[libvirt] xml format for openvz driver

[Daniel P. Berrange]

On Tue, Jul 22, 2008 at 08:41:36PM +0400, Evgeniy Sokolov wrote:
> >>For tag domain/os:
> >>need to add "ostemplate"
> >>desirable "config"
> >
> >Can you explain exactly what the semantics of the two desired attributes
> >are used for ?
> >
> "config" is name of sample config for container. It contains many 
> parameters
> http://wiki.openvz.org/UBC_parameters_table
> It is desirable because of many customers like to use config.

The problem including a 'config' parameter is that  this data becomes
totally opaque to the management app. Given a piece of XML describing
a domain, including a "config=xxxx' parameter, there's no way for the
app to find out what the underlying resources settings are.

> >For the filesystem stuff, for LXC we've got a section under <devices>
> >whcih looks like
> >
> >   <filesystem type="mount">
> >     <source dir='/some/path'/>
> >     <target dir='/'/>
> >   </filessytem>
> >
> >Which says 'make /some/path be the root filesystem, using a bind mount'.
> >
> >I could imagine representing the idea of a template with a slight 
> >variation like
> >
> >   <filesystem type="template">
> >      <source name="template name"/>
> >      <target dir='/'/>
> >   </filesystem>
> >
> Yes, we can. But template name is not property of file system.

Well, actually I'd argue that it is. The "source" element refers
to the resource in the host OS that forms the source of the
filesystem. So for a root filesystem instantiated from a template,
I think template name is the most applicable.

> >>For tag domain/devices/interface:
> >>How to describe, if want to add ip addresses for routing network?
> >
> >We'll probably want todo something based on <interface type='ethernet'
> >which is a generic catch all config.
> >
> >Does OpenVZ support bridging, or NAT for containers ?
> bridging is supported.
> NAT can be configured via iptables.

If it supports bridging that is sufficient. The libvirt networking
APIs, allow us to implement NAT for any VM in terms of the generic
bridge support. Basically libvirt creates a bridge device 'virbr0'
and sets up NAT rules for that device. A guest VM simply needs to
be connected to virbr0, and then NAT automagically works for it.

Daniel
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