[libvirt] Domain XML isn't dumping full backing chain

Deepak Shetty dpkshetty at gmail.com
Wed Mar 18 11:19:05 UTC 2015


Hi,
I am using libvirt version 1.2.9.2 on F21 and i am unable to get the
complete backing chain info in the virsh dumpxml output. Details below :

*My backing chain per qemu-img :*

[stack at devstack-f21 test]$ qemu-img info --backing-chain snap4.qcow2
image: snap4.qcow2
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 196K
cluster_size: 65536
backing file: ./snap3.qcow2
Format specific information:
    compat: 1.1
    lazy refcounts: false

image: ./snap3.qcow2
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 196K
cluster_size: 65536
backing file: ./snap2.qcow2 (actual path: ././snap2.qcow2)
Format specific information:
    compat: 1.1
    lazy refcounts: false

image: ././snap2.qcow2
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 196K
cluster_size: 65536
backing file: ./snap1.qcow2 (actual path: ./././snap1.qcow2)
Format specific information:
    compat: 1.1
    lazy refcounts: false

image: ./././snap1.qcow2
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 196K
cluster_size: 65536
backing file: ./base.qcow2 (actual path: ././././base.qcow2)
Format specific information:
    compat: 1.1
    lazy refcounts: false

image: ././././base.qcow2
file format: qcow2
virtual size: 1.0G (1073741824 bytes)
disk size: 196K
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false

I created 4 snapshots using commands (similar to the below, just dumping
the last one here ):

[stack at devstack-f21 test]$ virsh snapshot-create-as test-domain
on-test-snap4  --disk-only --reuse-external --diskspec
hda,snapshot=external,file=/home/stack/test/snap4.qcow2
Domain snapshot on-test-snap4 created

[stack at devstack-f21 test]$ virsh domblklist test-domain
Target     Source
------------------------------------------------
hda        /home/stack/test/snap4.qcow2



virsh dumpxml test-domain|more
....

    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/home/stack/test/snap4.qcow2'/>
      <backingStore type='file' index='1'>
        <format type='raw'/>
        <source file='/home/stack/test/./snap3.qcow2'/>
        <backingStore/>
      </backingStore>
      <target dev='hda' bus='ide'/>
      <alias name='ide0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>


.....

I think thats happening beccause the backingStore format is coming as 'raw'
What am i missing ?

thanx,
deepak
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