[H-GEN] dd or shred for secure deletes.

[Greg Black]

On 2005-11-28, Anthony Irwin wrote:

[Please figure out how to generate lines of a sensible length in
your mail application; mile-long lines are a pain.]

>  I was under the impression that dd bs=1024 if=/dev/zero of=foo_file would securely delete a file by adding /0 to every byte of the file and the dd bs=1024 if=/dev/zero of=/dev/hda would securely delete a hard drive.

It all depends on what you mean by "secure".  If you mean what I
mean, then no technique that relies on software can be secure
(in part because you can't tell what the various layers of
software are really doing, and in part because software can't
actually erase data from magnetic media).

So secure deletion involves mechanical processes, such as a disk
drive shredder, or a high temperature oven.

If you don't actually mean secure, then some of the techniques
you mentioned do a fair to poor job of it, depending on the
specific file system software and some other technical factors.
But my original caveat still applies.

Cheers, Greg