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Re: [libvirt-users] Need help using libvirt with qcow2 delta and base images



Hi Jeremy,

Thanks for responding, and for the suggestion.

I have tried several permutations of device type and bus (including vda/virtio), each of which seem to work on non-delta images.  The reason that I have given the example below using (target dev='hda' bus='ide') is because it most closely matches the working qemu command line:
  qemu-system-x86_64 -m 256 -hda ubuntu910server64_delta.qcow2

This problem may be related to the way that virt-manager calls qemu.  When I use virsh to start a working non-delta image, the command line found from "ps" is the following:

  /usr/bin/kvm <options removed> -drive file=/var/lib/libvirt/images/ubuntu910server64.img,if=virtio,index=0,boot=on <options removed>

This seems to match the "qemu" man page documentation at line 139, where it suggests that the -hda switch is an alias to the -drive option:

           Instead of -hda, -hdb, -hdc, -hdd, you can use:

                   qemu -drive file=file,index=0,media=disk

Assuming that qemu/kvm is called with the same options for the delta disk, the options should be correct.

I've attached a segment from the syslog, which shows an error at qemudReadLogOutput:816
--------------------------------------------------------------------
Apr 19 17:27:36 virtualserver3 kernel: [14202.390685] type=1505 audit(1271723256.496:74): operation="profile_load" pid=3144 name=libvirt-20030353-cdee-109a-1abb-dc4971d036c2
Apr 19 17:27:36 virtualserver3 kernel: [14202.400448] device vnet0 entered promiscuous mode
Apr 19 17:27:36 virtualserver3 kernel: [14202.402668] br0: port 2(vnet0) entering learning state
Apr 19 17:27:36 virtualserver3 kernel: [14202.411373] type=1503 audit(1271723256.513:75): operation="open" pid=3147 parent=1 profile="libvirt-20030353-cdee-109a-1abb-dc4971d036c2" requested_mask="r::" denied_mask="r::" fsuid=0 ouid=0 name="/data/virtual/var/lib/libvirt/images/ubuntu910server64.qcow2"
Apr 19 17:27:36 virtualserver3 kernel: [14202.516577] br0: port 2(vnet0) entering disabled state
Apr 19 17:27:36 virtualserver3 kernel: [14202.544518] device vnet0 left promiscuous mode
Apr 19 17:27:36 virtualserver3 kernel: [14202.544522] br0: port 2(vnet0) entering disabled state
Apr 19 17:27:36 virtualserver3 libvirtd: 17:27:36.718: error : qemudReadLogOutput:816 : internal error Process exited while reading console log output
Apr 19 17:27:36 virtualserver3 libvirtd: 17:27:36.718: error : qemudWaitForMonitor:1103 : internal error unable to start guest: qemu: could not open disk image /var/lib/libvirt/images/ubuntu910server64_delta.qcow2#012
Apr 19 17:27:36 virtualserver3 kernel: [14202.728382] type=1505 audit(1271723256.834:76): operation="profile_remove" pid=3149 name=libvirt-20030353-cdee-109a-1abb-dc4971d036c2 namespace=default
--------------------------------------------------------------------

Both the virtual host and guest machines are running Ubuntu 9.10 Server amd-64.

Has anyone have any success stories using delta images with virt-family tools?

Thanks!
-dave

________________________________________
From: jeremy avnet [mailto:brainsik saucelabs com] 
Sent: Tuesday, April 20, 2010 7:58 AM
To: Wang David
Cc: libvirt-users redhat com
Subject: Re: [libvirt-users] Need help using libvirt with qcow2 delta and base images

On Mon, Apr 19, 2010 at 5:31 PM, Wang David <David_Wang 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




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