Kubernetes Troubleshooting
Expert debugging and diagnostics for Kubernetes clusters using kubectl-mcp-server tools.
When to Apply
Use this skill when:
- User mentions: "debug", "troubleshoot", "diagnose", "failing", "crash", "not starting", "broken"
- Pod states: Pending, CrashLoopBackOff, ImagePullBackOff, OOMKilled, Error, Unknown
- Node issues: NotReady, MemoryPressure, DiskPressure, NetworkUnavailable, PIDPressure
- Keywords: "logs", "events", "describe", "why isn't working", "stuck", "not responding"
Priority Rules
| Priority | Rule | Impact | Tools |
|---|---|---|---|
| 1 | Check pod status first | CRITICAL | get_pods, describe_pod |
| 2 | View recent events | CRITICAL | get_events |
| 3 | Inspect logs (including previous) | HIGH | get_pod_logs |
| 4 | Check resource metrics | HIGH | get_pod_metrics |
| 5 | Verify endpoints | MEDIUM | get_endpoints |
| 6 | Review network policies | MEDIUM | get_network_policies |
| 7 | Examine node status | LOW | get_nodes, describe_node |
Quick Reference
| Symptom | First Tool | Next Steps |
|---|---|---|
| Pod Pending | describe_pod | Check events, node capacity, resource requests |
| CrashLoopBackOff | get_pod_logs(previous=True) | Check exit code, resources, liveness probes |
| ImagePullBackOff | describe_pod | Verify image name, registry auth, network |
| OOMKilled | get_pod_metrics | Increase memory limits, check for memory leaks |
| ContainerCreating | describe_pod | Check PVC binding, secrets, configmaps |
| Terminating (stuck) | describe_pod | Check finalizers, PDBs, preStop hooks |
Diagnostic Workflows
Pod Not Starting
1. get_pods(namespace, label_selector) - Get pod status
2. describe_pod(name, namespace) - See events and conditions
3. get_events(namespace, field_selector="involvedObject.name=<pod>") - Check events
4. get_pod_logs(name, namespace, previous=True) - For crash loops
Common Pod States
| State | Likely Cause | Tools to Use |
|---|---|---|
| Pending | Scheduling issues | describe_pod, get_nodes, get_events |
| ImagePullBackOff | Registry/auth | describe_pod, check image name |
| CrashLoopBackOff | App crash | get_pod_logs(previous=True) |
| OOMKilled | Memory limit | get_pod_metrics, adjust limits |
| ContainerCreating | Volume/network | describe_pod, get_pvc |
Node Issues
1. get_nodes() - List nodes and status
2. describe_node(name) - See conditions and capacity
3. Check: Ready, MemoryPressure, DiskPressure, PIDPressure
4. node_logs_tool(name, "kubelet") - Kubelet logs
Deep Debugging Workflows
CrashLoopBackOff Investigation
1. get_pod_logs(name, namespace, previous=True) - See why it crashed
2. describe_pod(name, namespace) - Check resource limits, probes
3. get_pod_metrics(name, namespace) - Memory/CPU at crash time
4. If OOM: compare requests/limits to actual usage
5. If app error: check logs for stack trace
Networking Issues
1. get_services(namespace) - Verify service exists
2. get_endpoints(namespace) - Check endpoint backends
3. If empty endpoints: pods don't match selector
4. get_network_policies(namespace) - Check traffic rules
5. For Cilium: cilium_endpoints_list_tool(), hubble_flows_query_tool()
Storage Problems
1. get_pvc(namespace) - Check PVC status
2. describe_pvc(name, namespace) - See binding issues
3. get_storage_classes() - Verify provisioner exists
4. If Pending: check storage class, access modes
DNS Resolution
1. kubectl_exec(pod, namespace, "nslookup kubernetes.default") - Test DNS
2. If fails: check coredns pods in kube-system
3. get_pods(namespace="kube-system", label_selector="k8s-app=kube-dns")
4. get_pod_logs(name="coredns-*", namespace="kube-system")
Multi-Cluster Debugging
All tools support context parameter for targeting different clusters:
get_pods(namespace="kube-system", context="production-cluster")
get_events(namespace="default", context="staging-cluster")
describe_pod(name="myapp-xyz", namespace="prod", context="prod-east")
Diagnostic Scripts
For comprehensive diagnostics, run the bundled scripts:
- See scripts/diagnose-pod.py for automated pod analysis
- See scripts/health-check.sh for cluster health checks
Decision Tree
See references/DECISION-TREE.md for visual troubleshooting flowcharts.
Common Errors Reference
See references/COMMON-ERRORS.md for error message explanations and fixes.
Related Tools
Core Diagnostics
get_pods,describe_pod,get_pod_logs,get_pod_metricsget_events,get_nodes,describe_nodeget_resource_usage,compare_namespaces
Advanced (Ecosystem)
- Cilium:
cilium_endpoints_list_tool,hubble_flows_query_tool - Istio:
istio_proxy_status_tool,istio_analyze_tool
Related Skills
- k8s-diagnostics - Metrics and health checks
- k8s-incident - Emergency runbooks
- k8s-networking - Network troubleshooting