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Troubleshooting the "ImagePullBackOff" Error

The "ImagePullBackOff" error is one of the most common issues you might run into with your Kubernetes deployment. In this post, we'll walk through the steps you should take to manually troubleshoot your problem.

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Have you deployed a new Service to your Kubernetes cluster lately and run into an issue? In this post, we’ll be diving into one of the most common reasons:

The ImagePullBackOff Error

After you deploy to add a new pod to your cluster, you will want to validate that everything worked. To do that, you can run this standard command:

kubectl get pods

If you see the Status say Running, then you’re all set. If you see ImagePullBackOff, then it’s time to troubleshoot.

What does “ImagePullBackOff” mean?

The ImagePullBackOff error is saying that a container was unable to start because Kubernetes couldn’t pull the container image. BackOff indicates that Kubernetes will keep attempting to pull the image at an increasingly delayed interval if it remains unsuccessful.

Without a runnable image, the container doesn’t have the runtime environment and executable software it needs. For more detail, you can read about kubelets, agents on each Node that facilitate the container manifest, ensuring that the containers described actually have everything they need to run successfully.

What causes an “ImagePullBackoff” error?

These are the main causes for receiving an ImagePullBackOff error:

  • Image Name is missing or misspelled
  • Image Tag is missing or misspelled
  • You need additional authentication
  • You have hit a rate or download limit on the registry

Manual Troubleshooting Steps:

  1. To start, run this command:
kubectl describe pod [name] command

By running this, you will receive details about your pods, including an Event log.

  1. Review the Message for the Failed event

Start with lines that have the Reason marked as “Failed” and review why they failed by looking at the accompanying Message.

If you see:

Error response from daemon: repository does not exist or may require ‘docker login’
  1. You should double-check that you spelled both the repository name and image name correctly.
  2. If they are both spelled correctly, then you have an issue with authentication.
  3. You will then need to create a Secret using the command line and apply it to your pod by referencing the Secret in the manifest YAML.

If you see:

Error response from daemon: manifest for [image name]: [tag] not found
  1. This means you may have a typo in the tag you are using, or the tag doesn’t exist in the repository.
  2. Fix the typo or specify a valid tag to resolve this error.

If you still are receiving an ImagePullBackOff error after addressing these common issues, then you may have hit a registry rate limit. For example, Docker Hub has a limit of 100 container pulls every 6 hours from one IP address. You can either wait for the cap to reset, or there are some other workarounds, like authenticating your account or setting up a private Docker registry.

Troubleshooting Made Simple with Blink:

You might have solved your problem quickly or ended up down a research rabbit hole. When you create a free Blink account, you can manage your Kubernetes troubleshooting in one place with all the commands at your fingertips to get the information you need.

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