[pve-devel] RFC: qemu-server : add cloudinit support

[Wolfgang Bumiller]

> On June 12, 2015 at 9:35 AM Alexandre DERUMIER <aderumier at odiso.com> wrote:
> dpkg-configure cloud-init , and choose configdrive as only datasource.
> 
> I think at start, cloud-init ask to his datasources if they are a new config.

Right, if you can disable this behavior then that's fine. Just need to somewhere
document that it's recommended to disable all the other unused datasources.

> >>But if you change the uuid a new directory appears in 
> >>/var/lib/cloud/instances without the old ones disappearing. New files on 
> >>every applied update. 
> >>
> >>Maybe I'm missing something obvious...? 
> I need to check that, I thinked that only the the symlink
> /var/lib/cloud/instance ---> /var/lib/cloud/instances/currentuuid/
> was applied.

Applied, yes, but the old directory still exists. The symlink is updated to the
new one.

> Maybe this is what about merge is doing ?
> http://cloudinit.readthedocs.org/en/latest/topics/merging.html

Perhaps. They only list «#include» as example though.

So,
basically, cloud-init does configuration instances which are applied
only once (but weirdly updated multiple times), and searches all of
the *guest*'s configured data sources.

Meaning much of the functionality depends on the guest system, and the
default configuration of most cloud-init packages is to just test all
data-sources.

This situation might need to be reflected in the GUI. If we simply
have an entry to type in a network configuration etc. there would be
no guarantee that it's even applied, because whether this will happen
is the guest's choice.

Here's a thought:
Maybe in order to reflect this situation the web UI could simply have
a (possibly even VM independent?) way of creating and manipulating a
config-drive (even if it's just network configuration and maybe a list
of ssh-keys), perhaps with a simple counter for an instance ID. And
you can attach a config drive from a list similarly to how you attach
an ISO image as cdrom (and from the CLI it would be a single option
like -configdisk ID, or -configdisk /path/ot/disk).
Because it's really more like a support-feature for a guest-feature
than providing a general feature on the PVE side.

Thoughts?