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

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 ??

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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

Answer 5

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.

Answer 6

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 <POD_NAME>
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

Answer 7

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.

Answer 8

Debugging step:
kubectl get pod [name] -o yaml
Run this command to get the YAML configuration of the pod (Get YAML for deployed Kubernetes services?). In my case, it was under this section:
state:
waiting:
message: 'rpc error: code = Unknown desc = Error response from daemon: Get
https://repository:9999/v2/abc/location/image/manifests/tag:
unauthorized: BAD_CREDENTIAL'
reason: ErrImagePull

Answer 9

My issue got resolved upon adding the appropriate tag to the image I wanted to pull from the DockerHub.
Previously:
containers:
- name: nginx
image: alex/my-app-image
Corrected Version:
containers:
- name: nginx
image: alex/my-app-image:1.1
The image has only one version, which was 1.1. Since I skipped that initially, it has thrown an error.
After correctly mentioning the version, it worked fine!!

Answer 10

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.

Answer 11

I had face same issue.
imagePullBackOff means it is not able to pull docker image from registry or smoking issue with your registry.
the solution would be as below.
1. Check you image registry name.
2. check image pull secrets.
3. check image is present with same tag or name.
4. check you registry is working.

Answer 12

ImagepullBackoff mesns you have not passed secret in your yaml or secret is wrong and might be you image name is wrong.
If you pulling image from private registry you have to provide image pull secret then it will able to pull image.
you also need to creat secrete before you deploy the pod. you can use below command to create secrete.
kubectl create secret docker-registry regcred --docker-server=artifacts.exmple.int --docker-username=<username> --docker-password=<password> -n <namespace>
you can pass secret in yaml like below.
imagePullSecrets:
- name: regcred

Answer 13

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.

Answer 14

I had the same issue.
[mayur#mayur_cloudtest ~]$ kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-598b589c46-zcr5d 0/1 ImagePullBackOff 0 6m21s
Later I found that the docker on which the pod is created is using a private registry for images and Nginx was not present in it.
I have changed the docker registry to default and reloaded the daemon.
Post that issue got resolved.
[mayur#mayur_cloudtest ~]$ kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-598b589c46-7cbjf 1/1 Running 0 33s
[mayur#mayur_cloudtest ~]$
[mayur#mayur_cloudtest ~]$
[mayur#mayur_cloudtest ~]$ kubectl exec -it nginx-598b589c46-7cbjf -- /bin/bash
root#nginx-598b589c46-7cbjf:/# ls
bin dev docker-entrypoint.sh home lib64 mnt proc run srv tmp var
boot docker-entrypoint.d etc lib media opt root sbin sys usr
root#nginx-598b589c46-7cbjf:/#

Answer 15

For my case, Kubernetes was not able to communicate to my private registry running on localhost:5000 after update to MacOS Monterey. It was running fine previously. The reason was Apple Airplay now listen to port 5000.
In order to resolve this issue, I disabled Apple Airplay receiver.
Go To System preference > Sharing > Disable checkbox for Airplay receiver.
Source Link: https://developer.apple.com/forums/thread/682332

Answer 16

To handle this error, Just have to create Kubernetes secrets and use it in manifest.yaml file
If it is private repository then it is mandatory to use user secrets
To generate secrets -
kubectl create secret docker-registry docker-secrets --docker-server=https://index.docker.io/v1/ --docker-username=ExamplaName --docker-password=ExamplePassword --docker-email=example#gmail.com
for --docker-server, use https://index.docker.io/v1/
apiVersion: v1
kind: Pod
metadata:
name: test-pod
spec:
containers:
- name: test
image: ExampleUsername/test:tagname
ports:
- containerPort: 3015
imagePullSecrets:
- name: docker-secrets