for Remote Installation”, Section 14.1.3 “Remote
511 No Bootable DVD Drive Available SUSE Linux Enterp… 11 SP4

Installation via VNC—PXE Boot and Wake on LAN” and Book “Deployment Guide”, Chapter 14
“Remote Installation”, Section 14.1 “Installation Scenarios for Remote Installation”, Section 14.1.6
“Remote Installation via SSH—PXE Boot and Wake on LAN” for details.
36.2.3.1 Booting from a Floppy Disk (SYSLINUX)
On some older computers, there is no bootable DVD drive available, but there is a floppy disk
drive present. To install on such a system, create boot disks and boot your system with them.
The boot disks include the loader called SYSLINUX and the program linuxrc. SYSLINUX enables
the selection of a kernel during the boot procedure and the specification of any parameters
needed for the hardware used. The program linuxrc supports the loading of kernel modules for
your hardware and subsequently starts the installation.
When booting from a boot disk, the boot procedure is initiated by the boot loader SYSLINUX
(package syslinux ). When the system is booted, SYSLINUX runs a minimum hardware detec-
tion that mainly consists of the following steps:
1. The program checks if the BIOS provides VESA 2.0–compliant framebuffer support and
boots the kernel accordingly.
2. The monitor data (DDC info) is read.
3. The rst block of the rst hard disk (MBR) is read to map BIOS IDs to Linux device names
during the boot loader configuration. The program attempts to read the block by means
of the the lba32 functions of the BIOS to determine if the BIOS supports these functions.
If you keep Shift pressed when SYSLINUX starts, all these steps are skipped. For troubleshoot-
ing purposes, insert the line
verbose 1
in syslinux.cfg for the boot loader to display which action is currently being performed.
If the machine does not boot from the floppy disk, you may need to change the boot sequence
in the BIOS to A,C,CDROM .
512 No Bootable DVD Drive Available SUSE Linux Enterp… 11 SP4

36.2.3.2 External Boot Devices
Linux supports most existing DVD drives. If the system has neither a DVD drive nor a floppy
disk, 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.
36.2.4 Booting from Installation Media Fails

One reason why a machine does not boot the installation media can be an incorrect boot se-
quence 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. Guidance for changing the BIOS boot sequence can be found the documentation provided
with your motherboard, 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 a number of 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 36.1: 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.
The boot sequence looks something like C,A or A,C . In the former case, the machine rst
searches the hard disk (C) then the floppy drive (A) to nd a bootable medium. Change
the settings by pressing PgUp or PgDown until the sequence is A,CDROM,C .
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 .
513 Booting from Installation Media Fails SUSE Linux Enterp… 11 SP4
PROCEDURE 36.2: CHANGING THE BOOT SEQUENCE IN A 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 depicted in the following figure:
Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12
~ ! @ # $ % ^ & * ( ) _ + |
- <--
` 1 2 3 4 5 6 7 8 9 0 = \
Tab Q W E R T Y U I O P { }
[ ]
Caps A S D F G H J K L : "
Lock ; ' Enter
Shift Z X C V B N M < > ? Shift
, . /
Ctrl Alt Alt Ctrl
FIGURE 36.3: US KEYBOARD LAYOUT
36.2.5 Fails to Boot

Some hardware types, mainly very old or very recent ones, fail to install. In many cases, this
may happen because support for this type of hardware is missing in the installation kernel, or
due to certain functionality included in this kernel, such as ACPI, that can still cause problems
on some hardware.
514 Fails to Boot SUSE Linux Enterp… 11 SP4

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 various 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 at all 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.
acpi=ht
515 Fails to Boot SUSE Linux Enterp… 11 SP4

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.
36.2.6 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.
PROCEDURE 36.3: CHANGE SCREEN RESOLUTION FOR INSTALLATION
1. Boot for installation.
516 Fails to Launch Graphical Installer SUSE Linux Enterp… 11 SP4

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 36.4: 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 36.5: 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 hit 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”.
Important
Installation via VNC works with any browser under any operating system, provided
Java support is enabled.
517 Fails to Launch Graphical Installer SUSE Linux Enterp… 11 SP4

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.
36.2.7 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 hit 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 36.2.5, “Fails to Boot”. To launch the instal-
lation process, press Enter .
Screen Resolutions
Use the F keys to determine the screen resolution for installation. If you need to boot in
text mode, choose F3 .
36.3 Boot Problems

