wipe /dev/sda

[Kent Borg]

Neil Aggarwal wrote :
>> The best way is to use a reasonably strong electromagnet and sweep it 
>> over the disk. In the old days we did it to wipe magnetic 
>> tapes.
>>     
>
> Would that work for hard drives? 

Kinda. Depends on how strong the magnet is. Basically a bad idea...

If, after wiping it your computer can't access it, then you are safe
from casual data retrievers. But you will also have destroyed the disk
making it unsuited for sale on Ebay. For quite a few years now disk
tracks have been made so small that the only way the disk can find them
is by reading markers recorded on the disk itself. Bulk erase and you
will damage those markers, making the disk worthless as a functioning disk.

If your magnet makes the disk no longer function, then you have
prevented the casual disk retrieval attempts.

If you are worried about a motivated foe, then you won't know. How
strong is the magnet? How close did you get it to each platter face?
Just because the disk quits working tell you nothing about whether fancy
techniques might recover data.

If you want to destroy a disk, dismantle it, put a strong magnet against
each platter face for the fun of it (much more effective close than at
even a slight distance), but then scrape off all the magnetic coating to
be sure.


-kb