Find the Ubuntu version and code-name

If you’re sitting in front of somebody else’s Ubuntu computer and want to quickly identify which version of Ubuntu it running (not always easy to do from the look and feel if it’s heavily customized), do the following: open a terminal window and type cat /etc/lsb-release. You can also
click Help → About Ubuntu, although bear in mind this won’t show the “point release” (for example, on my 8.04.1 installation, Help → About Ubuntu only mentioned the 8.04 release). This trick can also be used to ensure that you’ve upgraded to a newer version when one is released.

source:- ubuntukungfu