Kustomize

Kustomize is a template-free way to customise Kubernetes configuration. It changes a set of manifests without forking them, and it is built into kubectl.

Kustomize reads a base set of Kubernetes manifests and applies changes such as new names, labels or image tags. You can manage several distinct configurations from one base, for example one for each environment. Every file it uses is plain YAML, so the output can be validated and processed like any other manifest. It is available as a standalone binary and as a feature of kubectl through apply -k.

• Template-free changes to YAML manifests
• Built into kubectl as apply -k
• Several configurations from one base
• Standalone binary for other tools
• Plain YAML throughout

Kubernetes users who want to reuse off-the-shelf manifests across environments. Teams that prefer declarative YAML over templating will find the approach easy to read.

Kustomize is open source under the Apache-2.0 licence and is free to use. It is part of the Kubernetes project and ships with kubectl, so there is nothing separate to buy. Overlays can grow complex over time, so keep the layers simple and review the rendered output before you apply it.