What is ImagePullBackOff status on a Kubernetes pod ?

When I was trying to run kubernetes Pods in Google Cloud Platform, I got the status as ImagePullBackOff for one of the kubernetes pod. Let’s see what is ImagePullBackOff status and how to resolve the same.

ImagePullBackOff status on a Kubernetes Pod

After doing kubernetes pods deployment, I wanted to check if all pods are up and running. Therefore, I ran the following kubectl command to fetch all the pods running in the namespace “mv“.

One of the kubernetes pod “kafka-producer-service-776979bc89-bhvbm” was showing the status as ImagePullBackOff as shown below.

$ kubectl get pods -n mv

NAME                                           READY   STATUS             RESTARTS   AGE
kafka-producer-service-776979bc89-bhvbm        1/2     ImagePullBackOff   0          18s
kafka-77fb6497c9-h9lns                         2/2     Running            0          47m
zookeeper-65fcbf6ccb-5knt8                     2/2     Running            0          47m

Actually the expected status for all the pods is “Running” but one of the pod shows READY 1/2 which means there are two containers should be up and running in that pod, but one of the container is not ready.

Troubleshooting ImagePullBackOff Status

First, I had checked my kubernetes deployment YAML configuration file.

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: kafka-producer-service
spec:
  replicas: 1
  selector:
    matchLabels:
      app: kafka-producer-service
  template:
    metadata:
      labels:
        app: kafka-producer-service
    spec:
      containers:
        - name: kafka-producer-servicee
          image: sneppets/kafka-producer-service:latest
          ports:
            - containerPort: 8080
          env:
            - name: MONGODB_HOST
              value: mongodb
            - name: KAFKA_HOST
              value: kafka
          imagePullPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
  name: kafka-producer-service
spec:
  selector:
    app: kafka-producer-service
  ports:
    - port: 80
      targetPort: 8080

As you can see clearly that in the deployment YAML section, the containers spec for image was mentioned as “sneppets/kafka-producer-service:latest“. It means that when you run this deployment script, it will try to look for docker images in the docker hub registry.

Then I checked my Docker hub repositories for the specified image. And I could see that there is no docker image found in the name of kafka-producer-service in the repository “sneppets” in the docker hub.

Therefore, the issue ImagePullBackOff status is due to missing image in the public docker registry.

Solution

To fix the ImagePullBackOff issue, you need to run the following command and ensure you push the image to the docker registry.

First, build your application using tools like Maven.

$ mvn clean install -Dmaven.test.skip=true

Run the following command to build docker image locally.

$ docker image build -t kafka-producer-service .

Create a image tag by running the following command.

$ docker image tag kafka-producer-service sneppets/kafka-producer-service

Finally, push the image to the docker registry repository.

$ docker image push sneppets/kafka-producer-service

That’s all, now you can run the deployment YAML scripts again and try running the kubectl command, you would not see the status ImagePullBackOff status now.

$ kubectl get pods -n mv

NAME                                           READY   STATUS             RESTARTS   AGE
kafka-producer-service-776979bc89-bhvbm        2/2     Running            0          18s
kafka-77fb6497c9-h9lns                         2/2     Running            0          47m
zookeeper-65fcbf6ccb-5knt8                     2/2     Running            0          47m

Also, see that READY shows not 2/2 for kafka-producer-service which means that both the containers are up and running now.

Hope it helped 🙂

ImagePullBackOff status on a Kubernetes Pod

Troubleshooting ImagePullBackOff Status

Solution

References