Kubernetes for Developers: Getting Started Guide

Kubernetes felt like magic until it didn't work. Then it felt like torture. Let me simplify the core concepts you actually need to know as a developer.

Why Kubernetes?

• Self-healing: Crashed container? Auto-restarted
• Scaling: More traffic? More containers
• Rolling updates: Deploy without downtime
• Service discovery: Containers find each other

Core Concepts

Pod

Smallest deployable unit. Usually one container per pod.

# pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-app
spec:
  containers:
  - name: app
    image: myapp:1.0
    ports:
    - containerPort: 3000

Deployment

Manages pod replicas. This is what you'll use most.

# 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: myapp:1.0
        ports:
        - containerPort: 3000
        resources:
          limits:
            memory: "256Mi"
            cpu: "500m"

Service

Exposes pods to network traffic.

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

Essential Commands

# Apply configuration
kubectl apply -f deployment.yaml

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

# Describe (for debugging)
kubectl describe pod my-app-xyz123

# View logs
kubectl logs my-app-xyz123
kubectl logs -f my-app-xyz123  # Follow

# Execute command in container
kubectl exec -it my-app-xyz123 -- sh

# Delete resources
kubectl delete -f deployment.yaml

ConfigMaps and Secrets

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

---
# secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: app-secrets
type: Opaque
stringData:
  DATABASE_URL: postgres://...
  JWT_SECRET: mysupersecret

Using in deployment:

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

Local Development

Use Minikube or Docker Desktop Kubernetes:

# Start minikube
minikube start

# Enable dashboard
minikube dashboard

# Build image in minikube's Docker
eval $(minikube docker-env)
docker build -t myapp:1.0 .

Debugging Tips

Pod stuck in Pending:

kubectl describe pod <pod-name>
# Usually: insufficient resources or no matching nodes

Pod in CrashLoopBackOff:

kubectl logs <pod-name> --previous
# Check why the container crashed

Can't connect to service:

kubectl get endpoints <service-name>
# Empty? Your pod labels don't match service selector

What Next?

1. Deploy a simple app locally with Minikube
2. Learn about Ingress for HTTP routing
3. Explore Helm for package management
4. Understand namespaces for environment separation

Kubernetes has a steep learning curve, but modern cloud platforms (GKE, EKS) handle most of the complexity. Focus on understanding the abstractions.