This is a basic version of Rails installed on Ubuntu 14.04. I use this to start a new Rails App.
If you just want Rails installed without a Base App, use V1.
If you want a Base App installed, use V2. The base app is located in /var/app. This version also contains a script for starting the app that can be entered when creating a container:
docker run -d -p 80 blainedwards8/rails:v2 ./etc/init.d/start