Checking for ZFS upgrade 'Gotcha's"

Matthew Seaman m.seaman at
Wed Jan 5 19:07:05 UTC 2011

On 05/01/2011 16:06, Gene wrote:
> I'm just upgraded from FBSD 8.0 (amd64) to 8.1, I currently run with the ZFS 
> file system containing root. I understand that in the past, after rebuilding 
> world and kernel and upgrading the pool to version 14,  there have been some 
> issues concerning bootcode not being able to read the upgraded pools. Does 
> anyone know if this is still an issue?

Yes.  ZFS is not actually prescient, so older boot blocks tend not to be
able to read more recent versions of ZFS.

However the cure is simple: reinstall the bootblocks using the upgraded
version of ZFS you just installed.  This is the final stage of, and
should be a routine action when upgrading a ZFS based system: after
installing the new kernel, then the new world and rebooting, check the
kernel boot messages to see if ZFS says that upgraded zpool or zfs
versions are available.  If so, run 'zpool upgrade -a' and/or 'zfs
upgrade -a', plus 'gpt bootcoode ...' to update the bootblocks on all
relevant drives.  Then reboot again to verify that it all works.



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP:     Ramsgate
JID: matthew at               Kent, CT11 9PW

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