Gemfile.lock 의 내용은 하늘에서 OK입니다.

③ Dockerfile

FROM ruby:3.0.1

RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - && \
    echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
# yarnをインストールするための準備

RUN apt-get update -qq && \
    apt-get install -y build-essential \
                       libpq-dev \
                       nodejs \
                       default-mysql-client \
                       yarn \ # yarnをインストール
                       vim

RUN mkdir /myapp

WORKDIR /myapp

COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock

RUN bundle install

COPY . /myapp

④ docker-compose.yml

version: '3'

services:
  db:
    image: mysql:5.7
    environment:
      MYSQL_USER: user
      MYSQL_ROOT_PASSWORD: pass
    ports:
      - "3306:3306"
    volumes:
      - mysql_data:/var/lib/mysql

  web:
    build: .
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/myapp
    ports:
      - 3000:3000
    depends_on:
      - db

volumes:
  mysql_data:

rails new 실행

$ docker-compose run web rails new . --force --database=mysql

docker-compose build 실행

$ docker-compose build

database.yml 편집

# MySQL. Versions 5.1.10 and up are supported.
#
# Install the MySQL driver
#   gem install mysql2
#
# Ensure the MySQL gem is defined in your Gemfile
#   gem 'mysql2'
#
# And be sure to use new-style password hashing:
#   https://dev.mysql.com/doc/refman/5.7/en/password-hashing.html
#
default: &default
  adapter: mysql2
  encoding: utf8
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
# 以下２行を編集
  password: pass
  host: db

development:
  <<: *default
  database: myapp_development

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: myapp_test

# As with config/secrets.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read http://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
#   DATABASE_URL="mysql2://myuser:mypass@localhost/somedatabase"
#
# You can use this database configuration with:
#
#   production:
#     url: <%= ENV['DATABASE_URL'] %>
#
production:
  <<: *default
  database: myapp_production
  username: myapp
  password: <%= ENV['MYAPP_DATABASE_PASSWORD'] %>

docker-compose up -d로 컨테이너 시작

$ docker-compose up -d

데이터베이스 만들기

$ docker-compose exec web rails db:create

localhost:3000 방문

참고