title: Check Which operating system is installed ( CentOS, Ubuntu, Redhat, ... etc)
body: <p>I have been given a server with OS installed. I want to check which Operating system is installed in it. I have used uname -a with ouput of 
      Linux ctl 2.6.32-573.3.1.el6.x86_64 #1 SMP Mon Aug 10 09:44:54 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux</p>
  
  <p>Any suggestions ?</p>