MD5SUM is a programme designed to verify the integrity of data using MD5 (Message-Digest algorithm 5) 128-bit cryptographic hash.
How to use MD5SUM
$ md5sum intrepid-desktop-amd64.iso
-It will display the result like below
-To save the result as a text file
$ md5sum intrepid-desktop-amd64.iso > MD5SUM
-If there is already correct md5sum file, it can be used to check the integrity of disc images with the following command after moving to the directory in which the image files are located (notice that the md5sum file should be also in the same directory unless the path of md5sum file is otherwise specified).
$ md5sum -c MD5SUMs
$ md5sum -c ~/some_directory/MD5SUMs
-It will display the result like
intrepid-desktop-i386.iso: OK intrepid-desktop-amd64.iso: OK