Overlays

  • Kustomise allows us to take a base Kubernetes config and customise it on a per-environment basis.

    • Tweak on a dev, stg and prod.

  • In kustomize, the k8s/base directory is what is applied to everything.

    • Then in the k8s/overlays directory, this will have directories containing dev, stg and prod with their own kustomization.yaml files and config-map.yaml.
  • The base kustomization file looks like this: ``` resources:
    • nginx-depl.yaml
    • service.yaml
    • redis-depl.yaml ```
  • The base nginx-depl.yaml file looks like this: 
    apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
spec:
replicas: 1
  • An example overlay of /dev/kustomization: ``` bases:
    • ../../base

patch: |- - op: replace path: /spec/replicas value: 2


* We update the value of `replicas` in the above to a value of `2`.

* You can have new configs in your `overlays` set of directories, that weren't defined in the base config.

    * For example under `k8s/overlays/prod`, you can have these files:

kustomization.yaml config-map.yaml grafana-depl.yaml


* The `grafana-depl.yaml` doesn't exist in the base directory.

  * You can add as many brand new resources as you want in an environment specific directory.
  
* The above `grafana-depl.yaml` would be imported using the following:

prod/kustomization.yaml

bases:

  • ../../base

resources:

  • grafana-depl.yaml

patch: |- - op: replace path: /spec/replicas value: 2 ```

  • Kustomise doesn’t force you into a specific directory structure.

  • No need to place everything into the base directory. The sub-directories also do not matter.

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