Reboot an instance

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.


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, use the openstack server rescue command:

$ openstack server rescue SERVER


On running the openstack server rescue command, an instance performs a soft shutdown first. This means that the guest operating system has a chance to perform a controlled shutdown before the instance is powered off. 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 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.

To restart the instance from the normal boot disk, run the following command:

$ openstack server unrescue SERVER

If you want to rescue an instance with a specific image, rather than the default one, use the --image parameter:

$ openstack server rescue --image IMAGE_ID SERVER