zeroing a disk on linux using DD

WARNING: if you don't really understand what are you doing (even if you THINK you are), then start learning/reading first or asking someone who really understands linux BEFORE doing something stupid like erasing a wrong disk by mistake.

if you need to wipe the content of a hard disk (REPLACE /dev/sda with the appropiate device !):

dd if=/dev/zero of=/dev/sda bs=1M 

last parameter (block size) makes the process a lot faster