Is there any way to use environment variables in kustomization patches?

[devantler]

Note

I am sorry if I am asking something that has already been asked. I was not able to find the information.

I am creating a homelab where I want some of the default values to be dynamic. Can environment variables be read in Kustomization patches? I am thinking something like this:

# The Kustomization file
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources: 
  - ../../base/gitops-dashboard

patches:
  - path: patches/gitops-dashboard-values.yaml
    target:
      kind: HelmRelease
      name: gitops-dashboard

# The patch file
apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: gitops-dashboard
  namespace: flux-system
spec:
  values:
    adminUser:
      username: admin
      passwordHash: $2a$12$6twAYNqxU3Pz3PqVYTJN9uE5LaMDj3R1.TgLvalUoKeLnzKsFkK3i
    ingress:
      hosts:
        - host: gitops.${DOMAIN} # This where/how I would like to use an environment variable if at all possible.
          paths:
            - path: /
              pathType: ImplementationSpecific

If this is not possible in any way, what do you recommend as the best practice to accomplish this?

[makkes]

You can't feed environment variables into Kustomizations (how would kustomization-controller get them?) but you can use post-build substitutions: https://fluxcd.io/flux/components/kustomize/kustomization/#post-build-variable-substitution. This lets you either create multiple Kustomizations with pre-defined .spec.postBuild.substitute values or use a single Kustomization with .spec.postBuild.substituteFrom and create ConfigMaps for each environment.

[devantler]

Thanks - good point! I am a bit new to it all, and was trying to use approaches I have come to like from working a lot with docker-compose :-)

Your suggestion seems very reasonable, I will try it out!

[pallavkanaujiya]

can I also add conditions to post build as well ? if env is test then the value of susbstitute is different..

[stefanprodan]

You can use variables to load a diffrent overlay, example here: https://github.com/controlplaneio-fluxcd/d1-fleet/blob/bd889e6b51db513d20b0fc8bc1117f4e333a0f19/tenants/infra/components/monitoring.yaml#L16