kubedns

kubedns is the DNS add-on for Kubernetes clusters that provides name resolution for services and pods inside the cluster. It enables clients within the cluster to reach services using DNS names such as myservice.default.svc.cluster.local, rather than relying on IP addresses.

Operational overview: kubedns runs as a pod (or set of pods) in the kube-system namespace and is exposed via a cluster-wide DNS service. It watches the Kubernetes API for changes to services and endpoints and updates its DNS records in real time. When a pod makes a DNS query to the cluster DNS service, kubedns resolves the name to the appropriate service IP or to pod IPs when applicable. It can also forward queries for external domains to upstream DNS resolvers.

Implementation notes: historically the kubedns deployment included the DNS server component based on SkyDNS, often accompanied by a small caching/forwarding layer such as dnsmasq. The result is a straightforward, API-driven DNS service tailored for in-cluster name resolution.

Evolution and usage: CoreDNS has largely superseded kubedns as the default DNS solution in many Kubernetes distributions, offering modular plugins and greater flexibility. Kubedns remains available in older clusters or as an option in some environments.

See also: CoreDNS, Kubernetes DNS.