What is a Headless service in Kubernetes?

What is a Headless service in Kubernetes?

• A. A LoadBalancer that has no external IP
• B. A ClusterIP service that has no IP
• C. An ExternalName pointing to a DNS alias
• D. A NodePort without an accessible port

Answer: (B)

Headless services in Kubernetes mean there is no single internal IP (ClusterIP) for the service. This is achieved by setting clusterIP to None in the service spec. Without a ClusterIP, DNS for the service resolves to the individual pod IPs (the endpoints), so clients can connect directly to each pod rather than through a shared virtual IP. This pattern is useful for applications that need direct pod addressing or rely on per-pod DNS records, such as StatefulSets. The option that matches this behavior is describing a ClusterIP service with no IP, i.e., clusterIP set to none. The other descriptions refer to different service types or DNS behavior and do not define a headless service: a LoadBalancer without an external IP still provides a load-balanced endpoint; ExternalName maps the service to an external DNS name; NodePort exposes a port on each node rather than exposing pod endpoints via DNS.

Headless services in Kubernetes mean there is no single internal IP (ClusterIP) for the service. This is achieved by setting clusterIP to None in the service spec. Without a ClusterIP, DNS for the service resolves to the individual pod IPs (the endpoints), so clients can connect directly to each pod rather than through a shared virtual IP. This pattern is useful for applications that need direct pod addressing or rely on per-pod DNS records, such as StatefulSets.

The option that matches this behavior is describing a ClusterIP service with no IP, i.e., clusterIP set to none. The other descriptions refer to different service types or DNS behavior and do not define a headless service: a LoadBalancer without an external IP still provides a load-balanced endpoint; ExternalName maps the service to an external DNS name; NodePort exposes a port on each node rather than exposing pod endpoints via DNS.