Add additional server without overwriting the default one

[maxnitze]

Is it somehow possible to add an additional server to the Corefile without overwriting the default server?

The default values for servers are:

servers:
- zones:
  - zone: .
  port: 53
  # If serviceType is nodePort you can specify nodePort here
  # nodePort: 30053
  plugins:
  - name: errors
  # Serves a /health endpoint on :8080, required for livenessProbe
  - name: health
    configBlock: |-
      lameduck 5s
  # Serves a /ready endpoint on :8181, required for readinessProbe
  - name: ready
  # Required to query kubernetes API for data
  - name: kubernetes
    parameters: cluster.local in-addr.arpa ip6.arpa
    configBlock: |-
      pods insecure
      fallthrough in-addr.arpa ip6.arpa
      ttl 30
  # Serves a /metrics endpoint on :9153, required for serviceMonitor
  - name: prometheus
    parameters: 0.0.0.0:9153
  - name: forward
    parameters: . /etc/resolv.conf
  - name: cache
    parameters: 30
  - name: loop
  - name: reload
  - name: loadbalance

With this config the ConfigMap with the Corefile looks like this:

apiVersion: v1
kind: ConfigMap
data:
  Corefile: |-
    .:53 {
        errors
        health  {
            lameduck 5s
        }
        ready
        kubernetes   cluster.local  cluster.local in-addr.arpa ip6.arpa {
            pods insecure
            fallthrough in-addr.arpa ip6.arpa
            ttl 30
        }
        prometheus   0.0.0.0:9153
        forward   . /etc/resolv.conf
        cache   30
        loop
        reload
        loadbalance
    }

I want to add one additional hosts, so that it looks somewhat like this:

apiVersion: v1
kind: ConfigMap
data:
  Corefile: |-
    .:53 {
        errors
        health  {
            lameduck 5s
        }
        ready
        kubernetes   cluster.local  cluster.local in-addr.arpa ip6.arpa {
            pods insecure
            fallthrough in-addr.arpa ip6.arpa
            ttl 30
        }
        prometheus   0.0.0.0:9153
        forward   . /etc/resolv.conf
        cache   30
        loop
        reload
        loadbalance
    }
    my-internal-domain.com:53 {
        hosts {
          10.20.30.40 my-service.my-internal-domain.com
          fallthrough
        }
    }

Unfortunately the nameserver that is provided by the /etc/resolv.conf must not resolve this host. And running my own nameserver on the host (with dnsmasq) does not work well together with CoreDNS.

I got tat least the deployment working by adding another zoneFile. It was successfully mounted to the container, but the name did not resolve afterwards. Maybe I need to register it somewhere?

Thanks in advance!

[maxnitze]

Ok, I did it now with the following:

zoneFiles:
  - filename: my-internal-domain.com.conf
    domain: my-internal-domain.com
    contents: |
      my-internal-domain.com:53 {
          hosts {
            10.20.30.40 my-service.my-internal-domain.com
            fallthrough
          }
      }
extraConfig:
  import:
    parameters: /etc/coredns/my-internal-domain.com.conf

Is this the intended way? It does not feel like it.

[hagaibarel]

Yes, this is the intended way to support additional zone files. I'd love to hear if you comments or suggestions on how make it more clear

[hungran]

https://github.com/coredns/helm/issues/78#issuecomment-1434055772