651ee08f24
- Overhaul configuration fetching:
* Add udev rules to wait for either ignition, combustion or
fw_cfg drives
* Allow combustion.firstboot in addition to ignition.firstboot
M combustion
A combustion-prepare.service
M combustion.service
M module-setup.sh
- Bump version to 0.2
OBS-URL: https://build.opensuse.org/request/show/835192
OBS-URL: https://build.opensuse.org/package/show/devel:kubic:ignition/combustion?expand=0&rev=7
80 lines
3.3 KiB
Plaintext
80 lines
3.3 KiB
Plaintext
Combustion - configure MicroOS on the first boot
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================================================
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Combustion is a minimal module for dracut, which runs a user provided script on
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the first boot of a system.
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You can use this to create additional files, install packages, set up devices
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or even re-partition the hard disk. The configuration can be provided as a
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shell script, loaded from an external storage media and is run during boot in a
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new system snapshot. On success, the system will directly boot into that new
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snapshot, so that no reboot is needed.
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How to use it
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-------------
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The configuration files are copied from a filesystem with the LABEL
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"combustion", but to be compatible and co-installable with ignition
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(https://github.com/coreos/ignition), the LABEL "ignition" is used as fallback.
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It expects a directory "combustion" at the root level of the filesystem and
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a file "script" inside, which is executed inside a transactional-update shell.
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If a QEMU fw_cfg blob with the name "opt/org.opensuse.combustion/script" is
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found, it is preferred and the content of that is used as script.
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Example parameter for QEMU:
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-fw_cfg name=opt/org.opensuse.combustion/script,file=/var/combustion-script
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Example for formatting a USB drive and adding a config, which installs the
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"vim-small" package and creates a /root/welcome file:
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```
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mkfs.ext4 /dev/sdX
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e2label /dev/sdX ignition
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mount /dev/sdX /mnt
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mkdir -p /mnt/combustion/
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cat >/mnt/combustion/script <<EOF
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#!/bin/sh
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# combustion: network
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systemctl enable sshd.service
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zypper --non-interactive install vim-small
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cp welcome /root/welcome
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EOF
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echo "Hello User!" >/mnt/combustion/welcome
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umount /mnt
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```
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The "# combustion: network" comment indicates that network needs to be
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configured before running the script.
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You can do everything necessary for initial system configuration from this
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script, including addition of ssh keys, adding users, changing passwords
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or even doing partitioning changes.
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How it works
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------------
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The ignition-dracut-grub2 package created a flag file which tells GRUB 2 that
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it's the first boot of the system and so GRUB adds "ignition.firstboot" to the
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kernel commandline.
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If this option is found on the kernel cmdline, combustion.service's
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ConditionKernelCommandLine is fulfilled and it'll be required by initrd.target.
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This pulls in combustion-prepare.service, which runs after the config drive or
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QEMU fw_cfg blob appears (see combustion.rules for details). It is read and if
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the "network" flag comment is present, enables networking for later.
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After /sysroot is mounted and network is up (if enabled), combustion.service
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runs, which tries to activate all mountpoints in the system's /etc/fstab and
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then calls transactional-update in a chroot.
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In this transactional-update session the script is started and the exit code
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recorded. If the script failed, transactional-update rollback is called and
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combustion.service marked as failed, which causes booting to fail. Note that a
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missing config drive or script is not considered a fatal error and only results
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in a warning.
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/sysroot is unmounted and mounted again, so that the default subvolume gets
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reevaluated and directly booted into.
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The ignition-firstboot-complete service in the final system runs, which deletes
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the flag file. This means that combustion is not run on subsequent boots.
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