02 Feb 2022

Docker for rails developers:

1. We ran our first ever Docker command, a helloworld Ruby script, without needing Ruby installed on our machine.

   $ docker run ruby:2.6 ruby -e "puts :hello"
   

2. We saw how to list our running containers with docker ps and all containers (including stopped ones) with docker ps -a.
3. We deleted our old containers with docker rm and saw how to create throwaway containers using the docker run’s --rm option.
4. We generated a new Rails project using a container by:
   • Starting an interactive Bash shell running inside a container

      $ docker run -i -t --rm -v ${PWD}:/usr/src/app ruby:2.6 bash
     

   • Installing the Rails gem inside the container

      root@0c286e8bda42:/usr/src/app# gem install rails
     

   • Using the freshly installed Rails gem to generate our project

      root@0c286e8bda42:/usr/src/app# rails new myapp --skip-test --skip-bundle
     

5. We saw our first, rough-and-ready Dockerfile designed to allow us to run our app with a Rails server:

   > FROM ruby:2.6
   > RUN apt-get update -yqq
   > RUN apt-get install -yqq --no-install-recommends nodejs
   > COPY . /usr/src/app/
   > WORKDIR /usr/src/app
   > RUN bundle install
   

6. We built our custom image from this Dockerfile with:

   docker build .
   

7. We listed the images on our system by issuing:

   docker images
   

8. We started up a Rails server to run our app with:

   docker run -p 3000:3000 a1df0eddba18 bin/rails s -b 0.0.0.0
   

9. And we saw it running in a browser on http://localhost:3000.

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