[Ovirt-devel] VM Installation problem (and proposed solution)

Daniel P. Berrange berrange at redhat.com
Thu Aug 28 20:19:50 UTC 2008

On Thu, Aug 28, 2008 at 04:16:30PM -0400, Perry N. Myers wrote:
> Daniel P. Berrange wrote:
> >On Thu, Aug 28, 2008 at 05:20:06PM +0200, Chris Lalancette wrote:
> >>Hello all (Ian especially),
> >>     apevec pointed out a problem with installation of guests under 
> >>     oVirt.  What
> >>currently happens is that after you finish the installation of (say) 
> >>Fedora in a
> >>VM, the VM reboots, but then immediately PXE boots again.  This is 
> >>because we
> >>haven't killed the guest and re-defined the XML to have the boot device 
> >>be the
> >>hard drive, like it should.
> >
> >You don't have to wait for installation to finish before re-defining the 
> >XML with hard drive as the boot device
> >
> >You can define the post-install XML config the moment the guest has booted.
> >When it shuts down, libvirt will automatically switch over to the newly
> >defined config.  This is how virt-install handles it.
> >
> If the guest does a soft reboot does the libvirt configuration get 
> reloaded at all?  (I would think not)  In this case the process would look 
> like the following:

That depends on the 'on_reboot' setting in libvirt XML - you can either
allow it to be a soft-reboot or force the poweroff. Typically we do the
latter, to guarentee that the second boot uses the new XML.

> 1. Message sent to ovirtd on Node saying 'install_vm'
> 2. ovirtd defines vm to boot PXE/ISO or whatever and sets on reboot to
>    destroy
> 3. ovirtd starts vm
> 4. ovirtd redefines vm to boot hd and turns off destroy on reboot
> 5. When guest soft reboots, the vm is destroyed causing the new libvirt
>    configuration to be loaded when it is started next
> 6. ovirtd restarts the domain when it detects the domain has been
>    destroyed
> Does that sound reasonable?

Yes, that's the right approach.

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