Starter to use with https://docs.docker.com/compose/rails/

docker-compose.yml

version: '3'
services:

  postgres:
    image: postgres:10.3
    volumes:
      - ./tmp/db:/var/lib/postgresql/data

  memcached:
    image: memcached

  web:
    stdin_open: true
    tty: true
    build: .
    command: bundle exec rails s -p 3000 -b '0.0.0.0'
    volumes:
      - .:/myapp
    ports:
      - "80:3000"
    depends_on:
      - postgres
      - memcached

Dockerfile

FROM ruby:2.5
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
RUN mkdir /myapp
WORKDIR /myapp
COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
COPY . /myapp

Gemfile

source 'https://rubygems.org'
gem 'rails', '5.2.0'

Gemfile.lock

# Intentionally empty