[Bug 1940514] Re: It will prompt "Failed to unmount /oldroot" when shutdown or reboot

[Bin Li]

I installed 21.10(impish), I found this issue is gone, there are no error messages.
 
mdadm          4.2~rc2-2ubuntu1
finalrd        8
systemd        248.3-1ubuntu8

** Also affects: mdadm
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1940514

Title:
  It will prompt "Failed to unmount /oldroot" when shutdown or reboot

Status in mdadm:
  New
Status in OEM Priority Project:
  Triaged
Status in finalrd package in Ubuntu:
  New

Bug description:
  Summary]
  [ThinkPad]It will prompt error message after shutdown or reboot.

  [Reproduce steps]
  1. Preload Ubuntu OS 20.04.2
  2. Boot and enter to the os
  3. Shutdown or reboot the machine, it wouldn't show below error by default.
  4. Then installed finalrd, and do reboot or shutdown.

  Expected Result:
   It will not prompt error message after shutdown or reboot.
  Actual result:
   It will prompt error message after shutdown or reboot as the attached 'the page after shutdown or reboot.jpg'.

   sd-umoun[2406]: Failed to unmount /oldroot: Device or resource busy
   sd-umoun[2407]: Failed to unmount /oldroot/dev/pts: Device or resource busy
   sd-umoun[2408]: Failed to unmount /oldroot/dev: Device or resource busy
   shutdown[1]: Failed to finalize  file systems, ignoring

   We met this issue on several OEM projects, such as
  ThinkPad-P17-Gen-1, ThinkPad X13.

  [Additional information]
  Platform: ThinkPad X1 Titanium Gen1, ThinkPad X13, ThinkPad P17
  systemd:245.4-4ubuntu3.11
  finalrd: 6~ubuntu20.04.1

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