Choose initramfs generator based on Ubuntu release

[szaimen]

Problem

#2833 switched tpm2-unlock.sh to dracut -f unconditionally. That fixed 26.04, but 24.04 is still in the supported range (SUPPORTED_VERSION_MIN=24.04 in lib.sh) and generates its initramfs with initramfs-tools, so the unconditional switch regressed it.

That commit also installed both clevis-initramfs and clevis-dracut. Each ships a hook that injects clevis into the initramfs, so on 26.04 you get the dracut path plus a stale initramfs-tools hook.

Change

Pick the package and the update command together, once, based on the release codename:

Release	Package	Command
noble (24.04)	clevis-initramfs	update-initramfs -u -k 'all'
later (26.04+)	clevis-dracut	dracut -f

Three follow-on fixes:

• Only the release-appropriate clevis package is installed, so there are no competing initramfs hooks.
• The rollback apt-get purge matches what was installed, so it no longer fails on an absent package.
• The command is held in an array and invoked once, keeping the single msg_box/exit 1 error path rather than duplicating the condition.

The check keys off $CODENAME rather than a numeric comparison. check_distro_version already rejects anything outside the supported range, and this project only supports LTS releases, so $DISTRO can only be 24.04.x or 26.04.x here — a numeric cutoff would have needed a magic version number that appears nowhere in the project's policy. Testing for noble also makes dracut the default, so future releases land on the right path automatically.

The is_this_installed check still tests both package names on purpose: it's a "have you run this before?" probe, and anyone who ran the script at 58af3bc on 26.04 may have clevis-initramfs installed.

Testing

shellcheck -x not-supported/tpm2-unlock.sh passes clean.

I have not verified that clevis-dracut exists under exactly that name in the 26.04 archive — that rests on the report in #2833 and the Ubuntu clevis guide, as it did before this change. Worth a confirmation from someone with a 26.04 box, along with a real 24.04 run to confirm the restored path.

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI

[enoch85]

Thanks @szaimen!