A summary of the steps is as follows:

1. Create or update the Kubernetes secret resource with the new certificate and private key.
2. Create or update the tls-ca Kubernetes secret resource with the root CA certificate (only required when using a private CA).
3. Update the Rancher installation using the Helm CLI.
4. Reconfigure the Rancher agents to trust the new CA certificate.

The details of these instructions are below.

1. Create/update the certificate secret resource

First, concatenate the server certificate followed by any intermediate certificate(s) to a file named tls.crt and provide the corresponding certificate key in a file named tls.key.

If you are switching the install from using the Rancher self-signed certificate or Let’s Encrypt issued certificates, use the following command to create the tls-rancher-ingress secret resource in your Rancher HA cluster:

Alternatively, to update an existing certificate secret:

$ kubectl -n cattle-system create secret tls tls-rancher-ingress \
  --cert=tls.crt \
  --key=tls.key \

2. Create/update the CA certificate secret resource

If the new certificate was signed by a private CA, you will need to copy the corresponding root CA certificate into a file named cacerts.pem and create or update the tls-ca secret in the namespace. If the certificate was signed by an intermediate CA, then the cacerts.pem must contain both the intermediate and root CA certificates (in this order).

To create the initial secret:

$ kubectl -n cattle-system create secret generic tls-ca \
  --from-file=cacerts.pem

To update an existing tls-ca secret:

3. Reconfigure the Rancher deployment

This step is required if Rancher was initially installed with self-signed certificates (ingress.tls.source=rancher) or with a Let’s Encrypt issued certificate (ingress.tls.source=letsEncrypt).

It ensures that the Rancher pods and ingress resources are reconfigured to use the new server and optional CA certificate.

To update the Helm deployment you will need to use the same (--set) options that were used during initial installation. Check with:

$ helm get values rancher -n cattle-system

Also get the version string of the currently deployed Rancher chart:

$ helm ls -A

Upgrade the Helm application instance using the original configuration values and making sure to specify ingress.tls.source=secret as well as the current chart version to prevent an application upgrade.

If the certificate was signed by a private CA, add the argument as well. Also make sure to read the documentation describing the initial installation using custom certificates.

When the upgrade is completed, navigate to https://<Rancher_SERVER>/v3/settings/cacerts to verify that the value matches the CA certificate written in the tls-ca secret earlier.

4. Reconfigure Rancher agents to trust the private CA

This section covers three methods to reconfigure Rancher agents to trust the private CA. This step is required if either of the following is true:

• Rancher was initially configured to use the Rancher self-signed certificate (ingress.tls.source=rancher) or with a Let’s Encrypt issued certificate (ingress.tls.source=letsEncrypt)
• The root CA certificate for the new custom certificate has changed

Method 1 is the easiest one but requires all clusters to be connected to Rancher after the certificates have been rotated. This is usually the case if the process is performed right after updating the Rancher deployment (Step 3).

If the clusters have lost connection to Rancher but you have Authorized Cluster Endpoints enabled, then go with method 2.

Method 3 can be used as a fallback if method 1 and 2 are unfeasible.

For each cluster under Rancher management (except the local Rancher management cluster) run the following command using the Kubeconfig file of the Rancher management cluster (RKE or K3S).

kubectl patch clusters.management.cattle.io <REPLACE_WITH_CLUSTERID> -p '{"status":{"agentImage":"dummy"}}' --type merge

This command will cause all Agent Kubernetes resources to be reconfigured with the checksum of the new certificate.

Manually patch the agent Kubernetes resources by updating the CATTLE_CA_CHECKSUM environment variable to the value matching the checksum of the new CA certificate. Generate the new checksum value like so:

Using a Kubeconfig for each downstream cluster update the environment variable for the two agent deployments.

With this method you are recreating the Rancher agents by running a set of commands on a controlplane node of each downstream cluster.

Then, connect to a controlplane node of the downstream cluster via SSH, create a Kubeconfig and apply the definitions: