md5sum command is use to check or print MD5 (128-bit) checksums. For example purpose download your favorite Linux distribution from Linux distribution web site / project site. Now you will need to to check md5sum on a Linux ISO file.

1) Download Debian linux # 1 ISO please note down md5sum listed next to each ISO file with the help of wget command:
$ wget http://someproject.org/path/to/isofile.iso

2) Verify integrity of a Linux iso:
$ md5sum isofile.iso
Output:

a0b162e26281ef097ee8b39b8690a8c2 isofile.iso

Compare output (a0b162e26281ef097ee8b39b8690a8c2) with key listed online at linuxiso.org’s site.

You can read MD5 sums from the FILEs and check them:
$ md5sum -c xcache-1.2.2.tar.gz.md5.txt
Sample output:

xcache-1.2.2.tar.gz: OK

Online References:

• MD5 Readme file
• Read more of the Howto: Verify integrity of the tar balls or source code