Date: Sun, 8 Jul 2007 13:24:13 +0200 From: Paul Schenkeveld <fb-chat@psconsult.nl> To: freebsd-chat@freebsd.org Subject: Re: compressed HDD image using dd...clearing unused blocks Message-ID: <20070708112413.GA27077@psconsult.nl> In-Reply-To: <669580.92520.qm@web58104.mail.re3.yahoo.com> References: <669580.92520.qm@web58104.mail.re3.yahoo.com>
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On Sat, Jul 07, 2007 at 10:28:01PM -0700, Michael Eubanks wrote: > Hello all, > > I am updating a system that has been around for some > time now. I would like to make a compressed disk > image after the final setup is complete, although, I'm > guessing that the unused blocks will not allow me to > compress the image as well as I could with a > previously clean disk (considering the disk has been > in use for some time now). Is there a way to do this > - zero out unused blocks to optimize compression? I > generally do this with Windows machines using the > cipher command (killing cipher after it has finished > writing zeroes). After running cipher I use dd to > create a compressed HDD image for later use. I'd like > to be able to do the same with FreeBSD. What about: # dd < /dev/zero > BIG_EMPTY_FILE bs=128k # rm BIG_EMPTY_FILE Comes close to what you want, only a couple of indirect blocks are not zeroed this way but the majority of unused blocks will be. > -Michael S. Eubanks > mse0206@yahoo.com -- Paul Schenkeveld
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