[Bug 1990239] Re: Crash when unmounting cdrom

[Olivier Gayot]

As shown below, we attempt to unmount the cdrom twice:

2022-09-20 08:35:59,483 DEBUG subiquitycore.utils:114 astart_command called: ['systemd-run', '--wait', '--same-dir', '--property', 'SyslogIdentifier=subiquity_log.1973', '--setenv', 'PATH=/snap/subiquity/x1/bin:/snap/subiquity/x1/usr/bin:/usr/local/sbin:/
usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/subiquity/x1/bin:/snap/subiquity/x1/sbin', '--setenv', 'PYTHONPATH=:/snap/subiquity/x1/lib/python3.8/site-packages', '--setenv', 'PYTHON=/snap/subiquity/x1/usr/bin/pyt
hon3.8', '--setenv', 'SNAP=/snap/subiquity/x1', '--', 'umount', '/target/cdrom']
[...]
2022-09-20 08:36:04,159 DEBUG subiquitycore.utils:114 astart_command called: ['systemd-run', '--wait', '--same-dir', '--property', 'SyslogIdentifier=subiquity_log.1973', '--setenv', 'PATH=/snap/subiquity/x1/bin:/snap/subiquity/x1/usr/bin:/usr/local/sbin:/
usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/subiquity/x1/bin:/snap/subiquity/x1/sbin', '--setenv', 'PYTHONPATH=:/snap/subiquity/x1/lib/python3.8/site-packages', '--setenv', 'PYTHON=/snap/subiquity/x1/usr/bin/pyt
hon3.8', '--setenv', 'SNAP=/snap/subiquity/x1', '--', 'umount', '/target/cdrom']


We do it once explicitly and then a second time in the self.cleanup() method.


        await self.unmount(                                                                                                                                                                                                                                    
                Mountpoint(mountpoint=target_mnt.p('cdrom')),
                remove=False)
        os.rmdir(target_mnt.p('cdrom'))

        await _restore_dir('etc/apt')

        if self.app.base_model.network.has_network:
            await run_curtin_command(
                self.app, context, "in-target", "-t", target_mnt.p(),
                "--", "apt-get", "update", private_mounts=True)
        else:
            await _restore_dir('var/lib/apt/lists')

        await self.cleanup()

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Title:
  Crash when unmounting cdrom

Status in subiquity package in Ubuntu:
  New

Bug description:
  On the development version of Subiquity (currently
  60d6746a41ee38a0ac775febe39768bafca9c808), the installation fails late
  in the process when unmounting /target/cdrom.

  subprocess.CalledProcessError: Command '['systemd-run', '--wait', '--same-dir', '--property', 'SyslogIdentifier=subiquity_log.1561', '--setenv', 'PATH=/snap/subiquity/x1/bin:/snap/subiquity/x1/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/subiquity/x1/bin:/snap/subiquity/x1/sbin', '--setenv', 'PYTHONPATH=:/snap/subiquity/x1/lib/python3.8/site-packages', '--setenv', 'PYTHON=/snap/subiquity/x1/usr/bin/python3.8', '--setenv', 'SNAP=/snap/subiquity/x1', '--', 'umount', '/target/cdrom']' returned non-zero exit status 32.
  2022-09-19 18:07:02,223 ERROR subiquity.server.server:422 top level error

  After investigation, this seems to have been broken by this patch
  https://github.com/canonical/subiquity/commit/6d724c0a5be0ccbbf9e3b249e907aa2405993c69
  which is part of PR 1417:
  https://github.com/canonical/subiquity/pull/1417

  A partial revert of the patch fixes the issue:

  https://pastebin.canonical.com/p/pB6jSf6BTf/

  This could be caused by two processes (e.g., Subiquity & curtin?)
  trying to unmount cdrom. To be investigated further.

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