How to determine the linux distribution name or version

There are multiple ways to check what linux distribution and version you are using.

Here are some of them.

$ cat /etc/issue
Ubuntu 9.04 n l

$ uname -a
Linux riza-laptop 2.6.28-15-generic #49-Ubuntu SMP Tue
Aug 18 19:25:34 UTC 2009 x86_64 GNU/Linux

$ lsb_release -d
Description: Ubuntu 9.04