rescue of boot from volume image fails when --image is not specified

[Jonathan Rosser]

From an environment where all storage is on ceph, it was not possible to omit the --image parameter when rescuing a boot-from-volume instance as suggested near the end of this doc:

https://docs.openstack.org/nova/latest/user/rescue.html

The doc implies that omitting --image will use the image of the rescued instance as the rescue image.

Works:

openstack server rescue --image d0d00858-0672-4d19-9e5a-fb120d78c0fc 81057513-24cd-49e7-b1e5-939d4080bb21 --os-compute-api-version 2.87

Does not work:

openstack server rescue 81057513-24cd-49e7-b1e5-939d4080bb21 --os-compute-api-version 2.87

Not specifying --image appears to succeed with the command line client:

REQ: curl -g -i --insecure -X POST http://10.11.128.30:8774/v2.1/servers/81057513-24cd-49e7-b1e5-939d4080bb21/action -H "Accept: application/json" -H "Content-Type: application/json" -H "OpenStack-API-Version: compute 2.87" -H "User-Agent: python-novaclient" -H "X-Auth-Token: {SHA256}9418545bce89f055d82cf493560aaa6c1e0fb0180f7bae5615006283e83dd999" -H "X-OpenStack-Nova-API-Version: 2.87" -d '{"rescue": null}'
http://10.11.128.30:8774 "POST /v2.1/servers/81057513-24cd-49e7-b1e5-939d4080bb21/action HTTP/1.1" 200 29

However in the nova compute log we see this stacktrace http://paste.openstack.org/show/803379/

Environment
===========
1. OpenStack Victoria / OpenStack-Ansible 22.0.0

2. Which hypervisor did you use?
   Libvirt + KVM libvirt 6.0.0-0ubuntu8.5~cloud0

2. Which storage type did you use? Ceph

3. Which networking type did you use?
   Neutron / LinuxBridge

[Jonathan Rosser (jrosser)]

TO follow up on this - we subsequently found that it was not possible to use the original OS image as the FSID(?) matched and even though the rescue image was attached correctly the wrong device was used for booting.