[Libguestfs] Xen drivers for virt-builder images

[Dario Faggioli]

Hello everyone,

On gio, 2014-06-12 at 08:20 +0100, Richard W.M. Jones wrote:
> On Wed, Jun 11, 2014 at 10:02:22PM +0100, George Dunlap wrote:
> > On Wed, Jun 11, 2014 at 8:34 PM, Richard W.M. Jones <rjones at redhat.com> wrote:
> > > Do you know what extra packages have to be installed or commands need
> > > to be run to enable Xen drivers in Fedora?
> > 
> > The kernel already has a lot of the Xen stuff enabled.  AFAICT from
> > looking at the boot output it's just missing those two modules in the
> > initrd.  (Although it's possible you'll need more.)  I'm pretty sure
> > they should just come in the normal kernel rpm; there aren't really
> > any user-space components necessary for basic functionality of a Xen
> > guest.  (There are a few tools which someone might want to install for
> > one purpose or another -- tools for querying Xen state or acting as a
> > "driver domain" -- but they're something that should be added as
> > needed, not in the core.)
> 
> I suspect we may need to run a dracut command in %post.  Something
> like:
> 
> dracut --add-drivers "some list of xen kmods ..."
> 
> I'm not sure which Xen drivers are required.  The Fedora 21 kernel has
> 13 files named 'xen*.ko.xz'.
> 
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? :-)

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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