前提

いろいろな参考サイトを閲覧して、Dockerfile docker-compose.yml Gemfileを生成。

実行コマンド

$ docker-compose run web bundle exec rails new . --force --database=mysql --skip-bundle
$ docker-compose build
$ docker-compose up -d

試行錯誤したこと

キャッシュが貯まるという記事を得て実行 docker-compose build --no-cache にてコマンドを実行してみた
このコマンドを実行したら良いという情報を得て実行RUN gem install mysql2 -v '0.5.2' --source 'https://rubygems.org/' -- --with-cppflags=-I/usr/local/opt/openssl/include --with-ldflags=-L/usr/local/opt/openssl/lib
mysql-devel が必要ということで、RUN apt-get 時に mysql-develを実行

　結果エラーになりました。「E: Unable to locate package mysql-devel」

ファイル内容

Dockerfile docker-compose.yml Gemfileはそれぞれ下記に記載しております。

Dockerfile
1FROM ruby:2.6.5
2ENV LANG C.UTF-8
3
4RUN apt-get update -qq && apt-get install -y \
5    build-essential \
6    nodejs \
7    mysql-devel \
8 && rm -rf /var/lib/apt/lists/*
9
10RUN gem install bundler
11
12WORKDIR /tmp
13ADD Gemfile Gemfile
14ADD Gemfile.lock Gemfile.lock
15RUN bundle update
16RUN bundle config --local build.mysql2 "--with-ldflags=-L/usr/local/opt/openssl/lib --with-cppflags=-I/usr/local/opt/openssl/include"
17RUN bundle install --path=vendor/bundle
18RUN gem update
19
20ENV APP_HOME /myapp
21RUN mkdir -p $APP_HOME
22WORKDIR $APP_HOME
23ADD . $APP_HOME

docker
1version: '3'
2
3services:
4  web:
5    build: .
6    ports:
7      - "3000:3000"
8    command: bundle exec rails s -p 3000 -b '0.0.0.0'
9    volumes:
10      - .:/myapp
11      - bundle:/usr/local/bundle
12    depends_on:
13      - db
14  db:
15    image: mysql:5.7
16    environment:
17      MYSQL_ROOT_PASSWORD: password
18    ports:
19      - '3306:3306'
20    volumes:
21      - mysql_data:/var/lib/mysql
22volumes:
23  bundle:
24  mysql_data:

Gemfile
1source 'https://rubygems.org'
2git_source(:github) { |repo| "https://github.com/#{repo}.git" }
3
4ruby '2.6.5'
5
6# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
7gem 'rails', '~> 6.0.0'
8# Use mysql as the database for Active Record
9gem 'mysql2', '>= 0.4.4'
10# Use Puma as the app server
11gem 'puma', '~> 3.11'
12# Use SCSS for stylesheets
13gem 'sass-rails', '~> 5'
14# Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
15gem 'webpacker', '~> 4.0'
16# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
17gem 'turbolinks', '~> 5'
18# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
19gem 'jbuilder', '~> 2.7'
20# Use Redis adapter to run Action Cable in production
21# gem 'redis', '~> 4.0'
22# Use Active Model has_secure_password
23# gem 'bcrypt', '~> 3.1.7'
24
25# Use Active Storage variant
26# gem 'image_processing', '~> 1.2'
27
28# Reduces boot times through caching; required in config/boot.rb
29gem 'bootsnap', '>= 1.4.2', require: false
30
31group :development, :test do
32  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
33  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
34end
35
36group :development do
37  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
38  gem 'web-console', '>= 3.3.0'
39  gem 'listen', '>= 3.0.5', '< 3.2'
40  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
41  gem 'spring'
42  gem 'spring-watcher-listen', '~> 2.0.0'
43end
44
45group :test do
46  # Adds support for Capybara system testing and selenium driver
47  gem 'capybara', '>= 2.15'
48  gem 'selenium-webdriver'
49  # Easy installation and use of web drivers to run system tests with browsers
50  gem 'webdrivers'
51end
52
53# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
54gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]