Along the lines of asking first, “What is this thing?” before pulling a pin on a grenade: What does “rm -rf /” do? Is it a reformatting command?
rm -rf / is a recursive deletion starting at the root directory. Very damaging when run as a user, completely destructive if run as root user. Unix doesn’t ask “Are you sure?” Unix just does it. Unix is not for the uninitiated.
Nope, it's a ReMove command. The -r makes it recursive (so it goes up and down the hills).
fdisk is the reformatting command. And they are fairly serious about that. If you want file system afterward, you have to mkfs.
/johnny
In Unix/Linux/Mac land the "rm" is short for remove. The "-" denotes a switch and the letters that follow define the switch. In this case, "r" is for recursive. The "f" is for force. The last bit is "/" which denotes the root directory as the starting place. The "*" means ALL.
Ergo, rm -rf /* would be a command with switches that will force a removal of all files recursively from the root directory on down. Total destruction. Especially in Unix/Linux/Mac lands. In Winders, files are not deleted like this. They are marked for deletion and aren't actually, totally gone until the sectors used to store them are overwritten.