late-commands crashes when cat'ing /target/boot/grub/grub.cfg

[Guillaume]

Near the end of the late-commands section in autoinstall.yaml, subiquity crashes with a simple cat :
systemd-cat --level-prefix=false --identifier=subiquity_log.2105 sh -c cat '/target/boot/grub/grub.cfg' > /dev/console

It's just to debug, so disabling this command is enough to keep it going, but since it was working well with 22.04, i can't understand why it fails with 24.04 :
2024-04-05 07:28:14,431 DEBUG subiquitycore.utils:119 arun_command called: ['systemd-cat', '--level-prefix=false', '--identifier=subiquity_log.2105', 'sh', '-c', "cat '/target/boot/grub/grub.cfg' > /dev/console "]
2024-04-05 07:28:14,450 DEBUG subiquitycore.utils:133 arun_command ['systemd-cat', '--level-prefix=false', '--identifier=subiquity_log.2105', 'sh', '-c', "cat '/target/boot/grub/grub.cfg' > /dev/console "] exited with code 1
2024-04-05 07:28:14,450 ERROR root:30 finish: subiquity/Late/run/command_15: FAIL: Command '['systemd-cat', '--level-prefix=false', '--identifier=subiquity_log.2105', 'sh', '-c', "cat '/target/boot/grub/grub.cfg' > /dev/console "]' returned non-zero exit status 1.
2024-04-05 07:28:14,450 ERROR root:30 finish: subiquity/Late/run: FAIL: Command '['systemd-cat', '--level-prefix=false', '--identifier=subiquity_log.2105', 'sh', '-c', "cat '/target/boot/grub/grub.cfg' > /dev/console "]' returned non-zero exit status 1.
2024-04-05 07:28:14,451 ERROR subiquity.server.server:426 top level error
Traceback (most recent call last):
  File "/snap/subiquity/5645/lib/python3.10/site-packages/subiquity/server/controllers/cmdlist.py", line 139, in _run
    await self.run()
  File "/snap/subiquity/5645/lib/python3.10/site-packages/subiquitycore/context.py", line 149, in decorated_async
    return await meth(self, **kw)
  File "/snap/subiquity/5645/lib/python3.10/site-packages/subiquity/server/controllers/cmdlist.py", line 90, in run
    await arun_command(
  File "/snap/subiquity/5645/lib/python3.10/site-packages/subiquitycore/utils.py", line 137, in arun_command
    raise subprocess.CalledProcessError(proc.returncode, cmd, stdout, stderr)
subprocess.CalledProcessError: Command '['systemd-cat', '--level-prefix=false', '--identifier=subiquity_log.2105', 'sh', '-c', "cat '/target/boot/grub/grub.cfg' > /dev/console "]' returned non-zero exit status 1.
2024-04-05 07:28:14,475 DEBUG subiquity.common.errorreport:398 generating crash report
2024-04-05 07:28:14,476 INFO subiquity.common.errorreport:424 saving crash report 'unknown error crashed with CalledProcessError' to /var/crash/1712302094.475684404.unknown.crash
2024-04-05 07:28:14,476 INFO root:30 start: subiquity/ErrorReporter/1712302094.475684404.unknown/add_info:
2024-04-05 07:28:15,487 INFO root:30 finish: subiquity/ErrorReporter/1712302094.475684404.unknown/add_info: SUCCESS: written to /var/crash/1712302094.475684404.unknown.crash

[Chris Peterson (cpete)]

Based on the error I'm going to guess /target/boot/grub/grub.cfg isn't available yet by the time the command is run. Could you make do with something like this instead?:

  late-commands:
    - while [ ! -f /target/boot/grub/grub.cfg ] ; do sleep 1 ; done
    - cat /target/boot/grub/grub.cfg > /dev/console

FWIW I did a simple autoinstall in a VM with just the above cat command and I couldn't reproduce the issue.

[Guillaume (e1msih)]

I can, of course.
Thanks for looking into it.