For testing purpose, I setup a Freebsd instance on AWS, which is using zfs on root.
And then I add 10G disk space to the root volume. Even though I enabled auto-expand for zroot, it seems the 10G space is not added to system. Here are the steps to expand the disk for zroot:
1. Reboot the server. Even though it’s said that reboot is not necessary, I suggest to reboot the server to make sure server can recognize the new size.
2. As the disk size change, we need to fix the GPT partition table first.
gpart recovery ada0
3. Some documents said can use “zpool online -e” to expand the disk. As shown in above picture, the command can’t auto update GPT and assign the space to zfs partition.
4. We need to use gpart to update GPT first, then expand the zfs partition.
#gpart resize -i 2 ada0
#zpool online -e zrrot /dev/adap2