Update Docker docs

doc/SETUP_DEVELOPMENT.md

@@ -5,6 +5,10 @@ Gratulations, if you read this file locally, you have successfully cloned the
 foodsoft project from the git repository. Now you are only a few steps away
 from trying it out and then jumping into development.
 
+This document describes how to setup Foodsoft for development on your local system.
+Alternatively, you [run Foodsoft using Docker](SETUP_DOCKER.md).
+
+
 **System requirements**:
 [RVM](https://rvm.io/rvm/install),
 [Ruby 1.9.3+](https://www.ruby-lang.org/en/downloads/),

doc/SETUP_DOCKER.md

@@ -0,0 +1,69 @@
+# Foodsoft on Docker
+
+This document explains setting up and using Foodsoft with Docker.
+
+## Requirements
+
+* Docker (=> 1.5)
+* Docker Compose (=> 1.1)
+* Nothing more, no ruby, mysql, redis etc!
+
+For installing instructions see https://docs.docker.com/installation/.
+Docker runs on every modern linux kernel, but also with a little help on MacOS
+and Windows!
+
+## Setup
+
+Create docker volume for mysql data:
+
+    mkdir -p ~/.docker-volumes/foodsoft/mysql
+
+Setup foodsoft development data: (This will take some time, containers needs
+to be pulled from docker registry and a lot dependencies needs to be installed.)
+
+    docker-compose run app rake foodsoft:setup_development
+
+## Usage
+
+Start containers (in foreground, stop them with `CTRL-C`)
+
+    docker-compose up
+
+Run a rails/rake command
+
+    docker-compose run app rake db:migrate
+
+Open a rails console
+
+    docker-compose run app rails c
+
+Setup the test database
+
+    docker-compose run app rake db:setup RAILS_ENV=test DATABASE_URL=mysql2://root:secret@mysql/test
+
+Run the tests
+
+    docker-compose run app ./bin/test
+
+Jump in a running container for debugging.
+
+    docker exec -ti foodsoft_app_1 bash
+
+## Notes
+
+### Gemfile updates
+
+This is bit tricky, as the gemfiles are stored in the container and so we have
+to rebuild the container each time we change the Gemfile. To avoid installing
+all the gems from scratch we can use this workaround:
+
+```bash
+docker-compose run app bundle update rails # Update Gemfile.lock file
+docker ps -a # Look for the last exited container and grab the Container ID
+docker commit -m "Updated rails" <Container ID> foodsoft_app
+```
+
+### Database configuration
+
+To make this easier we use the environment variable `DATABASE_URL`
+(and `TEST_DATABASE_URL` when using the testing script).