From: Christopher L. Barnard (cbar44@tsg.cbot.com)
Date: Wed May 19 2004 - 12:44:08 EDT
I asked
> A followup to my question last week about wiping a disk:
>
> for those of you using
> dd if=/dev/random of=/dev/rdsk/cXtXdXsX
> how long does it usually take? On a 2gig disk after it had been running
> for over 24 hours I phoned Sun Support to see if maybe I had gotten the
> flags to dd wrong or something like that. The woman I spoke to was
> insistent that a repartition and newfs was all that was necessary to
> wipe a disk of all previous data. Yeah, right. Sure. And Microsoft
> will start making a secure and well written product. So, how long does
> that command usually take?
>
> TIA, and I will summarize.
Damn, that was fast.
/dev/random has to generate entropy and is very CPU intensive every time
it is called. Use /dev/urandom if you must (it is orders of magnitude
faster than /dev/random), but /dev/zero (which is orders of magnitude
faster than /dev/urandom) with multiple passes (7 for government specs,
I understand) is much faster and works fine. Also, tweak the block
size. bs=1024k seems to be the fastest.
dd if=/dev/zero of=/dev/rdsk/cXtXdXsX bs=1024k
format (to label the disk again)
rinse, lather, and repeat 7 times.
Thanks to the 15 or so people that responded to my query within minutes...
+-----------------------------------------------------------------------+
| Christopher L. Barnard O When I was a boy I was told that |
| cbarnard@tsg.cbot.com / \ anybody could become president. |
| (312) 347-4901 O---O Now I'm beginning to believe it. |
| http://www.cs.uchicago.edu/~cbarnard --Clarence Darrow |
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