[clug] md5sum and verifying DVD

Andrew Pollock andrew-clug at andrew.net.au
Thu Jul 28 02:53:27 GMT 2005

On Thu, Jul 28, 2005 at 10:34:48AM +1000, Carlo Hamalainen wrote:
> Hi,
> I have a Mondo ISO that I've burned to DVD using growisofs. When I
> verify the DVD against the iso with 
> cmp 1.iso /dev/hdc
> it looks like the DVD is good, but when I do the md5sums I get different
> answers:
> c at t40:~$ md5sum 1.iso
> d7563e63f8e6306de0466cd3b3576571  1.iso
> c at t40:~$ md5sum /dev/hdc
> 6b76ba56f97770f641012f156eba3a25  /dev/hdc
> Why are they different? What am I doing wrong here?
> This is on an IBM T40 laptop, kernel.

Firstly determine the exact size of the ISO:

isoinfo -d -i 1.iso

Note the block size (usually 2048) and volume size

Then, take the md5sum of just this much of the CD:

dd if=/dev/hdc bs=<block size determined above> count=<volume size
determined above> | md5sum



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