Suppose you want to erase all data on a hard-drive before selling or trowing it away.

Use the following commands to do so.

# sudo fdisk -l

to Identify the hard-drive to be deleted

# shred -vfz -n 10 /dev/sdb 

(where sdb correspondence to the devicename you identified via fdisk)
This will overwrite the hard-drive 10 times and should be enough for standard hard-drive deletion.


Options are:
(-n) 10 passes to overwrite the entire hard disk with (-z) zeros.
And shred (-f) forces the write by changing the permissions wherever necessary.