Kubernetes

Container orchestration for deploying and managing applications at scale.

When to Use

• Container orchestration
• Microservices deployment
• Auto-scaling applications
• High-availability setups

Quick Start

# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
        - name: myapp
          image: myapp:1.0.0
          ports:
            - containerPort: 3000
          resources:
            requests:
              memory: "128Mi"
              cpu: "250m"
            limits:
              memory: "256Mi"
              cpu: "500m"

Core Concepts

Service & Ingress

# service.yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp
spec:
  selector:
    app: myapp
  ports:
    - port: 80
      targetPort: 3000
---
# ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: nginx
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp
                port:
                  number: 80

ConfigMap & Secrets

apiVersion: v1
kind: ConfigMap
metadata:
  name: myapp-config
data:
  DATABASE_HOST: postgres.default.svc.cluster.local
  LOG_LEVEL: info
---
apiVersion: v1
kind: Secret
metadata:
  name: myapp-secrets
type: Opaque
stringData:
  DATABASE_PASSWORD: supersecret
  API_KEY: myapikey

Common Patterns

Horizontal Pod Autoscaler

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

Common Commands

# Cluster info
kubectl cluster-info
kubectl get nodes

# Resources
kubectl get pods -A
kubectl get deployments
kubectl describe pod myapp-xxx

# Debugging
kubectl logs myapp-xxx -f
kubectl exec -it myapp-xxx -- sh

# Apply/Delete
kubectl apply -f deployment.yaml
kubectl delete -f deployment.yaml

Best Practices

Do:

• Set resource requests/limits
• Use liveness/readiness probes
• Use namespaces for isolation
• Use Helm for templating

Don't:

• Run as root in containers
• Use latest tag
• Skip resource limits
• Store secrets in ConfigMaps

Troubleshooting

Issue	Cause	Solution
Pod pending	No resources	Check node capacity
CrashLoopBackOff	App crashing	Check logs
ImagePullBackOff	Can't pull image	Check registry/credentials

References

• Kubernetes Documentation
• Helm Documentation