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

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.

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.

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.

You can specify also imagePullPolicy: Never in the container's spec:

containers:
- name: nginx
  imagePullPolicy: Never
  image: custom-nginx
  ports:
  - containerPort: 80

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