Boot problems are situations when your system does not boot properly (does not boot to the
expected runlevel and login screen).
518 Only Minimalistic Boot Screen Started SUSE Linux Enterp… 11 SP4
36.3.1 Fails to Load the GRUB Boot Loader
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 reinstall the boot loader. To reinstall
the boot loader, proceed as follows:
1. Insert the installation media into the drive.
2. Reboot the machine.
3. Select Installation from the boot menu.
4. Select a language.
5. Accept the license agreement.
6. In the Installation Mode screen, select Repair Installed System.
7. Once in the YaST System Repair module, select Expert Tools then select Install New Boot
Loader.
8. Restore the original settings and reinstall the boot loader.
9. Leave YaST System Repair and reboot the system.
Other reasons for the machine not booting may be BIOS-related:
BIOS Settings
Check your BIOS for references to your hard drive. GRUB may simply not be started if the
hard drive 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.
519 Fails to Load the GRUB Boot Loader SUSE Linux Enterp… 11 SP4
36.3.2 No Graphical Login
If the machine comes up, but does not boot into the graphical login manager, anticipate problems
either with the choice of the default runlevel or the configuration of the X Window System. To
check the runlevel configuration, log in as the root user and check whether the machine is
configured to boot into runlevel 5 (graphical desktop). A quick way to check this is to examine
the contents of /etc/inittab , as follows:
tux@mercury:~> grep "id:" /etc/inittab

id:5:initdefault:
The returned line indicates that the machine's default runlevel ( initdefault ) is set to 5 and
that it should boot to the graphical desktop. If the runlevel is set to any other number, use the
YaST Runlevel Editor module to set it to 5 .
Important
Do not edit the runlevel configuration manually. Otherwise SuSEconfig (run by YaST) will
overwrite these changes on its next run. If you need to make manual changes here, disable
future SuSEconfig changes by setting CHECK_INITTAB in /etc/sysconfig/suseconfig
to no .
If the runlevel is set to 5 , your desktop or X Windows 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 /
var/log/messages . 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.
Tip: Starting X Window System Manually

One quick test: the startx command should force the X Window System to start with
the configured defaults if the user is currently logged in on the console. If that does not
work, it should log errors to the console.
520 No Graphical Login SUSE Linux Enterp… 11 SP4

36.4 Login Problems
Login problems are those where your machine does, in fact, boot to the expected welcome
screen or login prompt, but refuses to accept the username 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.).
36.4.1 Valid Username and Password Combinations Fail

This usually occurs when the system is configured to use network authentication or directory
services and, for some reason, is unable to 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 why a machine appears functional but is unable to process logins
correctly:
The network is not working. For further directions on this, turn to Section 36.5, “Network
Problems”.
DNS is not working at the moment (which prevents GNOME or KDE 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 36.5, “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 36.4.3,
“Login to Encrypted Home Partition Fails”.
521 Login Problems SUSE Linux Enterp… 11 SP4

