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From: "Deepak Shetty" <dpkshetty@gmail.com>
To: libvir-list@redhat.com
Sent: Wednesday, March 18, 2015 7:19:05 PM
Subject: [libvirt] Domain XML isn't dumping full backing chain

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@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

If you want prepare the backing chain yourself, you should  add "-o backing_fmt=$farmat" options,

like "qemu-img create -f qcow2 base.s1 -b base.qcow2 -o backing_fmt=qcow2"