Use dd to overwrite disk with zeroes, with progress information

dd is a great tool to overwrite disks quickly to erase all information on it (if you want to return them on warranty or sell them)¹⁾

Overwrite entire disk, e.g. /dev/sdX with zeroes, for example to sell the disk or send it in for warranty. Be VERY CAREFUL as overwriting the disk will permamently destroy all data on it.

CAUTION: Only do this if you know what your are doing. Do this at your own risk!

0. DON'T do this in a hurry

1. Verify that you have a backup of all your data!

2. Locate the disk, make 100% sure by checking the size and the model!:

ls /dev/disk-by-id -l

3. Verify that you are on the right disk (check paritions):

cfdisk /dev/sdX

4. Verify that the right hd light is lighting up if you read the disk

cat /dev/sdX > /dev/null

5. Overwrite the disk with zeros:

dd if=/dev/zero of=/dev/sdX bs=4096

6. Check the progress of your running dd, from another terminal window do ²⁾

watch killall -USR1 dd

Ref: http://www.vioan.ro/wp/2009/03/28/dd-command-progress-bar/

linux, dd, security

~~LINKBACK~~ ~~DISCUSSION~~

¹⁾

if you are required by law or are really paranoid, use shred, which overwrites the disk with random data, 25 times by default. But: overwriting once is enough to make the disk unrecoverable by professional data recovery services. If i had a disk with real top secret information, i would first overwrite it with shred and then physically destroy the platter

²⁾

this sends the USR1 signal to all running dd instances once every second, making them print out the progress information