kustomize

kustomize lets you customize raw, template-free YAML files for multiple purposes, leaving the original YAML untouched and usable as is. kustomize targets Kubernetes; it understands and can patch Kubernetes style API objects. It's like make, in that what it does is declared in a file, and it's like sed, in that it emits edited text. The kustomize build flow at v2.0.3 was added to kubectl v1.14. The kustomize flow in kubectl remained frozen at v2.0.3 until kubectl v1.21, which updated it to v4.0.5. It will be updated on a regular basis going forward, and such updates will be reflected in the Kubernetes release notes. In some directory containing your YAML resource files (deployments, services, configmaps, etc.), create a kustomization file. The resources in this directory could be a fork of someone else's configuration. If so, you can easily rebase from the source material to capture improvements, because you don't modify the resources directly.