zpool upgrade removes PMBR

[apb15]

I recently upgraded from 8.2 to 9.0. The upgrade went successfully. At the end I ran zpool upgrade -a. The command worked successfully and the usual message was output warning me to update my bootcode with an example using gpt partitioning. I foolishly ignored this message and now my machine will not boot and I am left with the boot: prompt.

I assume this is because the pmbr has been deleted and I need to rewrite it to the disk. I wanted to check if the easiest method to fixing this problem is to boot via a CD and then rewrite the pmbr as discussed in the instructions for zfs here: http://wiki.freebsd.org/RootOnZFS/GPTZFSBoot

Do I have any other options?

 

[kpa]

It's not about the /boot/pbmr but the ZFS GPT loader /boot/gptzfsloader. You'll have to boot with the 9.0 install disk and do this from a shell (select shell or the live cd option):

# gpart bootcode -b /boot/pmbr -p /boot/gptzfsloader -i 1 ada0

This assumes that the bootable disk is /dev/ada0 in FreeBSD 9 and that the GPT partition that holds the loader is the first partition, double check on your system with # gpart show before executing the command.

Edit: I included the -b option to update /boot/pmbr just in case, the 9.0 version of it shouldn't be too different to 8.2 version but you never know.