I was once asked at an interview to give my three most important rules of sysadmin. This is what I said: 1. Never enter a command if you don't understand what

I was once asked at an interview to give my three most important rules of sysadmin. This is what I said: 1. Never enter a command if you don't understand what it does. 2. Never make a change on a production system if you don't know how to undo it. 3. Get everything else wrong if you have to, but get the backups right. I realize this paints with a broad brush but it's a good baseline.