A Simple Analogy

Kubernetes is like an orchestra conductor. It manages many musicians (containers) playing together, ensuring they stay in sync, restart when needed, and scale up when the performance requires more sound. The conductor handles all the complex coordination so musicians focus on playing.

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What Is Kubernetes?

Kubernetes (k8s) is an open-source container orchestration platform that automates deployment, scaling, and management of containerized applications across clusters of machines.

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Why Use Kubernetes?

• Auto-scaling: Scale containers up or down based on demand
• Self-healing: Restart failed containers automatically
• Rolling updates: Deploy new versions without downtime
• Service discovery: Containers find each other automatically
• Load balancing: Distribute traffic across containers
• Multi-host deployment: Run across multiple machines

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Core Concepts

| Concept | Purpose | |---------|---------| | Pod | Smallest deployable unit (usually one container) | | Deployment | Manages replicas and updates of pods | | Service | Exposes pods to internal/external traffic | | Node | Worker machine running pods | | Cluster | Set of nodes managed together |

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Basic YAML Example

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: app
        image: my-app:1.0
        ports:
        - containerPort: 3000
---
apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  selector:
    app: my-app
  ports:
  - protocol: TCP
    port: 80
    targetPort: 3000
  type: LoadBalancer

Deploy with:

kubectl apply -f deployment.yaml

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Common kubectl Commands

kubectl get pods                    # List all pods
kubectl get services               # List services
kubectl describe pod <pod-name>    # Pod details
kubectl logs <pod-name>            # View logs
kubectl exec -it <pod-name> bash   # Access pod shell
kubectl scale deployment my-app --replicas=5  # Scale up
kubectl rollout status deployment/my-app      # Check deployment status

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Rolling Deployment Example

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api-deployment
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  selector:
    matchLabels:
      app: api
  template:
    metadata:
      labels:
        app: api
    spec:
      containers:
      - name: api
        image: my-api:2.0
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"

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Related Concepts to Explore

• Helm (package management for k8s)
• Ingress (advanced routing)
• StatefulSets (for stateful applications)
• ConfigMaps and Secrets (configuration management)
• Persistent volumes (data persistence)

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Summary

Kubernetes automates container orchestration at scale. Master pods, deployments, and services to reliably run and manage containerized applications in production environments.