035315b05b
This change introduces a new method of instance rescue to the Libvirt driver where all original devices remain attached in their original order while booting from the provided rescue image. This differs from the original method of instance rescue where only the rescue disk, original root disk and regenerated config drive would be attached. This new method is enabled by the presence of either the hw_rescue_device or hw_rescue_bus image metadata properties on the provided rescue image. As their name suggests these properties control the device and bus type used to attach the rescue boot device to the instance. The properties will allow users to rescue instances using the emulated equivalents of more traditional bare metal rescue media such as USB disks or CD-ROM ISOs. While the rescue disk is attached last to the instance we are able to boot directly from it using the boot element and order attribute when defining the disk within the Libvirt domain [1]. This is not however supported for Xen or LXC virt types and as a result this new method is not available for these types. To enable this new mode and building on I9c2d9013d741774e521021913ec0 we can now provide the full block_device_info for the instance when building the disk mapping where we now add the rescue boot device. This now allows instances with attached volumes to be rescued. Boot from volume instances however are still not supported and blocked within the compute API. Future work will remove this restriction. [1] https://libvirt.org/formatdomain.html#elementsNICSBoot Implements: blueprint virt-rescue-stable-disk-devices Change-Id: I0e1241ae691afd2af12ef15706c454c05d9f932c |
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