Sample implementation of running a rails app + db in docker

Initialize rails app

docker-compose run web rails new . --force --database=mysql --skip-bundle

Configure database

sed -i.bak s/localhost/db/g config/database.yml

Edit Gemfile and update any required gems

vi Gemfile

Install the bundle in a reusable docker image

docker-compose build

Create database schema

docker-compose run web rake db:create

Run application

docker-compose up -d