copying /dev/da0 with dd(1) to file: output differs

[Matthias Apitz]

El día Friday, November 19, 2010 a las 05:42:57PM -0700, Warren Block escribió:

> 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?

No. I just fired up the dd(1) a 2nd time to another file to check if it
would produce two times the same result. And, surprise, they differ,
they differ each time and in laptops differentes as well.

	matthias
-- 
Matthias Apitz
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