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. Enter 1 at the boot prompt to make the system boot into single-user mode.
3. Enter the username and password for root .
4. Make all the necessary changes.
5. Boot into the full multiuser and network mode by entering telinit 5 at the command
line.
36.4.2 Valid Username 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 /var/log/messages for error messages of the login process
and of PAM.
522 Valid Username and Password Not Accepted SUSE Linux Enterp… 11 SP4
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 desktop (GNOME or KDE). For
more information, refer to Section 36.4.4, “Login Successful but GNOME Desktop Fails” and Sec-
tion 36.4.5, “Login Successful but KDE Desktop Fails”.
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 graphical login still fails, do a console login with Ctrl – Alt – F1 . Try to start an X
session on another display—the rst one ( :0 ) is already in use:
startx -- :1
This should bring up a graphical screen and your desktop. If it does not, check the log
les of the X Window System ( /var/log/Xorg.displaynumber.log ) or the log le for
your desktop applications ( .xsession-errors in the user's home directory) for any ir-
regularities.
6. If the desktop could not start because of corrupt configuration les, proceed with Sec-
tion 36.4.4, “Login Successful but GNOME Desktop Fails” or Section 36.4.5, “Login Successful but
KDE Desktop Fails”.
The following are some common reasons why network authentication for a particular user may
fail on a specific machine:
The user may have entered the wrong password.
The username 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 hostnames, 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 username and password work on other machines to make sure
that his authentication data exists and is properly distributed.
4. See if another user can log in to the misbehaving machine. If another user can log in
without difficulty or if root can log in, log in and examine the /var/log/messages le.
Locate the time stamps that correspond to the login attempts and determine 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 desktop (GNOME or KDE). For more information, refer to
Section 36.4.4, “Login Successful but GNOME Desktop Fails” and Section 36.4.5, “Login Successful
but KDE 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 graphical login still fails, do a console login with Ctrl – Alt – F1 . Try to start an X
session on another display—the rst one ( :0 ) is already in use:
startx -- :1
This should bring up a graphical screen and your desktop. If it does not, check the log
les of the X Window System ( /var/log/Xorg.displaynumber.log ) or the log le for
your desktop applications ( .xsession-errors in the user's home directory) for any ir-
regularities.
8. If the desktop could not start because of corrupt configuration les, proceed with Sec-
tion 36.4.4, “Login Successful but GNOME Desktop Fails” or Section 36.4.5, “Login Successful but
KDE Desktop Fails”.
36.4.3 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 have 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:
/etc/init.d/boot.crypto restart
4. Enter your passphrase to unlock your encrypted partition.
5. Exit the text console and switch back to the login screen with Alt – F7 .
6. Log in as usual.
36.4.4 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
525 Login to Encrypted Home Partition Fails SUSE Linux Enterp… 11 SP4
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 username.
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.
36.4.5 Login Successful but KDE Desktop Fails

There are several reasons why a KDE desktop would not allow users to login. Corrupted cache
data can cause login problems as well as corrupt KDE desktop configuration les.
Cache data is used at desktop start-up to increase performance. If this data is corrupted, start-
up is slowed down or fails entirely. Removing them forces the desktop start-up routines to start
from scratch. This takes more time than a normal start-up, but data is intact after this and the
user can login.
To remove the cache les of the KDE desktop, issue the following command as root :
rm -rf /tmp/kde-user /tmp/ksocket-user
Replace user with your username. Removing these two directories just removes the corrupted
cache les. No real data is harmed using this procedure.
526 Login Successful but KDE Desktop Fails SUSE Linux Enterp… 11 SP4
Corrupted desktop configuration les can always be replaced with the initial configuration les.
If you want to recover the user's adjustments, carefully copy them back from their temporary
location after the configuration has been restored, using the default configuration values.
To replace a corrupted desktop configuration with the initial configuration values, proceed as
follows:
1. Switch to a text console by pressing Ctrl – Alt – F1 .
2. Log in with your username.
3. Move the KDE configuration directory and the .skel les to a temporary location:
For KDE3 use these commands:
mv .kde .kde-ORIG-RECOVER
mv .skel .skel-ORIG-RECOVER
For KDE4 use these commands:
mv .kde4 .kde4-ORIG-RECOVER
mv .skel .skel-ORIG-RECOVER
4. Log out.
5. Log in again.
6. After the desktop has started successfully, copy the user's own configurations back into
place:
cp -a KDEDIR/share .kde/share
Replace KDEDIR with the directory from Step 3.
Important
If the user's own adjustments caused the login to fail and continue to do so, repeat
the procedure as described above, but do not copy the .kde/share directory.
527 Login Successful but KDE Desktop Fails SUSE Linux Enterp… 11 SP4
36.5 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.
PROCEDURE 36.6: 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 set-
up. Either look them up in the appropriate YaST module or ask your system administrator.
The following list gives some of the 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 due to 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)
528 Network Problems SUSE Linux Enterp… 11 SP4

If any application needs data stored in an NFS mounted directory, it will not be able
to 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 or .kde subdirectories could not be found
due to a faulty NFS server.
Samba (File Service)

If any application needs data stored in a directory on a faulty Samba server, it will
not be able to start or function properly.
NIS (User Management)

If your SUSE Linux Enterprise Server system relies on a faulty NIS server to provide
the user data, users will not be able to 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 will not be able to 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
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 or hostname (replace hostname with the hostname 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
at all or not configured correctly.
If ping fails with unknown host , the name service is not configured correctly or the
hostname 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 hostname 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 Setting module (Hostname/DNS tab).
If your network connection is handled via DHCP, enable DHCP to change host-
name and name service information by selecting Change Hostname via DHCP
and Update Name Servers and Search List via DHCP in the YaST DNS and Host-
name module.
/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 ifconfig network_device (executed as root ) to check
whether this device was properly configured. Make sure that both inet address
and Mask are 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 at all. 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.

