DevOps Lesson 9: Kubernetes Intro

Kubernetes (K8s) orchestrates containers at scale — auto-scaling, self-healing, load balancing across hundreds of servers. The backbone of modern infrastructure.

Core Concepts

// Pod: smallest unit (1+ containers running together)
// Deployment: manages Pods (desired state, rolling updates)
// Service: network access to Pods (load balancing)
// Namespace: virtual clusters within a cluster
// ConfigMap/Secret: configuration and secrets
// Ingress: HTTP routing from outside the cluster

Deployment YAML

# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-api
spec:
  replicas: 3          # run 3 copies!
  selector:
    matchLabels:
      app: my-api
  template:
    metadata:
      labels:
        app: my-api
    spec:
      containers:
        - name: api
          image: myapp:1.0
          ports:
            - containerPort: 3000
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: app-secrets
                  key: database-url
          resources:
            requests: { cpu: "100m", memory: "128Mi" }
            limits: { cpu: "500m", memory: "512Mi" }
---
apiVersion: v1
kind: Service
metadata:
  name: my-api-service
spec:
  selector:
    app: my-api
  ports:
    - port: 80
      targetPort: 3000
  type: LoadBalancer

kubectl Commands

kubectl apply -f deployment.yaml    # deploy
kubectl get pods                     # list pods
kubectl logs my-api-abc123          # view logs
kubectl exec -it my-api-abc sh      # shell into pod
kubectl scale deployment my-api --replicas=5  # scale!
kubectl rollout status deployment/my-api
kubectl rollout undo deployment/my-api  # roll back!