How to clean-up old unused Kubernetes images/tags?

2 min read 07-10-2024

How to clean-up old unused Kubernetes images/tags?

Cleaning Up Old and Unused Kubernetes Images: A Guide to Optimizing Your Cluster

Kubernetes, with its containerized approach, offers incredible scalability and flexibility. However, this comes with a responsibility: managing the growing number of images within your cluster. Over time, unused images can bloat your storage, hinder performance, and even pose security risks.

The Problem:

You've deployed numerous applications over time, using different image versions. Some applications have been updated or even removed, leaving behind outdated images that consume precious storage space and potentially harbor vulnerabilities.

The Solution:

This article provides a comprehensive guide on identifying and cleaning up old, unused Kubernetes images, ensuring your cluster stays lean and efficient.

Identifying Unused Images

List all images:
```
kubectl get pods -A -o jsonpath='{.items[*].spec.containers[*].image}' | sort | uniq
```
This command retrieves the image names from all pods across your cluster, sorts them, and removes duplicates.
Compare with deployed images:
```
kubectl get deployments -A -o jsonpath='{.items[*].spec.template.spec.containers[*].image}' | sort | uniq
```
This command retrieves image names from all deployed deployments, ensuring you see only the actively used images.
Identify the unused images:

Compare the output of the previous two commands. Any image present in the first output but absent in the second is likely unused.

Cleaning Up Unused Images

Manual deletion:
```
docker rmi <image_name>
```
This command directly removes a specific image from your Docker registry. However, this method requires manual identification and can be tedious for a large number of images.
Automated solutions:
- Image cleanup tools: Several tools like image-cleaner or kubeslice are designed to identify and delete unused images based on various criteria like age, size, or usage patterns.
- Container image registries: Many registries like Docker Hub offer automatic cleanup features based on image tags or inactivity periods.

Additional Tips

Image tagging: Employ a consistent image tagging strategy (e.g., date-based, version-based) to simplify identification and management.
Regular cleaning: Schedule regular image cleanup tasks using cron jobs or Kubernetes cronjobs to maintain a clean and efficient cluster.
Image scanning: Regularly scan your images for vulnerabilities using tools like clair or grype to ensure security.

Conclusion

Efficiently managing your Kubernetes image repository is crucial for maximizing cluster performance, minimizing storage consumption, and ensuring security. By following the steps outlined above, you can proactively identify and clean up unused images, thereby optimizing your cluster's health and efficiency.

References

Note: Always back up your data and test the cleanup process in a non-production environment before implementing it in your production cluster.