36.5.1 NetworkManager Problems
If you have a problem with network connectivity, narrow it down as described in Procedure 36.6,
“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:
rcnetwork restart -o nm
3. Open a Web page, for example, http://www.opensuse.org as normal user to see, if you
can connect.
4. Collect any information about the state of NetworkManager in /var/log/NetworkMan-

ager .
For more information about NetworkManager, refer to Chapter 27, Using NetworkManager.
36.6 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. SUSE Linux Enterprise Server offers dedicated YaST modules for
system backup and restoration as well as a rescue system that can be used to recover a corrupted
system from the outside.
36.6.1 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 a exact copy of your disc. Combined with gzip you
save some space.
PROCEDURE 36.7: BACKING UP AND RESTORING HARDDISKS
1. Start a Shell as user root .
2. Select your source device. Typically this is something like /dev/sda (labeled as SOURCE ).
532 NetworkManager Problems SUSE Linux Enterp… 11 SP4

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 a partition to backup, 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.
36.6.2 Backing Up Critical Data
System backups can be easily managed using the YaST System Backup module:
1. As root , start YaST and select System System Backup.
2. Create a backup profile holding all details needed for the backup, filename of the archive
le, scope, and type of the backup:
a. Select Profile Management Add.
b. Enter a name for the archive.
c. Enter the path to the location of the backup if you want to keep a local backup. For
your backup to be archived on a network server (via NFS), enter the IP address or
name of the server and the directory that should hold your archive.
d. Determine the archive type and click Next.
e. Determine the backup options to use, such as whether les not belonging to any
package should be backed up and whether a list of les should be displayed prior
to creating the archive. Also determine whether changed les should be identified
using the time-consuming MD5 mechanism.
Use Expert to enter a dialog for the backup of entire hard disk areas. Currently, this
option only applies to the Ext2 le system.
533 Backing Up Critical Data SUSE Linux Enterp… 11 SP4

f. Finally, set the search constraints to exclude certain system areas from the backup
area that do not need to be backed up, such as lock les or cache les. Add, edit, or
delete items until your needs are met and leave with OK.
3. Once you have finished the profile settings, you can start the backup right away with
Create Backup or configure automatic backup. It is also possible to create other profiles
tailored for various other purposes.
To configure automatic backup for a given profile, proceed as follows:
1. Select Automatic Backup from the Profile Management menu.
2. Select Start Backup Automatically.
3. Determine the backup frequency. Choose daily, weekly, or monthly.
4. Determine the backup start time. These settings depend on the backup frequency selected.
5. Decide whether to keep old backups and how many should be kept. To receive an auto-
matically generated status message of the backup process, check Send Summary Mail to
User root.
6. Click OK to apply your settings and have the rst backup start at the time specified.
36.6.3 Restoring a System Backup

Use the YaST System Restoration module to restore the system configuration from a backup.
Restore the entire backup or select specific components that were corrupted and need to be
reset to their old state.
1. Start YaST System System Restoration.
2. Enter the location of the backup le. This could be a local le, a network mounted le, or
a le on a removable device, such as a floppy or a DVD. Then click Next.
The following dialog displays a summary of the archive properties, such as the filename,
date of creation, type of backup, and optional comments.
3. Review the archived content by clicking Archive Content. Clicking OK returns you to the
Archive Properties dialog.
4. Expert Options opens a dialog in which to ne-tune the restore process. Return to the
Archive Properties dialog by clicking OK.
534 Restoring a System Backup SUSE Linux Enterp… 11 SP4

5. Click Next to open the view of packages to restore. Press Accept to restore all les in the
archive or use the various Select All, Deselect All, and Select Files buttons to ne-tune your
selection. Only use the Restore RPM Database option if the RPM database is corrupted or
deleted and this le is included in the backup.
6. After you click Accept, the backup is restored. Click Finish to leave the module after the
restore process is completed.
36.6.4 Recovering a Corrupted System
There are several reasons why 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
configuration are the most common ones.
SUSE Linux Enterprise Server offers two different methods to resolve these situations. You can
either use the YaST System Repair functionality or boot the rescue system. The following sections
cover both types of system repair methods.
36.6.4.1 Using YaST System Repair
Note: Keyboard and Language Settings

