Docker introduced new namespaces and commands which everyone should finally learn and not stick to the old habbits.
Deleting no longer needed containers (stopped)
$ docker container prune
Deleting no longer needed images
which means, that it only deletes images, which are not tagged and are not pointed on by "latest" - so no real images you can regularly use are deleted
$ docker image prune
Delete all volumes, which are not used by any existing container
( even stopped containers do claim volumes ). This usually cleans up dangling anon-volumes of containers have been deleted long time ago. It should never delete named volumes since the containers of those should exists / be running.
Be careful, ensure your stack at least is running before going with this one
docker volume prune
Same for unused networks
docker network prune
And finally, if you want to get rid if all the trash - to ensure nothing happens to your production, be sure all stacks are running and then run
docker system prune
