How can we delete images from an Azure container registry (ACR) on an automated schedule?

Question

In Azure, there's no easy way to delete obsolete, untagged Docker images from the container registry. This quickly gets to be a problem with the basic 10GB storage space. As shown in the answers to this question, and in Microsoft's documentation, it is possible using az commands in the console. That's fine for one-time use, but we have containers being pushed up there by CI, and need to run it on a schedule.

I looked at Azure automation runbooks, scheduler jobs, and timer-triggered functions. They all offer ways to do things on a schedule, but none of them allows me to simply run something at the Azure console.

Do I have to schedule this on a local machine? That seems crazy.

score 2 · Answer 1 · answered Oct 27 '20 at 20:17

In case you are using Azure DevOps (Pipelines), there is an Azure CLI task, which could be used to cleanup after builds. Not quite the same as a scheduled task, but it worked for me.

The build agent must have the Azure CLI installed, authentication is handled by the task.

E.g. at the end of each build I do this:

az acr repository show-manifests \
  --name my-registry \
  --repository my-image \
  --orderby time_desc \
  --query "[5:].digest" \
  -o tsv \
  | xargs -I% az acr repository delete \
  --name my-registry \
  --image my-image@% \
  --yes

This allows me to delete all images except the latest 5 - something that does not seem to be possible even with the new ACR purge tool.

score 1 · Answer 2 · answered Oct 03 '18 at 15:40

Auto-purge (https://feedback.azure.com/forums/903958-azure-container-registry/suggestions/31243189-acr-auto-purge) is a feature we're working on. We'll have the first capabilities this fall, but it will likely just provide deleting untagged images.

I need to post our design plans to get feedback, but in the meantime; az acr repository delete is the most feasible. From the services you mentioned, if you run the az cli, logging in with --service-principal, you should be able to account for the delete. Let me see if we can publish a sample/blog for how to automate this.

How can we delete images from an Azure container registry (ACR) on an automated schedule?

2 Answers2