[libvirt-users] Attaching disks with external snapshots

Erlon Cruz sombrafam at gmail.com
Wed Aug 24 20:03:29 UTC 2016 

Just following up, this is indeed an apparmor issue. The attachment work
with apparmor disabled. This is a libvirt bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1361592

On Mon, Aug 22, 2016 at 2:26 PM, Erlon Cruz <sombrafam at gmail.com> wrote:

> If that was the case I wouldn't be able to attach a volume without
> snapshots. But just in case I did the following test, before attaching the
> file, I copied all the file to a local folder and changed the path in XML
> with the new paths. The problem repeats:
>
> *2016-08-22 17:14:19.795+0000: 3799: info : qemuMonitorIOProcess:423 :
> QEMU_MONITOR_IO_PROCESS: mon=0x7f68f800c4c0 buf={"return": "Could not open
> backing file: Could not open
> '/home/ubuntu/volumes/volume-d81f7e7e-4215-4433-aad2-50adcd31b29d.7a9ea169-a3ab-48bd-bd9d-e7585860abe4':
> Permission denied\r\n", "id": "libvirt-30"}*
>
> But, if I use the top backing file with same permissions
> (/home/ubuntu/volumes/volume-d81f7e7e-4215-4433-aad2-50adcd31b29d), the
> operation suceeds. Can this be a libvirt/QEMU bug?
>
> Han, can you tell me more details about the commands you used and the
> versions of or libvirt/qemu? I couldn't reproduce from the steps you
> outlined.
>
> On Fri, Aug 19, 2016 at 12:02 AM, Han Han <hhan at redhat.com> wrote:
>
>> Hi Erlon,
>> Since you say you got Permission denied error while the ACL mode is 777，
>> I guess it is due to security system like selinux or apparmor.
>> As I know, selinux defaultly will disable qemu to use volume based on
>> NFS. We need to use 'setsebool virt_use_nfs 1' to enable it.
>> Well, your OS is ubuntu, so I think apparmor causes the permission
>> problem. Try to find a way to enable virt_use_nfs or disable apparmor. Then
>> check if the problem can be reproduced.
>>
>> Han
>>
>> ----- Original Message -----
>> From: "Erlon Cruz" <sombrafam at gmail.com>
>> To: "Han Han" <hhan at redhat.com>
>> Cc: "Yang Yang" <yanyang at redhat.com>, "Yuan Dan" <dyuan at redhat.com>,
>> "Xuesong Zhang" <xuzhang at redhat.com>, libvirt-users at redhat.com
>> Sent: Thursday, 18 August, 2016 12:44:36 PM
>> Subject: Re: [libvirt-users] Attaching disks with external snapshots
>>
>> Hi Han,
>>
>> Any update on this?
>>
>> Erlon
>>
>> On Wed, Aug 17, 2016 at 9:58 AM, Erlon Cruz <sombrafam at gmail.com> wrote:
>>
>> > Han,
>> >
>> > Did the same test again with libvirt debug enabled. This time I added
>> the
>> > disk[1] without snaps (OK), and then added the disk[2] with snapshots.
>> The
>> > libvirt log[3] (line 320) says:
>> >
>> > *Could not open
>> > '/opt/stack/data/nova/mnt/a3b4c6ddd9bf82edd4f726872be58d05/
>> volume-a75b42e8-8175-4516-b724-43ee6f3d2520':
>> > Permission denied\r\n", "id": "libvirt-33"}]*
>> >
>> > But this file has 777 permissions. I can access it with any user I
>> > tried[4]. Tough its mounted over NFS, the permissions seems to be right.
>> >
>> > Erlon
>> >
>> > [1]  http://paste.openstack.org/show/556055/
>> > [2]  http://paste.openstack.org/show/556056/
>> > [3]  http://pastebin.com/CCFcKq5b
>> > [4]  http://paste.openstack.org/show/559018/
>> >
>> >
>> > On Tue, Aug 16, 2016 at 2:41 PM, Erlon Cruz <sombrafam at gmail.com>
>> wrote:
>> >
>> >> Hi Han,
>> >>
>> >> Thanks for helping. What is the XML before the snapshot is created? Can
>> >> you post the XML files you used too? The files are in the links
>> pointed by
>> >> the numbers [1], [2] etc.
>> >>
>> >> The versions are:
>> >> qemu-system-x86_64 --version
>> >> QEMU emulator version 2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.4), Copyright
>> >> (c) 2003-2008 Fabrice Bellard
>> >>
>> >> libvirtd --version
>> >> libvirtd (libvirt) 1.3.1
>> >>
>> >>
>> >>
>> >> Erlon
>> >>
>> >> On Mon, Aug 15, 2016 at 12:56 AM, Han Han <hhan at redhat.com> wrote:
>> >>
>> >>> Hi，Erlon
>> >>> I was not able to reproduce your problem. It is ok to attach disk with
>> >>> external snapshot.
>> >>> I did it with following steps:
>> >>> # qemu-img create /tmp/vdb 100M
>> >>> Formatting '/tmp/vdb', fmt=raw size=104857600
>> >>> # virsh start snap
>> >>> Domain snap started
>> >>> # virsh snapshot-create-as snap s1 --disk-only --diskspec
>> >>> vdb,file=/tmp/vdb.s1 --quiesce
>> >>> Domain snapshot s1 created
>> >>> # virsh dumpxml snap|awk '/<disk/,/<\/disk/'
>> >>>     <disk type='file' device='disk'>
>> >>>       <driver name='qemu' type='qcow2' cache='none'/>
>> >>>       <source file='/var/lib/libvirt/images/snap.s1'/>
>> >>>       <backingStore type='file' index='1'>
