I have a slightly unusual setup which might have broken the upgrade process. The upgrade broke in the same way on both
my desktop and laptop which both have a similar zfs setup, but not on my htpc which doesn't have any zfs volumes on it.
The short version is that it looks like the upgrade process breaks if zfs is used for home directories :(
Setting up zfsutils-linux (0.8.1-1ubuntu14) ...
Installing new version of config file /etc/zfs/zfs-functions ...
zfs-import-scan.service is a disabled or a static unit not running, not starting it.
Job for zfs-mount.service failed because the control process exited with error code.
See "systemctl status zfs-mount.service" and "journalctl -xe" for details.
invoke-rc.d: initscript zfs-mount, action "restart" failed.
● zfs-mount.service - Mount ZFS filesystems
Loaded: loaded (/lib/systemd/system/zfs-mount.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Fri 2019-10-25 18:44:58 AEDT; 9ms ago
Process: 3571 ExecStart=/sbin/zfs mount -a (code=exited, status=1/FAILURE)
Main PID: 3571 (code=exited, status=1/FAILURE)
Oct 25 18:44:58 episiarch systemd: Starting Mount ZFS filesystems...
Oct 25 18:44:58 episiarch zfs: cannot mount '/home': directory is not empty
Oct 25 18:44:58 episiarch systemd: zfs-mount.service: Main process exited, code=exited, status=1/FAILURE
Oct 25 18:44:58 episiarch systemd: zfs-mount.service: Failed with result 'exit-code'.
Oct 25 18:44:58 episiarch systemd: Failed to start Mount ZFS filesystems.
dpkg: error processing package zfsutils-linux (--configure):
installed zfsutils-linux package post-installation script subprocess returned error exit status 1
Upon reboot the zfs home directories are not mounted, and a new directory tree has been created on /home with all
directories empty and owned by root. I don't know what is doing this or at what stage in the upgrade, but I suspect this
is the cause of the problem.
Removing the /home directory and restarting the zfs-mount service seems to fix this (although prior to restarting the
service I also performed a zpool upgrade - don't know what (if any) effect this has). I can't remember for certain, but
I think the /data directories were mounted correctly:
$ zfs list
NAME USED AVAIL REFER MOUNTPOINT
zfstank.pool1 2.55T 875G 140K /mnt/pool/zfs/zfstank.pool1
zfstank.pool1/data 2.42T 875G 221K /data
zfstank.pool1/home 132G 875G 151K /home
zfstank.pool1/home/username 85.0G 875G 53.8G /home/username