- How to check your Ubuntu Linux Version

To check which version of Ubuntu you are running, click System > About Ubuntu. The first line of the page that loads will tell you the version number.

To check your Ubuntu version using the command line:

Open a Terminal (Applications > Accessories > Terminal) and type command cat /etc/issue
The Ubuntu version will be displayed on the screen.

source:http://linuxpoison.blogspot.com/2010/10/135781677517908.html