If you are planing sale your hard disk or give to some one else, you need wipe all data left on the hard disk / ssd disk. The simplest command to remove everything from Linux hard drive is as follows. Please note that the following commands will remove all data so be careful. You need any one of the following command:
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