Date: Sat, 15 Apr 2000 16:55:32 +0100 From: Ben Smithurst <ben@scientia.demon.co.uk> To: Scott Blachowicz <scott@sabami.seaslug.org> Cc: freebsd-questions@freebsd.org Subject: Re: Erasing an IDE disk Message-ID: <20000415165532.A16019@strontium.scientia.demon.co.uk> In-Reply-To: <20000414161657.A35142@sabami.seaslug.org> References: <20000414161657.A35142@sabami.seaslug.org>
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Scott Blachowicz wrote: > I'm fixing to remove a disk from my system and give it to someone else. I want > to erase it to try to make sure that no personal or sensitive data can be > recovered from it. So, my first attempt was to install FreeBSD 4.0 on it, then > try to do this kind of stuff: > > dd if=/dev/zero of=/dev/ad0s2c That will only erase slice 2, so that's not really good enough. You won't be able to erase the whole disk unless nothing on ad0 is mounted (did you check that; what does "mount" show?). I think what you'll have to do is to put this disk in another FreeBSD system as ad1 (or ad2, or whatever), and try erasing /dev/ad1 completely (not ad1s<something> or anything like that). Or, you could use the fixit CD (disc 2 in WC sets), and use dd from there. As for the person who suggested /dev/urandom, I'm not sure that would be better. It will use loads of CPU time, both ways will stop a casual nosy person, and neither way will stop someone who *really* wants the data off the disk. See <http://www.cs.auckland.ac.nz/~pgut001/secure_del.html>; for more on this sort of stuff. When I returned a disk to a shop recently because it was b0rken, I just wrote 0x0, 0xff, then 0x0 over the whole disk. Given that when I took it back they used Windows Scandisk to check if it really was faulty, I think that was overkill. :-) -- Ben Smithurst / ben@scientia.demon.co.uk / PGP: 0x99392F7D To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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