[openstack-dev] Odp.: [nova] Would be possible to modify metadata when instance is in rescued state?

Pawel Suder pawel.suder at corp.ovh.com
Tue May 9 14:04:25 UTC 2017


Hello Michael,


I did a quick grep over archive with mails from openstack-dev list. It seems that topic about rescue mode was raised in August last year. I did not find anything directly related to metadata.


Understand that changing user metadata (with command `nova meta {uuid} set key=value`) when VM is in rescue mode, could cause some issues.

Cheers,
Pawel

________________________________
Od: Michael Still <mikal at stillhq.com<mailto:mikal at stillhq.com>>
Temat: Odp: [openstack-dev] [nova] Would be possible to modify metadata when instance is in rescued state?
Data: 9 maja 2017 09:09:31 CEST
Do: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Odpowiedź-do: "OpenStack Development Mailing List \(not for usage questions\)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>

This sort of question comes up every six months or so it seems.

The issue is that for config drive users we don't have a way of rebuilding all of the config drive (for example, the root password is gone). That's probably an issue for rescue because its presumably one of the things you might reset.

I'm not opposed to exploring options, but I think we need someone to come up with a proposal which addresses previous concerns. I'd recommend a quick search of the mailing list archives for previous discussions.

Hope this helps,
Michael


On Tue, May 9, 2017 at 5:04 PM, Pawel Suder <pawel.suder at corp.ovh.com<mailto:pawel.suder at corp.ovh.com>> wrote:

Hello,


I would like to raise a topic regarding possibilities when metadata could be modified on instance.


We noticed that instance metadata could be modified only when vm_state is set to following values:


  *   active
  *   paused
  *   suspended
  *   stopped

Found:

https://github.com/openstack/nova/blob/master/nova/compute/api.py#L3916-L3920
https://github.com/openstack/nova/blob/master/nova/compute/api.py#L3905-L3908

>From time to time it is needed to have instance in rescued state.

Scenario: VM is rescued and special metadata attributes need to be set to allow cloud-init to act specifically for rescue mode. Metadata data should be available only during rescue mode.

Question: what kind of impact could be observed when checks for instance state will be modified for methods:

update_instance_metadata
delete_instance_metadata

Thank you,

Cheers,
Pawel


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