Resize an instance

You can change the size of an instance by changing its flavor. This rebuilds the instance and therefore results in a restart.

To resize an instance, use the openstack server resize command:

$ openstack server resize --flavor FLAVOR SERVER


By default, the openstack server resize command gives the guest operating system a chance to perform a controlled shutdown before the instance is powered off and the instance is resized. The shutdown behavior is configured by the shutdown_timeout parameter that can be set in the nova.conf file. Its value stands for the overall period (in seconds) a guest operating system is allowed to complete the shutdown. The default timeout is 60 seconds.

The timeout value can be overridden on a per image basis by means of os_shutdown_timeout that is an image metadata setting allowing different types of operating systems to specify how much time they need to shut down cleanly. See Useful image properties for details.

Resizing can take some time. During this time, the instance status will be RESIZE:

$ openstack server list
| ID                   | Name           | Status | Networks                                |
| 67bc9a9a-5928-47c... | myCirrosServer | RESIZE | admin_internal_net=      |

When the resize completes, the instance status will be VERIFY_RESIZE. You can now confirm the resize to change the status to ACTIVE:

$ openstack server resize --confirm SERVER


The resized server may be automatically confirmed based on the administrator’s configuration of the deployment.

If the resize fails or does not work as expected, you can revert the resize. This will revert the instance to the old flavor and change the status to ACTIVE:

$ openstack server resize --revert SERVER