Hash checking is very important when your transferring files between a server and an client. The purpose of this is to ensure the files which you have downloaded is 100% of the original source file and it hasn’t been modified. In addition to this it also ensures the file hasn’t been corrupted during the download process.
There are many ways to verify the hash of an downloaded file. Normally this is done via an MD5 hashing. Once you have downloaded the file, you can check the hash with:
This will provide you with the results of the hash for the file. Here is the hash sums for Ubuntu: https://help.ubuntu.com/community/UbuntuHashes