Mastering Kubernetes: A DevOps Engineer’s Ultimate Troubleshooting Cheatsheet

Creating a Kubernetes troubleshooting checklist is a great way to systematically address issues that may arise in your Kubernetes environment. This checklist can help you in you identify and resolve problems more efficiently. Here's a comprehensive cheatsheet to guide you through troubleshooting Kubernetes:

1. Cluster Health Checks

• Check Cluster Status: kubectl get nodes to ensure all nodes are in READY state.
• Control Plane Health: Verify the health of control plane components if you have access.
• System Logs: Review logs of Kubernetes components (kubelet, kube-apiserver, kube-scheduler, kube-controller-manager) for errors.

2. Pod and Container Issues

• Check Pod Status: kubectl get pods --all-namespaces to find any pods that are not in RUNNING state.
• Describe Pod Issues: kubectl describe pod <pod-name> -n <namespace> to get more details on issues.
• Container Logs: kubectl logs <pod-name> -n <namespace> for application-specific issues.
• Check for Resource Limits: Ensure pods are not being terminated due to reaching resource limits (CPU, memory).

3. Networking Troubleshooting

• Service Connectivity: Test if your services are reachable and correctly routing to your pods.
• Inspect Network Policies: Verify network policies are not blocking the intended traffic.
• DNS Resolution: Ensure internal DNS services are correctly resolving service names.

4. Storage Troubleshooting

• Persistent Volume Claims (PVCs): Check the status of PVCs with kubectl get pvc -n <namespace> to ensure they are bound and available.
• Access Modes: Verify that the access modes on your PVCs match how your pods are trying to use them.
• StorageClass Issues: Make sure the StorageClass is correctly configured and the underlying storage is accessible.

5. Performance and Resource Management

• Node Resources: Use kubectl top nodes to check if any node is overutilized.
• Pod Resources: Use kubectl top pods to identify if any pod is consuming excessive resources.
• Autoscaling: If using Horizontal Pod Autoscaler, check its status to ensure it's working as expected.

6. Security and Access Control

• RBAC Policies: Verify Role-Based Access Control (RBAC) policies are correctly configured for accessing cluster resources.
• Service Account Permissions: Check if the service accounts have the necessary permissions for their roles.

7. Application-Specific Troubleshooting

• Environment Variables: Ensure your containers are started with the correct environment variables.
• ConfigMaps and Secrets: Make sure these are correctly mounted and accessible to your pods.

8. External Dependencies

• Third-Party Services: Verify connectivity and availability of any external services your applications depend on.
• API Rate Limits: Check if there are any API rate limits affecting communication with external services.

9. General Debugging Tips

• Rolling Back: If recent changes caused the issue, consider rolling back deployments, config changes, etc.
• Kubernetes Events: kubectl get events -n <namespace> can provide insights into what's happening in the cluster.

10. Monitoring and Alerts

• Monitoring Tools: Utilize tools like Prometheus, Grafana, or ELK stack for insights into cluster metrics and logs.
• Set Up Alerts: Configure alerts for critical metrics and logs to proactively manage cluster health.

Tools and Commands

• kubectl: Your primary tool for interacting with Kubernetes.
• kubectl exec: Execute commands in a container.
• kubectl port-forward: For testing local connectivity to services.
• Monitoring Tools: Prometheus, Grafana, ELK Stack for deeper insights.

Documentation and Resources

• Kubernetes Official Documentation: Always a great resource for troubleshooting and best practices.
• Community Forums: Kubernetes Slack channels, Stack Overflow, and GitHub issues can be invaluable resources.

Final Notes

Keep this cheatsheet handy and customize it based on your specific environment and experiences. Troubleshooting Kubernetes can be complex, but a systematic approach will help you identify and solve issues more efficiently.