There is no command to format a hard drive. They are formatted by the manufacturer. rm -fr / simply removes all the pointers to the data on the drive. The data is still there until the data blocks are re-written to. mkfs, mkfs.ext2, mkfs.ext etc will install a new file system. That is what you are probably looking for.
Even in Windoze, when it says "Formatting C drive" is not actually reformatting the drive. A low level format takes a very very long time and should never be done.
You can put a file system on, and you can tune a disk drive with hdparm. If you are interested in completely wiping the data off the drive, just cat /dev/zero > /dev/hda (substitute the drive device if it is hdb or hdc or sda etc.