Kubernetes - Core Concepts & Architecture Flashcards

Question 1

Kubernetes Control Plane

Accepted Answer

The master management layer of a Kubernetes cluster that maintains the desired cluster state, makes global scheduling decisions, and responds to events via components like `kube-apiserver`, `etcd`, `kube-scheduler`, and `kube-controller-manager`.

Question 2

kube-apiserver

Accepted Answer

The central management front-end of the Control Plane that exposes the Kubernetes API. It validates and processes RESTful requests from users, external services, and worker node components.

Question 3

etcd

Accepted Answer

A consistent, highly available distributed key-value store used as Kubernetes' primary backend database to store all cluster state data and object specifications.

Question 4

kube-scheduler

Accepted Answer

The Control Plane component that monitors for unassigned Pods and selects an optimal worker node for them to run on based on resource availability, constraints, affinity policies, and taints/tolerations.

Question 5

kube-controller-manager

Accepted Answer

A single control plane binary running continuous background control loops (e.g., Node Controller, ReplicaSet Controller) that compare current state against desired state and make reconciliation adjustments.

Question 6

kubelet

Accepted Answer

The primary node agent running on every worker node. It reads `PodSpec` manifests, communicates with the container runtime to start/stop containers, and reports node health back to `kube-apiserver`.

Question 7

kube-proxy

Accepted Answer

A network proxy running on each node that maintains local network rules, handling IP/port forwarding and enabling network communications to Pods across internal and external network requests.

Question 8

Container Runtime

Accepted Answer

The underlying software responsible for running containers on a node (e.g., `containerd`, `CRI-O`). It pulls container images, executes them, and manages their container execution lifecycle.

Question 9

Pod

Accepted Answer

The smallest deployable unit in Kubernetes representing a single instance of a running process. A Pod encapsulates one or more co-located containers sharing storage, network namespace (IP), and execution context.

Question 10

Deployment

Accepted Answer

A declarative workload object that manages stateless application Pods via `ReplicaSets`. It provides declarative updates, rolling upgrades, dynamic scaling, and zero-downtime rollbacks.

Question 11

ReplicaSet

Accepted Answer

A controller object designed to guarantee that a specified number of identical Pod replicas are running at any given time to ensure application availability.

Question 12

StatefulSet

Accepted Answer

A workload object used to manage stateful applications requiring unique network identifiers, persistent persistent volume bindings, and ordered, deterministic deployment/scaling (e.g., databases).

Question 13

DaemonSet

Accepted Answer

A controller ensuring that a copy of a specific Pod runs on all (or a selected subset of) worker nodes. Commonly used for node monitoring agents, log collectors (`Fluentd`), or network plugins.

Question 14

Kubernetes Service

Accepted Answer

An abstraction object that defines a logical set of Pods and a policy to access them. It provides a stable internal IP address, DNS name, and load balancing across dynamic target Pods.

Question 15

Kubernetes Service Types

Accepted Answer

- `ClusterIP`: Exposes the Service on an internal IP (default).
- `NodePort`: Exposes the Service on a static port on each worker node's IP.
- `LoadBalancer`: Provisions an external cloud provider load balancer.
- `ExternalName`: Maps the Service to an external DNS CNAME.

Question 16

Ingress

Accepted Answer

An API object that manages external HTTP/HTTPS route access to cluster Services, providing Layer 7 routing, SSL/TLS termination, and name-based virtual hosting through an Ingress Controller.

Question 17

ConfigMap vs. Secret

Accepted Answer

- `ConfigMap`: Stores non-confidential configuration data in key-value pairs.
- `Secret`: Stores sensitive data (e.g., passwords, API keys, TLS certs) in base64-encoded format to avoid hardcoding secrets in image specs.

Question 18

PersistentVolume (PV) vs. PersistentVolumeClaim (PVC)

Accepted Answer

- `PersistentVolume (PV)`: A storage resource in the cluster provisioned by an administrator or dynamically via StorageClasses.
- `PersistentVolumeClaim (PVC)`: A user's request for storage with specific capacity and access modes that binds to a matching PV.

Question 19

Namespace

Accepted Answer

A virtual cluster mechanism inside physical clusters used to logically divide resources, isolate multi-tenant environments, enforce ResourceQuotas, and limit access control via RBAC.

Question 20

Liveness Probe vs. Readiness Probe

Accepted Answer

- `Liveness Probe`: Checks if the container is running; if it fails, Kubernetes kills and restarts the container.
- `Readiness Probe`: Checks if the container is ready to accept network traffic; if it fails, the Pod is removed from Service endpoints.

Question 21

Horizontal Pod Autoscaler (HPA)

Accepted Answer

A controller that automatically scales the number of Pod replicas in a Deployment or StatefulSet based on observed CPU/memory utilization or custom metrics.

Question 22

Self-Healing in Kubernetes

Accepted Answer

The cluster's automated capability to maintain desired state by restarting failed containers, rescheduling Pods when nodes die, replacing unresponsive Pods, and killing unhealthy containers based on probes.

Kubernetes - Core Concepts & Architecture

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