Kubernetes common errors

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.

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.

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.

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.

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.

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.

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.

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.

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.