Rescue an instance¶
Instance rescue provides a mechanism for access, even if an image renders the instance inaccessible. Two rescue modes are currently provided.
By default the instance is booted from the provided rescue image or a fresh copy of the original instance image if a rescue image is not provided. The root disk and optional regenerated config drive are also attached to the instance for data recovery.
Rescuing a volume-backed instance is not supported with this mode.
Stable device instance rescue¶
As of 21.0.0 (Ussuri) an additional stable device rescue mode is available. This mode now supports the rescue of volume-backed instances.
This mode keeps all devices both local and remote attached in their original
order to the instance during the rescue while booting from the provided rescue
image. This mode is enabled and controlled by the presence of
hw_rescue_bus image properties on the provided
As their names suggest these properties control the rescue device type
floppy) and bus type (
usb) used when attaching the rescue image to the instance.
Support for each combination of the
image properties is dependent on the underlying hypervisor and platform being
used. For example the
IDE bus is not available on POWER KVM based compute
This mode is only supported when using the Libvirt virt driver.
This mode is not supported when using the LXC hypervisor as enabled by
libvirt.virt_type configurable on the computes.
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.
To perform an instance rescue, 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
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 rescue an instance that boots from a volume you need to use the 2.87 microversion or later.
$ openstack --os-compute-api-version 2.87 server rescue SERVER
If you want to rescue an instance with a specific image, rather than the
default one, use the
$ openstack server rescue --image IMAGE_ID SERVER
To restart the instance from the normal boot disk, run the following command:
$ openstack server unrescue SERVER