RHEL (and by extension CentOS) 7 provides Ruby 2.0. And a 3.10 kernel even. If you're running docker with CentOS, this is what you're likely to use. RHEL/Cen

RHEL (and by extension CentOS) 7 provides Ruby 2.0. And a 3.10 kernel even. If you're running docker with CentOS, this is what you're likely to use. RHEL/CentOS 6 provides Ruby 1.8.7 and a 2.6.32 kernel. It can be made to run with docker, but it's unsupported and it won't be easy. RHEL/CentOS 5 provides Ruby 1.8.5. The 2.6.18 kernel it comes with won'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.