Chapter 2. Shutting down the cluster gracefully

Procedure

1. If you plan to shut down the cluster for an extended period of time, determine the date that cluster certificates expire.

   You must restart the cluster prior to the date that certificates expire. As the cluster restarts, the process might require you to manually approve the pending certificate signing requests (CSRs) to recover kubelet certificates.

   1. Check the expiration date for the kube-apiserver-to-kubelet-signer CA certificate:

      $ oc -n openshift-kube-apiserver-operator get secret kube-apiserver-to-kubelet-signer -o jsonpath='{.metadata.annotations.auth\.openshift\.io/certificate-not-after}{"\n"}'

      Example output

      2023-08-05T14:37:50Z

   2. Check the expiration date for the kubelet certificates:

      1. Start a debug session for a control plane node by running the following command:

         $ oc debug node/<node_name>

      2. Change your root directory to /host by running the following command:

         sh-4.4# chroot /host

      3. Check the kubelet client certificate expiration date by running the following command:

         sh-5.1# openssl x509 -in /var/lib/kubelet/pki/kubelet-client-current.pem -noout -enddate

         Example output

         notAfter=Jun  6 10:50:07 2023 GMT

      4. Check the kubelet server certificate expiration date by running the following command:

         sh-5.1# openssl x509 -in /var/lib/kubelet/pki/kubelet-server-current.pem -noout -enddate

         Example output

         notAfter=Jun  6 10:50:07 2023 GMT

      5. Exit the debug session.
      6. Repeat these steps to check certificate expiration dates on all control plane nodes. To ensure that the cluster can restart gracefully, plan to restart it before the earliest certificate expiration date.

2. Shut down all of the nodes in the cluster. You can do this from your cloud provider’s web console, or run the following loop:

   $ for node in $(oc get nodes -o jsonpath='{.items[*].metadata.name}'); do oc debug node/${node} -- chroot /host shutdown -h 1; done 1

   1

   -h 1 indicates how long, in minutes, this process lasts before the control-plane nodes are shut down. For large-scale clusters with 10 nodes or more, set to 10 minutes or longer to make sure all the compute nodes have time to shut down first.

   Example output

   Starting pod/ip-10-0-130-169us-east-2computeinternal-debug ...
   To use host binaries, run `chroot /host`
   Shutdown scheduled for Mon 2021-09-13 09:36:17 UTC, use 'shutdown -c' to cancel.
   
   Removing debug pod ...
   Starting pod/ip-10-0-150-116us-east-2computeinternal-debug ...
   To use host binaries, run `chroot /host`
   Shutdown scheduled for Mon 2021-09-13 09:36:29 UTC, use 'shutdown -c' to cancel.

   Shutting down the nodes using one of these methods allows pods to terminate gracefully, which reduces the chance for data corruption.

   Note

   Adjust the shut down time to be longer for large-scale clusters:

   $ for node in $(oc get nodes -o jsonpath='{.items[*].metadata.name}'); do oc debug node/${node} -- chroot /host shutdown -h 10; done

   Note

   It is not necessary to drain control plane nodes of the standard pods that ship with OpenShift Container Platform prior to shutdown.

   Cluster administrators are responsible for ensuring a clean restart of their own workloads after the cluster is restarted. If you drained control plane nodes prior to shutdown because of custom workloads, you must mark the control plane nodes as schedulable before the cluster will be functional again after restart.

3. Shut off any cluster dependencies that are no longer needed, such as external storage or an LDAP server. Be sure to consult your vendor’s documentation before doing so.

   Important

   If you deployed your cluster on a cloud-provider platform, do not shut down, suspend, or delete the associated cloud resources. If you delete the cloud resources of a suspended virtual machine, OpenShift Container Platform might not restore successfully.