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To simplify deployment and short term roll-back, it's useful to use a new Docker image tag for each new version to deploy on Kubernetes. Without clean-up this means that old images:tags are kept forever.
How can I list all image:tag that are used by a Kubernetes container so that I can find all old image:tag that are old and not used to delete them automatically from the Docker Registry?
My goal is ideally for Google Container Engine (GKE) to delete unused images a Google Container Registry.
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If we do not want to find dangling images and remove them one by one, we can use the docker image prune command. This command removes all dangling images. If we also want to remove unused images, we can use the -a flag. The command will return the list of image IDs that were removed and the space that was freed.
Kubernetes has a built-in garabage collection system that can clean up unused images. It's managed by Kubelet, the Kubernetes worker process that runs on each node. RELATEDHow Does Kubernetes Work? Kubelet automatically monitors unused images and will remove them periodically.
If you create pods directly (not via a deployment), you can delete them directly, and they will stay deleted. Pods (that were created directly), deployments, and services can all be deleted independently of one another, order doesn't matter. If you want to delete them but not the namespace, delete them in any order.
To remove one or more Docker containers, use the docker container rm command, followed by the IDs of the containers you want to remove. If you get an error message similar to the one shown below, it means that the container is running. You'll need to stop the container before removing it.
As an alternative approach, you might consider just letting Kubernetes handle reclamation of old images for you.
Presently, the ImageManager handles reclamation of candidate images. See: Garbage Collection
Garbage collection is a helpful function of kubelet that will clean up unreferenced images and unused containers. kubelet will perform garbage collection for containers every minute and garbage collection for images every five minutes.
Configuration is controlled via these two kublet cli parameters:
--image-gc-high-threshold=90: The percent of disk usage after which image garbage collection is always run. Default: 90%
--image-gc-low-threshold=80: The percent of disk usage before which image garbage collection is never run. Lowest disk usage to garbage collect to. Default: 80%
The high/low thresholds could be tuned to force collection at an interval that works for you.
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