Add a Zone File to Kubernetes CoreDNS

Internal

• CoreDNS in Kubernetes

Overview

The zone file is added as a ConfigMap entry which will be projected in CoreDNS pods as a file, under the zone file name. The Corefile projected as part of the same ConfigMap should be also modified to refer the new zone file with the "file" directive.

The CoreDNS deployment is then scaled down, the new configuration file is added as an "item" in configMap volume mount, and the deployment is then scaled up.

Procedure

Add the Zone File to ConfigMap

kubectl -n kube-system edit configmap coredns

You should get something similar to:

apiVersion: v1
data:
  Corefile: |
    .:53 {
        errors
        health
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           upstream
           fallthrough in-addr.arpa ip6.arpa
           ttl 30
        }
        prometheus :9153
        forward . /etc/resolv.conf
        cache 30
        loop
        reload
        loadbalance
    }
kind: ConfigMap
metadata:
  annotations:
    ...
  name: coredns
  namespace: kube-system
  ...