Login to your CentOS server using SSH and run the following command:
cat /etc/centos-release
This should return the following CentOS version information:
CentOS release 6.6 (Final)
CentOS version history follows that of Red Hat but it could be delayed, which is just one of a few things you should know before running a CentOS server.
Let's break this down:
CentOS – This is your Linux distribution. This may seem obvious but in doing outsourced support, we sometimes find surprises.
6.6 – There are two parts of this version number. 6 is the major release version for this Linux distribution. The 6 represents the sixth update for this release. Red Hat, Fedora and CentOS Linux distributions use this version system.
Kernel Versions
Know that you know your CentOS version, you may also want to check what kernel is running on your CentOS server. You can check which kernel you are using by running:
uname -a
This will return:
Linux tdweb 2.6.32-504.el6.x86_64 #1 SMP Wed Oct 15 04:27:16 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
