FreeNAS 8.0.1-BETA2

[Bex]

Try upgrading from ssh:
# xz -cd /pah/to/img.xz | /root/update && touch /data/need-update && reboot

I have the same "upgrade from GUI giving error: undefined"
To use your suggestion above do i just upload the upgrade file to a local share say /mnt/test
Then use your command string like this:
# xz -cd /mnt/test/FreeNAS-8.0.1-BETA2-amd64-GUI_Upgrade.xz | /root/update && touch /data/need-update && reboot