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Docker Management


This presentation is geared towards management of development environments. Not all of the recommendations apply for production environments!

Docker volume Management

Automatically created volumes

Docker Engine automatically creates a volume for every VOLUME command in the Dockerfile

docker run -d mariadb
docker volume ls

Mount a host path in the containers

Volumes can also be paths on the host

Paths specified this way must the absolute paths

docker run -d -v "$(pwd)/dockerdata:/var/lib/mysql" --name mariadb mariadb
docker inspect -f '{{ json .Mounts }}' mariadb | jq
    "Source": "/home/lukasgr/Docker_Workshop/dockerdata",
    "Destination": "/var/lib/mysql",
    "Mode": "",
    "RW": true,
    "Propagation": "rprivate"


What is docker-compose

docker-compose provides a layer of abstraction to avoid running multiple docker commands or using crazy long commands with multiple options

To configure it create a docker-compose.yml file in a directory, an example is provided on the next slide

Applications with docker-compose

docker-compose allows to combine multiple Docker containers to an application

version: '2'
    image: mariadb:10.1
      - "./.data/db:/var/lib/mysql"
    restart: always
      MYSQL_ROOT_PASSWORD: wordpress
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress

      - db
    image: wordpress:latest
      - "./.data/wp-content:/var/www/html/wp-content"
      - db
      - "8000:80"
    restart: always
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_PASSWORD: wordpress

Start you application with docker-compose

Copy the example from the previous slide to docker-compose.yml and run

docker-compose up

and open http://localhost:8000/ in your browser

Keep your environment clean

Remove exited containers

This command removes all containers in the exited state

docker ps -q -f status=exited | xargs -r docker rm -v

Remove dangling images

This command removes all Docker images which are not part of a Docker layer anymore

docker images -q -f dangling=true | xargs -r docker rmi

Since version 1.25:

docker system prune

Remove dangling volumes

This command removes all automatically created volumes which are not attached to a container anymore

docker volume ls -q -f dangling=true | xargs -r docker volume rm

Since version 1.25:

docker system prune --volumes

Update local Docker images to the newest version

This command will check for new versions of the each image:tag combination in docker images

docker images | awk '(NR>1) && ($2!~/none/) {print $1":"$2}' | xargs -L 1 docker pull

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