Mounting from zfs:zroot/ROOT/default failed with error 2: unknown file system after upgrade to 10.1-RELEASE

[Anton Eliasson]

Hi!
After upgrading a server from FreeBSD 10.0-RELEASE to 10.1-RELEASE it no 
longer starts up. The bootloader shows its usual menu and then proceeds 
to load zfs.ko, opensolaris.ko and some third module. Then kernel boots 
and continues all the way to mountroot where it fails with the message 
"Mounting from zfs:zroot/ROOT/default failed with error 2: unknown file 
system." The entire message: 
https://cloud.solid.lth.se/public.php?service=files&t=27c15a131ca63b19f619a7ee558fe8d1

Entering zfs:zroot, zfs:zroot/ROOT, zfs:zroot/ROOT/default or 
zfs:anythingelse results in the same error.

FreeBSD 10.0 was installed this summer. I believe I used the installer's 
guided procedure for installing on a mirrored ZFS root. Each drive has a 
GPT table with a 512k freebsd-boot, a freebsd-swap and a freebsd-zfs 
partition. No separate /boot.

There is no vfs.root.mountfrom directive in /boot/loader.conf and no / 
in /etc/fstab. If I set vfs.root.mountfrom="zfs:zroot" it fails with the 
same message but a slightly different path (zfs:zroot).

The motherboard is a Supermicro X9SRH-7TF. I can import and mount the 
root filesystem with a FreeBSD live CD without problems.

Some config files pulled from a very similar installation (same server 
model, installed at the same time). They should be more or less 
identical on the server that won't boot:

/etc/rc.conf:

     hostname="..."
     keymap="swedish.iso.kbd"
     # Use synchronous DHCP; pause boot until DHCP is completed.
     ifconfig_ix0="SYNCDHCP"
     sshd_enable="YES"
     ntpd_enable="YES"
     # Set dumpdev to "AUTO" to enable crash dumps, "NO" to disable
     dumpdev="AUTO"
     zfs_enable="YES"

     # IPFW
     [...]

/boot/loader.conf:

     zfs_load="YES"
     geom_mirror_load="YES"

/etc/fstab:

     fdesc    /dev/fd        fdescfs        rw    0    0
     /dev/mirror/swap none swap sw 0 0

Thanks!

-- 
Best Regards,
Anton Eliasson