Corefile

Corefile is the configuration file used by CoreDNS, an extensible DNS server and service discovery system. The Corefile defines how CoreDNS handles DNS queries by composing a chain of plugins that process requests.

Syntax and structure: The Corefile is organized into blocks. Each block starts with a zone identifier, such as a domain name followed by a colon and port (for example example.org:53), or a root block represented by a dot for all queries (. { ... }). Inside the block is a list of plugin directives, one per line, which are executed in order. Plugins may take arguments to customize behavior, such as cache duration, upstream forwarders, or file-based zone data.

Common plugins and concepts: CoreDNS ships with many plugins, including file (zone data from a file), hosts (static mappings), forward (forward unresolved queries to upstream resolvers), cache (response caching), log and errors (diagnostic output), and whoami (answering the queried name). In Kubernetes environments the kubernetes or autopath plugins enable service discovery and name resolution within clusters.

Usage: Corefile is typically mounted into the CoreDNS process at startup and loaded to configure handling of DNS queries. In cloud-native deployments, especially Kubernetes, CoreDNS runs as a pod and the Corefile is stored in a ConfigMap that can be updated to change DNS behavior.

Management: Editing the Corefile and reloading CoreDNS applies changes. Depending on deployment, reload may be automatic when the configuration source changes or may require a process restart or signal.

See also: CoreDNS, DNS, Kubernetes, service discovery.