data shredder

[Amedee Van Gasse (ub)]

On Mon, December 21, 2009 14:08, Fred Roller wrote:
> Gilles Gravier wrote:
>>
>>> The other suggestions are good, and if you want a low-tech solution:
>>>
>>> 1) delete your files with rm as usual
>>> 2) overwrite the empty disk space with zeroes or random data
>>> Use either one of these commands:
>>>
>>> dd if=/dev/null of=nullfile bs=1M
>>> dd if=/dev/random of=randomfile bs=1M

> Amedee - I am used to the zero/random clearing of disks but not quite
> clear on why you create an empty image.  Could you clarify?

Fred,

Suppose I have a 10MB filesystem with 3 files:
alice.txt - 1MB
bob.txt - 2MB
eve.txt - 3MB
I have 4 MB free disk space

I delete eve.txt but I keep Alice and Bob.

I want to wipe the free space on the filesystem, so I fill it up with a
zero file called charlie.txt. It will be 7MB: 4MB of the original free
space, and 3MB from eve.txt.

If I would zero/random clear the entire disk, then I would destroy the
filesystem and loose Alice and Bob.

-- 
Amedee