This is a CentOS7 S2I image with RVM (https://rvm.io) preinstalled ready to run Ruby based apps on OpenShift. To install a specific ruby version, set environment variable RUBY_VERSION or specify it in your Gemfile. Otherwise, the rvm default ruby will be installed.
To run commands in your docker container, create a Procfile and set PROCTYPE environment variable to the command name. For more information about Procfile: https://ddollar.github.io/foreman/#PROCFILE. If not specified the web command will be selected by default. The web command will always launch on port 8080.
The Dockerfile and source can be found here: https://github.com/hammady/s2i-centos-rvm