Diegolden

Topic 1: Custom Resources

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Topic 1: Custom Resources

Official baseline: (The Kubernetes Authors, 2026a, 2026b). My working version: A Custom Resource adds a new API shape. It becomes useful when a controller reconciles it.

Mental Model

A Custom Resource adds a new API shape. It becomes useful when a controller reconciles it.

Notes

  • CRDs extend the API but do not automatically add behavior.
  • Schema quality matters because users will build automation around it.
  • Versioning is a product commitment.

Homelab Angle

Build one small CRD only after you understand the object lifecycle with built-in resources.

Verify It

  • Read the object status before changing the manifest.
  • Check events for the controller or node that is actually complaining.
  • Confirm the official source linked below still matches the cluster version you run.

Common Failure Modes

  • Treating the YAML object as the system, instead of one input to a reconciliation loop.
  • Debugging from outside the cluster when the failure only exists inside cluster networking or node state.
  • Forgetting that Kubernetes version, addon version, and runtime behavior are linked.

Sources

  • Custom Resources - source path: content/en/docs/concepts/extend-kubernetes/api-extension/custom-resources.md, commit 8cc9e19b8eec8d5cf49eacd66f86a81648edb1a0.
  • The Kubernetes API - source path: content/en/docs/concepts/overview/kubernetes-api.md, commit 8cc9e19b8eec8d5cf49eacd66f86a81648edb1a0.
  • Kubernetes documentation is licensed under CC BY 4.0; these notes are original commentary and link back to the official source.
The Kubernetes Authors. (2026a). Custom Resources. https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/
The Kubernetes Authors. (2026b). The Kubernetes API. https://kubernetes.io/docs/concepts/overview/kubernetes-api/

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