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LAB03-DockerCompose.md

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LAB-03: Docker Compose and Creating WordPress Container Depends on MySql Container

This scenario shows how to run multiple Docker containers using the docker-compose.yml file. After running containers, it is shown how:

  • to step (enter) into the container,
  • to install binary packages into the container,
  • to see ethernet interfaces
  • to send ping packets to see the connection of the containers.

Steps

  • Create an "example" directory on your Desktop.
  • Create "docker-compose.yml" in the "example" directory.
  • Copy below and paste into "docker-compose.yml" (2 containers are created namely: 'mydatabase', 'mywordpress'. 'mydata' is volume object that binds to the container, environment variables are basically defined, new bridge network is created) (Normally, credentials are not defined this way, just example. Docker secret is used to define credentials, safety way).
version: "3.8"

services:
  mydatabase:
    image: mysql:5.7
    restart: always
    volumes: 
      - mydata:/var/lib/mysql
    environment: 
      MYSQL_ROOT_PASSWORD: somewordpress
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress
    networks:
      - mynet
  mywordpress:
    image: wordpress:latest
    depends_on: 
      - mydatabase
    restart: always
    ports:
      - "80:80"
      - "443:443"
    environment: 
      WORDPRESS_DB_HOST: mydatabase:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress
      WORDPRESS_DB_NAME: wordpress
    networks:
      - mynet
      
volumes:
  mydata: {}
  
networks:
  mynet:
    driver: bridge
  • Open a terminal where "docker-compose.yml" is. Run the following command:
docker-compose up -d

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  • Run on the terminal to see a list of containers:
docker container ls -a

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  • Open the browser (127.0.0.1) to see the result:

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  • If you want, you can enter one of the containers and ping to another container to see the connection between both containers. They are connected to each other via the bridge "mynet".
  • Run on the terminal to see a list of containers:
docker container ls -a
  • You can see the names of the containers. You should create “docker-compose.yml” under the “example” directory. Docker-compose creates containers and adds names according to the path (without using docker-compose, if the user does not enter the name for the container, the docker assigns a random name to the container). For example, your container names are "example_mywordpress_1", "example_mydatabase_1". The container name is important when you want to enter the container (like below).
  • Run on the terminal to enter into the container:
docker exec -it example_mywordpress_1 sh
  • Now you are in the container if you see "#". When you run "ifconfig" and "ping", these binaries are not found in the container. But we can update and install these binaries into this container.
  • Run on the terminal to update OS in the container:
apt-get update
  • Run on the terminal to install net-tools ('ifconfig') in the container:
apt-get install net-tools
  • Run on the terminal to install iputils-ping ('ping') in the container:
apt-get install iputils-ping

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  • Run on the terminal to see the IP of the current container. It could be "172.19.0.3":
ifconfig
  • Run on the terminal to send ping packets to another container (“example_mydatabase_1”):
ping 172.19.0.2

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  • Press CTRL+C to stop ping.
  • Press CTRL+P+Q to go out of the container to the host terminal.
  • Run on the terminal to stop and remove containers:
docker-compose down

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