Many years ago I was asked to image a new Samba server as the old one was throwing random errors due to age. I waited until everyone else had left the building

Many years ago I was asked to image a new Samba server as the old one was throwing random errors due to age. I waited until everyone else had left the building, grabbed the disk out of the old server, stuck it into the shiny new server and proceeded to dd the old disk to the new disk. Except I got the devices around the wrong way (/dev/sda , /dev/sdb) and proceeded to copy the contents of a blank hard drive over the top of the old server's drive. Didn't notice until the process had finished... I then discovered the benefit of DR plans the hard way (backups are useless unless you test a restore). Long story short, I managed to recover most of the files using a variety of disk recovery tools, but I was still in the office the next morning when other people started arriving and began to ask me why, for example, the payroll application couldn't find it's database. I spent the next few days in panicked forensics mode until the company was operating to everyone's satisfaction. When I left that company years later I had implemented many redundant layers of backups, proper DR plans that I religiously followed, and developed a meticulous habit of testing any commands that needed to be run on any production server.