Kubernetes most common error encounters

Kubernetes is a powerful and complex system, so there are several common errors that users might encounter. Here’s a rundown of typical Kubernetes errors and some troubleshooting methods:

1. Pods not starting / Container crash loops

Error: Pod is stuck in the CrashLoopBackOff or Pending state.

Troubleshooting:

• Check Pod logs:

    kubectl logs <pod-name> -n <namespace>
  

• Describe Pod:

    kubectl describe pod <pod-name> -n <namespace>
  

  This will show events related to the pod, such as failed scheduling or image pull issues.

• Check for resource limits: Ensure the pod is not exceeding memory or CPU limits.

• Check container images: Verify that the image exists in the container registry and that the container is configured correctly.

• Check node resources: Sometimes pods won't start due to insufficient resources. Check node resource availability:

    kubectl describe node <node-name>
  

2. Pod is stuck in Pending state

Error: The pod is scheduled but not running.

Troubleshooting:

• Check Scheduler logs: It could be a scheduling issue (e.g., not enough resources in the cluster).

• Check node status: Ensure that the nodes are not over-utilized.

    kubectl describe nodes
  

• Check PersistentVolume (PV) and PersistentVolumeClaim (PVC): If your pod is using PVCs, ensure the volume is correctly bound.

• Check network policies: Verify if network policies are preventing pod communication.

3. Service not accessible / Pod not reachable

Error: Applications in a pod are not accessible via the Kubernetes service.

Troubleshooting:

• Check Service configuration: Ensure the service is properly exposing the pod’s ports.

    kubectl describe svc <service-name> -n <namespace>
  

• Check Pod’s network connectivity: Make sure pods are running and have correct IPs.

    kubectl get pod -o wide
  

• Check ingress/egress rules: Review network policies or any firewall rules blocking communication.

• Check DNS resolution: Kubernetes relies on DNS, so ensure the DNS resolution is working.

    kubectl exec -it <pod-name> -- nslookup <service-name>
  

4. Image Pull Error

Error: Kubernetes fails to pull the container image, leading to a pod being stuck in Pending.

Troubleshooting:

• Check Image Name and Tag: Ensure the image name and tag are correct in the deployment.

• Check Image Pull Secrets: If the image is hosted on a private registry, ensure the correct imagePullSecrets are configured in your deployment.

• Check Registry Authentication: Make sure Kubernetes can authenticate to the container registry if needed.

    kubectl describe pod <pod-name> -n <namespace>
  

5. Resource Limit/Quota Errors

Error: Kubernetes is unable to allocate resources (memory, CPU) to the pod.

Troubleshooting:

• Check Resource Requests and Limits: Ensure the pod is not over-committing resources. Use:

    kubectl describe pod <pod-name>
  

• Check Resource Quotas: Ensure the namespace has not exceeded resource quotas. Check for resource usage:

    kubectl describe quota -n <namespace>
  

6. Node failures / Node Not Ready

Error: The node goes into a NotReady state.

Troubleshooting:

• Check Node status: If a node is not ready, you can inspect it:

    kubectl describe node <node-name>
  

• Check kubelet logs on the node: Look at the logs for issues like connectivity problems or misconfigurations.

• Check resource utilization: High resource usage (memory, CPU, disk) can cause node instability.

7. kubectl Not Working / Command Fails

Error: kubectl commands fail or return errors.

Troubleshooting:

• Check Kubeconfig file: Make sure the kubeconfig file is correctly set up and points to the right cluster.

    echo $KUBECONFIG
    kubectl config view
  

• Check Kubernetes Cluster Health:

    kubectl cluster-info
  

• Ensure Kubelet is Running: The kubelet on the nodes might be down.

    systemctl status kubelet
  

8. Ingress issues

Error: Ingress routes are not working or show 404s.

Troubleshooting:

• Check Ingress resource: Ensure the Ingress resource is defined correctly and points to the correct service.

    kubectl describe ingress <ingress-name> -n <namespace>
  

• Check Controller logs: If you’re using an Ingress controller (e.g., NGINX), inspect its logs to find any issues.

    kubectl logs <ingress-controller-pod> -n <namespace>
  

9. RBAC (Role-Based Access Control) Errors

Error: Users or service accounts are unable to perform certain actions.

Troubleshooting:

• Check RBAC Permissions: Ensure that the appropriate roles and role bindings are created for the user or service account.

    kubectl describe rolebinding <rolebinding-name> -n <namespace>
  

• Check Service Account: Make sure the service account is being used correctly in your resources (e.g., in deployments or pods).

10. High Latency or Performance Issues

Error: The application is slow or unresponsive.

Troubleshooting:

• Check Resource Usage: Inspect pod, node, and cluster-level metrics to see if resources are under heavy load.

    kubectl top pod
    kubectl top node
  

• Check for Network Issues: Latency can be network-related, so check for network performance or issues with ingress controllers.

• Check Pod Logs: High latency might also be related to application-level issues, so inspecting logs is critical.

General Best Practices:

• Use Liveness and Readiness Probes: These can help Kubernetes determine if your containers are healthy and properly running.

• Monitor with Prometheus/Grafana: Set up monitoring to detect issues early.

• Use kubectl get events to check for events related to the cluster resources.

By systematically working through these common error scenarios, you should be able to isolate and resolve most Kubernetes issues.