Install Docker

import gpg key

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

add repository

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

install

sudo apt-get update
sudo apt-get install -y docker-ce

update user permissions

sudo groupadd docker
sudo gpasswd -a ${USER} docker
sudo service docker restart

Install docker compose

sudo -i
curl -L https://github.com/docker/compose/releases/download/1.13.0/docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose
exit

using pip

sudo apt-get install -y python-pip
sudo pip install -U pip
sudo pip install -U docker-compose

Hello, World!

docker images
docker pull hello-world
docker run -it --rm hello-world

MySQL

docker pull mysql:latest
docker run --rm -d --name mysql-doc -e MYSQL_ROOT_PASSWORD=root -p 3300:3306 mysql
docker logs mysql-doc -f
mysql -P 3300 -h 0.0.0.0 -u root -p
docker ps
docker stop mysql-doc

Ruby

docker pull ruby:latest
docker run --rm --name ruby-doc ruby ruby -v

Running a rails app in docker

cd SampleApp
mkdir docker
cd docker

mkdir mysql
cd mysql
touch Dockerfile

copy the following in Dockerfile ......................................................................................

FROM mysql:latest

......................................................................................

cd ..

mkdir rails
cd rails
touch Dockerfile

copy the following in Dockerfile ......................................................................................

FROM ruby:latest
RUN apt-get update &&\
    apt-get -y install mysql-client postgresql-client sqlite3 nodejs --no-install-recommends &&\
    rm -rf /var/lib/apt/lists/*
RUN gem install bundler
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app
COPY ./Gemfile /usr/src/app/
COPY ./Gemfile.lock /usr/src/app/
RUN bundle install
COPY . /usr/src/app
COPY ./docker/rails/entry-point.sh /usr/src/app/entry-point.sh
COPY ./docker/rails/database.yml /usr/src/app/config/database.yml
EXPOSE 5000
CMD ["bash", "/usr/src/app/entry-point.sh"]

......................................................................................

touch entry-point.sh

copy the following in entry-point.sh ......................................................................................

#!/usr/bin/env bash
echo "Waiting for database server to start properly ..." && sleep 30
RAILS_ENV=development bundle exec rake db:create
RAILS_ENV=development bundle exec rake db:migrate
RAILS_ENV=development bundle exec rake db:seed
RAILS_ENV=development bundle exec rails server -b 0.0.0.0 -p 5000

......................................................................................

touch database.yml

copy the following in database.yml ......................................................................................

---
development:
  adapter: mysql2
  encoding: utf8
  pool: 5
  timeout: 5000
  username: root
  password: root
  database: sample_app_development
  host: databasehost
test:
  adapter: mysql2
  encoding: utf8
  pool: 5
  timeout: 5000
  username: root
  password: root
  database: sample_app_test
  host: databasehost
staging:
  adapter: mysql2
  encoding: utf8
  pool: 5
  timeout: 5000
  username: root
  password: root
  database: sample_app_staging
  host: databasehost
production:
  adapter: mysql2
  encoding: utf8
  pool: 5
  timeout: 5000
  username: root
  password: root
  database: sample_app_production
  host: databasehost

......................................................................................

cd ../..

docker build -f docker/mysql/Dockerfile -t mysql_rails .
docker build -f docker/rails/Dockerfile -t rails_app .

docker run --rm -d --name mysql_rails_1 -e MYSQL_ROOT_PASSWORD=root -p 3300:3306 mysql_rails
docker run --rm -d --name rails_app_1 --link mysql_rails_1:databasehost -p 5000:5000 rails_app

Using docker-compose

cd SampleApp
touch docker-compose.yml

copy the following in docker-compose.yml file ......................................................................................

version: '3'
services:
  rails:
    build:
      context: .
      dockerfile: ./docker/rails/Dockerfile/
    expose:
      - '5000'
    ports:
      - '5000:5000'
    links:
      - 'mysql:databasehost'
    depends_on:
      - mysql
  mysql:
    build:
      context: .
      dockerfile: ./docker/mysql/Dockerfile
    volumes:
      - './docker/mysql/data_dir:/var/lib/mysql:rw'
    ports:
      - '3300:3306'
    environment:
      - MYSQL_ROOT_PASSWORD=root

......................................................................................

docker-compose build --no-cache --force-rm --pull
docker-compose up -d
docker-compose logs -f
docker-compose stop
docker-compose down