Kubernetes Deployment

Last updated: 2025-09-25 02:29:54

Kubernetes Container Orchestration

Kubernetes automates deployment, scaling, and management of containerized applications.

Basic Kubernetes Objects

# Pod definition (pod.yaml)
apiVersion: v1
kind: Pod
metadata:
  name: my-app-pod
  labels:
    app: my-app
spec:
  containers:
  - name: app-container
    image: my-app:latest
    ports:
    - containerPort: 3000
    env:
    - name: NODE_ENV
      value: "production"
    - name: DB_HOST
      valueFrom:
        secretKeyRef:
          name: db-secret
          key: host

# Service definition (service.yaml)
apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  selector:
    app: my-app
  ports:
  - protocol: TCP
    port: 80
    targetPort: 3000
  type: LoadBalancer

Deployments and Scaling

# Deployment definition (deployment.yaml)
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: app-container
        image: my-app:latest
        ports:
        - containerPort: 3000
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 3000
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /ready
            port: 3000
          initialDelaySeconds: 5
          periodSeconds: 5

# Horizontal Pod Autoscaler (hpa.yaml)
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-app-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-app-deployment
  minReplicas: 2
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70

ConfigMaps and Secrets

# ConfigMap (configmap.yaml)
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  app.properties: |
    server.port=3000
    app.name=MyApp
    app.version=1.0.0
  nginx.conf: |
    server {
      listen 80;
      location / {
        proxy_pass http://localhost:3000;
      }
    }

# Secret (secret.yaml)
apiVersion: v1
kind: Secret
metadata:
  name: app-secrets
type: Opaque
data:
  database-url: cG9zdGdyZXM6Ly91c2VyOnBhc3N3b3JkQGRiOjU0MzIvbXlkYg==
  api-key: YWJjZGVmZ2hpams=

# Using ConfigMap and Secret in Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app-deployment
spec:
  template:
    spec:
      containers:
      - name: app-container
        image: my-app:latest
        env:
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: app-secrets
              key: database-url
        - name: API_KEY
          valueFrom:
            secretKeyRef:
              name: app-secrets
              key: api-key
        volumeMounts:
        - name: config-volume
          mountPath: /app/config
      volumes:
      - name: config-volume
        configMap:
          name: app-config

kubectl Commands

# Apply configurations
kubectl apply -f deployment.yaml
kubectl apply -f service.yaml
kubectl apply -f configmap.yaml
kubectl apply -f secret.yaml

# Get resources
kubectl get pods
kubectl get services
kubectl get deployments
kubectl get nodes

# Describe resources
kubectl describe pod my-app-pod
kubectl describe service my-app-service

# Scale deployment
kubectl scale deployment my-app-deployment --replicas=5

# Rolling update
kubectl set image deployment/my-app-deployment app-container=my-app:v2

# Check rollout status
kubectl rollout status deployment/my-app-deployment

# Rollback deployment
kubectl rollout undo deployment/my-app-deployment

# View logs
kubectl logs -f deployment/my-app-deployment
kubectl logs -f pod/my-app-pod

# Execute commands in pod
kubectl exec -it my-app-pod -- /bin/bash

# Port forwarding for debugging
kubectl port-forward service/my-app-service 8080:80

# Delete resources
kubectl delete -f deployment.yaml
kubectl delete pod my-app-pod
kubectl delete service my-app-service