If you change the language settings after booting, your keyboard is adapted as well.
Before launching the YaST System Repair module, determine in which mode to run it to best t
your needs. Depending on the severity and cause of your system failure (and your expertise),
there are three different modes to choose from:
Automatic Repair
If your system failed due to an unknown cause and you basically do not know which part of
the system is to blame for the failure, use Automatic Repair. An extensive automated check
will be performed on all components of your installed system. For a detailed description
of this procedure, refer to Section 36.6.4.1.1, “Automatic Repair”.
Customized Repair
535 Recovering a Corrupted System SUSE Linux Enterp… 11 SP4

If your system failed and you already know which component is to blame, you can cut
the lengthy system check with Automatic Repair short by limiting the scope of the system
analysis to those components. For example, if the system messages prior to the failure
seem to indicate an error with the package database, you can limit the analysis and repair
procedure to checking and restoring this aspect of your system. For a detailed description
of this procedure, refer to Section 36.6.4.1.2, “Customized Repair”.
Expert Tools
If you already have a clear idea of what component failed and how this should be xed,
you can skip the analysis runs and directly apply the tools necessary for the repair of the
relevant component. For details, refer to Section 36.6.4.1.3, “Expert Tools”.
Choose one of the repair modes as described above and proceed with the system repair as out-
lined in the following sections.
36.6.4.1.1 Automatic Repair
To start the automatic repair mode of YaST System Repair, proceed as follows:
1. Insert the installation medium of SUSE Linux Enterprise Server into your DVD drive.
2. Reboot the system.
3. On the boot screen, select Repair Installed System.
4. Confirm the license agreement and click Next.
5. Select Automatic Repair.

YaST now launches an extensive analysis of the installed system. The progress of the pro-
cedure is displayed at the bottom of the screen with two progress bars. The upper bar
shows the progress of the currently running test. The lower bar shows the overall progress
of the analysis. The log window in the top section tracks the currently running test and
its result. See Figure 36.4, “Automatic Repair Mode”.

FIGURE 36.4: AUTOMATIC REPAIR MODE
The following main test runs are performed with every run. They contain, in turn, a num-
ber of individual subtests:
Check Partition Tables

Checks the validity and coherence of the partition tables of all detected hard disks.
Check Swap Areas

The swap partitions of the installed system are detected, tested, and offered for ac-
tivation, where applicable. This offer should be accepted for the sake of a higher
system repair speed.
Check File Systems

All detected le systems are subjected to a le system–specific check.
Check fstab Entries

The entries in the le are checked for completeness and consistency. All valid par-
titions are mounted.
Check Package Database

This checks whether all packages necessary for the operation of a minimal installa-
tion are present. While it is optionally possible to also analyze the base packages,
this takes a long time because of their vast number.
Check Boot Loader Configuration

The boot loader configuration of the installed system (GRUB or LILO) is checked for
completeness and coherence. Boot and root devices are examined and the availability
of the initrd modules is checked.
6. Whenever an error is encountered, the procedure stops and a dialog opens outlining the
details and possible solutions.
Read the screen messages carefully before accepting the proposed x. If you decide to
decline a proposed solution, your system remains unchanged.
7. After the repair process has been terminated successfully, click OK and Finish and remove
the installation media. The system automatically reboots.
36.6.4.1.2 Customized Repair
To launch the Customized Repair mode and selectively check certain components of your
installed system, proceed as follows:
3. At the boot screen, select Repair Installed System.
5. Select Customized Repair.

Choosing Customized Repair shows a list of test runs that are all marked for execution at
rst. The total range of tests matches that of automatic repair. If you already know where
no damage is present, unmark the corresponding tests. Clicking Next starts a narrower test
procedure that probably has a significantly shorter running time.
Not all test groups can be applied individually. The analysis of the fstab entries is always
bound to an examination of the le systems, including existing swap partitions. YaST
automatically resolves such dependencies by selecting the smallest number of necessary
test runs. YaST does not support encrypted partitions. If you have one, YaST informs you
about it.

