FreeBSD upgrade pool zroot

Today I successfully upgraded my FreeBSD home nas server from 10.3 to 11.0. This is the final release of version 11.0, though the official announcement is expected to be made on September 28.

After the system upgrade, I need to also upgrade the 2 zpools (tank and zroot) so they can have new features. Upgrading tank was easy, all I needed to do was running this command:

# zpool upgrade tank
This system supports ZFS pool feature flags.

Enabled the following features on 'tank':
  sha512
  skein

For zroot, in addition to running the above command (by replacing the actually zpool name to zroot), I also need to update the boot code.

root@nas:~ # zpool upgrade zroot
This system supports ZFS pool feature flags.

Enabled the following features on 'zroot':
  sha512
  skein

If you boot from pool 'zroot', don't forget to update boot code.
Assuming you use GPT partitioning and da0 is your boot disk
the following command will do it:

        gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 da0

What’s the boot code? Good question. Not sure what it is, I’ll find out later by reading the FreeBSD document.

The boot disk in my server is not da0. How do we find out what it is?

root@nas:~ # gpart show
=>       34  125045357  ada4  GPT  (60G)
         34       1024     1  freebsd-boot  (512K)
       1058    4194304     2  freebsd-swap  (2.0G)
    4195362  120850029     3  freebsd-zfs  (58G)

In my case, the boot disk is actually ada4, and the partition the boot sits on is ada4p1.

So, I can now proceed to update the boot code:

root@nas:~ # gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada4
partcode written to ada4p1
bootcode written to ada4

After rebooting the machine, the system is still working, yay!