[fedora-virt] Trying to move VM efficiently, grub-install, guestfish

[Dennis J.]

On 10/29/2009 09:28 PM, Richard W.M. Jones wrote:
> On Thu, Oct 29, 2009 at 08:35:58PM +0100, Dennis J. wrote:
>> http://rwmj.wordpress.com/2009/05/11/rescuing-a-failed-vm-install-with-guestfish/
>> but when I issue the "grub-install / /dev/sda" all I get is:
>> "libguestfs: error: grub_install: grub-install: /dev/sda does not have
>> any corresponding BIOS drive."
>
> I read the rest of your comment with awe.  All I can say is good luck
> with your experiments.
>
> Just about the particular error above .. Is /dev/sda the real name of
> the drive?  (Try the list-devices command to list the real device
> names).

Success! The problem was that the guest is usually using /dev/vda but I 
couldn't get guestfish to start with:

[root at nexus ~]# guestfish -a /var/lib/libvirt/images/test2.img -m 
/dev/vg_test/lv_root -m /dev/vda1:/boot
libguestfs: error: mount: mount_stub: /dev/vda1: No such file or directory

Using /dev/sda1 instead lets guestfish start and /boot is mounted properly 
but grub-install didn't work. What did the trick was changing "/dev/vda" to 
"/dev/sda" in /boot/grub/device.map followed by a grub-install which now 
works and then changing the device.map back so I don't get problems when 
booting up the guest for real.

After that the "new" guest boots up perfectly.

I'm not very familiar with guestfish (yet) so I'm not sure if the /dev/vda1 
thing is a bug or simply not supposed to work.
The next step would be to automate the whole thing with a script even if 
it's only useful in some cases (where the guest only really uses a small 
part of the image).

Regards,
   Dennis