[Bug 1987679] Re: os-prober leaves filesystems (lvm-thin, lvm snap) mounted

[mike]

I don't think it is os-prober, at least if I run os-prober directly it doesn't leave systems mounted, but it does return that that it found a system on the snapshots or thin-LVs.
It is only when the output of os-prober is processed by grub (30_os-prober) do the mounts get left.

I guess one could argue that os-prober should not report systems found
on snapshots or thin-lvms or whatever other filesystem GRUB can't handle
and that would fix the problem.

As it stands the mount (that is "being left") is being done by grub.

I was unable to compile the source for grub (apt-get source
grub2-common) and I'm afraid I kinda got lost trying to figure out just
where the problem is by reading the source.

I have gone a different route and replaced 30_os-prober (would be better if os-prober still reported boot partitions), so that I can boot from linear lV boot partitions and thin-lv system partitions.
But I still have the original stuff to experiment with if needed.

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Title:
  os-prober leaves filesystems (lvm-thin, lvm snap) mounted

Status in os-prober package in Ubuntu:
  New

Bug description:
  If one happens to have by accident (or on purpose) a thick LVM snapshot, or a thin-LV with a copy of a system on it, update-grub reports
  /sbin/grub-probe: error: unknown filesystem.
  Found Ubuntu 22.04.1 LTS on /dev/mapper/vgxubuntu-s22.04
  and
  /sbin/grub-probe: error: disk `lvmid/X7waXv-rMDA-5fQA-aw6l-ei1I-8Gz3-pQl3lr/k3Ze1u-Mfwc-pxUt-7fXa-FjSZ-7IkX-HAxf3b' not found.
  Found Ubuntu 22.04.1 LTS (22.04) on /dev/mapper/vgxubuntu-XR22.04.1U

  and leaves the systems mounted rw on /var/lib/os-prober/mount.
  On subsequent invocations update-grub spews out multiple
  mdir: failed to remove '/var/lib/os-prober/mount': Device or resource busy

  I'm pretty sure this also causes a new install to hang (though a
  power-reset seems to load the new system - not sure if it is complete
  or not.)

  The missing umounts should be relatively easy to fix, but the thick
  snapshot error is particularly vague as most users (I think) would
  take the "unknown filesystem" to refer to the previous entry.

  I have been playing with grub2-common-2.06-2ubuntu7 on xubuntu
  22.04.1, though I am sure this has been around a while

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