What is the meaning of ImagePullBackOff status on a Kubernetes pod

Question

I m trying to run my first kubernetes pod locally  I ve run the following command  from here    export ARCH amd64 docker run -d       --volume    rootfs ro       --volume  sys  sys ro       --volume  var lib docker   var lib docker rw       --volume  var lib kubelet   var lib kubelet rw       --volume  var run  var run rw       --net host       --pid host       --privileged       gcr io google containers hyperkube-  ARCH    K8S VERSION         hyperkube kubelet           --containerized           --hostname-override 127 0 0 1           --api-servers http   localhost 8080           --config  etc kubernetes manifests           --cluster-dns 10 0 0 10           --cluster-domain cluster local           --allow-privileged --v 2   Then  I ve trying to run the following   kubectl create -f   run-aii yaml   run-aii yaml   apiVersion  extensions v1beta1 kind  Deployment metadata    name  aii spec    replicas  2   template      metadata        labels          run  aii     spec        containers        - name  aii         image  aii         ports          - containerPort  5144         env          - name  KAFKA IP           value  kafka         volumeMounts          - mountPath   root script           name  scripts-data           readOnly  true         - mountPath   home aii core           name  core-aii           readOnly  true         - mountPath   home aii genome           name  genome-aii           readOnly  true         - mountPath   home aii main           name  main-aii           readOnly  true       - name  kafka         image  kafkazoo         volumeMounts          - mountPath   root script           name  scripts-data           readOnly  true         - mountPath   root config           name  config-data           readOnly  true       - name  ws         image  ws         ports          - containerPort  3000       volumes        - name  scripts-data         hostPath            path   home aii general infra script       - name  config-data         hostPath            path   home aii general infra config       - name  core-aii         hostPath             path   home aii general core       - name  genome-aii         hostPath             path   home aii general genome       - name  main-aii         hostPath             path   home aii general main   Now  when I run  kubectl get pods I m getting   NAME                    READY     STATUS             RESTARTS   AGE aii-806125049-18ocr     0 3       ImagePullBackOff   0          52m aii-806125049-6oi8o     0 3       ImagePullBackOff   0          52m aii-pod                 0 3       ImagePullBackOff   0          23h k8s-etcd-127 0 0 1      1 1       Running            0          2d k8s-master-127 0 0 1    4 4       Running            0          2d k8s-proxy-127 0 0 1     1 1       Running            0          2d nginx-198147104-9kajo   1 1       Running            0          2d   BTW  docker images return   REPOSITORY                                 TAG                 IMAGE ID            CREATED             SIZE ws                                         latest              fa7c5f6ef83a        7 days ago          706 8 MB kafkazoo                                   latest              84c687b0bd74        9 days ago          697 7 MB aii                                        latest              bd12c4acbbaf        9 days ago          1 421 GB node                                       4 4                 1a93433cee73        11 days ago         647 MB gcr io google containers hyperkube-amd64   v1 2 4              3c4f38def75b        11 days ago         316 7 MB nginx                                      latest              3edcc5de5a79        2 weeks ago         182 7 MB docker kafka                               latest              e1d954a6a827        5 weeks ago         697 7 MB spotify kafka                              latest              30d3cef1fe8e        12 weeks ago        421 6 MB wurstmeister zookeeper                     latest              dc00f1198a44        3 months ago        468 7 MB centos                                     latest              61b442687d68        4 months ago        196 6 MB centos                                     centos7 2 1511      38ea04e19303        5 months ago        194 6 MB gcr io google containers etcd              2 2 1               a6cd91debed1        6 months ago        28 19 MB gcr io google containers pause             2 0                 2b58359142b0        7 months ago        350 2 kB sequenceiq hadoop-docker                   latest              5c3cc170c6bc        10 months ago       1 766 GB   why do I get the ImagePullBackOff

User · Answer

Despite all the other great answers none helped me until I found a comment that pointed out this Updating images:

The default pull policy is IfNotPresent which causes the kubelet to skip pulling an image if it already exists.

That's exactly what I wanted, but didn't seem to work.

Reading further said the following:

If you would like to always force a pull, you can do one of the following:

omit the imagePullPolicy and use :latest as the tag for the image to use.

When I replaced latest with a version (that I had pushed to minikube's Docker daemon), it worked fine.

$ kubectl create deployment presto-coordinator \
    --image=warsaw-data-meetup/presto-coordinator:beta0
deployment.apps/presto-coordinator created

$ kubectl get deployments
NAME                 READY   UP-TO-DATE   AVAILABLE   AGE
presto-coordinator   1/1     1            1           3s

Find the pod of the deployment (using kubectl get pods) and use kubectl describe pod to find out more on the pod.

User · Answer

By default Kubernetes looks in the public Docker registry to find images  If your image doesn t exist there it won t be able to pull it   You can run a local Kubernetes registry with the registry cluster addon    Then tag your images with localhost 5000   docker tag aii localhost 5000 dev aii   Push the image to the Kubernetes registry   docker push localhost 5000 dev aii   And change run-aii yaml to use the localhost 5000 dev aii image instead of aii  Now Kubernetes should be able to pull the image   Alternatively  you can run a private Docker registry through one of the providers that offers this  AWS ECR  GCR  etc    but if this is for local development it will be quicker and easier to get setup with a local Kubernetes Docker registry

User · Answer

You can specify also imagePullPolicy  Never in the container s spec   containers  - name  nginx   imagePullPolicy  Never   image  custom-nginx   ports    - containerPort  80

User · Answer

One issue that may cause an ImagePullBackOff especially if you are pulling from a private registry is if the pod is not configured with the imagePullSecret of the private registry   An authentication error may cause an imagePullBackOff

User · Answer

I had the same problem what caused  it was that I already had created a pod from the docker image via the  yml file  however I mistyped the name  i e test-app 1 0 1 when I needed test-app 1 0 2 in my  yml file  So I did kubectl delete pods --all to remove the faulty pod then redid the kubectl create -f name of file yml which solved my problem

User · Answer

I had this error when I tried to create a replicationcontroller  The issue was  I wrongly spelt the nginx image name in template definition   Note  This error occurs when kubernetes is unable to pull the specified image from the repository

User · Answer

The issue arises when the image is not present on the cluster and k8s engine is going to pull the respective registry  k8s Engine enables 3 types of ImagePullPolicy mentioned     Always   It always pull the image in container irrespective of changes in the image Never   It will never pull the new image on the container IfNotPresent   It will pull the new image in cluster if the image is not present    Best Practices   It is always recommended to tag the new image in both docker file as well as k8s deployment file  So That it can pull the new image in container

User · Answer

I too had this problem  when I checked I image that I was pulling from a private registry was removed If we describe pod it will show pulling event and the image it s trying to pull  kubectl describe pod  lt POD NAME gt   Events   Type     Reason   Age                  From              Message  ----     ------   ----                 ----              -------  Normal   Pulling  18h  x35 over 20h    kubelet  gsk-kub  Pulling image  registeryName tag   Normal   BackOff  11m  x822 over 20h   kubelet  gsk-kub  Back-off pulling image  registeryName tag   Warning  Failed   91s  x858 over 20h   kubelet  gsk-kub  Error  ImagePullBackOff

User · Answer

I had similar problem when using minikube over hyperv with 2048GB memory  I found that in HyperV manager the Memory Demand was higher than allocated    So I stopped minikube and assigned somewhere between 4096-6144GB  It worked fine after that  all pods running   I don t know if this can nail down the issue in every case  But just have a look at the memory and disk allocated to the minikube

[docker] What is the meaning of ImagePullBackOff status on a Kubernetes pod?

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