Kustomize is a Kubernetes-native configuration management tool that offers a template-free way to customize and manage application configurations for Kubernetes deployments. It operates directly on plain YAML manifests, enabling you to create variations of your base configurations (overlays) without altering the original files.

• **Template-Free Customization:** Kustomize introduces a template-free approach to configuration customization, allowing you to modify Kubernetes resources declaratively using simple patches and transformations.
• **Base and Overlays:** Kustomize utilizes a base configuration (representing the common elements of your deployment) and overlays (representing environment-specific customizations). This enables you to create and manage multiple variations of your configuration for different environments (e.g., development, staging, production) without duplicating code.
• **Generators:** Kustomize provides generators for ConfigMaps and Secrets, allowing you to generate these resources from external sources like files or environment variables.
• **Transformers:** Kustomize includes various transformers that enable you to perform common modifications on your Kubernetes manifests, such as adding labels, annotations, or environment variables.
• **Patching:** You can apply patches to specific resources within your base configuration, overriding specific fields or adding additional configuration elements.

• **Simplified Configuration Management:** Kustomize simplifies the management of Kubernetes configurations by providing a declarative and template-free approach to customization.
• **Improved Reusability:** The base and overlay structure promotes reusability of common configuration elements across different environments.
• **Reduced Complexity:** Kustomize eliminates the need for complex templating logic, making your configurations easier to read and maintain.
• **GitOps Compatibility:** Kustomize's declarative nature makes it well-suited for GitOps workflows, where configuration changes are tracked and managed through Git.

1. **Base Configuration (deployment.yaml):**

```yaml apiVersion: apps/v1 kind: Deployment metadata:

 name: my-app

 replicas: 3
 template:
   spec:
     containers:
     - name: my-app
       image: my-org/my-app:latest

2. **Overlay for Production Environment (production/kustomization.yaml):**

```yaml apiVersion: kustomize.config.k8s.io/v1beta1 kind: Kustomization resources: - ../base/deployment.yaml patchesStrategicMerge: - deployment-patch.yaml ```

3. **Patch File (production/deployment-patch.yaml):**

```yaml apiVersion: apps/v1 kind: Deployment metadata:

 name: my-app

 replicas: 5

In this example, the base configuration defines a Deployment with 3 replicas. The production overlay applies a patch that increases the replica count to 5 for the production environment.

• **Kustomize Official Website:** s://kustomize.io/(https://kustomize.io/)
• **Kustomize GitHub Repository:** s://github.com/kubernetes-sigs/kustomize(https://github.com/kubernetes-sigs/kustomize)
• **Kubernetes Documentation on Kustomize:** s://kubernetes.io/docs/tasks/manage-kubernetes-objects/kustomization/(https://kubernetes.io/docs/tasks/manage-kubernetes-objects/kustomization/)