Sometimes when building a system it is nice to make the disk blank, and I mean completely blank.  This is called zeroing a harddrive, and it writes a zero everywhere it can on the hard drive, which gets rid of all of the old formatting on the disk along with all of the files, but the coolest thing is that the bad sectors of the disk get marked as so and are not used anymore.  This can be very handy when trying to eliminate pesky problems that just won't seem to go away.

The first thing you need to do is find some sort of linux installation disc. In our office this usually means getting the "RedHat" install disc. Now put the cd in the drive and make sure that the system boots off of the disc. Once it has booted you will need to type "linux rescue" and follow the instructions to get a rescue shell.

Once you have gotten your shell, make sure that the disc did not mount, you should have been prompted to mount the the drive while you were getting to the shell, and you should have chosen "no."

Ok, here we go with the fun stuff:

For a regular hard drive type:

# cat /dev/zero > /dev/hda

This will zero out what is usually the C:\ drive on a windows machine, if you
have a second hard drive:

# cat /dev/zero > /dev/hdb

For a SCSI drive:

# cat /dev/zero > /dev/sda

For a second SCSI drive:

# cat /dev/zero > /dev/sdb

For a particular slice (partition of the hard drive)

# cat /dev/zero > /dev/hda(1 2 3 ... or what ever the number of the partition is) ie for the first partition on a drive
# cat /dev/zero > /dev/hda1