Kustomize

Kustomize is a tool for customizing Kubernetes configurations. It allows you to customize and manage Kubernetes configurations without modifying the original YAML files directly.

Key Concepts

• Kustomization: A file that defines how to customize Kubernetes resources.
• Base: A directory containing base Kubernetes resources.
• Overlay: A directory containing customized Kubernetes resources.

Installing Kustomize

You can install Kustomize by following the instructions on the official Kustomize website. Here is a quick example for installing Kustomize on a Linux system:

curl -s "https://raw.githubusercontent.com/kubernetes-sigs/kustomize/master/hack/install_kustomize.sh" | bash

Example: Creating a Kustomization

You can create a Kustomization file using the following command:

kustomize create --resources deployment.yaml,service.yaml

Example: Building a Kustomization

You can build a Kustomization using the following command:

kustomize build .

Example: Applying a Kustomization

You can apply a Kustomization using the following command:

kustomize build . | kubectl apply -f -
kubectl apply -k .

Kustomization File Example

kustomization.yaml

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- deployment.yaml
- service.yaml
patchesStrategicMerge:
- deployment-patch.yaml
images:
- name: my-app
  newTag: v2.0.0
configMapGenerator:
- name: my-config
  literals:
  - key1=value1
  - key2=value2

Example: Directory Structure

my-app/
├── base/
│   ├── deployment.yaml
│   ├── service.yaml
│   └── kustomization.yaml
└── overlays/
    ├── dev/
    │   └── kustomization.yaml
    └── prod/
        └── kustomization.yaml

In this example, the base directory contains the base Kubernetes resources, and the overlays directory contains customized resources for different environments (dev and prod).

Example: Overlay Kustomization

In the overlays/dev/kustomization.yaml file, you can specify customizations for the dev environment:

bases:
- ../../base
patchesStrategicMerge:
- deployment-patch.yaml

This overlay applies a patch to the base deployment for the dev environment.