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Frequently Asked Questions
This page is an auto-generated index of every deep-dive question answered across this documentation site.
Foundations
- Q. Origins of Kubernetes
- Q. How do Linux and virtualization concepts map to Kubernetes?
- Q. What are the interconnected ideas surrounding the core k8s concept?
- Q. The Anatomy of Kubernetes YAML
- Q. Deep Dive: Cgroups Architecture & v2 Evolution
- Q. Cgroups & Namespaces
- Q. Why Kubernetes?
Architecture
- Q. Kube Controller Manager
- Q. What is the Lifecycle of kubectl apply command?
- Q. How does kube-scheduler score nodes, and how do NodeAffinity, PodAffinity, and PodAntiAffinity differ in the Filter and Score phases?
- Q. Types of API Requests in Kubernetes
- Q. Mapping HTTP Methods to API Verbs
- Q. What are the core components of Kubernetes, and how do the control plane and worker nodes interact?
- Q. K8s architecture
- Q. What is a Controller
- Q. How do Custom Resource Definitions differ from built-in controllers
- Q. How does Kubernetes handle desired state management, and what role do controllers play in maintaining it?
- Q. What is etcd, what data does it store, and why is it so critical to cluster reliability and consistency?
- Q. What is the End-to-End Pod Creation Lifecycle
- Q. How do controllers use reconciliation loops to enforce desired state?
- Q. How does the kube-scheduler work internally, and what factors influence Pod placement decisions?
- Q. How do Taints and Tolerations work at the API level, and what triggers a NoExecute eviction?
- Q. What is the exact journey of a request through the API Server pipeline?
Workloads
- Q. How does Kubernetes support autoscaling (HPA, VPA, Cluster Autoscaler), and what signals drive scaling decisions?
- Q. How can I update a ConfigMap mounted as a volume?
- Q. How do I create a Deployment using kubectl?
- Q. How does In-Place Pod Resizing work in 1.35?
- Q. How does the OOM killer choose between RSS and cache?
- Q. What is a Pod, why is it the smallest deployable unit in Kubernetes, and what design trade-offs does this introduce?
- Q. How do resource requests and limits work, and how do they affect scheduling, performance, and stability?
- Q. What are Deployments, ReplicaSets, and StatefulSets, and when should each be used?
- Q. What is the difference between SIGTERM and SIGKILL in Kubernetes?
Networking
- Q. How does Cilium use eBPF to completely bypass kube-proxy and route a packet without touching iptables?
- Q. What is a CNI plugin in Kubernetes and how does it actually work?
- Q. Trace the sequence of events when a Pod is scheduled and the veth pair is physically created and attached.
- Q. Detail the crucial CNI file locations on the worker nodes.
- Q. How does DNS work inside a Kubernetes cluster, and how do applications discover each other?
- Q. What are the Advantages of using GRPCRoute for services
- Q. What is GatewayApi
- Q. Why Gateway API instead of Ingress?
- Q. Difference between Ingress and Gateway API
- Q. What is an Ingress, how does it differ from a Service, and how is external traffic routed into the cluster?
- Q. Explain how IP Address Management (IPAM) assigns CIDRs to Nodes and delegates individual Pod IPs.
- Q. Does Kubernetes use ipset? If yes, how is it different from iptables and IPVS, and when is it utilized?
- Q. Explain the packet traversal difference between kube-proxy iptables mode versus IPVS mode, and when mathmatically iptables begins to degrade.
- Q. How does Kubernetes networking work at a high level (Pod-to-Pod, Pod-to-Service, external traffic)?
- Q. Network Policy
- Q. What is a Service
- Q. What problem do Services solve, and how do ClusterIP, NodePort, and LoadBalancer differ in real-world usage?
- Q. What are the Linux networking primitives that underpin Kubernetes?
Storage
- Q. How does the attach/detach controller handle Pod migration, and what causes 'Multi-Attach' errors?
- Q. What is the exact workflow of CSI dynamic provisioning, and what are the roles of the sidecars?
- Q. How does Kubernetes talk to my specific storage vendor?
