When following this knowledgebase article to upgrade your SLES or OES server, be sure to bear in mind that the upgrade will overwrite any customisation that you’ve done in /boot.
While initially this may not seem like a problem, bear in mind that if you’re running a VM then it’s likely (one would hope) that you have the “clock=pit” kernel parameter implemented.
If this is not re-implemented after the upgrade your server’s time will go wild and you’ll kick yourself when you realise what happened!
Yes. It happened to me. 😉