docker-rails

Summary

This is a Docker-based environment for developing Ruby on Rails.

Setup

Clone the repo

git clone git@github.com:allknowingfrog/docker-rails.git

To build the initial docker image

Navigate into the repository directory and build the Docker image with this command:

sudo docker build -t rails .

This will name the new image "rails", but you can choose anything you like.

Note that Docker images and containers exist independent of the directories from which they are created, so the remaining commands can be run from anywhere. You can build multiple containers from the same image. You only need to rebuild if you change something in the Dockerfile.

To create a container from the new image

sudo docker run -it --name rails_server -p 3000:3000 -v ~/local/file/path:/container-file-path rails

The -it flags create an interactive session, while -p and -v map ports and volumes, respectively. Mounting a volume causes it to be shared between the local machine and the container (changes in one will be reflected in the other). Note that Git commands and other text editors can be used to interact with files mounted via the -v flag. The --name flag tags the new container and rails is the image to use.

To create a container with a database

You won't get very far in Rails without a database. You can install SQLite via the Dockerfile or in the container to use the Rails defaults. Alternatively, you may want to create and link to a database container. Here's an example for setting up PostgreSQL.

First, create a network to link the containers

sudo docker network create foo

Then, create the database container on the network

sudo docker run -d --name foo_postgres --network=foo --network-alias=db -e POSTGRES_PASSWORD=guest postgres

Finally create the Rails container on the same network

sudo docker run -it --name foo_rails -p 3000:3000 -v ~/local/file/path:/container-file-path --network=foo rails

In this example, you'll want to use the -d flag with rails new to set up your database, i.e. rails new container-file-path -d=postgresql. Then, set up config/database.yml with a host, username and password.

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  host: db
  username: postgres
  password: guest

development:
  <<: *default
  database: boats_development

test:
  <<: *default
  database: boats_test

production:
  <<: *default
  database: boats_production

Other useful commands

To stop a container

Stopped containers maintain their state and can be started again to resume work.

sudo docker stop foo_rails

To start a stopped container

sudo docker start -i foo_rails

To see all containers

sudo docker ps -a

To enter a new bash shell in a running container (from a separate terminal)

sudo docker exec -it foo_rails bash