6. Whenever an error is encountered, the procedure stops and a dialog opens outlining the
details and possible solutions.
Read the screen messages carefully before accepting the proposed x. If you decide to
decline a proposed solution, your system remains unchanged.
36.6.4.1.3 Expert Tools
If you are knowledgeable with SUSE Linux Enterprise Server and already have a very clear idea of
what needs to be repaired in your system, directly apply the tools, skipping the system analysis.
To make use of the Expert Tools feature of the YaST System Repair module, proceed as follows:
3. At the boot screen, select Repair Installed System.
5. Select Expert Tools and choose a repair option.
The Expert Tools provides the following options to repair your faulty system:
Install New Boot Loader

This starts the YaST boot loader configuration module. Find details in Section 11.2, “Config-
uring the Boot Loader with YaST”.
Boot Installed System

Try to boot an already-installed Linux system.
Start Partitioning Tool

This starts the expert partitioning tool in YaST.
Repair File System

This checks the le systems of your installed system. You are rst offered a selection of all
detected partitions and can then choose the ones to check.

Recover Lost Partitions
It is possible to attempt to reconstruct damaged partition tables. A list of detected hard
disks is presented rst for selection. Clicking OK starts the examination. This can take a
while depending on the speed of your computer and the size and speed of the hard disk.
Important: Reconstructing a Partition Table

The reconstruction of a partition table is tricky. YaST attempts to recognize lost
partitions by analyzing the data sectors of the hard disk. The lost partitions are added
to the rebuilt partition table when recognized. This is, however, not successful in
all imaginable cases.
Save System Settings to Floppy

This option saves important system les to a floppy disk. If one of these les becomes
damaged, it can be restored from disk.
Verify Installed Software

This checks the consistency of the package database and the availability of the most im-
portant packages. Any damaged installed packages can be reinstalled with this tool.
36.6.4.2 Using the Rescue System
SUSE Linux Enterprise Server contains a rescue system. 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 reinstall 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 website 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:
1. Insert the installation medium into your DVD drive.
3. At the boot screen, press F4 and choose DVD-ROM. Then choose Rescue System from the
main menu.
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 14
“Remote Installation”, Section 14.3 “Preparing the Boot of the Target System”, Section 14.3.7 “Wake
on LAN”.
Once you have entered the rescue system, you can make use of the virtual consoles that can be
reached with Alt – F1 to Alt – F6 .
A shell and many other useful utilities, such as the mount program, are available in the /bin
directory. The sbin directory contains important le and network utilities for reviewing and
repairing the le system. This directory also contains the most important binaries for system
maintenance, such as fdisk, mkfs, mkswap, mount, mount, init, and shutdown, and ifconfig, ip,
route, and netstat 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 le /var/log/mes-
sages .

36.6.4.2.1 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.
36.6.4.2.2 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. It is
strongly recommended to use the YaST System Repair for this task (see Section 36.6.4.1, “Using
YaST System Repair” for details). However, if you need to do a manual le system check or repair,
boot the rescue system. It contains the utilities to check and repair the btrfs , ext2 , ext3 ,
ext4 , reiserfs , xfs , dosfs , and vfat le systems.

36.6.4.2.3 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. First mount the root partition from the installed system and the device le system (change
the device name to your current settings):
mount /dev/sda6 /mnt

mount --bind /dev /mnt/dev
2. Now you can “change root” into the new environment:
chroot /mnt
3. Then mount /proc and /sys :
mount /proc
mount /sys
4. Finally, mount the remaining partitions from the installed system:
mount -a
5. 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 rescue
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 exactly the same. 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 USB stick. 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 .
36.6.4.2.4 Modifying and Reinstalling 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 reinstall the boot loader, proceed as follows:
1. Perform the necessary steps to access the installed system as described in Section 36.6.4.2.3,
“Accessing the Installed System”.
2. Check whether the following les are correctly configured according to the GRUB config-
uration principles outlined in Chapter 11, The Boot Loader GRUB and apply fixes if necessary.
/etc/grub.conf
/boot/grub/device.map
/boot/grub/menu.lst
/etc/sysconfig/bootloader
3. Reinstall the boot loader using the following command sequence:
4. Unmount the partitions, log out from the “change root” environment, and reboot the sys-
tem:
umount -a
exit
reboot

36.6.4.2.5 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.
A similar case is when you need to reinstall or update a broken driver for a device not supported
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 op-
erating system. The vendor typically releases a Driver Update Disk 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 36.6.4.2.3, “Accessing the Installed System”.
6. If using DUD, install/reinstall/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.
d. After the installation finishes, check that a new menu entry relevant for the new-
ly installed kernel was added to the boot loader configuration le ( /boot/grub/
menu.lst for grub ).
7. Update configuration les and reinitialize the boot loader if needed. For more information,
see Section 36.6.4.2.4, “Modifying and Reinstalling the Boot Loader”.
8. Remove any bootable media from the system drive and reboot.
36.7 IBM System z: Using initrd as a Rescue System

