command to find linux release version

The following command will show your linux release version

root@server-82:~# cat /etc/*release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04.3 LTS"
NAME="Ubuntu"
VERSION="12.04.3 LTS, Precise Pangolin"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu precise (12.04.3 LTS)"
VERSION_ID="12.04"

Similarly following command will give you same output

root@server-82:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 12.04.3 LTS
Release:        12.04
Codename:       precise

 
The following command will show your linux version

root@server-82:~# uname -a
Linux server-82 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

Here,
3.2.0-29-generic = kernel version
3.2.0-29-generic-pae = pae kernel version where more than 4GB ram in 32 bit kernel ** sometimes you can see like this in 32bit linux system
SMP = Kernel supporting multiple core and cpus