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

On 02/05/2026 6:23 pm, Frank Leonhardt wrote:

> 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.

Thanks - I have no idea how it could have gotten there.

> 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"

Booting from installer and doing a freebsd-update after
mounting the zpool seems to have solved the problem.

> Try "zpool get feature@com.klarasystems:vdev_zaps_v2 zroot" or whatever 
> the pool is called.

After the update the feature doesn't seem to be there any more.

> 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!

i am the only user, and I haven't installed any custom patches,
just kept doing freebsd-updates since initial install many years
ago.

	Julf