Originally Posted by klearview
Usually, you want to check the value against a reference one for the file to see if they're the same. If you use the command as you showed, you'd have to do this by hand. You can use the -c option to do this for you, e.g.
md5sum -c filename,
is not the ISO image, but a file containing the ISO image filename and its checksum. md5sum will then look for the file in the current directory and compare checksums.