[Bug 1965983] [NEW] ZFS snapshots without etc directory causes grub.cfg build failure

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Matthieu Clemenceau (mclemenceau):

In /etc/grub.d/10_linux_zfs (built during install from util/grub.d/10_linux_zfs.in), get_dataset_info() tries to unmount mount locations starting with the logic
```
case "${etc_dir}" in /.zfs/snapshot/*/etc)
```

This process occasionally and silently fails while building /boot/grub/grub.cfg when running in FIPS mode (with FIPS kernels), which leaves the generated /boot/grub/grub.cfg without any kernel (linux ...) lines.
It appears that not all ZFS snapsshots that match the switch statement actually have an .../etc directory.

As ZFS is only an option in the Focal Desktop installer, this issue was
only tested with Focal running Canonical's FIPS packages.

In order to reproduce this issue in FIPS mode, the ubuntu-fips and fips-
initramfs-generic packages both need to implement a couple of patches
that haven't released yet. Without these two patches and without manual
intervention, the FIPS kernel will be unable to boot with a ZFS /boot
device. I can provide these additional patches -- please feel free to
reach out to me!

** Affects: grub2 (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: grub2 (Ubuntu Focal)
     Importance: High
         Status: Triaged

** Affects: grub2 (Ubuntu Jammy)
     Importance: High
         Status: Triaged


** Tags: fr-2137 patch
-- 
ZFS snapshots without etc directory causes grub.cfg build failure
https://bugs.launchpad.net/bugs/1965983
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