How to check release version in Ubuntu

There are many ways to check from Ubuntu the release version.

~$ cat /etc/issue.net
Ubuntu 8.04.4 LTS

~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=8.04
DISTRIB_CODENAME=hardy
DISTRIB_DESCRIPTION="Ubuntu 8.04.4 LTS"

~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 8.04.4 LTS
Release:        8.04
Codename:       hardy

~$ cat /etc/issue
Ubuntu 8.04.4 LTS \n \l