Failed to unmount /oldroot/dev/pts: Device or resource busy

[Steve Langasek]

I have an armhf system which happens to not reboot from Linux, and as a result I can clearly see all the shutdown messages on it.

It is also using lvm for the root filesystem.

On focal, it is currently failing to cleanly unmount the filesystem and shutdown the LVM:

[67384.315925] sd-umoun[11498]: Failed to unmount /oldroot: Device or resource busy
[67384.331584] sd-umoun[11499]: Failed to unmount /oldroot/dev/pts: Device or resource busy
[67384.346125] sd-umoun[11500]: Failed to unmount /oldroot/dev: Device or resource busy
[67384.359495] shutdown[1]: Could not detach DM /dev/dm-0: Device or resource busy
[67384.400682] shutdown[1]: Failed to finalize file systems, DM devices, ignoring

There are similar bug reports about finalrd failing, but none with this particular list of busy filesystems, so filing a separate report.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Flauschie (flauschie)]

Getting this error on 20.04 as well as on 22.04 but only after installing an additional language.

This results in a filesystem check on every boot.

Failed to unmount /oldroot: Device or resource busy
sd-umoun[]: Failed to unmount /oldroot/dev: Device or resource busy
shutdown[1]: Could not detach DM /dev/dm-1: Device or resource busy
shutdown[1]: Could not detach DM /dev/dm-0: Device or resource busy
shutdown[1]: Failed to finalize file systems, DM devices, ignoring

sha256sum
84aeaf7823c8c61baa0ae862d0a06b03409394800000b3235854a6b38eb4856f ubuntu-22.04-live-server-amd64.iso

[Steve Langasek (vorlon)]

Please show the output of 'sudo lsblk' on this system.

[Flauschie (flauschie)]

Scratch the part with "only after installing an additional language" since this happens every time. I remembered it wrong. Same for the filesystem check.

From a VM:
```
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 61.9M 1 loop /snap/core20/1405
loop1 7:1 0 79.9M 1 loop /snap/lxd/22923
loop2 7:2 0 44.7M 1 loop /snap/snapd/15534
sda 8:0 0 10G 0 disk
├─sda1 8:1 0 512M 0 part /boot/efi
├─sda2 8:2 0 1G 0 part /boot
└─sda3 8:3 0 8.5G 0 part
  └─dm_crypt-0 253:0 0 8.5G 0 crypt
    └─ubuntu--vg-ubuntu--lv 253:1 0 8.5G 0 lvm /
sr0
```

I attached the partitioning part of the deployment in case it should matter.