RHEL (and by extension CentOS) 7 provides Ruby 2.0.  And a 3.10 kernel even.  If you&#x27;re running docker with CentOS, this is what you&#x27;re likely to use.<p>RHEL&#x2F;CentOS 6 provides Ruby 1.8.7 and a 2.6.32 kernel.  It can be made to run with docker, but it&#x27;s unsupported and it won&#x27;t be easy.<p>RHEL&#x2F;CentOS 5 provides Ruby 1.8.5.  The 2.6.18 kernel it comes with won&#x27;t even run go binaries such as docker, much less lxc.  Yes this is ancient.  It was released in 2007 and it will be supported until 2017.