I'm in the process of building a Gentoo Linux 2004.0 distribution system for the Alpha processor family. I've got a second system (the old thebrain), which I'm using to do development. I stuck a second hard disk in it to do test installations on.
In the following, note that /dev/sda is the first hard disk, with the development system on it, and /dev/sdb is the second hard disk that I'd intended to use for testing. Partitions on /dev/sda are named /dev/sda1 and /dev/sda2, and similarly for the other disk.
livecd root # fdisk /dev/sdb (define the partitions on /dev/sdb...when finished:) livecd root # mkswap /dev/sda1 (define a swap partition) livecd root # mke2fs -j /dev/sda2 (make a filesystem)
Notice that the last two commands were issued to the wrong disk. I managed, in two simple commands, to completely clobber the development work I'd done. Most of it is recoverable, but I won't find out for sure until I reinstall the system from scratch and see what's missing.