[libvirt] cloud-init integration

[Daniel P. Berrange]

On Fri, Jun 19, 2015 at 12:44:51PM +0200, Tobias Florek wrote:
> Hi,
> 
> if that has been discussed before, please point me to it. I have not
> been able to find anything about it.
> 
> It would be great to easily generate and cd-attach cloud-init isos when
> starting a vm. The config files could be taken from the file system
> (e.g. %sysconfdir/cloud-init/host-name) and put into an iso. when the
> host stops the generated iso should be removed.
> 
> What do you think? If that's a worthwhile cause, I would be glad to
> start to implement it, if pointers are given. My C i a little rusty
> unfortunately.

I'm not convinced that libvirt needs to be in the business of dynamically
generating application specific disk images. It feels like that is a task
that is more easily accomplished outside of libvirt, by a variety of
pre-existing tools.  There are a tonne of tools for building images in
general. Richard Jones illustrated how to build disk images specifically
for cloud init using libguestfs as an example

   https://rwmj.wordpress.com/2013/12/10/creating-a-cloud-init-config-disk-for-non-cloud-boots/

So it seems sufficient to leave it to external apps. I'm not saying
you shouldn't create some general purpose tool to build it from
templates though - just that it doesn't need to be in libvirt. I could
see value in perhaps adding some code for doing this, and a CLI tool
into the virt-manager project for example. eg so virt-manager and
virt-install could simplify the task of initializing cloud init when
they deploy Vms.

Regards,
Daniel
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