If the kernel of the SUSE® Linux Enterprise Server for IBM System z 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. This most commonly occurs if a new or updated SUSE Linux
Enterprise Server kernel has been installed and the zipl program has not been run to update the
IPL record. In this case, use the standard installation package as a rescue system from which the
zipl program can be executed to update the IPL record.
36.7.1 IPLing the Rescue System
Important: Making the Installation Data Available

For this method to work, the SUSE Linux Enterprise Server for IBM System z installation
data must be available. For details, refer to Book “Deployment Guide”, Chapter 4 “Installation
on IBM System z”, Section 4.2 “Preparing for Installation”, Section 4.2.1 “Making the Installation
546 IBM System z: Using initrd as a Rescue System SUSE Linux Enterp… 11 SP4
Data Available”. Additionally, you need the channel number of the device and the partition
number within the device that contains the root le system of the SUSE Linux Enterprise
Server installation.
First, IPL the SUSE Linux Enterprise Server for IBM System z installation system as described in
Book “Deployment Guide”, Chapter 4 “Installation on IBM System z”, Section 4.2 “Preparing for Installa-
tion”. A list of choices for the network adapter to use is then presented.
Select Start Installation or System then Start Rescue System to start the rescue system. Depending
on the installation environment, you now must specify the parameters for the network adapter
and the installation source. The rescue system is loaded and the following login prompt is shown
at the end:
Skipped services in runlevel 3: nfs nfsboot
Rescue login:
You can now log in as root without a password.
36.7.2 Configuring Disks

In this state, no disks are configured. You need to configure them before you can proceed.
PROCEDURE 36.8: 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 36.9: CONFIGURING A ZFCP DISK
1. To configure a zFCP disk, it is necessary to rst configure the zFCP adapter. Do this with
the following command:
zfcp_host_configure 0.0.4000 1
547 Configuring Disks SUSE Linux Enterp… 11 SP4

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
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.
36.7.3 Mounting the Root Device

If all needed disks are online, you should now be able to mount the root device. Assuming that
the root device is on the second partition of the DASD device ( /dev/dasda2 ), the corresponding
command is mount /dev/dasda2 /mnt .
Important: File System Consistency

If the installed system has not been shut down properly, it may be advisable to check the
le system consistency prior to mounting. This prevents any accidental loss of data. Using
this example, issue the command fsck /dev/dasda2 to ensure that the le system is
in a consistent state.
By just issuing the command mount , it is possible to check whether the le system could be
mounted correctly.
EXAMPLE 36.1: OUTPUT OF THE MOUNT COMMAND
SuSE Instsys suse:/ # mount

shmfs on /newroot type shm (rw,nr_inodes=10240)
devpts on /dev/pts type devpts (rw)
virtual-proc-filesystem on /proc type proc (rw)
/dev/dasda2 on /mnt type reiserfs (rw)
548 Mounting the Root Device SUSE Linux Enterp… 11 SP4

36.7.4 Changing to the Mounted File System
For the zipl command to read the configuration le from the root device of the installed system
and not from the rescue system, change the root device to the installed system with the chroot
command:
EXAMPLE 36.2: CHROOT TO THE MOUNTED FILE SYSTEM
SuSE Instsys suse:/ # cd /mnt

SuSE Instsys suse:/mnt # chroot /mnt
36.7.5 Executing zipl

Now execute zipl to rewrite the IPL record with the correct values:
EXAMPLE 36.3: INSTALLING THE IPL RECORD WITH ZIPL
sh-2.05b# zipl
building bootmap : /boot/zipl/bootmap
adding Kernel Image : /boot/kernel/image located at 0x00010000
adding Ramdisk : /boot/initrd located at 0x00800000
adding Parmline : /boot/zipl/parmfile located at 0x00001000
Bootloader for ECKD type devices with z/OS compatible layout installed.
Syncing disks....
...done
36.7.6 Exiting the Rescue System

To exit the rescue system, rst leave the shell opened by the chroot command with exit .
To prevent any loss of data, ush all unwritten buers to disk with the sync command. Now
change to the root directory of the rescue system and unmount the root device of SUSE Linux
Enterprise Server for IBM System z installation.
EXAMPLE 36.4: UNMOUNTING THE FILE SYSTEM
SuSE Instsys suse:/mnt # cd /

