Md5sum is a software utility used to check the integrity of an ISO image before the file is used to create a CD (compact disc). Computers running Linux have this utility installed on their default system. Users of other operating systems may need to download an md5sum utility before being able to check the integrity.
How to use md5sum
In Linux, run md5sum with the name of a file, as shown below, to calculate and display the MD5 hash.
The output shows the md5 hash, and the name of the file hashed:
Once you have gathered the hash, you can compare it with the hash information from where you downloaded the .iso file. In our example, we have an Ubuntu .iso file. The MD5 hash information is listed in the UbuntuHashes overview. If the MD5 does not match the file, it is either incomplete, been changed, or is otherwise compromised.