Day 18: Kubernetes – Managing Kubernetes with Kustomize

Introduction to Kustomize

Kubernetes applications often require managing configuration across multiple environments, such as development, staging, and production. Manually handling these configurations can lead to errors and inefficiencies. Kustomize, a Kubernetes-native configuration management tool, simplifies this process by enabling declarative management of Kubernetes configurations without the need for templating.

This guide will explore the key features of Kustomize, how it works, and practical examples to demonstrate its benefits.

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What is Kustomize?

Kustomize is a configuration management tool built into kubectl. It provides a way to customize Kubernetes configurations using overlays, which modify existing base configurations without altering the original files.

Key Features of Kustomize:

1. No Templating: Declarative and straightforward configuration management without embedding logic.
2. Overlays: Manage environment-specific configurations (e.g., dev, staging, prod) using overlays.
3. Native Integration: Directly supported by kubectl.
4. Reusability: Base configurations can be reused across multiple environments.

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Installing Kustomize

Kustomize is integrated with kubectl starting from version 1.14. However, you can also install it as a standalone tool if needed.

Verify Kustomize with kubectl:

kubectl kustomize --help

Install Standalone Kustomize:

If you need the standalone version, download it from the official Kustomize GitHub releases page.

curl -Lo kustomize https://github.com/kubernetes-sigs/kustomize/releases/latest/download/kustomize
chmod +x kustomize
mv kustomize /usr/local/bin/

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Core Concepts in Kustomize

1. Base Configuration

A base configuration contains the common Kubernetes manifests used across environments.

2. Overlays

Overlays extend or modify base configurations for specific environments (e.g., dev, staging, prod).

3. Kustomization File

The kustomization.yaml file defines resources, patches, and transformations for a configuration.

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Example: Using Kustomize

Directory Structure

kustomize-demo/
├── base/
│   ├── deployment.yaml
│   ├── service.yaml
│   └── kustomization.yaml
├── overlays/
    ├── dev/
    │   ├── kustomization.yaml
    │   └── patch.yaml
    └── prod/
        ├── kustomization.yaml
        └── patch.yaml

Base Configuration

base/deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app
        image: nginx:latest
        ports:
        - containerPort: 80

base/service.yaml

apiVersion: v1
kind: Service
metadata:
  name: my-app
spec:
  selector:
    app: my-app
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

base/kustomization.yaml

resources:
- deployment.yaml
- service.yaml

Overlay for Development Environment

overlays/dev/kustomization.yaml

resources:
- ../../base

patchesStrategicMerge:
- patch.yaml

overlays/dev/patch.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 1
  template:
    spec:
      containers:
      - name: my-app
        image: nginx:dev

Applying the Configuration

1. Navigate to the overlay directory:cd overlays/dev
2. Apply the configuration using kubectl:kubectl apply -k .

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Best Practices for Kustomize

1. Organize Configurations: Maintain a clear directory structure for base and overlay files.
2. Use Strategic Merge Patches: Modify only the necessary parts of the configuration.
3. Leverage Generators: Use built-in generators for ConfigMaps and Secrets.
4. Avoid Overloading Bases: Keep base configurations simple and reusable.
5. Validate Configurations: Test overlays in isolated environments before applying them in production.

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Conclusion

Kustomize simplifies Kubernetes configuration management by enabling declarative, reusable, and environment-specific customizations. With its native integration into kubectl, it’s a powerful tool for streamlining your Kubernetes workflows.

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References

• Kustomize Documentation
• Kustomize GitHub Repository

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Feedback and Discussion

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