tail -f -n 0 /var/log/messages
– I see updates to the running system, whilst the user is logged in to the desktop environment.
Any number of applications might be started, by the user, during this routine, before the set of installed packages is in a self-consistent state. There is, I suspect, a slight risk of issues occurring if the user does not refrain from touching the system until there's an invitation to restart.
Compare with a more cautious routine, which I follow with desktop environments on FreeBSD:
- create a boot environment
- activate the environment
- boot the environment
- refrain from log in to the desktop environment
- upgrade the boot environment