Re: [Xen-devel] Cloning(making copies) of VMs

["M.A. Williamson" <maw48@xxxxxxxxx>]

> A more generic approach would probably question if one should save the
> IP address and such information when saving a VM. This is because
> information such as IP addresses are "perishable" ie they may not be
> valid when restoring the VM.
>
> Probably one should identify such information and selectively save
> such information?? -- thinking out aloud.
Yes... But you still need the guest's help here - if its IP address 
changes, something needs to run ifconfig (or similar) else it'll be 
restored and ignored messages to its new IP address.
The current IP address setting in the config file relies on being able to 
set the IP on the kernel command line. The command line is only read at 
boot time, so when we restore we don't get to change it.
We really need some sort of daemon / hotplug script in the guest to react 
to this sort of thing.
Cheers,
Mark

> DM
>
> On 11/9/05, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:
> > > The problem is that while you are probably sucessful in telling the
> > > host environment (xen + linux in domain0) that your cloned VM has IP
> > > 10.10.10.2, the Linux inside VM2 does not know that it is supposed to
> > > answer the new IP rather than 10.10.10.1, and will just silently drop
> > > all traffic on 10.10.10.2. It would probably be quite simple (and
> > > useful, see the Potemkin paper for instance) to have your domain
> > > answer any incoming IP, or to rewrite all ingoing and outgoing packets
> > > with a generic address, but you will need to hack either your guest
> > > Linux or the networking scripts in dom0 to make that happen.
> >
> > I guess it might be nice (eventually) to have a set of "Xen guest 
> > tools", including a hotplug script that gets run on restore, enabling 
> > this sort of thing to be configured. The domain would be told about the 
> > new IP using xenstore.
> > Of course, this doesn't solve the immediate problem of making it work 
> > without hacking the code ;-)
> > Cheers,
> > Mark
> >
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