[Openstack] nova: instance states and commands

Anne Gentle anne at openstack.org
Tue Nov 20 21:20:35 UTC 2012


Hi Marco -
Great questions, and I won't tell you to read the fine manual because
I know you do and log the most excellent bugs. :) But more commentary
below for how to do some detective work. I would still like for
someone to answer these questions in detail.

On Tue, Nov 20, 2012 at 4:46 AM, Marco CONSONNI <mcocmo62 at gmail.com> wrote:
> Hello,
>
>
>
> I’m playing with nova CLI and I found that there are several commands for
> managing the current state of instances running in the cloud.
>
>
>
> These are the states I found:
>
>
>
> ·         initial
> ·         build
> ·         active
> ·         shutoff
> ·         suspended
> ·         rescue
> ·         paused
> ·         reboot
>
>
>
> And these are the nova commands for changing the current state:
>
>
>
> ·         boot
> ·         pause
> ·         reboot
> ·         rescue
> ·         resume
> ·         start
> ·         stop
> ·         suspend
> ·         unpause
> ·         unrescue
>
>
>
> QUESTION: Is there any explanation on the meaning of the states? In
> particular, what’s the difference between SUSPENDED, PAUSED and RESCUE?

The document for this info is the Compute API spec, specifically
http://docs.openstack.org/api/openstack-compute/2/content/List_Servers-d1e2078.html.
However since it is a spec it is likely that there are undocumented
things going on here.

Also the API definitions don't tell the whole story because the nova
CLI parameter "pause" is doing something with the API that you can
find out using the nova --debug command.

nova --debug pause <servername>

It seems like it's doing something with extensions, such as
"OS-EXT-STS:vm_state" "OS-EXT-STS:power_state" so dig further there.
You can search for Extended Server status on
http://api.openstack.org/api-ref.html.

Boy, trying to find this info myself shows what a nightmare this info
is to dig into, and I apologize for that. Sure shows a need for more
API documentation for real usage.

Thanks,
Anne

>
>
> Another command changes the status and, from what I found, it always changes
> that to ERROR.
>
> The command is “nova reset-state”.
>
>
>
> QUESTION: what’s the semantics of this command?
>
>
>
>
>
> Then, I found some other commands that sound like status management command
> but, actually they are not:
>
>
>
> ·         Lock
> ·         Unlock
>
>
>
> QUESTION: What’s the meaning of these?
>
>
>
>
>
> Marco.
>
>
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