9.4. Rebooting Compute Nodes

Reboot each Compute node individually and ensure zero downtime of instances in your OpenStack Platform environment. This involves the following workflow:
  1. Select a Compute node to reboot
  2. Migrate its instances to another Compute node
  3. Reboot the empty Compute node

From the undercloud, list all Compute nodes and their UUIDs:
$ source ~/stackrc
$ nova list | grep "compute"

Select a Compute node to reboot and first migrate its instances using the following process:
  1. From the undercloud, select a Compute Node to reboot and disable it:
    $ source ~/overcloudrc
    $ nova service-list
    $ nova service-disable [hostname] nova-compute
  2. List all instances on the Compute node:
    $ nova list --host [hostname]
  3. Select a second Compute Node to act as the target host for migrating instances. This host needs enough resources to host the migrated instances. From the undercloud, migrate each instance from the disabled host to the target host.
    $ nova live-migration [instance-name] [target-hostname]
    $ nova migration-list
    $ nova resize-confirm [instance-name]
  4. Repeat this step until you have migrated all instances from the Compute Node.


For full instructions on configuring and migrating instances, see Section 7.8, “Migrating VMs from an Overcloud Compute Node”.

Reboot the Compute node using the following process
  1. Log into the Compute Node and reboot it:
    $ sudo reboot
  2. Wait until the node boots.
  3. Enable the Compute Node again:
    $ source ~/overcloudrc
    $ nova service-enable [hostname] nova-compute
  4. Select the next node to reboot.