CoreDNS is a DNS server that chains plugins
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README.md

CoreDNS

Documentation Build Status Code Coverage Go Report Card FOSSA Status CII Best Practices

CoreDNS is a DNS server that started as a fork of Caddy. It has the same model: it chains plugins.

CoreDNS is a Cloud Native Computing Foundation inception level project.

CoreDNS is the successor to SkyDNS. SkyDNS is a thin layer that exposes services in etcd in the DNS. CoreDNS builds on this idea and is a generic DNS server that can talk to multiple backends (etcd, kubernetes, etc.).

CoreDNS aims to be a fast and flexible DNS server. The keyword here is flexible: with CoreDNS you are able to do what you want with your DNS data. And if not: write a plugin!

CoreDNS can listen for DNS request coming in over UDP/TCP (go’old DNS), TLS (RFC 7858) and gRPC (not a standard).

Currently CoreDNS is able to:

  • Serve zone data from a file; both DNSSEC (NSEC only) and DNS are supported (file).
  • Retrieve zone data from primaries, i.e., act as a secondary server (AXFR only) (secondary).
  • Sign zone data on-the-fly (dnssec).
  • Load balancing of responses (loadbalance).
  • Allow for zone transfers, i.e., act as a primary server (file).
  • Automatically load zone files from disk (auto).
  • Caching (cache).
  • Health checking endpoint (health).
  • Use etcd as a backend, i.e., a 101.5% replacement for SkyDNS (etcd).
  • Use k8s (kubernetes) as a backend (kubernetes).
  • Serve as a proxy to forward queries to some other (recursive) nameserver (proxy).
  • Provide metrics (by using Prometheus) (metrics).
  • Provide query (log) and error (error) logging.
  • Support the CH class: version.bind and friends (chaos).
  • Profiling support (pprof).
  • Rewrite queries (qtype, qclass and qname) (rewrite).
  • Echo back the IP address, transport and port number used (whoami).

Each of the plugins has a README.md of its own.

Status

CoreDNS can be used as an authoritative nameserver for your domains. All in all, CoreDNS should be able to provide you with enough functionality to replace parts of BIND 9, Knot, NSD or PowerDNS and SkyDNS. Most documentation is in the source and blog articles can be found here. If you do want to use CoreDNS in production, please let us know.

Compilation

CoreDNS (as a servertype plugin for Caddy) has a dependency on Caddy, but this is not different than any other Go dependency. If you have the source of CoreDNS checked out in the appropriate place in your GOPATH, get all dependencies:

go get ./...

(You can do the checkout and dependency resolution as a single step with: go get github.com/coredns/coredns.)

And then go build as you would normally do:

go build

This should yield a coredns binary.

Compilation with Docker

CoreDNS requires Go to compile. However, if you already have docker installed and prefer not to setup a Go environment, you could build coredns easily:

$ docker run --rm -i -t -v $PWD:/go/src/github.com/coredns/coredns \
      -w /go/src/github.com/coredns/coredns golang:1.9 make

The above command alone will have coredns binary generated.

Examples

When starting CoreDNS without any configuration, it loads the whoami plugin and starts listening on port 53 (override with -dns.port), it should show the following:

.:53
2016/09/18 09:20:50 [INFO] CoreDNS-001
CoreDNS-001

Any query send to port 53 should return some information; your sending address, port and protocol used.

If you have a Corefile without a port number specified it will, by default, use port 53, but you can override the port with the -dns.port flag:

./coredns -dns.port 1053, runs the server on port 1053.

Start a simple proxy, you’ll need to be root to start listening on port 53.

Corefile contains:

.:53 {
    proxy . 8.8.8.8:53
    log
}

Just start CoreDNS: ./coredns. Then just query on that port (53). The query should be forwarded to 8.8.8.8 and the response will be returned. Each query should also show up in the log.

Serve the (NSEC) DNSSEC-signed example.org on port 1053, with errors and logging sent to stdout. Allow zone transfers to everybody, but specifically mention 1 IP address so that CoreDNS can send notifies to it.

example.org:1053 {
    file /var/lib/coredns/example.org.signed {
        transfer to *
        transfer to 2001:500:8f::53
    }
    errors
    log
}

Serve example.org on port 1053, but forward everything that does not match example.org to a recursive nameserver and rewrite ANY queries to HINFO.

.:1053 {
    rewrite ANY HINFO
    proxy . 8.8.8.8:53

    file /var/lib/coredns/example.org.signed example.org {
        transfer to *
        transfer to 2001:500:8f::53
    }
    errors
    log
}

IP addresses are also allowed. They are automatically converted to reverse zones:

10.0.0.0/24 {
    # ...
}

Means you are authoritative for 0.0.10.in-addr.arpa..

The netmask must be dividable by 8, if it is not the reverse conversion is not done. This also works for IPv6 addresses. If for some reason you want to serve a zone named 10.0.0.0/24 add the closing dot: 10.0.0.0/24. as this also stops the conversion.

Listening on TLS and for gRPC? Use:

tls://example.org grpc://example.org {
    # ...
}

Specifying ports works in the same way:

grpc://example.org:1443 {
    # ...
}

When no transport protocol is specified the default dns:// is assumed.

Community

Deployment

Examples for deployment via systemd and other use cases can be found in the deployment repository.