Re: zfs snapshot
Just to be pedantic, by running the zfs snapshot
command, you don't have actually have a 'backup'. Everything is still on the same disk(s), so pool or disk failure can still cause you to lose the lot. You need to send a copy of that snapshot somewhere else with zfs send -R
to create a real backup (preferably to another ZFS pool).
Apologies if you're already aware of that, but some people may look at this and think "ah, that's the command to backup my full ZFS system".
In regard to your second post, the command without -r will only create a snapshot of the zroot dataset. If you have any child datasets, such as zroot/home, etc, you'll need to use the recursive option (or create separate snapshots for each dataset manually).