When you manage Linux systems it's usually pretty clear how to reboot a system. But do you know how to check whether a system requires a reboot? Cause you don't want to reboot a system if it is not necessary
Debian-based systems
There are some posts out there which talks about this topic. Check for a required reboot on Debian and Ubuntu systems is an interesting one which speaks about a /var/run/reboot-required.pkgs.
I actually don't fine anything about the `reboot-required` file or mechanism in the Debian documentation but only on the UbuntuNotifier documentation