Troubleshooting Application Issues

ImagePullBackOff

If you encounter an ImagePullBackOff error with one or more pods, the image may no longer be available upstream (i.e. no longer on DockerHub) or within the specified private repository.

It may be possible to still leverage this image if it is present one or more nodes, indicated by running pods for the same StatefulSet or Deployment. For example:

$ kubectl get pods -n <namespace> -o wide -l app=minio NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES minio-0 0/1 ImagePullBackOff 0 141m 10.3.70.76 10.2.99.39 <none> <none> minio-1 1/1 Running 0 146m 10.3.4.4 10.2.99.42 <none> <none> minio-2 1/1 Running 0 152m 10.3.92.8 10.2.99.43 <none> <none> minio-3 1/1 Running 0 148m 10.3.17.4 10.2.99.44 <none> <none>

Save/Load Docker Image from Cache

  1. Identify the image – either by name, or image ID, which can be found in the kubectl describe pod or kubectl get pod output – for any Running pod.

$ kubectl get pod minio-1 -n <namespace> -o json | jq '.spec.containers[].image' "minio/minio:RELEASE.2021-05-27T22-06-31Z"

  1. SSH to the Node on which the targeted Running pod resides, and list the Docker images.

$ sudo docker images REPOSITORY TAG IMAGE ID CREATED SIZE minio/minio RELEASE.2021-05-27T22-06-31Z 375bd7b2cc2c 4 weeks ago 264MB

  1. Save the Docker image – specifying the Image ID , Repository , and Tag .

$ sudo docker save <image-id> -o <filename.tar <repository>:<tag>
Attention

Note: If the <repository>:<tag> is not specified, the Docker image will be imported without any identifying information and Kubernetes will continue to fail to spawn the pod as a result.

  1. Transfer the file (i.e. using rsync or scp ) to the destination Node where the pod is in ImagePullBackOff state.

  2. Load the Docker image on that Node .

$ sudo docker load -i <filename>.tar

Example

$ sudo docker load -i <filename>.tar Loaded image ID: sha256:375bd7b2cc2ce76d6216ae68f68b54913a8f2df4a3d2c34919bd33d23a02f409

CrashLoopBackOff

NodeAffinity

$ kubectl get pods -A | grep -i sentry platform9-system pf9-sentry-688cfcf9-h52v6 1/1 Running 1 3h22m *platform9-system pf9-sentry-688cfcf9-s4fjm 0/1 NodeAffinity 0 3h33m*
---- ------ ---- ---- ------- Warning FailedScheduling 11m default-scheduler 0/1 nodes are available: 1 node(s) had taint {node.kubernetes.io/not-ready: }, that the pod didn't tolerate. Warning FailedScheduling 11m default-scheduler 0/1 nodes are available: 1 node(s) had taint {node.kubernetes.io/not-ready: }, that the pod didn't tolerate. Normal Scheduled 11m default-scheduler Successfully assigned platform9-system/pf9-sentry-688cfcf9-s4fjm to 10.128.230.29 Normal Pulled 11m kubelet Container image "platform9/pf9-sentry:1.0.0" already present on machine Normal Created 11m kubelet Created container pf9-sentry Normal Started 11m kubelet Started container pf9-sentry Warning Unhealthy 6m29s kubelet Liveness probe failed: Get http://10.20.244.65:8080/v1/healthz: net/http: request canceled (Client.Timeout exceeded while awaiting headers) Warning NodeAffinity 87s kubelet Predicate NodeAffinity failed

You may delete the pod stuck in node affinity status as another pod is spawned for the same application.

  Last updated by Anagha Pamidi on Jan 26, 2026
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Troubleshooting Network Issues

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Troubleshooting Application IssuesImagePullBackOffCrashLoopBackOffNodeAffinitySave/Load Docker Image from CacheExample