You can soft or hard reboot a running instance. A soft reboot attempts a graceful shut down and restart of the instance. A hard reboot power cycles the instance. By default, when you reboot an instance, it is a soft reboot. $ nova reboot SERVER To perform a hard reboot, pass the --hard parameter, as follows: $ nova reboot --hard SERVER It is also possible to reboot a running instance into rescue mode. This operation may be required, if a filesystem of an instance becomes corrupted with a prolonged usage, for example. Pause, suspend, and stop operations are not allowed when an instance is running in rescue mode, as triggering these actions causes the loss of the original instance state and makes it impossible to unrescue the instance. Rescue mode provides a mechanism for access, even if an image renders the instance inaccessible. By default, it starts an instance from the initial image attaching the current boot disk as a secondary one. To perform an instance reboot into rescue mode, run the following command: $ nova rescue SERVER To restart the instance from the normal boot disk, run the following command: $ nova unrescue SERVER If you want to rescue an instance with a specific image, rather than the default one, use the --rescue_image_ref parameter, as follows: $ nova rescue --rescue_image_ref IMAGE_ID SERVER