☸️ Kubernetes Architecture – A Beginner-Friendly Guide

📌 What is Kubernetes?

Kubernetes (K8s) is an open-source platform that automates the deployment, scaling, and management of containerized applications.

It helps developers and DevOps teams run applications efficiently across multiple environments on-premise or in the cloud.

🔹 Quick Facts about Kubernetes

✅ Developed by Google and later donated to the Cloud Native Computing Foundation (CNCF).
✅ Inspired by Google’s internal cluster management system, Borg.
✅ Why "K8s"? The 8 represents the number of letters between K and s in Kubernetes → K8s.

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🎯 Why Use Kubernetes? (Key Benefits)

✅ Automated Scaling – Adjusts the number of running containers based on traffic.
✅ Self-Healing – Restarts failed containers, replaces them, and reschedules on healthy nodes.
✅ Load Balancing – Distributes traffic evenly across containers.
✅ Service Discovery – Helps services find and communicate with each other.
✅ Declarative Configuration – Uses YAML/JSON files to define infrastructure.
✅ Multi-Cloud Support – Works on AWS, Azure, GCP, or on-premises.

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🏗 Kubernetes Architecture

Kubernetes follows a Master-Worker Node Architecture, where the Control Plane(Master) manages the Worker Nodes.

📌 Main Components

1] Control Plane (Master Node) – The "Brain" of Kubernetes

• Manages the overall cluster.

• Ensures workloads run where needed.

• Main Responsibilities

  ✅ Schedules workloads on worker nodes.
  ✅ Handles cluster-wide decisions.
  ✅ Manages communication between components.

2] Worker Nodes – The Machines Running Applications

• Handle the actual execution of applications.

3] kubectl – The Command-Line Tool

• Used to interact with Kubernetes.

• Sends instructions to the API Server.

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🖥 Control Plane Components

Manages the entire cluster, ensuring apps run as expected.

🔹 API Server 🌐 – The entry point for all requests, like a city hall processing permits.
🔹 Scheduler 📝 – Assigns workloads (pods) to worker nodes, like a dispatcher.
🔹 Controller Manager ⚙️ – Watches over the cluster, fixing issues automatically.
🔹 etcd 🛢 – The memory, storing all cluster configurations.

🏗 Worker Nodes (The Workforce 💪)

These are the machines where actual applications run.

🔹 Kubelet 🔹 – Ensures containers run properly, like a site supervisor.
🔹 Kube Proxy 🔹 – Handles networking, ensuring smooth communication.
🔹 CNI 🌍 – Manages IP addresses and connections between pods.

🎮 kubectl (Command-Line Interface)

• Installed on the user's machine.

• Interacts with the API Server to manage Kubernetes clusters.

• Common commands:
  🔹 kubectl apply – Deploy apps
  🔹 kubectl get pods – View running applications
  🔹 kubectl delete – Remove applications

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🔄 Difference Between kubectl and kubelet

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🌐 The Role of the API Server

The API Server is the heart of Kubernetes. It serves as the main gateway for all communication inside the cluster.

📌 What Does the API Server Do?

✅ Accepts requests from kubectl, UI, or other tools.
✅ Validates and processes those requests.
✅ Stores cluster configurations in etcd.
✅ Acts as the single source of truth for the cluster.

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