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Date:      Thu, 17 Jan 2008 17:06:29 -0800
From:      "Nerius Landys" <nlandys@gmail.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: Gutman Method on Empty Space
Message-ID:  <560f92640801171706w7023ee1eq746b2dfec468b675@mail.gmail.com>
In-Reply-To: <31AE442CCBC1094ABC40CE85B0149F0652370B@MAIL1.registry.otago.ac.nz>
References:  <478F0D5A.9090107@highperformance.net> <31AE442CCBC1094ABC40CE85B0149F0652370B@MAIL1.registry.otago.ac.nz>

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> > Can anyone recommend a utility for the secure overwriting of
> > unused disc
> > space?
>
> split -b 200m /dev/random randomdata ; sync && rm randomdata*
>
> Run as many times as your paranoia factor requires on your file system.
> Gutman suggests in his own writings that overwriting with random data
> makes the most sense with modern disks.  Run as root to extend the
> writes past the soft filesystem limit.  Use whatever split parameters
> you fancy for the file sizes.  The "srm" port has fancy features for
> file/directory deletions.


 If I didn't misunderstand your question.  If you're trying to write bits
onto your disk so that nobody could recover data from it, there is a very
simple way to blank out either YOUR WHOLE HARD DRIVE or AN ENTIRE SLICE ON
YOUR HARD DRIVE.

Using the `dd' utility you can write zero bits to an entire slice of your
hard drive (or to the whole hard drive):

dd if=/dev/zero of=/dev/<disk-or-slice-ID>

Don't do this unless you want to lose all data on a slice or hard drive.



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