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From: Bruce Cran <bruce@cran.org.uk>
To: freebsd-questions@freebsd.org
Date: Mon, 8 Mar 2010 23:16:28 +0000
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Cc: Christoph Kukulies <kuku@kukulies.org>
Subject: Re: md5 of /dev/acd0
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On Monday 08 March 2010 11:25:20 Christoph Kukulies wrote:
> I was trying to determine a md5sum from a DVD I had inserted into a
> FreeBSD 8.0
> on my Dell Inspiron 9400 notebook.
> 
> I thought dd if=/dev/acd0 | md5 would work but I got "Invalid argument".
> 
> Trying dd if=/dev/acd0 bs=1048k | md5 worked  in so far that it didn't
> yield an error
> but after the DVD stopped spinning the command  hung and I only could
> bail out using ^C.

Try using bs=2048 .

-- 
Bruce Cran