Customize Helm Chart values for RKE2 default addons

Rancher 2.6/2.7/2.8
RKE2 downstream cluster

By default, RKE2 installs multiple addons, including CoreDNS, Local-Storage, Nginx-Ingress, etc.:

kubectl -n kube-system get addons

Many of these addons are deployed from a Helm chart and represented within the cluster via a HelmChart custom resource:

kubectl -n kube-system get helmchart

These built-in addons deployed from a Helm chart can be customized with the use of a HelmChartConfig custom resource:

kubectl -n kube-system get helmchartconfig

This is where you can use the Helm chart values to change an addon's default installation.

To edit the values of a Helm chart, you must find the currently installed version. To do this navigate to the RKE2 GitHub repository releases page to find the Packaged Component Versions (https://github.com/rancher/rke2/releases/) for the specific RKE release.

For example, RKE2 1.23.10+rke2r1 uses ingress-nginx 4.1.0 (https://github.com/rancher/rke2/releases/tag/v1.23.10+rke2r1). Checking the values for this version of the ingress-nginx chart  within the ingress-nginx GitHub repository you can determine the possible values
(https://github.com/kubernetes/ingress-nginx/blob/helm-chart-4.1.0/charts/ingress-nginx/values.yaml).

Thus, to add tolerations to the ingress-nginx controller, you can use the below manifest as an example. All of the values from the chart can be customised via this schema.

---
apiVersion: helm.cattle.io/v1
kind: HelmChartConfig
metadata:
  name: rke2-ingress-nginx
  namespace: kube-system
spec:
  valuesContent: |-
    controller:
      tolerations:
        - key: "key"
          operator: "Exists"
          effect: "NoSchedule"

After creating the HelmChartConfig manifest, you need to apply it via Rancher. To do so:
1. Navigate to Cluster Management.
2. On the selected cluster, click Edit Config.
3. Click on the Add-On Config tab and enter the manifest at the bottom in Additional Manifest.