Kubernetes Overview

This lesson introduces the core building blocks of Kubernetes so you can follow along with hands-on labs and real-world scenarios. While it won’t make you a Kubernetes expert overnight, you’ll gain the foundational knowledge needed to deploy and manage containerized applications. For a deep dive, explore our KodeKloud Kubernetes courses.

Kubernetes Architecture

Kubernetes is composed of two primary component groups:

Control Plane Components

• API Server (kube-apiserver)
  Exposes the Kubernetes REST API; processes kubectl and other client requests.

• etcd
  A distributed key-value store holding all cluster state, configuration, and metadata.

• Controller Manager (kube-controller-manager)
  Runs controllers for replication, node lifecycle, health checks, and more.

• Scheduler (kube-scheduler)
  Assigns new Pods to nodes based on resource requirements, affinity, and taints/tolerations.

Node (Agent) Components

• kubelet
  Watches the API server for PodSpecs and ensures containers described in those specs are running.

• kube-proxy
  Implements Service abstraction by programming network rules and load-balancing traffic to Pods.

• Container Runtime
  The software responsible for pulling images and running containers. On Windows, the CRI integrates with Host Compute Service (HCS) and Host Networking Service (HNS).

Component Interaction: Creating a Deployment

When you run a command like:

kubectl create deployment nginx --image=nginx

Kubernetes executes the following workflow:

1. kubectl → API Server
   Sends the Deployment manifest via the Kubernetes API.

2. API Server → etcd
   Validates and persists the Deployment object.

3. Deployment Controller
   Detects the new Deployment and creates a ReplicaSet.

4. ReplicaSet Controller
   Observes the ReplicaSet and launches the desired number of Pods.

5. Scheduler
   Assigns each unscheduled Pod to an appropriate node.

6. kubelet
   Retrieves PodSpecs, then invokes the Container Runtime Interface (CRI) to start containers and the Container Network Interface (CNI) to configure networking.

7. Container Runtime → Host Services (Windows-specific)

   • Calls HCS to instantiate the container.
   • Calls HNS to establish network endpoints.

8. kube-proxy
   Monitors new Services and Endpoints, programming load-balancing and network rules so traffic reaches the correct Pods.

Below is a diagram illustrating how the control plane and node components collaborate during a Deployment:

Next Steps

With a solid grasp of Kubernetes core components and their interplay, you’re ready to:

• Deploy a Kubernetes cluster in Azure using AKS
• Explore workload objects (Deployments, StatefulSets, DaemonSets)
• Configure Services, Ingress, and network policies
• Implement scaling, self-healing, and rollouts

Links and References

• Kubernetes Documentation
• Azure Kubernetes Service (AKS) Overview
• KodeKloud Kubernetes Courses