Q:

My ZFS dataset is gone after system upgrade/reboot (ubuntu)

I did recently upgrade my little NAS to ubuntu 14.04 and initially everything worked fine. 
I'm used to re-import my ZFS pools after restarts and so it was no surprise when the mount point was gone after a restart 2 days ago. 
But this time i was not able to re-import it and when i started looking closer the whole ZFS dataset disappeared too and i start to run out of ideas what to try (as do the google results i find). 
$ zpool list or zpool status
no pools available
$ zfs list
no datasets available
$ ls /dev/disk/by-id/
... disks as i have used them in my config ...none missing
Everything was working fine before a reboot 2 days ago, and before that reboot i did run some upgrades including the kernel (standard upgrade via apt). 
Re-installing/further upgrading or going back to previous versions (selected in grub) all did not help. 
It would be really cool to get it back running, especially since i switched to ZFS for its promised reliability.  The nice data redundancy does not help me if the whole storage disappears out of nowhere... 
Any ideas? 

A:

I had the same Problem.  
Doing 
apt-get install ubuntu-zfs zfsutils

and rebooting solved it for me.  
For some Reasons ubuntu did not update all zfs-packages. 
You can see if this is the case at the end of apt-get update output (packages held back)

