[ubuntu-uk] Shredding HDD data

Tony Arnold tony.arnold at manchester.ac.uk
Wed Aug 11 13:54:53 BST 2010


On Wed, 2010-08-11 at 11:12 +0100, Bill Cumming wrote:
> Best way is probavly just to use the "dd" command:
> If you run off of a live CD then just point "dd" to the drive instead
> of a file.
> Example: sudo dd if=/dev/urandom of=/dev/sda 
> That will overwrite the entire drive that's on /dev/sda with random
> data destroying any Filesystem on that drive.
> You should at least do multiple alternating runs of
> "/dev/zero" (quick) and "/dev/urandom" (slow)

Only one run is necessary unless you think the CIA or GCHQ are
interested in the data. Even then the equipment required to recover
anything costs millions of pounds.

You may want read about 'The Great Zero Challenge'[1] where a disk
overwritten with zeroes using dd and the challenge was to recover the
data. It ran from Jan 15th 2008 until Jan 15th 2009. Nobody took up the


Tony Arnold,                        Tel: +44 (0) 161 275 6093
Head of IT Security,                Fax: +44 (0) 705 344 3082
University of Manchester,           Mob: +44 (0) 773 330 0039
Manchester M13 9PL.                 Email: tony.arnold at manchester.ac.uk

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