Alauda Container Platform

Kustomize

Introduction

Kustomize is a Kubernetes-native configuration management tool that enables users to customize Kubernetes resource definitions (YAML files) through overlays and composition without directly modifying original files.

Core Concepts of Kustomize

  • Base: Base configurations containing common Kubernetes resource definitions.
  • Overlay: Customization layers that modify Base configurations.
  • kustomization.yaml: A configuration file defining how resources are composed and modified.

Argo CD's integration with Kustomize enhances GitOps practices by enabling declarative continuous delivery. Example:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: kustomize-example
spec:
  project: default
  source:
    path: examples/helloWorld
    repoURL: 'https://github.com/kubernetes-sigs/kustomize'
    targetRevision: HEAD
  destination:
    namespace: default
    server: 'https://kubernetes.default.svc'

If a kustomization.yaml file exists at the repoURL and path location, Argo CD will render manifests using Kustomize.

Kustomize supports the following configuration options:

  • namePrefix: Prefix appended to Kustomize-generated resource names.
  • nameSuffix: Suffix appended to Kustomize-generated resource names.
  • images: List of Kustomize image overrides.
  • replicas: List of Kustomize replica overrides.
  • commonLabels: Map of labels added to all resources.
  • labelWithoutSelector: Boolean defining whether common labels should apply to resource selectors and templates.
  • forceCommonLabels: Boolean allowing override of existing labels.
  • commonAnnotations: Map of annotations added to all resources.
  • namespace: Kubernetes resource namespace.
  • forceCommonAnnotations: Boolean allowing override of existing annotations.
  • commonAnnotationsEnvsubst: Boolean enabling environment variable substitution in annotation values.
  • patches: List of Kustomize patches supporting inline updates.
  • components: List of Kustomize components.

To use Kustomize with overlays, point your path to the overlay directory.

Advantages

  • Declarative Configuration: Uses YAML files (via kustomization.yaml) to define resource composition and modifications.

  • Template-Free: Customizes configurations through patches and overlays without template engines.

  • Kubernetes-Native Integration: Kustomize is built into kubectl, requiring no additional tools.

Use Cases

  • Multi-Environment Distribution: Achieve environment-specific configurations (e.g., apps, clusters) via Base and Overlay.

  • Configuration Reuse: Ideal for reusing base configurations across projects.

  • Progressive Delivery: Gradually adjust resource configurations through patches.

References

For more detailed information, please refer to: Kustomize

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