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Re: [debian-knoppix] Include wipe into Knoppix

Am Freitag, 1. November 2002 14:55 schrieb Klaus Knopper:
> Hello Christian,
> Sorry, I'm not going to include wipe, because it's useless.

Since with wipe I'm able to securely destroy sensible data with one simple 
command (i.e. wipe -r /path/to/sensible/data) I think, wipe is definitely not 
useless. :)

> We had this discussion before, but I'm summarizing it anyways. ;-)

Thank you very much. :)

> Depending on which filesystem you use, erasing a file by copying random
> data over it is not going to physically destroy the file contents on
> your harddisk. Journaling filesystems for example create new blocks
> when you overwrite a file, rather than overwriting existing ones. So,
> even doing a dd if=/dev/urandom of=file_to_be_shred (which is what wipe
> does), does not necessarily do what you expect.

I always thought wipe does not only writes several times random data over the 
data to be wiped out. I understood this tool, as it would write some special 
patterns in a special sequence, so that the possibility of getting old data 
out of the effect of the magnetical remanence, is decreased more than just 
writing random patterns. But I'm open to other explanations. :)

Another 'problem' is that if I want to overwrite a file with dd i need to say 
dd the size of the wile. wipe deals that automatically.

> Concerning tapes: use dd. it is faster and present on every Unix
> installation.

What I have to do here is to securely delete sensible data in only a few 
directories (usually /home/<data> and /usr/local/<data>) with together about 
one or two gigs of data on some computers when for example the harddisks are 
getting more and more badblocks and needs to be replaced, the computer goes 
to another division in our institute or the computer is sorted out and 
donated to a school or similar.

The easiest way would be to boot those computers with KNOPPIX, mount the 
partitions, run a "sudo wipe -r /mnt/partition/sensible/data", wait for half 
an hour or so and that's it. If i had to run several write cycles with random 
data on the entire disk, this would last much longer than only wiping the 
sensible data itself.

The problem ist, that I don't have network on those maschine when I delete 
these files, so that I could simplay download the tool over the net and 
floppy drives are also unuseable in that situation I had to experience 
(defective floppies, floppy drives, floppy controllers or even there is no 
floppy drive available).



Christian Wenke
Bereich Embedded Systems
Escherweg 2 - 26121 Oldenburg - Germany
E-Mail: christian.wenke@offis.de - URL: http://www.offis.de/

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