[rhelv6-list] How do you know when a reboot is required after yum update?

[Hearn, Stan J.]

My Package Updater (PUP) in Centos 5 somehow knows when a reboot is needed after an update.

How does it know?

My concern is that we have systems that appear in satellite to be up-to-date.  But if they were never rebooted after an update, they really aren't.

I see this question asked frequently, however I've not found the answer.

Thanks,
Stan