Rotate certificate authorities

Version 1.28 (latest)

• Version 1.28 (latest)
• Version 1.16
• Version 1.15
• Earlier versions (unsupported)

GKE on Bare Metal uses certificates and private keys to authenticate and encrypt connections between system components in clusters. The cluster certificate authority (CA) manages these certificates and keys. When you run the bmctl update credentials certificate-authorities rotate command, GKE on Bare Metal performs the following actions:

• Creates and uploads new cluster certificate authorities (CAs) for the cluster CA, the etcd CA, and the front-proxy CA to the user cluster namespace in the admin cluster.

• The admin cluster controllers replace the user cluster certificate authorities with the newly generated ones.

• The admin cluster controllers distribute the new public CA certificates and leaf certificate key pairs to user cluster system components.

To maintain secure cluster communication, rotate your user cluster CA periodically and whenever there is a possible security breach.

Important: If your cluster certificates have expired, you must renew them manually to regain cluster operation. For more information and instructions, see Renew expired cluster certificates manually.

Before you begin

Before you rotate your cluster's certificate authority, plan according to the following conditions and impacts:

• Ensure admin and user clusters are at version 1.9.0 or higher before starting the CA rotation.

• CA rotation is incremental, allowing system components to communicate during the rotation.

• The CA rotation process restarts the API server, control plane processes, and pods in the user cluster.

• Expect workloads to restart and be rescheduled during CA rotation.

• For non-high-availability cluster configurations, expect brief periods of control plane downtime during CA rotation.

• Cluster management operations aren't allowed during CA rotation.

• CA rotation duration depends on the size of your cluster. For example, CA rotation may take close to two hours to complete for a cluster with one control plane and 50 worker nodes.

Limitations

The certificate authority rotation capability has the following limitations:

• CA rotation doesn't update certificates issued manually by an administrator, even if the cluster CA signs the certificates. Update and redistribute any manually issued certificates after user cluster CA rotation is complete.

• Once started, CA rotation can't be paused or rolled back.

Start a cluster CA rotation

Use the following command to start the CA rotation process:

bmctl update credentials certificate-authorities rotate --cluster CLUSTER_NAME \
    --kubeconfig KUBECONFIG

Replace the following:

• CLUSTER_NAME: the name of the cluster for which you want to rotate CAs.
• KUBECONFIG: the path to the admin cluster kubeconfig file. For self-managing clusters, this file is the cluster's kubeconfig file.

The bmctl command exits after the CA is rotated successfully and a new kubeconfig file is generated. The standard path for the kubeconfig file is bmctl-workspace/CLUSTER_NAME/CLUSTER_NAME-kubeconfig.

Troubleshoot a cluster CA rotation

The bmctl update credentials command displays the progress of the CA rotation. The associated update-credentials.log file is saved to the following timestamped directory:

bmctl-workspace/CLUSTER_NAME/log/update-credentials-TIMESTAMP