You want to backup something or you have to burn a directory on a cd/dvd and you want to create a md5 checksum to save on the same medium.
You try to use md5sum utility but it allow only 1 file at a time so you can't use on a CD/DVD unless you create an ISO for this only purpose! Furthemore, if you create a checksum of the iso, you can't put into the iso/cd/dvd because that would change the checksum itself! But it's very awful to keep it apart unless the purpose is not only for publishing a distro on a website. But we don't want that. We want a backup with the checksum inside, all-in-once.
sudo apt-get update && sudo apt-get install md5deep
You can now use this command
md5deep -rl * > mychecksum
Now you put the file mychecksum on the medium with all the other files.
When you want to check the integrity of the files on the medium you have 2 solutions: Negative match: will show only the wrong files
md5deep -rx mychecksum *
or even using the onnipresent md5sum
md5sum -c --quiet mychecksum
The only difference between the two solution is that md5deep can also show you if there are files in excess, but that is useless for integrity check of a cd/dvd; can be useful only in case of synchronizations.