Tag Archives: xen

Converting Xen Linux VMs to VMWare

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A year ago I wrote about how to convert from Xen to VMWare (which is a similar process to a Xen virtual-to-physical or V2P conversion). Now I found a much simpler solution, thanks to http://www.zomo.co.uk/2012/04/moving-disks-from-xen-to-kvm/ .

In this example, I’m using LVM disks, but the process is no different from using Xen disk images.

  1. Install Debian Wheezy into a VMWare virtual machine. Attach a secondary virtual disk (it will be called /dev/sdc from now on) that’s sized about 500 MB larger than your Xen DomU (just to be safe). Fire up the VM. All subsequent commands will be run from inside that VM.
  2. Check whether your DomU disk has a partition table: ssh root@xen fdisk -l /dev/xenvg/4f89402b-8587-4139-8447-1da6d0571733.disk0. If it does, proceed to step 3. If it does not, proceed to step 4.
  3. Clone the Xen DomU onto the secondary virtual disk via SSH: ssh root@xen dd bs=1048576 if=/dev/xenvg/4f89402b-8587-4139-8447-1da6d0571733.disk0 | dd bs=1048576 of=/dev/sdc. Proceed to step 7.
  4. Zero out the beginning of the target disk: dd if=/dev/zero of=/dev/sdc bs=1048576 count=16
  5. Partition it and add a primary partition 8 MB into the disk: fdisk /dev/sdc, o Enter w Enter, fdisk /dev/sdc, n Enter p Enter 1 Enter 16384 Enter Enter, w Enter
  6. Clone the Xen DomU onto the secondary virtual disk’s first partition via SSH: ssh root@lara dd bs=1048576 if=/dev/xenvg/4f89402b-8587-4139-8447-1da6d0571733.disk0 | dd bs=1048576 of=/dev/sdc1
  7. reboot
  8. Mount the disk: mount -t ext3 /dev/sdc1 /mnt; cd /mnt
  9. Fix fstab: nano etc/fstab: change root disk from to /dev/sda1
  10. Fix the virtual console: nano etc/inittab: replace hvc0 with tty1
  11. Chroot into the disk: mount -t proc none /mnt/proc; mount -t sysfs none /mnt/sys; mount -o bind /dev /mnt/dev; chroot /mnt /bin/bash
  12. Fix mtab so the Grub installer works: grep -v rootfs /proc/mounts > /etc/mtab
  13. Install Grub: apt-get install grub2. When the installer asks to which disks to install, deselect all disks.
  14. Install Grub to MBR: grub-install –force /dev/sdc
  15. Update Grub configuration: update-grub
  16. Leave the chroot: exit; umount /mnt/* /mnt
  17. shutdown

Now you can detach the secondary virtual disk and create a new VM with it. If everything worked correctly, it will boot up.

Xen 4.0 and Citrix WHQL PV drivers for Windows

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Xen 4.0 is supposed to be able to use Citrix’s WHQL certified Windows paravirtualization drivers. Their advantage over the GPLPV drivers is that they are code-signed, meaning they run on 64-bit Windows without disabling some of Windows’ security features.

UPDATE 2011-10-17: Signed GPLPV drivers are now available. I have not yet tested them, but I assume the fix below is no longer necessary.

While the Citrix drivers included in XenServer 5.5 work (after making a single registry tweak), the more recent ones included in e.g. Xen Cloud Platform 1.0 do not work right away:

If you install the XCP drivers, make that registry tweak and reboot the DomU, you’ll notice messages like XENUTIL: WARNING: CloseFrontend: timed out in XenbusWaitForBackendStateChange: /local/domain/0/backend/console/[id]/0 in state INITIALISING; retry. in your /var/log/xen/qemu-dm-*.log and Windows just gets stuck during boot and keeps spinning forever. To get it back to work, you’ll need to
xenstore-rm /local/domain/0/backend/console/[id]
xenstore-rm /local/domain/0/backend/vfb/[id]
after starting the VM (thanks to Keith Coleman‘s mailing list post!).

To automatically run these commands upon DomU start, create a script named /usr/lib/xen/bin/qemu-dm-citrixpv with the following contents
#!/bin/sh

xenstore-rm /local/domain/0/backend/console/$2
xenstore-rm /local/domain/0/backend/vfb/$2

sh -c "sleep 10; xenstore-rm /local/domain/0/backend/console/$2; xenstore-rm /local/domain/0/backend/vfb/$2" &

exec /usr/lib/xen/bin/qemu-dm $*
and chmod +x it.

Then, edit your DomU config file and modify the device_model line and point it to your new script:
device_model = '/usr/lib/xen/bin/qemu-dm-citrixpv'

Now your Windows Server 2008 R2 x64 HVM-DomU is all set!