3a390c2c82
This hasn't been validated upstream and there doesn't appear to be anyone using it. It's time to drop support for this. This is mostly test and documentation damage, though there is some other cleanup going on, like the removal of the essentially noop 'pick_disk_driver_name' helper. Change-Id: I73305e82da5d8da548961b801a8e75fb0e8c4cf1 Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
95 lines
3.2 KiB
ReStructuredText
95 lines
3.2 KiB
ReStructuredText
==================
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Rescue an instance
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==================
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Instance rescue provides a mechanism for access, even if an image renders the
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instance inaccessible. Two rescue modes are currently provided.
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Instance rescue
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---------------
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By default the instance is booted from the provided rescue image or a fresh
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copy of the original instance image if a rescue image is not provided. The root
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disk and optional regenerated config drive are also attached to the instance
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for data recovery.
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.. note::
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Rescuing a volume-backed instance is not supported with this mode.
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Stable device instance rescue
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-----------------------------
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As of 21.0.0 (Ussuri) an additional stable device rescue mode is available.
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This mode now supports the rescue of volume-backed instances.
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This mode keeps all devices both local and remote attached in their original
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order to the instance during the rescue while booting from the provided rescue
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image. This mode is enabled and controlled by the presence of
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``hw_rescue_device`` or ``hw_rescue_bus`` image properties on the provided
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rescue image.
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As their names suggest these properties control the rescue device type
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(``cdrom``, ``disk`` or ``floppy``) and bus type (``scsi``, ``virtio``,
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``ide``, or ``usb``) used when attaching the rescue image to the instance.
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Support for each combination of the ``hw_rescue_device`` and ``hw_rescue_bus``
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image properties is dependent on the underlying hypervisor and platform being
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used. For example the ``IDE`` bus is not available on POWER KVM based compute
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hosts.
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.. note::
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This mode is only supported when using the Libvirt virt driver.
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This mode is not supported when using the LXC hypervisor as enabled by
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the :oslo.config:option:`libvirt.virt_type` configurable on the computes.
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Usage
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-----
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.. note::
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Pause, suspend, and stop operations are not allowed when an instance
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is running in rescue mode, as triggering these actions causes the
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loss of the original instance state and makes it impossible to
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unrescue the instance.
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To perform an instance rescue, use the :command:`openstack server rescue`
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command:
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.. code-block:: console
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$ openstack server rescue SERVER
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.. note::
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On running the :command:`openstack server rescue` command,
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an instance performs a soft shutdown first. This means that
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the guest operating system has a chance to perform
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a controlled shutdown before the instance is powered off.
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The shutdown behavior is configured by the
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:oslo.config:option:`shutdown_timeout` parameter that can be set in the
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``nova.conf`` file.
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Its value stands for the overall period (in seconds)
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a guest operating system is allowed to complete the shutdown.
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The timeout value can be overridden on a per image basis
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by means of ``os_shutdown_timeout`` that is an image metadata
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setting allowing different types of operating systems to specify
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how much time they need to shut down cleanly.
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If you want to rescue an instance with a specific image, rather than the
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default one, use the ``--image`` parameter:
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.. code-block:: console
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$ openstack server rescue --image IMAGE_ID SERVER
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To restart the instance from the normal boot disk, run the following
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command:
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.. code-block:: console
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$ openstack server unrescue SERVER
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