kcna 1

What is the fundamental reason Kubernetes uses Pods as the smallest deployable unit, rather than individual containers directly?

• To simplify network configuration for containers
• To enable co-location and shared resources for containers
• To enforce stricter security boundaries than containers
• To provide a unique IP address per container
• To reduce container image size

Answer explanation

Pods allow tightly coupled containers to share resources like network namespace (IP, port space) and storage volumes, facilitating communication and data sharing for helper or sidecar patterns.

Which Kubernetes control plane component is responsible for persisting the cluster’s desired state and configuration?

• kube-scheduler
• kube-apiserver
• etcd
• kubelet
• controller-manager

Answer explanation

etcd is a distributed key-value store that reliably stores all Kubernetes cluster data, serving as the single source of truth for the cluster’s state.

A developer needs to expose a web application running in a set of Pods within the cluster using a stable internal IP address. Which Kubernetes resource is most appropriate?

• Ingress
• NodePort Service
• ClusterIP Service
• ExternalName Service
• ReplicaSet

Answer explanation

A ClusterIP Service provides a stable internal IP address and DNS name for accessing Pods, only reachable from within the cluster. NodePort exposes on nodes, Ingress is for external HTTP/S.

What is the primary purpose of the Kubernetes API server in the control plane architecture?

• To run containerized applications directly
• To schedule Pods onto available worker nodes
• To validate and process REST requests for API objects
• To manage network traffic between Pods
• To store cluster state in a time-series database

Answer explanation

The kube-apiserver is the frontend of the control plane, exposing the Kubernetes API. It processes and validates API requests, and updates the corresponding objects in etcd.

When a Pod is scheduled, what is the primary factor the kube-scheduler considers from the Pod’s specification?

• Container image version
• restartPolicy
• Resource requests and limits
• serviceAccountName
• labels

Answer explanation

The kube-scheduler filters nodes based on whether they can satisfy the Pod’s resource requests (CPU, memory) and then ranks them based on various priority functions.

Which component is NOT part of the Kubernetes control plane?

• kube-apiserver
• etcd
• kube-scheduler
• kube-proxy
• kube-controller-manager

Answer explanation

kube-proxy runs on every node in the cluster and is responsible for maintaining network rules on nodes, enabling network communication to Pods from network sessions inside or outside of the cluster. It’s a node component, not control plane.

What core benefit does containerization (e.g., using Docker or containerd) provide for application deployment?

• Automatic scaling of applications
• Abstraction of the underlying operating system and kernel
• Consistent runtime environment across different machines
• Built-in service discovery and load balancing
• Secure by default inter-container communication

Answer explanation

Containers bundle an application with its dependencies, ensuring it runs consistently regardless of the host environment, solving ”it works on my machine” problems.

What is the main advantage of using a declarative approach (e.g., YAML manifests) to manage Kubernetes resources?

• It allows for more complex scripting logic
• It enables direct manipulation of etcd data
• It focuses on what desired state, not how to achieve it
• It provides faster API response times
• It simplifies single-container Pod deployments only

Answer explanation

Declarative configurations define the desired state, and Kubernetes controllers work to reconcile the current state to this desired state. This is more robust and idempotent than imperative commands.

Why is container orchestration essential for managing microservices at scale?

• It simplifies writing microservice code
• It automatically converts monolithic apps to microservices
• It handles service discovery, scaling, and fault tolerance
• It provides a centralized logging solution by default
• It guarantees zero-downtime deployments

Answer explanation

Orchestrators like Kubernetes automate complex tasks like service discovery, load balancing, scaling based on demand, and self-healing, which are crucial for managing a distributed microservices architecture.

Which part of the Container Runtime Interface (CRI) specification is containerd primarily responsible for implementing?

• Image distribution and storage
• Low-level container execution and lifecycle management
• Network namespace creation and IP address assignment
• Defining container image format standards
• Implementing pod-level resource sharing

Answer explanation

containerd is a core container runtime that manages the complete container lifecycle on a single host – image transfer, storage, container execution, supervision, and network attachments.