Kubernetes common errors

1. CrashLoopBackOff:

   • Description: A pod repeatedly crashes and restarts.
   • Troubleshooting:
   • Check pod logs: kubectl logs <pod-name>.
   • Describe the pod for more details: kubectl describe pod <pod-name>.
   • Investigate the application's start-up and initialization code.

2. ImagePullBackOff:

   • Description: Kubernetes cannot pull the container image from the registry.
   • Troubleshooting:
   • Verify the image name and tag.
   • Check the image registry credentials.
   • Ensure the image exists in the specified registry.

3. Pending Pods:

   • Description: Pods remain "Pending" and are not scheduled.
   • Troubleshooting:
   • Check node resources (CPU, memory) to ensure there is enough capacity.
   • Ensure the nodes are labeled correctly if using node selectors or affinities.
   • Verify there are no taints on nodes that would prevent scheduling.

4. Node Not Ready:

   • Description: One or more nodes are in a "NotReady" state.
   • Troubleshooting:
   • Check node status: kubectl describe node <node-name>.
   • Review kubelet logs on the affected node.
   • Ensure the node has network connectivity.

5. Service Not Working

   • Description: Services are not accessible or routing traffic correctly.
   • Troubleshooting:
   • Check the service and endpoints: kubectl get svc and kubectl get endpoints.
   • Verify network policies and firewall rules.
   • Ensure the pods backing the service are healthy and running.

6. Insufficient Resources:

   • Description: Pods cannot be scheduled due to insufficient resources.
   • Troubleshooting:
   • Review resource requests and limits in pod specifications.
   • Scale the cluster by adding more nodes.

7. PersistentVolume Claims Pending:

   • Description: PVCs remain in a "Pending" state.
   • Troubleshooting:
   • Check if there are available PVs that match the PVC specifications.
   • Ensure the storage class exists and is configured correctly.
   • Verify that the underlying storage backend is healthy.

8. Pod Stuck Terminating:

   • Description: Pods get stuck in a "Terminating" state.
   • Troubleshooting:
   • Check for finalizers that might be preventing pod deletion.
   • Review the logs for shutdown hooks or long-running processes.
   • Force delete the pod if necessary: kubectl delete pod <pod-name> --force --grace-period=0.

9. DNS Resolution Issues:

   • Description: DNS lookups within the cluster fail.
   • Troubleshooting:
   • Check the DNS pod logs (e.g., CoreDNS): kubectl logs <coredns-pod>.
   • Ensure the DNS service is running: kubectl get svc -n kube-system.
   • Verify network policies and firewall rules do not block DNS traffic.