alex@alex-nb:/media/cdrom0$ md5sum /dev/cdrom
13331240b8bd291ae49606c8967fe416 /dev/cdrom
alex@alex-nb:/media/cdrom0$ md5sum -c md5sum.txt | grep -v 'OK$'
./preseed/ubuntu-server.seed: FAILED
./ebox/ubuntu-ebox.seed: FAILED
md5sum: WARNING: 2 of 1658 computed checksums did NOT match