[Bug 1899372] Re: update-grub 10_linux_zfs fails when /usr is a separate filesystem

[Dimitri John Ledkov]

So, /etc/os-release is an obsolete file location, which is normally a
symlink to /usr/lib/os-release.

When mounting snapshots, the grub script doesn't parse /etc/fstab; to
mount the snapshots of where the /usr is, and mount that.....

However, I don't know how having /usr as a subvolumen (if that is the
right term) even supported or usable with zsys.

What do you mean by /usr is a separate filesystem? which filesystem is
it?

We only support zsys when everything is managed by it.

** Changed in: grub2 (Ubuntu)
       Status: Confirmed => Incomplete

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Title:
  update-grub 10_linux_zfs fails when /usr is a separate filesystem

Status in grub2 package in Ubuntu:
  Incomplete
Status in grubzfs-testsuite package in Ubuntu:
  New

Bug description:
  Description:    Ubuntu 20.04.1 LTS
  Release:        20.04
  grub-common: 2.04-1ubuntu26.4

  I expect grub-update to create grub.cfg with Linux entries for ZFS.
  Instead I am left with an empty list and an unbootable OS.

  The output from update-grub:
  Sourcing file `/etc/default/grub'
  Sourcing file `/etc/default/grub.d/init-select.cfg'
  Sourcing file `/etc/default/grub.d/kdump-tools.cfg'
  Generating grub configuration file ...
  /etc/grub.d/10_linux_zfs: 404: .: Can't open /tmp/zfsmnt.stGSQC/etc/os-release
  Found memtest86+ image: /memtest86+.elf
  Found memtest86+ image: /memtest86+.bin
  done

  This is failing because I have a separate ZFS filesystem for /usr.
  The 10_linux_zfs script is gathering information from /etc/os-release
  which is a symlink to ../usr/lib/os-release.

  The first issue I see in 10_linux_zfs is under function get_dataset_info() at line 382:
  mount -o noatime,zfsutil -t zfs "${base_dataset}" "${mntdir}"

  Since /usr is under a separate filesystem, the symlink would be broken
  and the script fails.  This should mount /usr as well if it is a
  separate filesystem.

  The next issue I see is when the script iterates the zsys snapshots at line 514:
  for snapshot_dataset in $(zfs list -H -o name -t snapshot "${dataset}"); do
      boot_list="${boot_list}$(get_dataset_info ${snapshot_dataset} ${mntdir})\n"
  done

  You would get a similar error message about os-release.
  /etc/grub.d/10_linux_zfs: 410: .: Can't open /.zfs/snapshot/autozsys_oiimb5/etc/os-release

  Again, the script should consider reading the /usr snapshot as well if
  it is a separate filesystem.

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