Docker Janitor

Why do I need a janitor?

Ever notice how docker leaves behind Gigabytes and Gigabytes worth of junk on your hard drive? Me too, and I need that space back! Enter Docker Janitor

Docker is an aggressive cacher. This saves you a lot of time on rebuilds, which is important because it saves you a lot of time. However, it can often leave your disk full of old cache objects that you don't really need anymore.

My drive is full! How do I fix it?

Well good sir or madam, you're in the right place. All you need is this gem.

gem install docker_janitor

Then run it!

Usage

Commands:
  docker-janitor clean           # Clean up leftover docker cruft (does containers, images, volumes)
  docker-janitor containers      # Delete exited containers
  docker-janitor help [COMMAND]  # Describe available commands or one specific command
  docker-janitor images          # Delete unlabeled imaged
  docker-janitor volumes         # Delete orphaned volumes

Options:
  dry-run, d, [--dryrun], [--no-dryrun]

What does all that mean?

Well there are 3 places docker-janitor looks for junk. Containers that have exited, images that are unlabeled, and volumes that are orphaned. To clean everything:

docker-janitor clean

If you don't make regular and disciplined use of the --rm flag with docker and docker-compose, you can end up with a lot of containers lying around that ran and exited. Chances are you will never need these again (tho sometimes you do, so pay attention to the caveat). By keeping them around, you waste disk space. Furthermore, you lock the image that they're based on so it can't be cleaned up. The caveat is that if you have data-only containers or containers that store data, you will lose that data if you delete/clean them. To fix this, you should mount a volume into the container that includes the data. This way data persists after a container is deleted/recreated. If you want to protect against unintentional deletion of a container, add a regex to ~/docker-janitor.yml (this file can be generating with docker-janitor config-file.

To clean only stopped containers:

docker-janitor containers

or

docker-janitor clean --containers

Unlabeled images can also take up a lot of space. These are often leftover from previous builds (which docker caches aggressively). If you've changed the Dockerfile or source in any way, these images will never be used again. This happens a lot when you're writing Dockerfiles.

To clean only unlabeled images:

docker-janitor images

or

docker-janitor clean --images

Orphaned volumes are the result of containers that have been deleted. To avoid data loss, docker will not remove the volume. However, if you've deleted the container, you've probably left a volume behind.

To clean only orphaned volumes:

docker-janitor volumes

or

docker-janitor clean --volumes