Chapter 5. Rebooting the overcloud After a minor Red Hat OpenStack version update, reboot your overcloud. The reboot refreshes the nodes with any associated kernel, system-level, and container component updates. These updates may provide performance and security benefits. Plan downtime to perform the following reboot procedures. 5.1. Rebooting Controller and composable nodes Complete the following steps to reboot Controller nodes and standalone nodes based on composable roles, excluding Compute nodes and Ceph Storage nodes. Procedure Log in to the node that you want to reboot. Optional: If the node uses Pacemaker resources, stop the cluster: Reboot the node: Wait until the node boots. Check the services. For example: If the node uses Pacemaker services, check that the node has rejoined the cluster: If the node uses Systemd services, check that all services are enabled: If the node uses containerized services, check that all containers on the node are active: 5.2. Rebooting a Ceph Storage (OSD) cluster Complete the following steps to reboot a cluster of Ceph Storage (OSD) nodes. Procedure Log in to a Ceph MON or Controller node and disable Ceph Storage cluster rebalancing temporarily: Select the first Ceph Storage node that you want to reboot and log in to the node. Reboot the node: Wait until the node boots. Log in to the node and check the cluster status: Check that the pgmap reports all pgs as normal ( active+clean ). Log out of the node, reboot the node, and check its status. Repeat this process until you have rebooted all Ceph storage nodes. When complete, log into a Ceph MON or Controller node and re-enable cluster rebalancing: Perform a final status check to verify that the cluster reports HEALTH_OK : 5.3. Rebooting Compute nodes Complete the following steps to reboot Compute nodes. To ensure minimal downtime of instances in your Red Hat OpenStack Platform environment, this procedure also includes instructions about migrating instances from the Compute node that you want to reboot. This involves the following workflow: Decide whether to migrate instances to another Compute node before rebooting the node. Select and disable the Compute node you want to reboot so that it does not provision new instances. Migrate the instances to another Compute node. Reboot the empty Compute node. Enable the empty Compute node. Prerequisites Before you reboot the Compute node, you must decide whether to migrate instances to another Compute node while the node is rebooting. If for some reason you cannot or do not want to migrate the instances, you can set the following core template parameters to control the state of the instances after the Compute node reboots: NovaResumeGuestsStateOnHostBoot Determines whether to return instances to the same state on the Compute node after reboot. When set to False , the instances will remain down and you must start them manually. Default value is: False NovaResumeGuestsShutdownTimeout Number of seconds to wait for an instance to shut down before rebooting. It is not recommended to set this value to 0 . Default value is: 300 NovaResumeGuestsShutdownTimeout Number of seconds to wait for an instance to shut down before rebooting. It is not recommended to set this value to 0 . Default value is: 300 For more information about overcloud parameters and their usage, see Overcloud Parameters . Procedure Log in to the undercloud as the stack user. List all Compute nodes and their UUIDs: Identify the UUID of the Compute node that you want to reboot. From the undercloud, select a Compute node. Disable the node: List all instances on the Compute node: If you decide not to migrate instances, skip to this step . If you decide to migrate the instances to another Compute node, use one of the following commands: Migrate the instance to a different host: Let nova-scheduler automatically select the target host: Live migrate all instances at once: Note The nova command might cause some deprecation warnings, which are safe to ignore. Wait until migration completes. Confirm that the migration was successful: Continue to migrate instances until none remain on the chosen Compute node. Log in to the Compute node and reboot the node: Wait until the node boots. Re-enable the Compute node: Check that the Compute node is enabled: 5.4. Rebooting HCI Compute nodes The following procedure reboots Compute hyperconverged infrastructure (HCI) nodes. Procedure Log in to a Ceph MON or Controller node and disable Ceph Storage cluster rebalancing temporarily: Log in to the undercloud as the stack user. List all Compute nodes and their UUIDs: Identify the UUID of the Compute node you aim to reboot. From the undercloud, select a Compute node and disable it: List all instances on the Compute node: Use one of the following commands to migrate your instances: Migrate the instance to a specific host of your choice: Let nova-scheduler automatically select the target host: Live migrate all instances at once: Note The nova command might cause some deprecation warnings, which are safe to ignore. Wait until the migration completes. Confirm that the migration was successful: Continue migrating instances until none remain on the chosen Compute node. Log in to a Ceph MON or a Controller node and check the cluster status: Check that the pgmap reports all pgs as normal ( active+clean ). Reboot the Compute HCI node: Wait until the node boots. Enable the Compute node again: Verify that the Compute node is enabled: Log out of the node, reboot the node, and check its status. Repeat this process until you have rebooted all Ceph storage nodes. When complete, log in to a Ceph MON or Controller node and enable cluster rebalancing again: Perform a final status check to verify the cluster reports HEALTH_OK :

Commands:
[heat-admin@overcloud-controller-0 ~]USD sudo pcs cluster stop
[heat-admin@overcloud-controller-0 ~]USD sudo reboot
[heat-admin@overcloud-controller-0 ~]USD sudo pcs status
[heat-admin@overcloud-controller-0 ~]USD sudo systemctl status
[heat-admin@overcloud-controller-0 ~]USD sudo podman ps
sudo podman exec -it ceph-mon-controller-0 ceph osd set noout sudo podman exec -it ceph-mon-controller-0 ceph osd set norebalance
sudo reboot
sudo podman exec -it ceph-mon-controller-0 ceph status
sudo podman exec -it ceph-mon-controller-0 ceph osd unset noout sudo podman exec -it ceph-mon-controller-0 ceph osd unset norebalance
sudo podman exec -it ceph-mon-controller-0 ceph status
source ~/stackrc (undercloud) USD openstack server list --name compute
source ~/overcloudrc (overcloud) USD openstack compute service list (overcloud) USD openstack compute service set [hostname] nova-compute --disable
(overcloud) USD openstack server list --host [hostname] --all-projects
(overcloud) USD openstack server migrate [instance-id] --live [target-host]--wait
(overcloud) USD nova live-migration [instance-id]
nova host-evacuate-live [hostname]
(overcloud) USD openstack server list --host [hostname] --all-projects
[heat-admin@overcloud-compute-0 ~]USD sudo reboot
source ~/overcloudrc (overcloud) USD openstack compute service set [hostname] nova-compute --enable
(overcloud) USD openstack compute service list
sudo podman exec -it ceph-mon-controller-0 ceph osd set noout sudo podman exec -it ceph-mon-controller-0 ceph osd set norebalance
source ~/stackrc (undercloud) USD openstack server list --name compute
source ~/overcloudrc (overcloud) USD openstack compute service list (overcloud) USD openstack compute service set [hostname] nova-compute --disable
(overcloud) USD openstack server list --host [hostname] --all-projects
(overcloud) USD openstack server migrate [instance-id] --live [target-host]--wait
(overcloud) USD nova live-migration [instance-id]
nova host-evacuate-live [hostname]
(overcloud) USD openstack server list --host [hostname] --all-projects
sudo podman exec USDCEPH_MON_CONTAINER ceph -s
sudo reboot
source ~/overcloudrc (overcloud) USD openstack compute service set [hostname] nova-compute --enable
(overcloud) USD openstack compute service list
sudo podman exec USDCEPH_MON_CONTAINER ceph osd unset noout sudo podman exec USDCEPH_MON_CONTAINER ceph osd unset norebalance
sudo podman exec USDCEPH_MON_CONTAINER ceph status