That container provides a fully working cartodb development solution without the installation hassle.
Just run and connect to locahost:3000 into you browser.
The default login is dev/pass. You may want to change it when you'll run it for the outside.
git clone https://github.com/fleu42/docker-cartodb.git
docker build -t="fleu42/docker-cartodb" docker-cartodb/
docker run -t -i fleu42/docker-cartodb -p 3000:3000 /bin/bash
You might need to add dev.localhost to your hosts file.