- Q. What is the role of a Default StorageClass?
- Q. What are Ephemeral Volumes?
- Q. How do Kubernetes filesystems and volume mounts work under the hood?
- Q. How does Kubernetes handle storage, and what are PersistentVolumes, PersistentVolumeClaims, and StorageClasses?
- Q. How does dynamic volume provisioning actually work?
- Q. How does the Pod lifecycle affect container storage?
- Q. What does storageClassName: "" actually mean?
- Q. How do Union Filesystems (like overlayfs and aufs) power container image layers and Copy-on-Write (CoW)?
- Q. How exactly do I share data between multiple running Pods?
Security
- Q. What are authentication, authorization, and admission — and where do they sit in that request flow?
- Q. What exactly happens when Kubernetes certificates expire, and how do you manually renew and rotate them using kubeadm?
- Q. Specify the location of all types of certs used and provide linux or kubectl commands used to check, renew and create the certs.
- Q. How does Kubernetes manage configuration and secrets, and what are best practices for using ConfigMaps and Secrets securely?
- Q. How do Kubernetes NetworkPolicies actually isolate workloads?
- Q. What is the complete PKI architecture required to bootstrap a Kubernetes control plane?
- Q. How does Kubernetes RBAC work?
- Q. How does Kubernetes implement security at multiple layers (RBAC, namespaces, network policies, Pod security)?
- Q. What are the security primitives used to harden containerized workloads?
- Q. What is a ServiceAccount?
Runtime
- Q. What is the Container Runtime Interface (CRI), and how does Kubernetes interact with container runtimes like containerd?
- Q. How does the Container Runtime Interface interact with containerd specifically?
- Q. What is the specific role of the pause container in pods?
- Q. How does Kubernetes manage internal container processes, and what are Zombie processes?
- Q. What is the CRI and how does it work?
Operations
- Q. How do I monitor etcd latency in a production cluster?
- Q. How should I handle etcd restores when API servers are active?
- Q. What happens to the cluster if the etcd storage quota is exceeded, and how do we manage it?
- Q. What is the difference between stacked and external etcd topologies?
- Q. Why is the Kubelet managed by Systemd, and how do they interact?
- Q. Q : What is the process for running Kubelet in standalone mode?
- Q. Bootstraping - Deploying K8S cluster
- Q. Kubernetes Cluster Discovery & Storage Investigation
- Q. How do I discover the state of an unfamiliar cluster and its storage?
- Q. How should Kubernetes clusters be upgraded and operated in production to minimize downtime and risk?
- Q. How do I create a new context?
- Q. What is a Kubernetes Context?
- Q. How do I add a default namespace to a context?
- Q. What happens when a Pod or Node fails, and how does Kubernetes detect and recover from failures?
- Q. What are some useful Commands?
- Q. How do I trace container logs to their source on the node filesystem?
- Q. What are important Log and Binary files location in k8s?
- Q. How does the kubelet start, and how do you troubleshoot node initialization failures?
- Q. How do you observe and troubleshoot Kubernetes clusters (logs, metrics, events, probes, debugging patterns)?
- Q. How do Kubernetes resource limits translate to Linux kernel primitives?
- Q. Common commands for finding pods with high resource use
- Q. Understanding Kubernetes Contexts
Troubleshooting
- Q. How do I troubleshoot pods stuck in a CrashLoopBackOff state?
- Q. Scenario: Why is Ingress returning 502 Bad Gateway?
- Q. How do I trace system calls using strace in containers?
- Q. Scenario: Why can't my Pod resolve Service names?
- Q. Scenario: Multi-Attach Error
- Q. Scenario: Why is my Pod stuck in "Pending"?
- Q. Scenario: PVC Stuck Terminating
- Q. Kubernetes Volume Troubleshooting: Essential Commands & Quick Fixes
Tooling
- Q. Etcd Operations & Disaster Recovery
- Q. Kubectl Filtering Masterclass
- Q. Lab Setup: Ubuntu 24.04 Cluster
- Q. Deployment Strategies
- Q. Vim Shortcuts for CKA