Kubernetes ImagePullBackOff: Troubleshooting with Examples

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Currently we are seeing how to troubleshoot the Kubernetes issue and related topics. Part of that, today let see another important error, you may have experienced sometime this error when you worked on the Kubernetes. This error could frustrate if you are unfamiliar with it, as this doesn’t have single reason to fail, there is varies possible reason beyond this error. Like that we have picked on the error which is nothing but “Kubernetes ImagePullBackOff error”, in this post, we are going to see what could be a reason for this error and how to troubleshoot it.

What Does an ImagePullBackOff Error Mean?

The ImagePull part of the ImagePullBackOff error primarily relates to your Kubernetes container runtime unable to pull the image from a private or public container registry. The Backoff part indicates that Kubernetes will continuously pull the image with an increasing backoff delay. Kubernetes will keep on increasing the delay with each attempt until it reaches the limit of five minutes.

Here are some of the possible causes behind your pod getting stuck in the ImagePullBackOff state:

  • Image is not defined properly
  • Tag may changed/missing/incorrect
  • Image name/path not correct
  • Image missing/incorrect
  • Image may private, and there is a auth failure
  • Check pull secret defined or not
  • Secret name Is correct?
  • Secrets are correct?
  • Network issue
  • Container registry Rate Limits

How we can Troubleshoot ImagePullBackOff?

Live Demo:

Let’s check one by one reason listed above, and how to fid the issue.

Image is not defined properly

In most cases, the error could be either from a typo or the reference is not correct, and you’re referring to an image with different path. Let’s try to replicate this by creating a pod with a fake image name.

                # kubectl run demoapp --image=foxutech/foxutechimage:latest
deployment.apps/demoapp created
            

As you can see, the pod is stuck in an ImagePullBackOff because the image doesn’t exist and we cannot pull the image.

                # kubectl get pod
NAME                       READY   STATUS             RESTARTS   AGE
demoapp-6fbd57ff7c-78ms8   0/1     ImagePullBackOff   0          28s
            

For better understand the issue and find more details about this error, use the kubectl describe command, if there is details, you can use kubectl get events command. With this error we could see what is the main reason the pod is stuck. In the describe, you can check on events section which will contains detailed explanations.

Issue with Tag

There could be cases where the image tag you’re trying to pull is retired, or you entered the wrong tag name. In those cases, your pod will again get stuck in the ImagePullBackOff state, as seen in the following code snippet.

Let’s try to declare some wrong tag and see, how it looks like. continue reading on Kubernetes ImagePullBackOff: Troubleshooting with Examples (foxutech.com)


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