checking a downloaded and created cd

ok do a md5sum on the download to check it is ok
then do
ls - filename
this tells you the $size

then do
let $value= $size/2048

dd if=/dev/cdrom bs=2048 count=$value |md5sum
and check this against the file to check you cut the disk right


https://help.ubuntu.com/community/HowToMD5SUM