Date: Fri, 19 Nov 2010 21:46:39 +0100 From: Matthias Apitz <guru@unixarea.de> To: Warren Block <wblock@wonkity.com> Cc: freebsd-usb@freebsd.org Subject: Re: copying /dev/da0 with dd(1) to file: output differs Message-ID: <20101119204639.GA1521@tiny.Sisis.de> In-Reply-To: <alpine.BSF.2.00.1011191231200.95921@wonkity.com> References: <20101119143337.GA3023@current.Sisis.de> <201011191821.09308.hselasky@c2i.net> <20101119173519.GA3933@current.Sisis.de> <201011191916.53655.hselasky@c2i.net> <20101119183900.GA1221@tiny.Sisis.de> <alpine.BSF.2.00.1011191231200.95921@wonkity.com>
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El día Friday, November 19, 2010 a las 12:39:13PM -0700, Warren Block escribió: > > Just an idea: The USB key in question was new and I only created the > > file system on it the usual way (fdisk, bsdlabel, newfs). Then I > > restored the dump on it (which took 26 hours for 3.1 GByte dump file). > > The USB key boots fine, btw. > > 26 *hours*? USB 1.1? I don't think so. It is the Acer One D250 netbook. > Well, they could be anything. But the original filesystem has > formerly-used blocks with old data from deleted files. dump doesn't > copy those, but dd does. > > > Should I overwrite the full USB key from /dev/zero? > > Possibly there would still be differences. Filesystem metadata like > date last mounted, for example. If you want a block-by-block duplicate, > the brute-force method is to just dd the whole drive. Use bs=64k or > bs=1m to help reduce overhead. Warren, perhaps you missed my point. I have a prepared boot-able key and I want to give away a copy of it as a file on DVD. So I dd(1)'ed the key to disk and did this twice to ensure that the copy was fine, but the two files differ. How can I make sure that the file on disk (or DVD) is a exact copy of the key? matthias -- Matthias Apitz t +49-89-61308 351 - f +49-89-61308 399 - m +49-170-4527211 e <guru@unixarea.de> - w http://www.unixarea.de/
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