[Bug 1928200] Autopkgtest regression report (systemd/245.4-4ubuntu3.8)

[Ubuntu SRU Bot]

All autopkgtests for the newly accepted systemd (245.4-4ubuntu3.8) for focal have finished running.
The following regressions have been reported in tests triggered by the package:

asterisk/1:16.2.1~dfsg-2ubuntu1 (armhf)
gvfs/1.44.1-1ubuntu1 (amd64)
linux-oem-5.6/5.6.0-1057.61 (amd64)
munin/2.0.56-1ubuntu1 (ppc64el)


Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-
migration/focal/update_excuses.html#systemd

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

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https://bugs.launchpad.net/bugs/1928200

Title:
  Prompt error message "Failed to unmount /oldroot" when shutdown or
  reboot

Status in OEM Priority Project:
  Confirmed
Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Focal:
  Fix Committed

Bug description:
  [impact]

  root fs is not cleanly unmounted on shutdown

  [test case]

  create a file in /etc/binfmt.d/TestFormat.conf with the following
  content:

  :TestFormat:M::XX::/bin/true:F

  reboot the system, and then shutdown or reboot again, and watch the
  serial console for the error message:

  sd-umount[1334]: Failed to unmount /oldroot: Device or resource busy

  [regression potential]

  any regression would likely cause problems on shutdown and/or reboot,
  or may cause problems with unmounted root fs on shutdown/reboot

  [scope]

  this is needed only for f

  this is fixed upstream with PR 15566 which is included in v246, so
  this is fixed already in g and later

  this isn't reproducable on b

  [original description]

  On ubuntu 20.04, with latest kernel and systemd, it will show error on
  ThinkPad X1.

  sd-umount[1334]: Failed to unmount /oldroot: Device or resource busy

  systemd 245.4-4ubuntu3.6
  kernel: 5.8.0-53

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