How to customize rke2-coredns

Details on the customization of components via HelmChartConfig resources can be found within the RKE2 documentation. 

In the example below, we will use a HelmChartConfig to add a custom zonefile to rke2-coredns for the domain example.com
 

apiVersion: helm.cattle.io/v1
kind: HelmChartConfig
metadata:
  name: rke2-coredns
  namespace: kube-system
spec:
  valuesContent: |-
    zoneFiles:
      - filename: example.com.conf
        domain: example.com
        contents: |
          example.com:53 {
              errors
              cache 30
              forward . 10.0.254.1
          }
    extraConfig:
      import:
        parameters: /etc/coredns/example.com.conf

Rancher-provisioned RKE2 cluster

To apply this HelmChartConfig customization in a Rancher-provisioned RKE2 cluster, navigate to the Cluster Management view and click Edit Config for the desired cluster. Click the Add-On Config tab and add the HelmChartConfig manifest into the Additional Manifest section, before clicking Save.
 

Standalone RKE2 cluster

Create the file /var/lib/rancher/rke2/server/manifests/rke2-coredns-config.yaml, containing the HelmChartConfig manifest, on a server node within the RKE2 cluster. After that, the rke2-server service on the node should be restarted to apply the change.
 

Verify the customization

In this case, with a customization to the rke2-coredns configuration, the configmap rke2-coredns-rke2-coredns can be reviewed to determine if the change was successful:

kubectl -n kube-system get configmap rke2-coredns-rke2-coredns -o json