If you are running a bare-metal cluster you probably run kubernetes on top of some linux os, these systems have to be regularly updated. But an update means sometimes that you have to reboot your servers. This also means during a reboot that particular node is node available to schedule workload.
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