Kubernestes interview questions

Core Kubernetes Concepts 1. What happens when you run kubectl apply -f deployment.yaml? API server receives request Validates YAML Stores desired state in etcd Scheduler assigns Pod to node Kubelet pulls image & starts container 2. Difference between Deployment, StatefulSet, and DaemonSet? Deployment → stateless apps (web apps) StatefulSet → stateful apps (DBs like MySQL) DaemonSet → runs one pod per node (logging, monitoring agents) 3. What is etcd? Distributed key-value store Stores cluster state (source of truth) 4. What is a Pod? Smallest deployable unit Can have one or multiple containers Shares network + storage 🔹 Networking (Very Important) 5. How does Kubernetes networking work? Each Pod gets unique IP Flat network (no NAT between pods) Uses CNI plugins (Calico, Flannel) 6. Difference between ClusterIP, NodePort, and LoadBalancer? ClusterIP → internal access NodePort → exposes via node IP LoadBalancer → cloud external LB 7. What is Ingress? HTTP/HTTPS routing Works with Ingress Controller (NGINX) 8. Debug: Pod not reachable Check: kubectl get pods kubectl describe pod kubectl logs kubectl get svc kubectl get endpoints 🔹 Storage 9. What is PV and PVC? PV (Persistent Volume) → actual storage PVC (Persistent Volume Claim) → request for storage 10. Difference between emptyDir and Persistent Volume? emptyDir → temporary PV → permanent 🔹 Security 11. What is RBAC? Role-Based Access Control Controls user permissions 12. How do you secure a cluster? RBAC Network Policies Secrets management Disable root containers 🔹 Config & Secrets 13. Difference between ConfigMap and Secret? ConfigMap → plain text Secret → base64 encoded (sensitive data) 🔹 Scaling & Availability 14. What is HPA (Horizontal Pod Autoscaler)? Scales pods based on CPU/memory 15. What is rolling update? Zero downtime deployment Replaces pods gradually 🔹 Troubleshooting (Most Important) 16. Pod stuck in Pending state No resources (CPU/memory) Node issue PVC not bound 17. CrashLoopBackOff issue Application crash Wrong config Check logs: kubectl logs 18. ImagePullBackOff Wrong image name Private repo auth issue 🔹 Real-Time Scenarios (VERY IMPORTANT) 19. How will you deploy an application in Kubernetes? Steps: Create Docker image Push to registry Create Deployment YAML Expose via Service Setup Ingress 20. How do you perform zero downtime deployment? Use rolling updates Configure readiness/liveness probes 21. How will you monitor Kubernetes? Prometheus Grafana ELK stack 22. How do you handle node failure? Pods rescheduled automatically Use multiple replicas 23. How do you upgrade a cluster? Drain node Upgrade master Upgrade worker nodes 🔹 DevOps Integration 24. How do you integrate Kubernetes with CI/CD? Jenkins / GitHub Actions Helm charts kubectl apply 25. What is Helm? Package manager for Kubernetes Manages YAML templates 🔹 Advanced (For 5+ Years) 26. What is CNI? Container Network Interface Handles pod networking 27. What is Service Mesh? Example: Istio Handles traffic, security, observability 28. What is Pod Disruption Budget (PDB)? Ensures minimum pods running during maintenance 29. What are taints and tolerations? Controls pod scheduling on nodes 30. Difference between liveness and readiness probe? Liveness → restart container Readiness → control traffic 🔥 Pro Tip for Your Interview

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