Volumes

• We leaned how we can attach volumes using docker run command.
• There was one problem, we had to use very long command.
• Using big command is not a problem, if we use it only once or twice.
• But we want to be able to run container multiple times.
• You already know docker-compse tries to simply process of running container.
• Compose supports volumes as well.
• We simply use volumes properties for a service

version: '3'
services:
  myApp:
    image: amantuladhar/docker-kubernetes:v1-web
    ports:
      - 9090:8080
  myDb:
    image: mysql:5.7
    environment:
      - MYSQL_ROOT_PASSWORD=password
      - MYSQL_DATABASE=docker_kubernetes
    volumes:                                       # 1
      - "./volume/mysql-compose/:/var/lib/mysql/"  # 2

• #1 we use volumes properties to map the volumes
• #2 In this case we are mapping host volume to /var/lib/mysql.
• Play around with the service.
• Add a table, insert a data then, dispose all services and start up again.
• Check if all data are still there.

Different ways to map volumes

volumes:
  # Just specify a path and let the Engine create a volume
  - /var/lib/mysql

  # Specify an absolute path mapping
  - /opt/data:/var/lib/mysql

  # Path on the host, relative to the Compose file
  - ./cache:/tmp/cache

  # Named volume
  - datavolume:/var/lib/mysql

Named volumes

• If you want to use named volume in docker-compose, you don't need to create one yourself.
• You have volumes root property where you can define your volumes.

version: '3'
services:
  myApp:
    image: amantuladhar/docker-kubernetes:v1-web
    ports:
      - 9090:8080
  myDb:
    image: mysql:5.7
    environment:
      - MYSQL_ROOT_PASSWORD=password
      - MYSQL_DATABASE=docker_kubernetes
    volumes:
      - "./volume/mysql-compose/:/var/lib/mysql/"
      - "namedVolume:/test/path"                   # 3                        
volumes:                                           # 1
  namedVolume:                                     # 2

• #1 root volumes property, where we can define n number for volumes.
• #2 name of the volume. You can add some properties inside namedVolume too.