On Fri, Jan 20, 2012 at 2:17 PM, Mike Miller <mbmiller+l at gmail.com> wrote: > But seriously -- regarding /dev/zero -- does anyone think there are any > *real* worries about data recovery after you've filled the drive with zeros? Yes. I once used a tool (Ontrack maybe?) that found bits of file structures after wiping with /dev/zero. Ever since then, I rely on no less than a 3 pass DBAN wipe. > I know if I was working on a secret project at Microsoft, I wouldn't fill > my old drive with zeros and then hand it to developers at Apple or Oracle, > but if we're talking about giving a personal hard drive to someone who just > wants to use it in their personal computer, isn't use of /dev/zero plenty? I trust no one, but I'm weird that way. > Jeremy pointed out that /dev/urandom would use random bits. I would think > that /dev/urandom would be a better choice than /dev/zero. Is there any > reason to prefer /dev/zero? In other words, isn't this a really good > answer: > dd if=/dev/urandom of=/dev/<drive> > Is it really even necessary to do that twice? In theory, alternating bit patterns mask magnetic signatures better than a single stream of 0s. Multiple passes increase the masking effect and make software based recovery impossible. If I don't have DBAN handy, I'll usually do two passes of urandom and one pass of zeros. It makes me feel better for some reason. Irrational paranoia is fun sometimes. > To properly mess up that drive, can I just do this?: > dd if=/dev/urandom of=/dev/sdb Can and should. As others have stated, this whacks the whole partition table, boot sector, and of course all areas of the drive with data. Brian