[libvirt-users] 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
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
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
On Tue, Apr 20, 2010 at 11:01 AM, Wang David <David_Wang@prn.com> wrote:
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 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
These indicate that AppArmor is denying access to the backing store, thus, your delta image will not work. You're going to need add a rule into /etc/apparmor.d/abstractions/libvirt-qemu so that the backing store can be read. Something like: /data/virtual/var/lib/libvirt/images/ubuntu910server64.qcow2 r, or /data/virtual/var/lib/libvirt/images/* r, .:. jeremy
Jeremy, Thank you so much for resolving my problem ;) The AppArmor configuration fix worked. I am sure that you have saved me many more days of research. It looks like I have to research this AppArmor business. Thanks! -dave ________________________________________ From: jeremy avnet [mailto:brainsik@saucelabs.com] Sent: Tuesday, April 20, 2010 11:46 AM To: Wang David Cc: libvirt-users@redhat.com Subject: Re: [libvirt-users] Need help using libvirt with qcow2 delta and base images On Tue, Apr 20, 2010 at 11:01 AM, Wang David <David_Wang@prn.com> wrote: 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 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 These indicate that AppArmor is denying access to the backing store, thus, your delta image will not work. You're going to need add a rule into /etc/apparmor.d/abstractions/libvirt-qemu so that the backing store can be read. Something like: /data/virtual/var/lib/libvirt/images/ubuntu910server64.qcow2 r, or /data/virtual/var/lib/libvirt/images/* r, .:. jeremy
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