387a5753de
As called out in the review for Ib7b9f4fd7673525129c03dc2943deedd0c7ad81f the use of a numerical anchor causes a sequence id to be used that can change over time in the document and thus is not stable to reference externally. This change simply switches to a non-numerical anchor ensuring that sphinx generates a stable anchor we can always reference. Change-Id: I550f7fd89a13e58031b0ddfbcb4f6a5239dbf335
102 lines
3.4 KiB
ReStructuredText
102 lines
3.4 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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To rescue an instance that boots from a volume you need to use the
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:ref:`2.87 microversion or later <microversion 2.87>`.
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.. code-block:: console
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$ openstack --os-compute-api-version 2.87 server rescue SERVER
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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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