dockerでrails5環境構築 ref: https://qiita.com/pocari/items/456052a291381895f8b3

database.yml

 <%
 database_host = ENV['DATABASE_HOST'] || 'localhost'
 database_port= ENV['DATABASE_PORT'] || 3306
 %>
 default: &default
   adapter: mysql2
   encoding: utf8
   pool: 5
   username: <%= ENV['DATABASE_USER'] %>
   password: <%= ENV['DATABASE_PASS'] %>
   port: <%= database_port %>
   host: <%= database_host %>

 development:
   <<: *default
   database: <%= ENV['DATABASE_NAME'] %>

 # testとproductionは省略

docker-compose.sh

  db:
    container_name: db
    build: ${DB_DOCKERFILE_DIR}
    ports:
      - "3306:3306"
    environment:
      MYSQL_DATABASE: ${MYSQL_DATABASE}
      MYSQL_USER: ${MYSQL_USER}
      MYSQL_PASSWORD: ${MYSQL_PASSWORD}
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}

  web:
    container_name: web
    build: ${WEB_DOCKERFILE_DIR}
    ports:
      - "3000:3000"
    links:
      - db:db
    volumes:
      - ${WEB_APP_ROOT_DIR}:/var/myapp
    environment:
      DATABASE_NAME: ${MYSQL_DATABASE}
      DATABASE_USER: ${MYSQL_USER}
      DATABASE_PASS: ${MYSQL_PASSWORD}
      DATABASE_HOST: db
    command: sh -c "bundle install --path=vendor/bundle && rm tmp/pids/server.pid; bin/rails s -b 0.0.0.0"

Dockerfile

  FROM ruby:2.3

  ############################################################
  # ruby setting bundlerだけはglobalに入れておく
  RUN gem install bundler

  #####################################################
  # misc settings
  RUN usermod -u 1000 www-data
  RUN \cp -fp /usr/share/zoneinfo/Asia/Tokyo /etc/localtime

  VOLUME /var/myapp
  WORKDIR /var/myapp

  EXPOSE 3000

  CMD ["bash"]

file0.sh

   % tree
   .
   ├── app               # railsアプリケーションディレクトリ
   └── docker            # dockerの関連ディレクトリ
       ├── bin            #   docker-compose用のディレクトリ
       ├── db             #   mysql用のdockerディレクトリ
       └── web            #   rails用のdockerディレクトリ

file10.txt

 docker/bin/run-docker-compose.sh up

file11.txt

  app/tmp/*
  app/vendor/*  

file12.txt

  git init
  git add -A
  git commit -m "initial commit"

file13.txt

   # hello コントローラ作成
   bundle exec bin/rails g controller hello

file14.txt

   class HelloController < ApplicationController
     def hello
       @msg = "world"
     end
   end

file15.txt

   Hello, <%= @msg %>

file16.txt

   Rails.application.routes.draw do
    # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html

    # Serve websocket cable requests in-process
    # mount ActionCable.server => '/cable'
    get 'hello' => 'hello#hello'
  end

file17.txt

  class HelloController < ApplicationController
    def hello
      @msg = "docker"
    end
  end

file18.txt

  config.file_watcher = ActiveSupport::FileUpdateChecker  

file19.txt

  class HelloController < ApplicationController
    def hello
      @msg = "docker docker docker"
    end
  end

file20.txt

  sudo VBoxControl guestproperty set "/VirtualBox/GuestAdd/VBoxService/--timesync-set-threshold" 5000

file21.txt

  sudo VBoxControl guestproperty set "/VirtualBox/GuestAdd/VBoxService/--timesync-set-threshold" 5000

file22.txt

  config.web_console.whitelisted_ips = %w( 0.0.0.0/0 ::/0 )

file5.sh

 docker/bin/run-docker-compose.sh build

file6.sh

 docker run --rm -it -v $(pwd)/app:/var/myapp bin_web bash  #docker-composeでイメージを作成するとbin_${yamlの定義名}になります。

 # 以降このコードブロックの終わりまでコンテナ内での作業

 # Gemfile初期化
 bundle init

 # この記事を作成中の最新の5.0.0.beta3を指定します。
 echo "gem 'rails', '5.0.0.beta3'" >> Gemfile

 # プロジェクトローカルにrails5をインストール
 bundle install --path=vendor/bundle

 # railsのアプリケーションを作成します。
 # とりあえず雛形のGemfileを作りたいだけなのであとでこのアプリケーションは全部削除します。
 bundle exec rails new sample_app --skip-bundle
 #できたGemfileを持ってきます。
 mv sample_app/Gemfile .
 #sample_appはもういらないので削除します。
 rm -rf sample_app

 # 次にrailsのアプリケーションを作っていきますがファイルの編集はホストの方がやりやすいので一旦コンテナから出ます。
 exit

file7.rb

 source 'https://rubygems.org'

 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '>= 5.0.0.beta3', '< 5.1'
 # Use sqlite3 as the database for Active Record
 gem 'mysql2'
 # Use Puma as the app server
 gem 'puma'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets
 gem 'uglifier', '>= 1.3.0'
 # Use CoffeeScript for .coffee assets and views
 gem 'coffee-rails', '~> 4.1.0'
 # See https://github.com/rails/execjs#readme for more supported runtimes
 gem 'therubyracer', platforms: :ruby

 # Use jquery as the JavaScript library
 gem 'jquery-rails'
 # Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
 gem 'turbolinks', '~> 5.x'
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
 gem 'jbuilder', '~> 2.0'
 # Use Redis adapter to run Action Cable in production
 # gem 'redis', '~> 3.0'
 # Use ActiveModel has_secure_password
 # gem 'bcrypt', '~> 3.1.7'

 # Use Capistrano for deployment
 # gem 'capistrano-rails', group: :development

 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug'
 end

 group :development do
   # Access an IRB console on exception pages or by using <%= console %> in views
   gem 'web-console', '~> 3.0'
   gem 'listen', '~> 3.0.5'
   # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
   gem 'spring'
   gem 'spring-watcher-listen', '~> 2.0.0'
 end

 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

file8.sh

 docker run --rm -it -v $(pwd)/app:/var/myapp bin_web bash

 # 以降このコードブロックの終わりまでコンテナ内での作業
 # dbmsはmysqlにする。
 bundle install && bundle exec rails new . -d mysql

file_update_checker.rb

    # This method returns the maximum mtime of the files in +paths+, or +nil+
    # if the array is empty.
    #
    # Files with a mtime in the future are ignored. Such abnormal situation
    # can happen for example if the user changes the clock by hand. It is
    # healthy to consider this edge case because with mtimes in the future
    # reloading is not triggered.
    def max_mtime(paths)
      time_now = Time.now
      paths.map {|path| File.mtime(path)}.reject {|mtime| time_now < mtime}.max
    end

run-docker-compose.sh

  #!/bin/sh

  SCRIPT_DIR=$(cd $(dirname $0) && pwd)

  export DB_DOCKERFILE_DIR=${SCRIPT_DIR}/../db
  export WEB_DOCKERFILE_DIR=${SCRIPT_DIR}/../web
  export WEB_APP_ROOT_DIR=${SCRIPT_DIR}/../../app

  export MYSQL_DATABASE=mydb
  export MYSQL_USER=dbuser
  export MYSQL_PASSWORD=dbuser_pass
  export MYSQL_ROOT_PASSWORD=root

  YML_FILE=$SCRIPT_DIR/docker-compose.yml

  docker-compose -f $YML_FILE $*