Wiping donated computers for recycling question

[Theo Schmidt]

Jonathan D. Proulx schrieb:
...
> dd if=/dev/urandom of=/dev/sda
> 
> is better as it will write random data which makes recovery that much
> harder.  The "secure" wisdom is to do this three times to prevent
> software attacks and atleast make hardware attacks (like paying alot
> of money to a discrecovery specialist) really expensive.

I read about this about a year ago but can't find the reference now. The gist 
was that a single wipe even with zeros is enough to prevent recovery with any 
normal means, however that theoretically a electron microscope used on an opened 
disk can find data bits even if they have been overwritten many times. However 
this is so slow that it will only work if you know exactly where the data is on 
the platter and would otherwise take thousands of years to do with present 
technology.


> But for me if you're talking about reinstalling a class room computer
> then using that in another classroom setting this is overkill, infact
> nomatter what was on it if the end use is in a supervised class room
> the  reinstall is likely fine.

This is true, but if you get PCs e.g. from a bank they want reassurance that 
nobody can reconstruct their old data, and a single wipe with dd (as root or 
with sudo) can give them this reassurance. This is what we do with donated 
hardware at Linuxola.org - but only if they ask, as wiping a large disk can take 
an hour or so.

The problem with dd is that it gives no feedback except when it is finished (It 
only says "so and so records in, so and so records out). If you make a mistake 
it can erase the wrong disk or partition. There is no undo or progress bar or 
indication if it gets stuck, e.g. with a faulty disk.

So it might be easier to use the specialist live disk DABAN. http://www.dban.org
This is a small live-image (11 MB) to be burned onto a CD-R.

This was recommeneded here, where there also some other tips:
http://linuxhelp.blogspot.com/2006/06/how-to-securely-erase-hard-disk-before.html

Happy wiping, Theo