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.
To reboot a server, use the openstack server reboot command:
$ openstack server reboot SERVER
By default, when you reboot an instance it is a soft reboot. To perform a hard reboot, pass the
--hard parameter as follows:
$ openstack server reboot --hard SERVER
It is also possible to reboot a running instance into rescue mode. For example, this operation may be required if a filesystem of an instance becomes corrupted with prolonged use. See rescue for more details.