Official tool: For cleanup, the crictl tool from cri-tools have now a rmi --prune feature. Thanks to Franco Martin (https://discuss.kubernetes.io/t/microk8s-images-prune-utility-for-production-servers/15874/2) for the info
New: selected output results in JSON format for easy pipe reuse
As you can expect, this small utility is doing for a microk8s / containerd environment the same operation that docker system prune does : it search for images unused by container to list them and/or delete them to recover space
You will need a python3 running environnment and the containerd library.
Note: Protobuf project, used by containerd through grpc layer, introduced a breaking change between 3.x and 4.x version, mainly for performance gains. The containerd python library is not yet available in a compatible version with protobuf 4.x. Thus it is recommended to stay with 3.x (ideally the last release before 4.x, at time of writing, 3.20.3). Unless your are explicitely using protobuf 4.x in your applications that would create installation conflict, this will not have undesirable effects on the utility behavior. Would you need elsewhere protobuf v4.x, it is always possible to run the utility in a small dedicated container (mounting the sock, see below, as a volume).
if you chmod +x the utility, just run it with :
./microk8s_prune.py [ciuspfj]
Parameters:
- c : List containers and associated images (line output prefixed with C:)
- i : List all found images names (prefixed with I:)
- u : List unused images names (prefixed with U:)
- s : Print summary information (# containers, total images, unused images)
- p : DELETE unused images (will require confirmation if run interactively)
- f : Force delete without confirmation
- j : All requested output in json format for pipe reuse
Without any parameter, it will do the job of identifying unused images but do not display anything nor delete anything. Without p and/or f parameter, the utility is strictly read-only.
The ctr utility to manage containerd do not provide such feature and considering that microk8s is especially usefull for small appliances where resources are limited I think it would be nice to have it.
In the meantime, this utility will solve the problem 😊
This utility could be used in non microk8s containerd environment, just replace the namespace which is harcoded to k8s.io and reference the appropriate sock in place of the microk8s one unix:///var/snap/microk8s/common/run/containerd.sock