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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

  1. Log in to the node that you want to reboot.

  2. Optional: If the node uses Pacemaker resources, stop the cluster: 

    [heat-admin@overcloud-controller-0 ~]$ sudo pcs cluster stop

  3. Reboot the node: 

    [heat-admin@overcloud-controller-0 ~]$ sudo reboot
  4. Wait until the node boots.

  5. Check the services. For example:

    1. If the node uses Pacemaker services, check that the node has rejoined the cluster: 

      [heat-admin@overcloud-controller-0 ~]$ sudo pcs status

    2. If the node uses Systemd services, check that all services are enabled: 

      [heat-admin@overcloud-controller-0 ~]$ sudo systemctl status

    3. If the node uses containerized services, check that all containers on the node are active: 

      [heat-admin@overcloud-controller-0 ~]$ sudo podman ps

5.2. Rebooting a Ceph Storage (OSD) cluster

Complete the following steps to reboot a cluster of Ceph Storage (OSD) nodes.

Procedure

  1. Log in to a Ceph MON or Controller node and disable Ceph Storage cluster rebalancing temporarily: 

    $ sudo podman exec -it ceph-mon-controller-0 ceph osd set noout
$ sudo podman exec -it ceph-mon-controller-0 ceph osd set norebalance
  2. Select the first Ceph Storage node that you want to reboot and log in to the node.

  3. Reboot the node: 

    $ sudo reboot
  4. Wait until the node boots.

  5. Log in to the node and check the cluster status: 

    $ sudo podman exec -it ceph-mon-controller-0 ceph status

    Check that the pgmap reports all pgs as normal (active+clean).

  6. Log out of the node, reboot the next node, and check its status. Repeat this process until you have rebooted all Ceph storage nodes.

  7. When complete, log into a Ceph MON or Controller node and re-enable cluster rebalancing: 

    $ sudo podman exec -it ceph-mon-controller-0 ceph osd unset noout
$ sudo podman exec -it ceph-mon-controller-0 ceph osd unset norebalance

  8. Perform a final status check to verify that the cluster reports HEALTH_OK: 

    $ sudo podman exec -it ceph-mon-controller-0 ceph status

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

  1. Log in to the undercloud as the stack user.

  2. List all Compute nodes and their UUIDs: 

    $ source ~/stackrc
(undercloud) $ openstack server list --name compute

    Identify the UUID of the Compute node that you want to reboot.

  3. From the undercloud, select a Compute node. Disable the node: 

    $ source ~/overcloudrc
(overcloud) $ openstack compute service list
(overcloud) $ openstack compute service set [hostname] nova-compute --disable

  4. List all instances on the Compute node: 

    (overcloud) $ openstack server list --host [hostname] --all-projects
  5. If you decide not to migrate instances, skip to this step.

  6. If you decide to migrate the instances to another Compute node, use one of the following commands:

    • Migrate the instance to a different host: 

      (overcloud) $ openstack server migrate [instance-id] --live [target-host]--wait

    • Let nova-scheduler automatically select the target host: 

      (overcloud) $ nova live-migration [instance-id]

    • Live migrate all instances at once: 

      $ nova host-evacuate-live [hostname]
      Note

      The nova command might cause some deprecation warnings, which are safe to ignore.

  7. Wait until migration completes.

  8. Confirm that the migration was successful: 

    (overcloud) $ openstack server list --host [hostname] --all-projects
  9. Continue to migrate instances until none remain on the chosen Compute node.

  10. Log in to the Compute node and reboot the node: 

    [heat-admin@overcloud-compute-0 ~]$ sudo reboot
  11. Wait until the node boots.

  12. Re-enable the Compute node: 

    $ source ~/overcloudrc
(overcloud) $ openstack compute service set [hostname] nova-compute --enable

  13. Check that the Compute node is enabled: 

    (overcloud) $ openstack compute service list

5.4. Rebooting HCI Compute nodes

The following procedure reboots Compute hyperconverged infrastructure (HCI) nodes.

Procedure

  1. Log in to a Ceph MON or Controller node and disable Ceph Storage cluster rebalancing temporarily: 

    $ sudo podman exec -it ceph-mon-controller-0 ceph osd set noout
$ sudo podman exec -it ceph-mon-controller-0 ceph osd set norebalance
  2. Log in to the undercloud as the stack user.

  3. List all Compute nodes and their UUIDs: 

    $ source ~/stackrc
(undercloud) $ openstack server list --name compute

    Identify the UUID of the Compute node you aim to reboot.

  4. From the undercloud, select a Compute node and disable it: 

    $ source ~/overcloudrc
(overcloud) $ openstack compute service list
(overcloud) $ openstack compute service set [hostname] nova-compute --disable

  5. List all instances on the Compute node: 

    (overcloud) $ openstack server list --host [hostname] --all-projects

  6. Use one of the following commands to migrate your instances:

    1. Migrate the instance to a specific host of your choice: 

      (overcloud) $ openstack server migrate [instance-id] --live [target-host]--wait

    2. Let nova-scheduler automatically select the target host: 

      (overcloud) $ nova live-migration [instance-id]

    3. Live migrate all instances at once: 

      $ nova host-evacuate-live [hostname]
      Note

      The nova command might cause some deprecation warnings, which are safe to ignore.

  7. Wait until the migration completes.

  8. Confirm that the migration was successful: 

    (overcloud) $ openstack server list --host [hostname] --all-projects
  9. Continue migrating instances until none remain on the chosen Compute node.

  10. Log in to a Ceph MON or a Controller node and check the cluster status: 

    $ sudo podman exec $CEPH_MON_CONTAINER ceph -s

    Check that the pgmap reports all pgs as normal (active+clean).

  11. Reboot the Compute HCI node: 

    $ sudo reboot
  12. Wait until the node boots.

  13. Enable the Compute node again: 

    $ source ~/overcloudrc
(overcloud) $ openstack compute service set [hostname] nova-compute --enable

  14. Verify that the Compute node is enabled: 

    (overcloud) $ openstack compute service list
  15. Log out of the node, reboot the next node, and check its status. Repeat this process until you have rebooted all Ceph storage nodes.

  16. When complete, log in to a Ceph MON or Controller node and enable cluster rebalancing again: 

    $ sudo podman exec $CEPH_MON_CONTAINER ceph osd unset noout
$ sudo podman exec $CEPH_MON_CONTAINER ceph osd unset norebalance

  17. Perform a final status check to verify the cluster reports HEALTH_OK: 

    $ sudo podman exec $CEPH_MON_CONTAINER ceph status
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