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🧠 The Ultimate Kubernetes Guide — From Zero to Pro (With Hands-On YAML)

#devops #kubernetes #yam #programming

Kubernetes is the operating system of the cloud—and understanding it is essential for modern DevOps, SaaS, and full-stack development. Whether you're a beginner or looking to deepen your knowledge, this tutorial will walk you through every core concept with real-world examples.

📦 What is Kubernetes?

Kubernetes (K8s) is an open-source container orchestration platform that helps you deploy, scale, and manage containerized applications.

Imagine running 100+ microservices. How do you keep them alive, ensure networking, balance traffic, and roll out updates safely? That’s what Kubernetes automates.

🔧 Why Use Kubernetes?

  • 🚀 Auto-scaling and load balancing
  • 🔁 Self-healing (crash recovery, restart)
  • 🛠️ Rolling updates with zero downtime
  • 🔐 Secrets & configuration management
  • 🗃️ Persistent storage
  • 🌐 Ingress + traffic routing
  • 🧱 Infrastructure-as-Code (YAML)

🛠️ Kubernetes Core Components (Visualized)

Component Description
Pod Smallest unit in K8s. Runs 1+ containers.
Deployment Manages pods & versions over time.
Service Exposes your pods within/outside the cluster.
Ingress Manages HTTP/HTTPS routing to services.
ConfigMap Externalizes config data (non-sensitive).
Secret Injects sensitive data (passwords, tokens).
PVC Persistent storage requests for stateful apps.
Node A VM or physical machine in the cluster.

🧱 Hands-On: Create a Complete K8s App Stack

We'll now walk through creating:

  1. A simple Node.js app
  2. A Deployment to manage it
  3. A Service to expose it
  4. A ConfigMap and Secret
  5. A PersistentVolumeClaim

📁 Step 1: deployment.yaml 

apiVersion: apps/v1 kind: Deployment metadata: name: my-app spec: replicas: 2 selector: matchLabels: app: my-app template: metadata: labels: app: my-app spec: containers: - name: my-app image: node:18 command: ["node", "-e", "require('http').createServer((_,res)=>res.end('Hi')).listen(3000)"] ports: - containerPort: 3000
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✅ What it does:

  • Launches 2 pods of a Node.js app
  • Uses node:18 as base image
  • Exposes port 3000 inside the container

🌐 Step 2: service.yaml 

apiVersion: v1 kind: Service metadata: name: my-app-service spec: type: NodePort selector: app: my-app ports: - port: 80 targetPort: 3000 nodePort: 30080
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✅ What it does:

  • Makes the app available via port 30080on your node
  • Load-balances between the pods
  • Accepts requests on port 80, routes to 3000

⚙️ Step 3: configmap.yaml 

apiVersion: v1 kind: ConfigMap metadata: name: app-config data: APP_ENV: production
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✅ What it does:

  • Stores non-sensitive environment variables
  • Can be injected into your pod like this: 
envFrom: - configMapRef: name: app-config
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🔐 Step 4: secret.yaml 

apiVersion: v1 kind: Secret metadata: name: db-secret type: Opaque data: DB_PASSWORD: bXlTZWNyZXRQYXNz
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✅ What it does:

  • Encodes secrets in base64 (e.g. mySecretPass)
  • You can inject it in your pod: 
env: - name: DB_PASSWORD valueFrom: secretKeyRef: name: db-secret key: DB_PASSWORD
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💾 Step 5:pvc.yaml 

apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 1Gi
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✅ What it does:

  • Requests 1 GB of storage
  • You can mount it into your pod at /data: 
volumes: - name: storage persistentVolumeClaim: claimName: my-pvc volumeMounts: - name: storage mountPath: /data
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🚀 Running Everything 

kubectl apply -f deployment.yaml kubectl apply -f service.yaml kubectl apply -f configmap.yaml kubectl apply -f secret.yaml kubectl apply -f pvc.yaml
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📚 Bonus: Useful K8s Commands 

kubectl get pods kubectl get svc kubectl describe pod <pod-name> kubectl logs <pod-name> kubectl delete -f deployment.yaml
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