This is a cross post from https://github.com/canonical/ubuntu-desktop-installer/issues/2312.
On mantic daily (25 Aug 2023), running installer 0+git.1792d817, x1 carbon gen9.
When selecting ZFS disk partitioning subiquity fails when installing grub to target. Extract from subiquity logs:
```text
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Running command ['umount', '/target/dev'] with allowed return codes [0] (capture=False)
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/install-grub: FAIL: installing grub to target devices
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/configuring-bootloader: FAIL: configuring target system bootloader
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks: FAIL: curtin command curthooks
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Traceback (most recent call last):
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/commands/main.py", line 202, in main
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: ret = args.func(args)
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/commands/curthooks.py", line 1933, in curthooks
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: builtin_curthooks(cfg, target, state)
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/commands/curthooks.py", line 1898, in builtin_curthooks
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: setup_grub(cfg, target, osfamily=osfamily,
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/commands/curthooks.py", line 836, in setup_grub
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: install_grub(instdevs, target, uefi=uefi_bootable, grubcfg=grubcfg)
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/commands/install_grub.py", line 451, in install_grub
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: in_chroot.subp(cmd, env=env, capture=True)
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/util.py", line 791, in subp
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: return subp(*args, **kwargs)
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/util.py", line 283, in subp
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: return _subp(*args, **kwargs)
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: File "/snap/ubuntu-desktop-installer/1202/lib/python3.10/site-packages/curtin/util.py", line 147, in _subp
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: raise ProcessExecutionError(stdout=out, stderr=err,
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: curtin.util.ProcessExecutionError: Unexpected error while running command.
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/target', 'update-grub']
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Exit code: 1
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Reason: -
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Stdout: ''
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Stderr: Sourcing file `/etc/default/grub'
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Sourcing file `/etc/default/grub.d/init-select.cfg'
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Generating grub configuration file ...
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: /etc/grub.d/10_linux_zfs: 425: version_find_latest: not found
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: umount: /tmp/zfsmnt.sVyvTn: target is busy.
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: rmdir: failed to remove '/tmp/zfsmnt.sVyvTn': Device or resource busy
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]:
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Unexpected error while running command.
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/target', 'update-grub']
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Exit code: 1
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Reason: -
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Stdout: ''
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Stderr: Sourcing file `/etc/default/grub'
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Sourcing file `/etc/default/grub.d/init-select.cfg'
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Generating grub configuration file ...
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: /etc/grub.d/10_linux_zfs: 425: version_find_latest: not found
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: umount: /tmp/zfsmnt.sVyvTn: target is busy.
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: rmdir: failed to remove '/tmp/zfsmnt.sVyvTn': Device or resource busy
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]:
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: {'current': '001D', 'timeout': '0 seconds', 'order': '001D,0000,0010,0011,0012,0013,0014,0015,0016,001A,001B,001C,001E,001F,0020,0021,0022'}
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: {'current': '001D', 'timeout': '0 seconds', 'order': '001D,0000,0010,0011,0012,0013,0014,0015,0016,001A,001B,001C,001E,001F,0020,0021,0022'}
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]:
Aug 25 10:01:37 ubuntu subiquity_log.5305[13012]: Stderr: ''
```
