bin/bash script to build a clean install of docker/rails (run from inside a new directory ... mkdir rails_project && cd rails_project && bash <(curl -s https://gist.githubusercontent.com/curtisspendlove/5b4d2d931a1023f0fa3c653c0038967e/raw/357db84f9bb7cc566425e772802ae56ad11e2aab/clean_docker_rails.sh))

clean_docker_rails.sh

#!/usr/bin/env bash

#touch Gemfile
touch Gemfile.lock
#touch Dockerfile
#touch docker-compose.yml

cat > Dockerfile << EOF
FROM ruby:2.4.1
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
RUN mkdir /myapp
WORKDIR /myapp
ADD Gemfile /myapp/Gemfile
ADD Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
ADD . /myapp
EOF

cat > Gemfile << EOF
source 'https://rubygems.org'
gem 'rails', '~> 5.1'
EOF

cat > docker-compose.yml << EOF
version: '2'
services:
  db:
    image: postgres
  web:
    build: .
    command: bundle exec rails s -p 3000 -b '0.0.0.0'
    volumes:
      - .:/myapp
    ports:
      - "3000:3000"
    depends_on:
      - db
EOF

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

docker-compose build

cat > config/database.yml << EOF
development: &default
  adapter: postgresql
  encoding: unicode
  database: myapp_development
  pool: 5
  username: postgres
  password:
  host: db

test:
  <<: *default
  database: myapp_test
EOF

docker-compose build

docker-compose run web rake db:create

docker-compose up