SuSE Instsys suse:/ # umount /mnt
Finally, halt the rescue system with the halt command. The SUSE Linux Enterprise Server
system can now be IPLed as described in Book “Deployment Guide”, Chapter 6 “Installation with
YaST”, Section 6.15 “Performing the Installation”, Section 6.15.1 “IBM System z: IPLing the Installed System”.
549 Changing to the Mounted File System SUSE Linux Enterp… 11 SP4
A An Example Network
This example network is used across all network-related chapters of the SUSE® Linux Enterprise
Server documentation.

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551 GNU Free Documentation License SUSE Linux Enterp… 11 SP4

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it permission from the previous publisher that Entitled "Dedications". You must delete all sec-
added the old one. tions Entitled "Endorsements".
The author(s) and publisher(s) of the Docu-
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imply endorsement of any Modified Version. You may make a collection consisting of the
Document and other documents released un-
der this License, and replace the individual
5. COMBINING DOCUMENTS
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list them all as Invariant Sections of your com- der this License, provided you insert a copy of
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preserve all their Warranty Disclaimers. follow this License in all other respects regard-
The combined work need only contain one ing verbatim copying of that document.
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WORKS cense, and all the license notices in the Docu-
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If the Cover Text requirement of section 3 is

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Translation is considered a kind of modifica-

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www.gnu.org/copyleft/ . merge those two alternatives to suit the situa-
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ADDENDUM: How to use this License for

your documents
Copyright (c) YEAR YOUR NAME.

Permission is granted to copy,
distribute and/or modify this document
under the terms of the GNU Free
Documentation License, Version 1.2
or any later version published by the
Free Software Foundation;
with no Invariant Sections, no Front-
Cover Texts, and no Back-Cover Texts.
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er Texts and Back-Cover Texts, replace the
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Administration Guide

SUSE Linux Enterprise Server 11 SP4

Publication Date: July 24, 2020

About This Guide xix

3 Documentation Conventions xxii

I SUPPORT AND COMMON TASKS 1

1 YaST Online Update 2

1.2 Installing Patches 6

1.3 Automatic Online Update 7

2 Gathering System Information for Support 9

2.2 Submitting Information to Global Technical Support 13

2.3 Support of Kernel Modules 15

2.4 For More Information 17

3 YaST in Text Mode 18

3.2 Restriction of Key Combinations 21

iii Administration Guide

4 Snapshots/Rollback with Snapper 23

4.2 Using Snapper to Undo System Changes 24

4.3 Manually Creating and Managing Snapshots 35

4.5 Frequently Asked Questions 40

4.6 Using Snapper on Thin-Provisioned LVM Volumes 41

5 Remote Access with VNC 42

5.2 Persistent VNC Sessions 44

6 Managing Software with Command Line Tools 47

6.2 RPM—the Package Manager 62

7 Bash and Bash Scripts 73

7.2 Writing Shell Scripts 78

7.3 Redirecting Command Events 79

7.4 Using Aliases 80

7.5 Using Variables in Bash 81

7.6 Grouping And Combining Commands 83

7.7 Working with Common Flow Constructs 84

7.8 For More Information 85

8 Using Third-Party Software 87

9 32-Bit and 64-Bit Applications in a 64-Bit System

9.2 Software Development 90

9.4 Kernel Speciﬁcations 92

10 Booting and Conﬁguring a Linux System 94

10.2 The init Process 98

10.3 System Conﬁguration via /etc/sysconfig 106

11 The Boot Loader GRUB 109

11.2 Conﬁguring the Boot Loader with YaST 120

11.3 Uninstalling the Linux Boot Loader 126

11.4 Creating Boot CDs 126

11.5 The Graphical SUSE Screen 128

11.6 Troubleshooting 128

11.7 For More Information 130

12.2 For More Information 138

13 Special System Features 139

13.2 Virtual Consoles 145

13.3 Keyboard Mapping 146

13.4 Language and Country-Speciﬁc Settings 146

14 Printer Operation 151

14.2 Methods and Protocols for Connecting Printers 153

14.3 Installing the Software 153

14.4 Network Printers 154

14.5 Printing from the Command Line 157

14.6 Special Features in SUSE Linux Enterprise Server 157

vii Administration Guide