[Bug 1876506] [NEW] eoan to focal upgrade hangs when lvm snapshot is present

[David Wittman]

Public bug reported:

When upgrading from 19.10 (w/ LVM + encypted disks) to 20.04, the
installer hangs when trying to probe an LVM snapshot volume created
before the upgrade.

Steps to reproduce:

lvcreate -s -L 20G -n preupgrade /dev/vgubuntu/root 
do-release-upgrade -d

The installer will hang after the following message:

/usr/sbin/grub-probe: error: unknown filesystem.
Found Ubuntu 19.10 (19.10) on /dev/mapper/vgubuntu-preupgrade
done

Resolution:

Killing the grub-mount process which is probing the LVM snapshot seems
to unhang the installer and allow the upgrade to complete without issue.

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: eoan2focal

** Attachment added: "Contents of /var/log/dist-upgrade"
   https://bugs.launchpad.net/bugs/1876506/+attachment/5365254/+files/dist-upgrade-logs-20200502.tgz

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https://bugs.launchpad.net/bugs/1876506

Title:
  eoan to focal upgrade hangs when lvm snapshot is present

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  When upgrading from 19.10 (w/ LVM + encypted disks) to 20.04, the
  installer hangs when trying to probe an LVM snapshot volume created
  before the upgrade.

  Steps to reproduce:

  lvcreate -s -L 20G -n preupgrade /dev/vgubuntu/root 
  do-release-upgrade -d

  The installer will hang after the following message:

  /usr/sbin/grub-probe: error: unknown filesystem.
  Found Ubuntu 19.10 (19.10) on /dev/mapper/vgubuntu-preupgrade
  done

  Resolution:

  Killing the grub-mount process which is probing the LVM snapshot seems
  to unhang the installer and allow the upgrade to complete without
  issue.

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