LAB14b: Kustomize (Overlay / Patching Approach)

LAB 500b: Use Kustomize to deploy helloworld

Directory Structure

helloworld-app/
 ├── base/
 │   ├── configmap.yaml
 │   ├── deployment.yaml
 │   ├── service.yaml
 │   ├── ingress.yaml
 │   └── kustomization.yaml
 ├── dev/
 │   ├── index.html
 │   ├── kustomization.yaml
 │   └── patch-ingress.yaml
 └── prod/
     ├── index.html
     ├── kustomization.yaml
     └── patch-ingress.yaml

✔ Dev & Prod each maintain their own index.html ✔ Overlays override ConfigMap content ✔ Avoids repeating YAML (DRY principle)

BASE (Shared across dev + prod)

This folder contains all common manifests. Environments override only what they need.

base/configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: website-config
data:
  index.html: "HELLO FROM BASE"

The content will be replaced in overlays.

base/deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: website
  labels:
    app: website
spec:
  replicas: 1
  selector:
    matchLabels:
      app: website
  template:
    metadata:
      labels:
        app: website
    spec:
      containers:
      - name: website
        image: nginx
        volumeMounts:
        - name: html
          mountPath: /usr/share/nginx/html
      volumes:
      - name: html
        configMap:
          name: website-config

base/service.yaml

apiVersion: v1
kind: Service
metadata:
  name: website-svc
spec:
  selector:
    app: website
  ports:
    - port: 80

base/ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: website-ing
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: website-svc
            port:
              number: 80

base/kustomization.yaml

resources:
  - configmap.yaml
  - deployment.yaml
  - service.yaml
  - ingress.yaml

DEV Overlay

dev/index.html

Hello from Dev Environment

dev/kustomization.yaml

namespace: hello-dev

nameSuffix: -dev

commonLabels:
  env: dev

resources:
  - ../base

patches:
  - path: patch-ingress.yaml

configMapGenerator:
  - name: website-config
    behavior: replace
    files:
      - index.html=./index.html

✔ Injects dev HTML ✔ Adds namespace, suffix, labels ✔ Replaces ConfigMap ✔ No TLS patch

dev/patch-ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: website-ing
spec:
  rules:
  - host: dev.hello-world.xyz

Only overrides host.

PROD Overlay

prod/index.html

Hello from Production Environment

prod/kustomization.yaml

namespace: hello-prod

nameSuffix: -prod

commonLabels:
  env: prod

resources:
  - ../base

patches:
  - path: patch-ingress.yaml

configMapGenerator:
  - name: website-config
    behavior: replace
    files:
      - index.html=./index.html

✔ Injects prod HTML ✔ Replaces ConfigMap content ✔ Enables TLS via ingress patch

prod/patch-ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: website-ing
spec:
  tls:
  - hosts:
    - hello-world.xyz
    secretName: website-tls
  rules:
  - host: hello-world.xyz

Adds:

• TLS section

• Prod domain

How to Deploy (Kustomize)

DEV Deployment

Preview generated YAML:

kubectl kustomize dev/

Apply:

kubectl apply -k dev/

Verify:

kubectl get all -n hello-dev
kubectl get ingress -n hello-dev
kubectl get configmap -n hello-dev -o yaml

---

PROD Deployment

Preview:

kubectl kustomize prod/

Apply:

kubectl apply -k prod/

Verify:

kubectl get all -n hello-prod
kubectl get ingress -n hello-prod
kubectl get configmap -n hello-prod -o yaml

---

Clean Up

DEV:

kubectl delete -k dev/

PROD:

kubectl delete -k prod/