Kubernetes Kustomize

Luke Hebert

- 2 minutes read - 233 words

Kustomize is a native Kubernetes configuration management tool that enables declarative, template-free customization of Kubernetes objects using YAML files. Available as a standalone binary and built into kubectl since version 1.14, it supports hierarchical base-and-overlay structures, targeted patches, and built-in generation of ConfigMaps and Secrets, making it a practical choice for managing environment-specific configurations without introducing templating complexity.

Key Features and Concepts

  • Template-free customization: Unlike templating engines, Kustomize works directly with raw, un-templated YAML files, allowing you to modify and patch them without altering the original source.
  • Kustomization file: A kustomization.yaml file defines the resources and the customizations to be applied (e.g., patches, name prefixes, labels, annotations, or the generation of ConfigMaps and Secrets).
  • Bases and overlays: Kustomize supports a hierarchical structure where a “base” defines common resources and configurations, and “overlays” apply environment-specific customizations (e.g., for development, staging, or production environments) on top of the base.
  • Patches: Patches are partial resource declarations that modify specific fields within a base resource, allowing for targeted changes without redefining the entire resource.
  • Built into kubectl: Kustomize functionality is integrated into kubectl, allowing users to build and apply configurations directly using commands like kubectl kustomize <directory> to view resources or kubectl apply -k <directory> to apply them.
  • Declarative approach: Kustomize emphasizes a declarative workflow, where all configurations and transformations are defined in files and can be tracked in source control, promoting consistency and reproducibility.

References