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Kustomize provides a declarative approach to customize Kubernetes manifests without templates. It allows you to maintain a base configuration and create environment-specific overlays.

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Installing Kustomize

1

Download Kustomize

Use the official installation script:
curl -s "https://raw.githubusercontent.com/kubernetes-sigs/kustomize/master/hack/install_kustomize.sh" | bash
2

Install to System Path

Move Kustomize to a directory in your PATH:
sudo install -o root -g root -m 0755 kustomize /usr/local/bin/kustomize
3

Verify Installation

Check the installed version:
kustomize version

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Directory Structure

Create an organized directory structure for base and overlays: 
mkdir -p ~/myapp/{base,overlays/{dev,prod}}
Your structure should look like: 
myapp/
├── base/
│   ├── deployment.yaml
│   ├── service.yaml
│   └── kustomization.yaml
└── overlays/
    ├── dev/
    │   ├── kustomization.yaml
    │   ├── deployment-dev.yaml
    │   └── service-dev.yaml
    └── prod/
        ├── kustomization.yaml
        ├── deployment-prod.yaml
        └── service-prod.yaml

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Creating Base Configuration

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Base Deployment

~/myapp/base/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

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Base Service

~/myapp/base/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: web-service
spec:
  selector:
    app: web
  ports:
    - name: http
      port: 80

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Base Kustomization

~/myapp/base/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- deployment.yaml
- service.yaml

commonLabels:
  company: networknuts

namespace: default
namePrefix: bike-
nameSuffix: -dev

commonAnnotations:
  branch: master

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Development Overlay

1

Create Namespace

~/myapp/overlays/dev/namespace.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev
2

Create Deployment Patch

~/myapp/overlays/dev/deployment-dev.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-deployment
spec:
  replicas: 3
  template:
    spec:
      containers:
      - name: nginx
        resources:
          limits:
            cpu: "200m"
            memory: "256Mi"
          requests:
            cpu: "100m"
            memory: "128Mi"
3

Create Service Patch

~/myapp/overlays/dev/service-dev.yaml
apiVersion: v1
kind: Service
metadata:
  name: web-service
spec:
  type: NodePort
4

Create Dev Kustomization

~/myapp/overlays/dev/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

namespace: dev
namePrefix: dev-

resources:
- ../../base
- namespace.yaml

patches:
- path: deployment-dev.yaml
- path: service-dev.yaml

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Production Overlay

apiVersion: v1
kind: Namespace
metadata:
  name: prod

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Building and Applying

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Preview Changes

Build and preview the manifests before applying: 
cd ~/myapp
kustomize build overlays/dev
kustomize build overlays/prod

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Apply to Cluster

kubectl apply -k overlays/dev
Kubectl has built-in Kustomize support. You can use kubectl apply -k instead of building first with the kustomize binary.

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Key Features

Kustomize supports strategic merge patches and JSON patches to modify resources without duplicating the entire configuration.
Automatically add prefixes or suffixes to resource names to distinguish between environments.
Apply labels and annotations across all resources in a single place.
Generate ConfigMaps and Secrets from files or literals with automatic hash suffixes for rolling updates.
Kustomize promotes a purely declarative approach. There’s no templating language to learn - just YAML patches and overlays.

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