Validating An MD5 Hash
MD5 (message digest algorithm 5) is a cryptographic hash that generates a 128-bit digital signature of a message. The message could be text or a file. The md5 message is a unique id and in theory, no two files could ever have the same md5 hash. Typically in the Linux world, md5 hashes are used to verify the validity of files. Links for popular Linux distribution download .iso files are typically listed along with their md5 hash. After you download an .iso file, you can check its md5 hash to ensure that the file is intact and not corrupted. You can do this with the linux command md5sum as follows:
md5sum rhel-server-5.3-x86_64-disc1.iso 1fb6b886cd6b2e5ed37565ccd85ee6d3 rhel-server-5.3-x86_64-disc1.iso
Compare the generated hash value with the listed md5 has value and if they are the same, the file is good. If they differ, you don’t have a good file or the file has been compromised somehow. Either way, the file is no good.