Kustomize: Using environment variables for configuration
Kustomize is a widely used tool for Kuberenetes config management that provides a template free way to change your manifests during application deployment. It uses a kustomization.yaml file to define the actions taken during the build process. The file itself can be seen a collection of optional ordered processes: resources, generators, transformers, validators, configMapGenerator, patches and so on.
We wont dive too deep into these but look at a specific way of using the transformer property to use configuration values (as environment variables) from a file to drive your configuration.