I'm studying for LPI certification. They have three levels. I got to tell you, the first level I'm on now is fairly detailed. Much of it is fairly easy, like commands for working with files, like cd, cp,, mv, less, more. But some of it goes into setting environment variables, and bios setup for IDE and SCSI. It's worth it, if you just study for the test, the worst that will happen is you'll learn Linux.