Common Real-Time Errors Faced by DevOps Engineers in Kubernetes

Kubernetes (K8s) is a powerful container orchestration tool that has revolutionized the way applications are deployed and managed. However, as with any complex system, DevOps engineers frequently encounter real-time challenges while working with Kubernetes. In this article, we'll explore some common Kubernetes errors and their solutions.

1. CrashLoopBackOff

Error Message: CrashLoopBackOff

What is “CrashLoopBackOff“ error:

Your container keeps crashing, and Kubernetes continuously attempts to restart it, but it fails to recover. The container starts and stops in a loop.

Possible causes:

• Bugs in your app causing it to crash.

• Insufficient resources (CPU, memory) allocated.

• Misconfigured environment variables or secrets.

Solution:

• Check logs: kubectl logs <pod-name> -n <namespace>

• Describe the pod: kubectl describe pod <pod-name> -n <namespace>

• Verify resource limits in YAML files.

• Ensure necessary environment variables and secrets are correctly configured.

2. ErrImagePull

Error Message: ErrImagePull

What is “ErrImagePull” error:

Kubernetes fails to pull the container image from the registry, preventing the pod from starting.

Possible causes:

• Docker image does not exist.

• Network issues preventing image pull.

Solution:

• Verify if the image exists: docker pull <image>

• Ensure your cluster has internet access.

• Check for typos in the image name.

3. ImagePullBackOff

Error Message: ImagePullBackOff

What is “ImagePullBackOff”:

Kubernetes repeatedly fails to pull the container image and backs off before retrying, delaying further attempts.

Causes:

• Incorrect container image name or tag.

• Image registry authentication failure.

• Private registry access issue.

Solution:

• Verify the image name: kubectl describe pod <pod-name>

• Authenticate to the private registry if needed.

• Ensure Docker Hub or other registry credentials are correctly configured.

4. Pending Pods

Error Message: Pending

What is Pending Pod error:

Your Pod is stuck in the "Pending" state and won’t schedule.

Causes:

• Insufficient worker nodes/resources.

• NodeSelector or Toleration issues.

• PersistentVolume claims not binding.

Solution:

• Check node capacity: kubectl get nodes -o wide

• View detailed pod info: kubectl describe pod <pod-name>

• Ensure PersistentVolume claims match available storage.

5. OOMKilled

Error Message: OOMKilled

What is “OOMKilled”’ error:

The container exceeded its memory limit, causing the Kubernetes Out of Memory (OOM) killer to terminate it.

Causes:

• Container exceeded memory limits.

• Memory-intensive application running with low allocation.

Solution:

• Increase memory limits in deployment YAML:

    resources:
      limits:
        memory: "512Mi"
      requests:
        memory: "256Mi"
  

• Monitor usage: kubectl top pod

• Optimize the application’s memory consumption.

6. Node Not Ready

Error Message: NotReady

What is Node Not Ready error:

The node is in an unhealthy state or unreachable, preventing it from scheduling or running pods.

Causes:

• Node is out of resources.

• Network issues.

• Kubelet is down.

Solution:

• Check node status: kubectl get nodes

• SSH into the node and restart Kubelet:

    sudo systemctl restart kubelet
  

• Verify CNI plugins are running correctly.

7. Node Disk Pressure

Error Message:

Conditions:
  Type              Status  Reason        Message
  ----              ------  ------        -------
  DiskPressure      True    KubeletHasDiskPressure  kubelet has disk pressure

What is “DiskPressure“:

The node is experiencing high disk usage, triggering Kubernetes to restrict pod scheduling and evict existing pods.

Causes:

• Node is running out of disk space.

• Logs or temporary files consuming disk storage.

• Misconfigured disk resource allocation.

Solution:

• Check node disk usage: df -h

• Identify large files and clean up:

    du -sh /* | sort -h
  

• Adjust disk eviction threshold settings in the Kubelet config.

• Increase disk space if necessary.

8. Kubelet Failures

Error Message:

kubectl describe node

Conditions:
  Type             Status  Reason
  ----             ------  ------
  Ready           False    KubeletNotReady

What is Kubelet Failure:

The Kubelet on a node has failed or stopped running, preventing the node from managing containers and communicating with the cluster.

Causes:

• Kubelet service is not running.

• Misconfigured system resources.

• API server communication failure.

Solution:

• Restart the Kubelet service:

    sudo systemctl restart kubelet
  

• Check logs for errors:

    journalctl -u kubelet --no-pager | tail -50
  

• Ensure API server is reachable: kubectl cluster-info

• Verify that /var/lib/kubelet has sufficient disk space.

Conclusion

Kubernetes is a robust but complex system, and real-time errors can disrupt workflows. By understanding common errors and their resolutions, DevOps engineers can troubleshoot efficiently and maintain high availability of applications. Keep debugging, keep learning, and happy K8s-ing!