[ubuntu-uk] Shredding HDD data

Glen Mehn glen.mehn at oba.co.uk
Wed Aug 11 13:31:53 BST 2010

  If you really want to do something like this, you'd need to write a 
bit of C or something that outputs 1s and compile it. You could, I 
suppose, in python (or even bash) do something like

while true()
     print chr(0xff)

though if you do the equivalent in C (or anything compiled) as it'll be 
much faster, then

runYourProg | dd of=/dev/(yourdevice)

but I haven't a clue as to why you'd want to do this. It'll still be 
slower than using /dev/zero

(unless, I suppose, you write your own kernel module to create it?)


On 11/08/2010 12:41, Bill Cumming wrote:
> Quick question:
> With dd (and dcfldd) it's east to write "0" (zeros) out to a drive but 
> how can you write just *1" (ones) out instead?
> On 11 August 2010 12:33, Vince Marsters <vince at marsters.co.uk 
> <mailto:vince at marsters.co.uk>> wrote:
>     On Wed, 2010-08-11 at 12:15 +0100, John Matthews wrote:
>>     What about hd you are still using, but have deleted stuff on
>>     them. Is there any way to bring that back, or even completely
>>     delete it?
>>     I had a program for windows when i used it, but I cant find
>>     anything for linux.
>     For data recovery you can use testdisk (its in the Universe repo
>     for Lucid).
>     As for completely delete it then the only way to be 100% certain
>     is to physically destroy the drive but I have been informed by a
>     KrollOntrack employee (they do commercial data recovery as well as
>     commercial erasing solutions) that 3 overwrites with different
>     data stops them from recovering data from a drive.
>     Also it is important to make sure that when doing secure erases
>     that the bit pattern is different for each wipe (e.g. if you write
>     zeros on the first pass then there should be no zeros in the
>     second). Using one of the Gov approved schemes will usually do this.
>     For most home users a single random wipe will be more than enough
>     as this prevents most people getting at any of the data.
>     Vince
>     --
>     ubuntu-uk at lists.ubuntu.com <mailto:ubuntu-uk at lists.ubuntu.com>
>     https://lists.ubuntu.com/mailman/listinfo/ubuntu-uk
>     https://wiki.ubuntu.com/UKTeam/
> -- 
> Regards
> Bill Cumming
> Twitter: @s0l_uk
> Skype: s0litaire
> eMail: bill at s0l.co.uk <mailto:bill at s0l.co.uk>

Glen Mehn
e: glen.mehn at oba.co.uk | t: @gmehn
m: +44 7942 675 755 | w: http://glen.mehn.net
b: http://glen.mehn.net/mba

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