>> >>>         <format type='qcow2'/>
>> >>>         <source file='/var/lib/libvirt/images/snap.qcow2'/>
>> >>>         <backingStore/>
>> >>>       </backingStore>
>> >>>       <target dev='vda' bus='virtio'/>
>> >>>       <alias name='virtio-disk0'/>
>> >>>       <address type='pci' domain='0x0000' bus='0x00' slot='0x07'
>> >>> function='0x0'/>
>> >>>     </disk>
>> >>>     <disk type='file' device='disk'>
>> >>>       <driver name='qemu' type='qcow2'/>
>> >>>       <source file='/tmp/vdb.s1'/>
>> >>>       <backingStore type='file' index='1'>
>> >>>         <format type='raw'/>
>> >>>         <source file='/tmp/vdb'/>
>> >>>         <backingStore/>
>> >>>       </backingStore>
>> >>>       <target dev='vdb' bus='virtio'/>
>> >>>       <alias name='virtio-disk1'/>
>> >>>       <address type='pci' domain='0x0000' bus='0x00' slot='0x0c'
>> >>> function='0x0'/>
>> >>>     </disk>
>> >>>
>> >>> Save the dumped vdb's xml to /tmp/vdb.xml
>> >>> # virsh detach-device snap /tmp/vdb.xml
>> >>> Device detached successfully
>> >>> # virsh attach-device snap /tmp/vdb.xml
>> >>> Device attached successfully
>> >>> # virsh dumpxml snap|awk '/<disk/,/<\/disk/'
>> >>>     <disk type='file' device='disk'>
>> >>>       <driver name='qemu' type='qcow2' cache='none'/>
>> >>>       <source file='/var/lib/libvirt/images/snap.s1'/>
>> >>>       <backingStore type='file' index='1'>
>> >>>         <format type='qcow2'/>
>> >>>         <source file='/var/lib/libvirt/images/snap.qcow2'/>
>> >>>         <backingStore/>
>> >>>       </backingStore>
>> >>>       <target dev='vda' bus='virtio'/>
>> >>>       <alias name='virtio-disk0'/>
>> >>>       <address type='pci' domain='0x0000' bus='0x00' slot='0x07'
>> >>> function='0x0'/>
>> >>>     </disk>
>> >>>     <disk type='file' device='disk'>
>> >>>       <driver name='qemu' type='qcow2'/>
>> >>>       <source file='/tmp/vdb.s1'/>
>> >>>       <backingStore type='file' index='1'>
>> >>>         <format type='raw'/>
>> >>>         <source file='/tmp/vdb'/>
>> >>>         <backingStore/>
>> >>>       </backingStore>
>> >>>       <target dev='vdb' bus='virtio'/>
>> >>>       <alias name='virtio-disk1'/>
>> >>>       <address type='pci' domain='0x0000' bus='0x00' slot='0x0c'
>> >>> function='0x0'/>
>> >>>     </disk>
>> >>>
>> >>> So I managed to attach disks with snapshot.
>> >>> I want to know what is your libvirt and qemu-kvm version?
>> >>> And can you provide your files: /tmp/disk.xml[1],
>> >>> /tmp/snap-from-disk.xml[2], /tmp/disk-with-snap.xml[4],
>> >>> /tmp/disk-with-snap.xml . I need more details.
>> >>>
>> >>> Han Han
>> >>>
>> >>> ----- Original Message -----
>> >>> From: "Erlon Cruz" <sombrafam at gmail.com>
>> >>> To: libvirt-users at redhat.com
>> >>> Sent: Friday, August 12, 2016 10:23:24 AM
>> >>> Subject: [libvirt-users] Attaching disks with external snapshots
>> >>>
>> >>> Hi folks,
>> >>>
>> >>> I'm trying to to attach a disk to an instance using libvirt. The
>> problem
>> >>> is, this disk has external snapshots. The process tried was:
>> >>>
>> >>> 1 - Attach a disk in the domain:
>> >>> virsh# attach-device instance-00000006 /tmp/disk.xml[1] --live
>> >>>
>> >>> 2 - Snapshot the disk[2]:
>> >>> virsh# snapshot-create instance-00000006 --quiesce --xmlfile
>> >>> /tmp/snap-from-disk.xml[2] --disk-only
>> >>>
>> >>> 3 - Dump the domain XML and create a new disk file from it:
>> >>> virsh# dumpxml instance-00000006
>> >>> ... [3]
>> >>>
>> >>> 4 - Dettach the device and re-add it using the new disk file:
>> >>> virsh# detach-device instance-00000006 /tmp/disk-with-snap.xml[4]
>> >>> Device detached successfully
>> >>> virsh# attach-device instance-00000006 /tmp/disk-with-snap.xml
>> >>> error: Failed to attach device from /tmp/disk-with-snap.xml
>> >>> error: internal error: unable to execute QEMU command 'device_add':
>> >>> Property 'virtio-blk-device.drive' can't find value
>> 'drive-virtio-disk1'
>> >>>
>> >>> Question, is this operation supported? If yes, how is the correct
>> >>> procedure?
>> >>>
>> >>> Erlon
>> >>>
>> >>>
>> >>> [1] http://paste.openstack.org/show/556055/
>> >>> [2] http://paste.openstack.org/show/556056/
>> >>> [3] http://paste.openstack.org/show/556063/
>> >>> [4] http://paste.openstack.org/show/556064/
>> >>>
>> >>> _______________________________________________
>> >>> libvirt-users mailing list
>> >>> libvirt-users at redhat.com
>> >>> https://www.redhat.com/mailman/listinfo/libvirt-users
>> >>>
>> >>
>> >>
>> >
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/libvirt-users/attachments/20160824/44b83c10/attachment.htm>

More information about the libvirt-users mailing list