a) dd command – convert and copy a file.

b) shred command (secure wipe+erase) – Overwrite the specified FILE(s) repeatedly, in order to make it harder for even very expensive hardware probing to recover the data.

c) scrub command (secure wipe+erase) – Writes patterns on magnetic media to thwart data recovery.

Method #1: Old good dd command

Use the following dd command to remove data from /dev/hdX:

dd if=/dev/zero of=/dev/hdX  bs=512  count=1

OR for sata disk, use the following syntax:

dd if=/dev/zero of=/dev/sdX  bs=512  count=1

In this example, empty sata disk /dev/sdb, enter (you must be login as the root user):

fdisk /dev/sdb
dd if=/dev/zero of=/dev/sdb  bs=512  count=1
fdisk -l /dev/sdb

Method #2: Securely wipe hard disk with shred command

You can use the shred command to securely remove everything so that no one recover any data:
shred -n 5 -vz /dev/sdb

Method #3: Say hello to scrub command

You can also use disk scrubbing program such as scrub. It overwrites hard disks, files, and other devices with repeating patterns intended to make recovering data from these devices more difficult. Type the following command to securely wipe out /dev/sdb:
# scrub -p dod /dev/sdb

See also

• Linux : How to delete file securely
• Man pages – shred(1),dd(1),scrub(1)