1. check if updates nightly
    freebsd-update fetch install
    pkg update
    pkg upgrade
    pkg audit -F -q

2. if so, automatically create BE, ask user to reboot into new BE
3. on bootup, apply patches
4. check for additional updates, repeat
5. automatically prune old BE / patches and recycle #'s

https://forums.freebsd.org/threads/how-to-properly-update-a-system.83844/#post-553044