wiping/recovering data from drives (was: ByteWorks, FLOSS, and refurbishing machines)

[Robert Citek <rwcitek@alum.calberkeley.org>]

On Jun 19, 2006, at 9:30 AM, asouza@siu.edu wrote:
> What do you recommend for verifying that all the data has been erased?

od works pretty well.  For example, to wipe and verify /dev/hda:

   shred -v -n 4 -z /dev/hda
   od /dev/hda

shred will overwrite the drive (/dev/hda) 4 times (-n 4) with a final  
write of zeros (-z) while showing its progress (-v).  od will read  
the data from /dev/hda, collapse consecutive runs of data, and  
display it in octal.  It should look something like this:

$ od /dev/hda
0000000 000000 000000 000000 000000 000000 000000 000000 000000
*
620000000

For more information on the DoD spec, see wikipedia[1] and the DoD  
source[2].

> Is there a certain boot-able distro that specializes in data recovery?

Knoppix has a number of tools including shred, od, dd, testdisk, and  
dd_rescue, among others.  It's what we use at ByteWorks to wipe,  
test, backup, and clone drives.  The book Hacking Knoppix[3] covers  
these and many other tools for examining a drive.  Have a look at  
"Part II: Rescuing and Recovering Systems using Knoppix."   
Disclosure: I was one of the technical editors for the book.  Despite  
that, the book is a good read.

[1] http://en.wikipedia.org/wiki/DOD_5220.22-M
[2] http://www.usaid.gov/policy/ads/500/d522022m.pdf
[3] http://www.amazon.com/gp/product/0764597841/

Regards,
- Robert
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