As system admins sometimes you have to check what Linux distribution you are using via the command line. Below is how you do this:
For example on my VPS I would then get this in return:
DISTRIB_ID=Ubuntu DISTRIB_RELEASE=10.04 DISTRIB_CODENAME=lucid DISTRIB_DESCRIPTION="Ubuntu 10.04.1 LTS"
For more information regarding the cat command visit the cat man page