In this article we are going to cover What is Kustomize? Different Tools to Practice Kustomize.
Kustomize is a powerful tool for managing Kubernetes configurations, enabling developers to customize YAML manifests without resorting to templating. Whether you’re a beginner or an experienced Kubernetes user, practicing Kustomize can improve your workflow for managing configurations across multiple environments. This article explores how to practice Kustomize effectively and the tools that can aid your journey.
Table of Contents
What is Kustomize?
Kustomize is a native Kubernetes tool for customizing application configurations. Unlike templating solutions like Helm, Kustomize works with declarative YAML files, maintaining readability and reducing complexity.
Key Benefits of using Kubernetes configuration using Kustomize
- Declarative and template-free configuration management.
- Environment-specific customization without duplicating base manifests.
- Integrated directly into
kubectl, ensuring seamless usage.
Setting Up Your Environment for Kustomize
Before practicing Kustomize, ensure you have the following:
- A Kubernetes cluster: Use tools like Minikube or kind to create a local cluster.
- Installed tools: Ensure kubectl and Kustomize CLI are installed on your system.
How to Install Kustomize?
- Install
kubectlusing package managers like apt, yum, or brew. - Download and install the Kustomize CLI from the official Github Repository.
Getting Started with Kustomize
Core Concepts
- Base: Core YAML configuration applicable to all environments.
- Overlays: Environment-specific modifications layered on top of the base.
- Resources: The actual Kubernetes objects managed by Kustomize.
Example Workflow:
Let’s assume you’re deploying a web application with the following files:
Kustomize directory structure:
.
├── base
│ ├── deployment.yaml
│ ├── kustomization.yaml
│ └── service.yaml
└── overlays
└── dev
├── deployment-patch.yaml
└── kustomization.yamlBase Configuration (base/deployment.yaml):
apiVersion: apps/v1
kind: Deployment
metadata:
name: web-app
spec:
replicas: 2
selector:
matchLabels:
app: web-app
template:
metadata:
labels:
app: web-app
spec:
containers:
- name: web-app
image: nginx:1.21
ports:
- containerPort: 80Base Configuration (base/service.yaml):
apiVersion: v1
kind: Service
metadata:
name: web-app-service
spec:
selector:
app: web-app
ports:
- protocol: TCP
port: 80
targetPort: 80
type: ClusterIP
Customization File (base/kustomization.yaml):
resources:
- deployment.yaml
- service.yaml
Creating Overlays:
For a development environment, you might modify the replicas and add a custom tag.
Overlay (overlays/dev/kustomization.yaml):
resources:
- ../../base
patchesStrategicMerge:
- deployment-patch.yaml
Patch File (overlays/dev/deployment-patch.yaml):
apiVersion: apps/v1
kind: Deployment
metadata:
name: web-app
spec:
replicas: 1
template:
spec:
containers:
- name: web-app
image: nginx:1.21-dev
To apply the development configuration:
kubectl apply -k overlays/dev
How to Practice Kustomize?
ConfigMap and Secret Generators using Kustomize
Use Kustomize to dynamically create ConfigMaps and Secrets.
Example (base/kustomization.yaml):
resources:
- deployment.yaml
- service.yaml
# ConfigMap generator for app configuration
configMapGenerator:
- name: app-config
literals:
- APP_ENV=production
- APP_DEBUG=false
# Secret generator for database credentials
secretGenerator:
- name: db-credentials
literals:
- DB_USER=admin
- DB_PASSWORD=securepassword
Updated Configuration (base/deployment.yaml):
apiVersion: apps/v1
kind: Deployment
metadata:
name: web-app
spec:
replicas: 2
selector:
matchLabels:
app: web-app
template:
metadata:
labels:
app: web-app
spec:
containers:
- name: web-app
image: nginx:1.21
envFrom:
- configMapRef:
name: app-config
- secretRef:
name: db-credentials
ports:
- containerPort: 80
Reapply the changes with:
kubectl apply -k .Result
ConfigMaps and Secrets will be generated and applied without maintaining separate YAML files.
Use kustomize build to Preview the Final Resources:
You can run kustomize build in the base directory to see how your resources (ConfigMap, Secret, and Deployment) will be applied by Kustomize.
kustomize build .Example Result:
apiVersion: v1
data:
APP_DEBUG: "false"
APP_ENV: production
kind: ConfigMap
metadata:
name: app-config-4m6tkk8md8
---
apiVersion: v1
data:
DB_PASSWORD: c2VjdXJlcGFzc3dvcmQ=
DB_USER: YWRtaW4=
kind: Secret
metadata:
name: db-credentials-fmd58tg5tc
type: Opaque
---
apiVersion: v1
kind: Service
metadata:
name: web-app-service
spec:
ports:
- port: 80
protocol: TCP
targetPort: 80
selector:
app: web-app
type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: web-app
spec:
replicas: 2
selector:
matchLabels:
app: web-app
template:
metadata:
labels:
app: web-app
spec:
containers:
- envFrom:
- configMapRef:
name: app-config-4m6tkk8md8
- secretRef:
name: db-credentials-fmd58tg5tc
image: nginx:1.21
name: web-app
ports:
- containerPort: 80Different Tools to Practice Kustomize
Local Clusters
- Minikube: A simple way to run a Kubernetes cluster locally.
- kind: Lightweight and ideal for testing Kustomize configurations.
Cluster Management
- Lens: Visualizes and manages clusters while allowing you to test Kustomize overlays.
Integration Tools
- kubectl kustomize: Built into
kubectl, enabling direct use of Kustomize configurations.
Online Platforms
- Katacoda: Interactive Kubernetes and Kustomize learning environments.
- Play with Kubernetes: Cloud-hosted clusters for practicing YAML configurations.
Conclusion:
Kustomize simplifies managing Kubernetes configurations, and practicing its features can help you deploy applications efficiently. By leveraging tools like Minikube, Lens, and CI/CD pipelines, you can explore and master Kustomize for real-world applications.
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