Date: Fri, 19 Nov 2010 17:42:57 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: Matthias Apitz <guru@unixarea.de> Cc: freebsd-usb@freebsd.org Subject: Re: copying /dev/da0 with dd(1) to file: output differs Message-ID: <alpine.BSF.2.00.1011191739240.97011@wonkity.com> In-Reply-To: <20101119204639.GA1521@tiny.Sisis.de> 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> <20101119204639.GA1521@tiny.Sisis.de>
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On Fri, 19 Nov 2010, Matthias Apitz wrote: > El d?a Friday, November 19, 2010 a las 12:39:13PM -0700, Warren Block escribi?: > >>> 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? Okay, that makes more sense. Did you mount the key in between the two times it was dd-ed?
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