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List:       openbsd-misc
Subject:    Re: Make a backup
From:       Stuart Henderson <stu () spacehopper ! org>
Date:       2005-10-31 16:55:02
Message-ID: 3D9ACF76E73841512FA1C018 () megalith ! spacehopper ! org
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--On 31 October 2005 12:23 +0100, Abel TalaverC3n Estevez wrote:

> If I make the backup with 'dd if=/dev/wd0c of=/image bs=512' the
> image is a  file of about 2 GB because the hard disk is of 40 GB. But
> with a 'du -sh /' I  can see that all files are only 221 MB.

The free space probably contains old data, which may not be 
compressible. For each filesystem, dd /dev/zero into a file until you 
run out of space, then rm the file. I think I learned the trick from 
flashboot or some similar toolkit.

N.B. Don't count on being able to restore a dd image to another machine 
or HD.

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