How to wipe a HD?

[Bruno Wolff III]

On Sat, Apr 23, 2005 at 14:00:21 -0400,
  "Robert P. J. Day" <rpjday at mindspring.com> wrote:
> On Sat, 23 Apr 2005, Bruno Wolff III wrote:
> 
> another solution is to boot from a CD and just rewrite the entire
> drive several times using "dd" -- enough times to wipe that trace
> magnetization.  start with
> 
>   # dd if=/dev/zero of=/dev/hda ...
> 
> now, it's too bad there's no /dev/ones.
> 
>   but you could also keep overwriting with /dev/random.  after a
> while, i'm pretty sure there won't be much salvageable from the drive.

That won't cover remapped sectors. You should be able get a count of
remapped sectors using smartctl. But I think if you are worried about
people paying to have data extracted from the trace magnetization, you
are better off destroying the drive with witnesses.