<p>Dd if=/randomladygaga.mp3 of=/dev/sda</p>
<div class="gmail_quote">On Aug 26, 2011 3:15 PM, "Lightner, Jeff" <<a href="mailto:JLightner@water.com">JLightner@water.com</a>> wrote:<br type="attribution">> Yep - I started using /dev/urandom instead of /dev/zero when I read something that said if the overwrite data is predictable (e.g. all zeros) it might be easier to decide what real data it was trying to mask.<br>
> <br>> <br>> <br>> <br>> <br>> -----Original Message-----<br>> From: <a href="mailto:ale-bounces@ale.org">ale-bounces@ale.org</a> [mailto:<a href="mailto:ale-bounces@ale.org">ale-bounces@ale.org</a>] On Behalf Of David Tomaschik<br>
> Sent: Friday, August 26, 2011 2:52 PM<br>> To: Atlanta Linux Enthusiasts<br>> Subject: Re: [ale] erasing a hard drive<br>> <br>> On Fri, Aug 26, 2011 at 1:37 PM, Lightner, Jeff <<a href="mailto:JLightner@water.com">JLightner@water.com</a>> wrote:<br>
>> Of course you don't need a software at all.<br>>><br>>> Erasing the data in a filesystem then unmounting the filesystem and running:<br>>> dd if=/dev/urandom of=/dev/sda1/scramble bs=1M<br>>><br>
>> - will write random data on the partition (sda1 in the above - you can substitute other partitions/drive letters as necessary)<br>>><br>>> However, any time I've seen this question come up someone invariably posts that it really isn't necessary for "modern drives". They never quite say what their definition of "modern" is.<br>
>><br>>> In the past it was required to do something like the above multiple times but it really isn't necessary unless you're doing DOD or CIA work.<br>> <br>> It is necessary to do at least one overwrite pass. Recovering data<br>
> from a drive that has not been overwritten at all (e.g., mkfs or rm<br>> only) is trivial.<br>> <br>> The theory behind multiple overwrites has to do with the fact that<br>> data isn't really stored in discrete chunks on the drive, and there<br>
> are algorithms that can theoretically recover/rebuild data from the<br>> "edges" of the tracks. However, this is substantially less of an<br>> issue these days. For one, those techniques were developed against<br>
> MFM and RLL encoded drives. Drives using PRML and EPRML and<br>> perpendicular recording are believed to be far more resistant to this<br>> (as they have less area in which other traces are left.)<br>> <br>
> For a better explanation than I could write, see<br>> <a href="http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html">http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html</a> (especially<br>> the epilogue).<br>
> <br>> <br>> --<br>> David Tomaschik, RHCE, LPIC-1<br>> System Administrator/Open Source Advocate<br>> OpenPGP: 0x5DEA789B<br>> <a href="http://systemoverlord.com">http://systemoverlord.com</a><br>> <a href="mailto:david@systemoverlord.com">david@systemoverlord.com</a><br>
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