Useful issues resolved in the past

Basic usage steps:

1. study and practice system recovery
   

2. install the package

pacman -S mkinitcpio-systemd-tool

3. activate required hooks in /etc/mkinitcpio.conf:

HOOKS=(base ... systemd systemd-tool)

4. configure, override and enable/disable provided units, for example:
   for remote unlocking of luks root with cryptsetup and tinysshd use:

edit /etc/mkinitcpio-systemd-tool/config/crypttab
edit /etc/mkinitcpio-systemd-tool/config/fstab
systemctl enable initrd-cryptsetup.path
systemctl enable initrd-tinysshd.service
systemctl enable initrd-debug-progs.service
systemctl enable initrd-sysroot-mount.service

5. build image, review content and finally reboot:

mkinitcpio -v -p linux > /tmp/initrd.log
lsinitcpio -l /boot/initramfs-linux.img | grep initrd
systemctl reboot

pacman install actions:

• take a look in arch repo and make file
• provision user config and vendor systemd units into:
• /etc/mkinitcpio-systemd-tool (with backup)
• /usr/lib/systemd/system (with silent overwrite)

mkinitcpio install hook actions:

• look for enabled units in the /etc/systemd/system
• include in initrd units containing marker /etc/initrd-release
• activate transitively in initrd any discovered systemd service units
• auto provision into initramfs resources declared inside initrd service units

what is the mkinitcpio hook entry provided by this package?

• hook name: systemd-tool
• required hooks are: base systemd systemd-tool
• recommended hooks are: base autodetect modconf block filesystems keyboard fsck systemd systemd-tool

how can I customize installed service units?

• follow regular approaches to editing provided units
• create service unit override with systemctl edit $unit_name
• enable/disable with systemctl enable $unit_name / systemctl disable $unit_name

how can I review generated /boot/initramfs-linux.img?

• to review initramfs.img after mkinitcpio but before reboot, use:
• visually, with midnight commander or scripted, with mkinitcpio lsinitcpio

how systemd unit transitive dependency provisioning works?

• see mkinitcpio-install.sh/add_systemd_unit_X()
• units found in [Unit]/Requires|OnFailure are recursively installed

what is the purpose of [X-SystemdTool] section in service unit files?

• see systemd/systemd#3340
• this section provides configuration interface for mkinitcpio provisioning actions
• directives: InitrdPath InitrdLink InitrdBinary InitrdBuild InitrdCall InitrdUnit

how can I auto-provision my custom service unit binaries into initramfs?

• use InitrdBinary=/path/target-exec to provision service binary
• also will be provisioned all Exec* entries such as ExecStart=/usr/bin/program

how can I auto-provision my custom service unit resources into initramfs?

• use InitrdPath=/path/to/host/folder-or-file

how can I relocate folder during provisioning?

• not implemented, source and target folder must use the same location

how can I relocate file and/or change file mode during provisioning?

• use InitrdPath=/target-file source=/source-file mode=NNN

how can I filter directory content during provisioning?

• use InitrdPath=/target-folder glob=*.example

how can I provision optional folder or file?

• use InitrdPath=/target-file source=/source-file optional=yes

is there a way to create empty folder or file?

• for empty dir, use InitrdPath=/path/target-dir/ create=yes note trailing SLASH
• for empty file, use InitrdPath=/path/target-file create=yes note NO trailing slash

how can I provision a symbolic link?

• use InitrdLink=/path-to-link/link-name target=/path-to-target/target-name
• note that link target /path-to-target/target-name must be provisioned separately

can I invoke a provisioning script related to my service during mkinitcpio build time?

• use InitrdBuild=/path-to/script.sh command=function_name

can I call a little provisioning script snippet during mkinitcpio build time?

• check for available mkinitcpio functions in /usr/lib/initcpio/functions.sh
• use InitrdCall=inline-bash-code-here to call these functions

how can I provide custom interactive user shell for ssh client

• change sample shell file located in /usr/lib/mkinitcpio-systemd-tool/initrd-shell.sh

which ssh user keys are used by initramfs sshd server(s)?

• they come from host /etc/mkinitcpio-systemd-tool/config/authorized_keys

there is a initrd-shell.sh script provided, what does it do?

• it is used as both interactive login shell and as a systemd service
• when crypto disks are present, it acts as password agent
• when in ssh console, it offers simple interactive menu
• when in systemd service mode, it acts as service

how can I review initrd-shell.sh actions during last boot?

• use journalctl -b -t shell

what does CTRL-C do to initrd-shell.sh in different modes?

• initrd-shell.sh provides appropriate reaction to interrupt, depending on the context
• while in ssh terminal password agent prompt, it will start a menu form initrd-shell.sh
• while in /dev/tty local debug console, it will exit from initrd-shell.sh
• while in /dev/console password agent prompt, it will restart the initrd-shell.sh service

is there a silent or no-echo mode during password entry in initrd-shell.sh?

• there are two ways to enter silent mode (see systemd-ask-password.c):
• either by pressing BACKSPACE as first key or by pressing TAB at any time
• then the prompt will show extra text: (no echo)