[Libguestfs] Xen drivers for virt-builder images

[Richard W.M. Jones]

On Thu, Jun 12, 2014 at 02:20:49PM +0200, Dario Faggioli wrote:
> So, first of all, forgive my libguestfs / virt-builder ignorance. :-)
> 
> About the modules, what I know is that if I point virt-install to this
> location:
> http://mirror.euserv.net/linux/fedora/linux/releases/20/Fedora/x86_64/os/
> 
> it just works, i.e., the installer is able to see the virtual disk and
> network interface while running in a Xen (PV) guest.
> 
> Looking inside the initrd.img that the above uses, here's what I find:
> 
> $ find lib/modules/3.11.10-301.fc20.x86_64/ -iname xen*
> lib/modules/3.11.10-301.fc20.x86_64/kernel/drivers/block/xen-blkfront.ko
> lib/modules/3.11.10-301.fc20.x86_64/kernel/drivers/net/xen-netback
> lib/modules/3.11.10-301.fc20.x86_64/kernel/drivers/net/xen-netback/xen-netback.ko
> lib/modules/3.11.10-301.fc20.x86_64/kernel/drivers/net/xen-netfront.ko
> 
> So, if we're talking about an initrd, or an initrd-like thing, the above
> is probably all we need. Is that what we're talking about? :-)

I believe the problem is that we use KVM to build the virt-builder
guest images.  When the kernel package is installed by kickstart,
since the hypervisor at build time != Xen, dracut decides not to
include the Xen drivers.

I think we can fix this by running dracut again in %post, and I
propose that running dracut as follows should fix this:

  %post
  dracut --add-drivers "xen:vbd xen:vif"

(assuming what Olaf says works), or:

  %post
  dracut --add-drivers "xen-blkfront xen-netback xen-netfront"

I will try it shortly.

Rich.

PS. Why would a Xen domU need the netback driver?

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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