How to check Ubuntu version

There are a few command to check the Ubuntu version. See below.

Command : lsb_release -a
root@ubuntu:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 8.10
Release: 8.10
Codename: intrepid

Command : cat /etc/issue
root@ubuntu:~# cat /etc/issue
Ubuntu 8.10 \n \l

Command : cat /etc/lsb-release
root@ubuntu:~# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=8.10
DISTRIB_CODENAME=intrepid
DISTRIB_DESCRIPTION="Ubuntu 8.10"

Command : cat /etc/apt/sources.list
root@ubuntu:~# cat /etc/apt/sources.list
#
# deb cdrom:[Ubuntu-Server 8.10 _Intrepid Ibex_ - Release amd64 (20081028.1)]/ intrepid main restricted

#deb cdrom:[Ubuntu-Server 8.10 _Intrepid Ibex_ - Release amd64 (20081028.1)]/ intrepid main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://my.archive.ubuntu.com/ubuntu/ intrepid main restricted
deb-src http://my.archive.ubuntu.com/ubuntu/ intrepid main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://my.archive.ubuntu.com/ubuntu/ intrepid-updates main restricted
deb-src http://my.archive.ubuntu.com/ubuntu/ intrepid-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://my.archive.ubuntu.com/ubuntu/ intrepid universe
deb-src http://my.archive.ubuntu.com/ubuntu/ intrepid universe
deb http://my.archive.ubuntu.com/ubuntu/ intrepid-updates universe
deb-src http://my.archive.ubuntu.com/ubuntu/ intrepid-updates universe

## OpenNMS
deb http://debian.opennms.org stable main
deb-src http://debian.opennms.org stable main

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://my.archive.ubuntu.com/ubuntu/ intrepid multiverse
deb-src http://my.archive.ubuntu.com/ubuntu/ intrepid multiverse
deb http://my.archive.ubuntu.com/ubuntu/ intrepid-updates multiverse
deb-src http://my.archive.ubuntu.com/ubuntu/ intrepid-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://my.archive.ubuntu.com/ubuntu/ intrepid-backports main restricted universe multiverse
# deb-src http://my.archive.ubuntu.com/ubuntu/ intrepid-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository. This software is not part of Ubuntu, but is
## offered by Canonical and the respective vendors as a service to Ubuntu
## users.
# deb http://archive.canonical.com/ubuntu intrepid partner
# deb-src http://archive.canonical.com/ubuntu intrepid partner

# Line commented out by installer because it failed to verify:
#deb http://security.ubuntu.com/ubuntu intrepid-security main restricted
# Line commented out by installer because it failed to verify:
#deb-src http://security.ubuntu.com/ubuntu intrepid-security main restricted
# Line commented out by installer because it failed to verify:
#deb http://security.ubuntu.com/ubuntu intrepid-security universe
# Line commented out by installer because it failed to verify:
#deb-src http://security.ubuntu.com/ubuntu intrepid-security universe
# Line commented out by installer because it failed to verify:
#deb http://security.ubuntu.com/ubuntu intrepid-security multiverse
# Line commented out by installer because it failed to verify:
#deb-src http://security.ubuntu.com/ubuntu intrepid-security multiverse