Nuke a Disk on OS X10 Jul 2016
For security reasons, or in case you want to sell your hard drive, formatting the disk is not enough. The reason lies in the formatting process itself: formatting only resets the content list of a drive. Your data is still written on the disk, as long as you do not overwrite them.
There are different apps providing different overwriting strategies. The following simple comand overwrites a disk once with a random sequence of 0s and 1s:
cat /dev/random > /dev/disk[X]
X is here the index of the disk you want to overwrite. With
you can list all your partitions.