libvirt users - Apr 2010 - Need help using libvirt with qcow2 delta and base images

Hi,

 

I am having trouble configuring a virtual machine domain and its
corresponding xml definition to use a qcow2 delta disk.  The delta disk
is backed by a qcow2 base disk.  I am able to successfully start the
guest OS with the delta disk at the command line using qemu.  However, I
am not able to start the guest OS using the libvirt tools including
virsh and virt-manager.  I am hoping that someone knows how to configure
a virtual machine domain that works with a qcow2 delta disk, and have it
managed by the virt-family tools.

 

First, I create a delta and base disk from a raw image file with the
following commands:

  qemu-img convert ubuntu910server64.img -O qcow2
ubuntu910server64_base.qcow2

  qemu-img create -b ubuntu910server64_base.qcow2 -f qcow2
ubuntu910server64_delta.qcow2

 

Then, I can successfully start the guest OS on the command line with

  qemu-system-x86_64 -m 256 -hda ubuntu910server64_delta.qcow2

 

My attempt to modify the virtual machine domain configuration fails.
Here are my steps:

-- Edit the configuration

   # virsh edit ubuntu910server64

-- Replace some lines

    <disk type='file' device='disk'>

-     <source
file='/var/lib/libvirt/images/ubuntu910server64.img'/>

-      <target dev='vda' bus='virtio'/>

+     <source
file='/var/lib/libvirt/images/ubuntu910server64_delta.qcow2'/>

+      <target dev='hda' bus='ide'/>

    </disk>

-- Attempt to start the machine

   # virsh start ubuntu910server64

   Connecting to uri: qemu:///system

   error: Failed to start domain ubuntu910server64

   error: internal error unable to start guest: qemu: could not open
disk image /var/lib/libvirt/images/ubuntu910server64_delta.qcow2

 

If I have posted this to the wrong forum, please direct me to the right
location.

 

Thanks!

-dave

-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://listman.redhat.com/archives/libvirt-users/attachments/20100419/a89f2fc3/attachment.htm>

On Mon, Apr 19, 2010 at 5:31 PM, Wang David <David_Wang at prn.com> wrote:
>  -      <target dev='vda' bus='virtio'/>
>
> +      <target dev='hda' bus='ide'/>
>
Why are you changing this? Unless you've gone through extra steps to
configure your guest OS to use this different driver and location of the
boot disk, it's going to fail to boot. Perhaps try leaving this line
unchanged and see how that goes. From the VM's perspective, the
copy-on-write image (delta) is no different than the backing store.

.:. jeremy
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://listman.redhat.com/archives/libvirt-users/attachments/20100420/19fbf6a4/attachment.htm>