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

[mike]

Heitor,

I thought I was crossing some etiquette boundary and being ignored (snubbed!) and was hesitant to comment further!!! Regardless, some caution as you are testing the memory of a 70 year old who is taking bad (perscription) drugs that **** up my memory (yes I am still sick after 5 years - it sucks).
That said I believe grub-mount has access to the full running linux system of filesystems, but grub-probe (intentionally) doesn't.

In the two cases I discovered thin-lvms and thick lvm snapshots, both
were mountable by grub-mount and grub-probe failed (i.e. returned an
error code).

As I wrote at the beginning of the bug report, when I fixed the bug as
you have I discovered that the thin-lvm was ignored, but the thick
snapshot was added to the cfg file, but as the base by one of the
"mounted" probes". This results in the really bad situation that all
will work until the user tries to update grub or the cfg file in the
thick snapshot as it will have no effect and I expect the user will have
a really hard time figuring it out.

My latest suggestion may not be perfect, but it makes things better
(never leaves a file system mounted - even if it is because of user
error) and never makes it worse.

Perhaps juliank can provide better insight on grub-mount vs grub-probe.

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

Status in os-prober package in Ubuntu:
  In Progress
Status in os-prober source package in Focal:
  In Progress
Status in os-prober source package in Jammy:
  In Progress
Status in os-prober source package in Kinetic:
  Won't Fix
Status in os-prober source package in Noble:
  In Progress
Status in os-prober source package in Oracular:
  In Progress
Status in os-prober source package in Plucky:
  In Progress

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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