[lxc-users] LXD in OpenStack confusion

Paul Hummer paul.hummer at canonical.com
Fri Apr 29 15:17:32 UTC 2016

Hi Muneeb-

On Fri, Apr 29, 2016 at 7:29 AM, Muneeb Ahmad <muneeb.gandapur at gmail.com>
> First I'm confused about how flavors in OpenStack work when we are dealing
> with LXC containers. Because one of the ideas behind containers is that
> they can use as much resources as they want unless there's a limitation. So
> I'm confused when we have to choose a flavor for any instance, is it really
> going to limit the resources used by that container-instance? And let's say
> my compute node has 1gb RAM and I use a flavor that has 256mb RAM
> allocation, I can only launch 3 containers, after that I get 'no valid
> hosts found' error although in reality I can run much more containers than
> that. How all this work in containers environment?

The "flavor" idea is a nova artifact, and nova-lxd forwards that over to
LXD via profiles. When nova-lxd creates a container instance, it assigns a
profile to it with the resource constraints of the nova flavor. You can see
this in lxd with `lxc profile list` and `lxc profile show`

> Another question I have is that when we run a container on OpenStack, it
> automatically copy an image into local lxc image list. Even if all the
> containers are using the same image, it just keeps on adding the image to
> it's list with a different name. Isn't this a waste of memory?

This is a bug that I have discovered recently. I filed a bug right before I
read this email. :) https://github.com/lxc/nova-lxd/issues/124

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