[CentOS-virt] overlay image on centos 6 do not work

Tue Oct 4 07:59:02 UTC 2011
Kai Krueger <kai.krueger at itwm.fraunhofer.de>

Hello,

   I have some problems with overlay images on a host running centos 6.0

* I have 2 physical hosts, one running centos 5.5, the other running    
centos 6.0
* I created a virtual linux host with a raw file image centos6.img
   I can start this vm on both machines.
* then I created an overlay of the file image with
qemu-img create -b centos6.img -f qcow2 centos6.ovl

when I start the VM from the ovelay on the centos6 machine I get:
---
Booting from Hard Disk...
Boot failed: not a bootable disk

No bootable device
---

When booting from the raw-image and adding the overlay as second disk  
I see the following:
========== cut here ==========
fdisk -l

Disk /dev/vda: 8598 MB, 8598323200 bytes
255 heads, 63 sectors/track, 1045 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000bb12f

    Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *           1        1046     8395776   83  Linux

Disk /dev/vdb: 0 MB, 262144 bytes
16 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/vdb doesn't contain a valid partition table
========== cut here ==========

As one can see, the overlay image does not have any partition table.

Starting the vm with exactly these images (per nfs-mount) on the  
centos-5.5 host works properly.

Is my problem an known bug or is it an old feature that has been removed?

Best regards,

       Kai Krueger


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