[Xen-users] Success: HVM RH domU to Para Virt domU

["David Morris" <david.morris@xxxxxxxxxx>]

After a few tribulations, I was able to convert a RH EL 5 HVM domU guest into a 
para virtual guest. Actually, I cloned the HVM guest as a para virtual guest.

I stated with RH EL 5 with the virtualization RPMs installed. This was Xen 
3.0.3 as I recall.

I use logical volumes for my Xen guest disk space.

I used virt-manager to attempt to kick start an HVM guest. I had difficulty 
getting the kickstart devices to align with the HVM config and ultimately 
edited the /etc/xen/CONFIG file to have 
the appropriate devices and cdrom iso file reference and then used 
    xm create /etc/xen/CONFIG
to boot the install media. I followed my normal hardware kick start procedure 
and ended
up with a RHEL5 installation. The install disk was /dev/vg/CONFIG
which was a partitioned drive.

For the ParaVM, I wanted the logical volume to be a directly mountable file 
system as this approach is needed for my pre-existing Xen management tool set.

So I used fdisk (sfdisk?) to find the first byte of hda1 and then used 
   losetup -o FIRSTBYTE -f
to define a loop back device
   mount /dev/loopX /mnt/CONFIG
create a compressed tarball of the image
   tar -C /mnt/CONFIG -cjf /xen/templates/CONFIGtarball.tz2 .
there was some noise re sockets.

   umount -d /mnt/CONFIG

define a new logical volume 
   /dev/vg/NEW
of the desired resulting size  
make the desired file sys on /dev/vg/NEW
and then 
   mount /dev/vg/NEW /mnt/NEW
   tar -C /mnt/NEW -xjf /xen/templages/CONFIGtarball.tz2
   EDIT any configuration values in the system image such as IP address
   umount /mnt/NEW

xm create NEW -c

Clone a new config file, NEW, from CONFIG:
   a.  remove the HVM builder reference
   b.  assign a new uuid
   c.  a new name for the instance
   d.  a new MAC address ... low bit of first byte must be ZERO
   e.  change the disk reference to /dev/hda1 and the /dev/vg/NEW
       device
   f.  Specify the kernel and initrd files .... I used the dom0
       xen kernel and initrd.


OOOPs ... I couldn't get the boot to finish...

Eventually, I downloaded ELRH5 RPMs for Xen3.1 from the xensource site ....

Played remove / fix dependancy games and forced the new kernel install

Edited the /boot/grub/menu.1st file to specify and activate the new kernel
and xen hypervisor.

Now the the ParaVM guest boots and appears operational ... limited testing thus
far.

And the VNC mouse issues in my windows XP HVM are less obnoxious ... not 
perfect yet.

This is of course an outline so I may have missed something I repaired in the 
heat of the moment, but hopefully, this will provide the guidance someone else 
needs.

Dave Morris

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