Kubernetes CRD Demo

Building a Kubernetes Custom Resource Definition (CRD) following professional patterns.

🎯 What we'll Learn

• How to define custom resources using Go types
• How Kubernetes code generation works
• How to install and use custom resources
• Professional patterns used by major Kubernetes tools

📋 Prerequisites

• Kubernetes cluster (kind, minikube, or any K8s cluster)
• kubectl installed and configured

📋 The 3-Step Process

Step 1: Define the CRD Go Type

Create Go structs that define your custom resource schema

Step 2: Generate Boilerplate Code

Use Kubernetes code generators to create client libraries automatically

Step 3: Install the CRD into the Cluster

Register your custom resource type with Kubernetes

k8s code generator

This project uses Kubernetes code-generator to generate clients, informers, and listers for the NamespaceCleaner CRD. Starting with Kubernetes 1.30+ (code-generator v0.30.x+), generate-groups.sh has been removed. To make code generation work, I have pin code-generator to v0.27.3 or lower:

go get k8s.io/[email protected]
go mod tidy

Then you can generate your CRD clients by running:

./hack/update-codegen.sh

Quick Start

1. Generate the code

bash hack/update-codegen.sh

2. Install the CRD

kubectl apply -f config/crd/namespacecleaners.yaml

3. Create a NamespaceCleaner

kubectl apply -f example-namespacecleaner.yaml

4. Check it works

kubectl get namespacecleaners

Files

• pkg/apis/clusterops/v1alpha1/types.go - Go type definitions
• pkg/apis/clusterops/v1alpha1/register.go - API registration
• config/crd/namespacecleaners.yaml - CRD definition
• hack/update-codegen.sh - Code generation script