What is CRD (Custom Resource Definition)?
A Kubernetes extension mechanism for defining custom object types.
A Custom Resource Definition (CRD) extends the Kubernetes API with new resource types. Once a CRD is installed, you can create, update, and delete instances of the new resource type using kubectl just like built-in resources. CRDs are the foundation of the Operator pattern — tools like ArgoCD, Cert-Manager, and Prometheus Operator all define CRDs for their domain objects (Application, Certificate, PrometheusRule, etc.).
Related Terms
More Kubernetes Terms
Admission Controller
A Kubernetes plugin that intercepts API requests before objects are persisted.
Auto Scaling
Automatically adjusting the number of compute resources based on demand.
ClusterIP
The default Kubernetes Service type that exposes a service on an internal cluster IP.
ConfigMap
A Kubernetes object for storing non-sensitive configuration data as key-value pairs.
Controller Manager
Kubernetes control plane component running control loops to maintain desired state.
CoreDNS
The default DNS server in Kubernetes clusters for service discovery.
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