Interview › Kubernetes, Docker, Helm & Podman
How do you troubleshoot a Pod stuck in Pending?
Kubernetes, Docker, Helm & Podman · Intermediate level
Answer
A Pod stuck in Pending usually means it cannot be scheduled or bound to required resources. I check events for insufficient resources, taints, affinity conflicts, unbound PVCs, quota limits, node selectors, or autoscaler behavior.
Technical explanation
Pending can happen before the image is ever pulled because the Pod has not been assigned to a node.
Always read the scheduling events before changing container images or app code.
Troubleshooting starts from state and events: get, describe, logs, previous logs, events, and then node/runtime/network checks.
Separate scheduling failures, image pull failures, runtime failures, app failures, and traffic-routing failures so you do not fix the wrong layer.
Operational commands like drain and rollback must respect PDBs, probes, and workload disruption tolerance.
Hands-on example
1. In a non-production namespace, create this safe broken scenario: create a Pending Pod with impossible resource requests and diagnose events.
2. Follow a fixed triage order: kubectl get, describe, logs or logs --previous, events, rollout status, node status, and then runtime/network checks.
3. Fix only one variable at a time so the root cause is clear rather than accidentally masked.
4. Save the commands and final diagnosis as an interview-ready incident walkthrough.
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- What is a Pod, and why does Kubernetes schedule Pods rather than containers?
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- How does a Deployment perform a rolling update, and how do maxSurge and maxUnavailable work?
- How do you roll back a Deployment, and how does Kubernetes track revisions?
- What is a Service, and what are the types (ClusterIP, NodePort, LoadBalancer, ExternalName)?