First, set up a test environment. That is a mini version of your network with exactly the same hardware as your production system. Test stuff here first!!! Get everything working the way you want before you deploy.
Second, clone your hard drive (a poor man’s go-back insurance policy). In a simple server have two identical drives. Before you make big changes (or any changes) to your working system, boot to a cd and run # dd if=/etc/hda of=/etc/hdb – That way you can go back to exactly the same way things were before you screwed it all up.
Third, take notes!
….thank you, …that was today’s lecture.