Add Shared Kubernetes Resource

• Use this when adding or changing resources shared by both clusters through clusters/base/. General GitOps flow is in Runbooks/Kubernetes GitOps Change.

• Pattern

  • Shared resources live under clusters/base/.

  • Each shared component should be a directory with its own kustomization.yaml.

  • Cluster overlays reference the shared directory, not individual files.

• Add a shared component

  • Create a directory:

  • clusters/base/<category>/<component>/

  • Add a kustomization.yaml that lists the component's resource files:

  • apiVersion: kustomize.config.k8s.io/v1beta1
    kind: Kustomization
    resources:
      - resource.yaml

  • Templatize cluster-specific values with Flux substitutions such as ${CLUSTER_NAME} or ${SECRET_DOMAIN} when the parent Flux Kustomization provides them.

  • Reference the shared directory from each cluster overlay:

  • resources:
      - ../../../base/<category>/<component>

  • Add cluster-specific patches in the overlay only when the clusters genuinely differ.

• Constraints

  • Kustomize cannot reference individual files outside the kustomization root. Always reference a directory with its own kustomization.yaml.

  • Flux postBuild.substituteFrom performs variable replacement at deploy time.

  • Variables generally come from the cluster topology/config ConfigMaps and SOPS-encrypted cluster secrets.

• Usually cluster-specific

  • cilium/ BGP peers, IP pools, and Hubble settings.

  • Gateway listeners and routes.

  • Tailscale connector names, routes, and tags.

  • Cloudflare tunnel credentials.

  • Some cert-manager issuers and certificates.

• Validate

  • Build each consuming cluster overlay:

  • kubectl kustomize clusters/folly/<category>
    kubectl kustomize clusters/offsite/<category>

  • If only one cluster consumes the base path today, validate that cluster and note the asymmetry in the PR.

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