Re: Wiping a drive: /dev/zero or /dev/urandom better?

[Adriel Desautels <adriel () netragard com>]

use dban, it works wonders.

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JW wrote:
> I've got a theoretical question: when wiping a drive (I'm talking about Linux 
> here), which of the following is more: fill the drive with data 
> from /dev/zero or /dev/urandom?
>
> I ask because I often see people suggest something like the following for 
> wiping disks:
>
> cat /dev/zero > /dev/hda
>
> (and of course do it multiple times)
>
> I got to thinking that (if you are really paranoid) it would probably be 
> easier for "the bad guy" to recover original data if you use /dev/zero 
> because it's so uniform, the "bad guy" can just look for anything other then 
> zeros - if it's not zero, it's data.
>
> Which would imply that overwriting the data with /dev/urandom or /dev/random 
> would be more secure.
>
> But I don't know enough about the internals of hard drives to know if it 
> really matters or not.
>
> For clarity I'll point out that I'm not talking about wiping files in the 
> filesystem, I'm talking about wiping whole disks - I guess you'd say "at the 
> block level".
>
> What do the resident experts here think? 
>
>       JW