Command to Find Current Ubuntu Version

Run this command to find the installed version of Ubuntu.

cat /etc/lsb-release

You will get the following info.

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=8.04
DISTRIB_CODENAME=hardy
DISTRIB_DESCRIPTION="Ubuntu 8.04.3 LTS"

You could also use

cat /etc/issue

Which will display the version only:

Ubuntu 8.04.3 LTS \n \l