Kubernetes Deploying

Deploy and manage applications on Kubernetes.

Core Resources

Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-app
          image: my-registry/my-app:v1.2.3
          ports:
            - containerPort: 3000
          resources:
            requests:
              cpu: 100m
              memory: 128Mi
            limits:
              cpu: 500m
              memory: 512Mi
          livenessProbe:
            httpGet:
              path: /healthz
              port: 3000
            initialDelaySeconds: 10
            periodSeconds: 30
          readinessProbe:
            httpGet:
              path: /ready
              port: 3000
            initialDelaySeconds: 5
            periodSeconds: 10
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: my-app-secrets
                  key: database-url
            - name: NODE_ENV
              value: production

Service

apiVersion: v1
kind: Service
metadata:
  name: my-app
spec:
  selector:
    app: my-app
  ports:
    - port: 80
      targetPort: 3000
  type: ClusterIP

Ingress

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  tls:
    - hosts:
        - app.example.com
      secretName: my-app-tls
  rules:
    - host: app.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app
                port:
                  number: 80

ConfigMap & Secret

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-app-config
data:
  LOG_LEVEL: info
  FEATURE_FLAGS: '{"darkMode": true}'
---
apiVersion: v1
kind: Secret
metadata:
  name: my-app-secrets
type: Opaque
stringData:
  database-url: postgresql://user:pass@host:5432/db
  api-key: sk-abc123

Common Commands

# Apply manifests
kubectl apply -f k8s/

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

# View pods
kubectl get pods -l app=my-app

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

# Execute into a pod
kubectl exec -it <pod-name> -- /bin/sh

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

# Rollback
kubectl rollout undo deployment/my-app

# Port forward for local debugging
kubectl port-forward svc/my-app 3000:80

Deployment Strategies

Strategy	How	When
Rolling update (default)	Replace pods one at a time	Most deployments
Recreate	Kill all old pods, start new ones	When you can't run two versions simultaneously
Blue/green	Run two full environments, switch traffic	Need instant rollback
Canary	Route small % of traffic to new version	High-risk changes

Rolling update config:

spec:
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0

Health Checks

Always set both:

• livenessProbe: "Is the process healthy?" — restarts the pod if it fails
• readinessProbe: "Can it handle traffic?" — removes from service if it fails

Common probe types:

• httpGet: Hit an HTTP endpoint (most common)
• exec: Run a command in the container
• tcpSocket: Check if a port is open

Horizontal Pod Autoscaler

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-app
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-app
  minReplicas: 2
  maxReplicas: 10
  metrics:
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: 70

Tips

• Always set resource requests and limits
• Use namespaces to isolate environments (dev, staging, prod)
• Never put secrets in plaintext YAML committed to git — use Sealed Secrets, SOPS, or external secret managers
• Tag images with specific versions, never use :latest in production
• Set PodDisruptionBudget for high-availability workloads