CoreDNS: Service Discovery and DNS in Kubernetes

A service call fails with "no such host." The service exists, the name looks right, the Pod is running. You check kubectl get svc: it's there. You check the pod logs: it's clearly trying to resolve the name. Nothing obvious is broken, but DNS isn't resolving it.

Every service-to-service call in a Kubernetes cluster goes through CoreDNS. It's the cluster's phonebook. This lesson covers how CoreDNS is deployed, what DNS records it maintains, how the Corefile plugin chain works, and how ndots:5 shapes every name resolution in your cluster. For custom Corefile configuration, stub domains, and a step-by-step troubleshooting runbook, see DNS Troubleshooting and Custom CoreDNS Configuration.