Re: System not booting after upgrade 14.3->14.4 with "ZFS: unsupported feature: com.klarasystems: vdev_zaps_v2"

On 30/04/2026 10:28, Johan Helsingius wrote:
> Was doing an upgrade from 14.3-R7 to 14.4, and after the freebsd-update
> install, the reboot fails with "ZFS: unsupported feature:
> com.klarasystems: vdev_zaps_v2"

It's an extension form Klara Inc :-)

As no ZFS expert has turned up, I'll have a go.

As you can probably guess, it's not supported in 14.4/OpenZFS. A ZAP is 
a key/value store and I assume Klara has an enhanced format one, and how 
you got it on what I assume is your root vdev is anyone's guess.

You might be able to fix it by reinstalling the bootloader. Keep a 
backup of the bootloader before you reinstall it.

Beyond that you're going beyond anything I've done myself. I assume 
you've tried everything possible to roll back?
Boot from something else and try importing the zpool with "-o readonly=on"

Try "zpool get [email protected]:vdev_zaps_v2 zroot" or whatever 
the pool is called.

Then, if you feel lucky, you may be able to set it to disabled (zpool 
set [email protected]:vdev_zaps_v2=disabled zroot), export and 
reboot. This is a general fix for problem features and I have never been 
in the same situation as you have here with this one.

I suggest you post the results at every stage and it might ring a bell 
with someone.

Regards, Frank.

P.S. I'm pretty sure this is not on any FreeBSD base system ever 
released - I wouldn’t know about FreeNAS? All I can think og is that 
someone ran zpool upgrade when the system was running on a Klara-patched 
version of ZFS and this set the flag, in which case I'd be fairly 
confident that turning the feature off as described above would do the 
trick - unless the enhanced ZAP has been used on the disk, in which case 
find what did it, boot from that, import your zpool R/O and dump all the 
important stuff to tape!