Goodies to know for Docker & Docker-Compose

This is the colleton of useful knowledge this kitty has gathered for Docker and Docker-Compose over a long time.

Find out what is using disk space

To find what is using up space you can run the command:

docker system df

And it will show you a compact summary of how much space is being used by containers, images, networks, volumes etc.

If you need a more detailed view of what exactly is using up space you can run the command with the ‘-v’ flag:

docker system df -v

And it will show you all the containers, volumes, build caches and images that are taking up space.

How to cleanup (unused) resources

Once in a while, you may need to cleanup resources (containers, volumes, images, networks) …

If you use a Docker version newer than > 1.13 you can use Dockers builtin cleanup tool purge.

The new way (Docker > 1.13)

Network

To purge the networks (Docker Docs)

docker network prune

Containers, Volumes, Images

And to purge the docker system (Docker Docs)

docker system prune

The old way (Docker < 1.13)

Delete Volumes

docker volume rm $(docker volume ls -qf dangling=true)

or

docker volume ls -qf dangling=true | xargs -r docker volume rm

Delete Networks

docker network ls

docker network ls | grep "bridge"

docker network rm $(docker network ls | grep "bridge" | awk '/ / { print $1 }')

or

docker network ls | awk '$3 == "bridge" && $2 != "bridge" { print $1 }'

Build system leftovers

If your system is also used for building images you might have a look at cleaning up garbage created by the builders using:

docker buildx prune --all

and

docker builder prune --all

Health Checks

Docker Compose has a built in health check feature that can be used to check if your containers are up and running.

Docker Compose depends on health check pass

You can also use the health check feature to make sure that a service is up and running before starting services that depending on it.

    depends_on:
      <service name>:
        condition: service_healthy

Docker Compose Postgres health check

    healthcheck:
      test: ["CMD-SHELL", "pg_isready"]
      interval: 10s
      timeout: 5s
      retries: 5

Docker Compose Redis/Valkey health check

    healthcheck:
      test: "redis-cli ping"
      interval: 10s
      timeout: 5s
      retries: 10

Conclusion

First of thanks for reading this.

I hope this has been helpful and if you have any questions, suggestions or something i may have missed, please let me know.