[libvirt] Update on host interface configuration

[David Lutterkort]

On Fri, 2009-02-27 at 10:07 +0200, Dan Kenigsberg wrote:
> The real issue is, that in this stage, management may have lost
> connectivity to the node.

What exactly is the scenario here ? Are you trying to manage any old
node as long as it has libvirt installed ? As soon as you need any sort
of management-specific code on the node, you might as well implement the
logic below in your management code.

> >         if (! newConfigIsWorking()) {
> >           virInterfaceDefine(goodConfig);
> >           virInterfaceRestart(ifaceName);
> >         }
> 
> How about having netcf/libvirt be aware of what is a goodConfig (with
> additional API verb), and back it up somewhere? Any change to to network
> configuration would have immediate effect, but unless explicitly set as
> "good", reverted on next boot.

While what you suggest will work in theory (with the minor caveat that
reverting to a "good" config can only be triggered by a restart of
libvirtd, not a reboot) it is a poor man's workaround for management
systems that do not provide proper failsafe functionality.

In particular, if you are part of the management system, you have a much
better idea (on the node) what it means to have a working network
configuration, and can recover from misconfigured network much more
gracefully than with the big hammer of a system reboot.

David