MD5

MD5 refers to the MD5 Message Digest Algorithm∞. MD5 hashes are often used to check if a file downloaded correctly. If the MD5 hashes are different, then the file is corrupted or a different version. A MD5 hash (or checksum) is typically a 32-character hexadecimal number that can result from running the md5sum program against a particular file. Since any difference between two files results in two different values, MD5 values can be used to determine that the file (e.g. puppy-release.iso) you downloaded is an exact copy of the original file. The file with the MD5 value usually has the same name as the file you downloaded, but it ends with an additional .md5 and/or .txt extension (e.g. puppy-release.iso.md5.txt).

A MD5 check is not necessary when a file is downloaded using the BitTorrent protocol as BitTorrent automatically provides error correction.

Download the ISO file.

Open a console in the directory that contains this file.

Issue the command to generate the md5sum:

$ md5sum puppy-version.iso

Compare manually the output with the given md5sum.

Download both the ISO file and the md5sum file.

Open a console in the directory that contains both those files.

Issue the command to have the md5sum checked automatically:

$ md5sum -c puppy-version.iso

If there is no exact match you will get an error message. If the downloaded file is error-free the program ends without a message.

Users of DOS or DOS-based versions of Windows (Windows 95, 98 & ME) one can use this MS-DOS compatible application (only 48K): md5sum.exe∞. Right-click on the file name and save it to the folder that your downloaded file is in.

Create a MD5 checksum file using the standard command line utility by typing:

md5sum puppy-puplet.iso > puppy-puplet.iso.md5

MD5sums for Windows∞