Kubernetes Basics

# Install minikube (local K8s)
brew install minikube

# Start cluster
minikube start

# Enable addons
minikube addons enable ingress
minikube addons enable metrics-server

# Access dashboard
minikube dashboard

# pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  containers:
    - name: app
      image: my-app:latest
      ports:
        - containerPort: 3000
      env:
        - name: NODE_ENV
          value: "production"
      resources:
        requests:
          memory: "128Mi"
          cpu: "100m"
        limits:
          memory: "256Mi"
          cpu: "500m"

kubectl apply -f pod.yaml
kubectl get pods
kubectl logs my-app
kubectl exec -it my-app -- /bin/sh

# deployment.yaml
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:v1.0.0
          ports:
            - containerPort: 3000
          env:
            - name: NODE_ENV
              value: "production"
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: app-secrets
                  key: database-url
          resources:
            requests:
              memory: "128Mi"
              cpu: "100m"
            limits:
              memory: "256Mi"
              cpu: "500m"
          readinessProbe:
            httpGet:
              path: /health
              port: 3000
            initialDelaySeconds: 5
            periodSeconds: 10
          livenessProbe:
            httpGet:
              path: /health
              port: 3000
            initialDelaySeconds: 15
            periodSeconds: 20

kubectl apply -f deployment.yaml
kubectl get deployments
kubectl rollout status deployment/my-app
kubectl scale deployment/my-app --replicas=5

# service.yaml
apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  selector:
    app: my-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3000
  type: ClusterIP  # Internal only

---
# LoadBalancer for external access (cloud)
apiVersion: v1
kind: Service
metadata:
  name: my-app-lb
spec:
  selector:
    app: my-app
  ports:
    - port: 80
      targetPort: 3000
  type: LoadBalancer

# ClusterIP - Internal only (default)
type: ClusterIP

# NodePort - Expose on each node's IP
type: NodePort

# LoadBalancer - Cloud load balancer
type: LoadBalancer

# ExternalName - DNS alias
type: ExternalName

# configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  NODE_ENV: "production"
  LOG_LEVEL: "info"
  API_URL: "https://api.example.com"

---
# secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: app-secrets
type: Opaque
stringData:
  database-url: "postgresql://user:pass@host:5432/db"
  jwt-secret: "super-secret-key"

spec:
  containers:
    - name: app
      envFrom:
        - configMapRef:
            name: app-config
        - secretRef:
            name: app-secrets

# ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: nginx
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app-service
                port:
                  number: 80
          - path: /api
            pathType: Prefix
            backend:
              service:
                name: api-service
                port:
                  number: 80
  tls:
    - hosts:
        - myapp.example.com
      secretName: tls-secret

# hpa.yaml
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-app-hpa
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
    - type: Resource
      resource:
        name: memory
        target:
          type: Utilization
          averageUtilization: 80

# k8s/app.yaml
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  NODE_ENV: "production"

---
apiVersion: v1
kind: Secret
metadata:
  name: app-secrets
type: Opaque
stringData:
  DATABASE_URL: "postgresql://..."

---
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: myregistry/my-app:v1.0.0
          ports:
            - containerPort: 3000
          envFrom:
            - configMapRef:
                name: app-config
            - secretRef:
                name: app-secrets
          resources:
            requests:
              memory: "128Mi"
              cpu: "100m"
            limits:
              memory: "256Mi"
              cpu: "500m"
          readinessProbe:
            httpGet:
              path: /health
              port: 3000
            initialDelaySeconds: 5
          livenessProbe:
            httpGet:
              path: /health
              port: 3000
            initialDelaySeconds: 15

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

---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app-ingress
spec:
  ingressClassName: nginx
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: my-app-service
                port:
                  number: 80

---
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-app-hpa
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

# Apply configuration
kubectl apply -f k8s/

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

# Describe resource
kubectl describe pod my-app-xxx

# Logs
kubectl logs my-app-xxx
kubectl logs -f my-app-xxx  # Follow

# Execute in pod
kubectl exec -it my-app-xxx -- /bin/sh

# Port forward (local testing)
kubectl port-forward service/my-app-service 8080:80

# Rolling update
kubectl set image deployment/my-app app=my-app:v2.0.0
kubectl rollout status deployment/my-app
kubectl rollout undo deployment/my-app  # Rollback