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The XML for quite a longish backing chain is shown below:
<disk type='network' device='disk'>
<driver name='qemu' type='qcow2'/>
<source protocol='nbd' name='bar'>
<host transport='unix' socket='/var/run/nbdsock'/>
</source>
<backingStore type='block' index='1'>
<format type='qcow2'/>
<source dev='/dev/HostVG/QEMUGuest1'/>
<backingStore type='file' index='2'>
<format type='qcow2'/>
<source file='/tmp/image2.qcow'/>
<backingStore type='file' index='3'>
<format type='qcow2'/>
<source file='/tmp/image3.qcow'/>
<backingStore type='file' index='4'>
<format type='qcow2'/>
<source file='/tmp/image4.qcow'/>
<backingStore type='file' index='5'>
<format type='qcow2'/>
<source file='/tmp/image5.qcow'/>
<backingStore type='file' index='6'>
<format type='raw'/>
<source file='/tmp/Fedora-17-x86_64-Live-KDE.iso'/>
<backingStore/>
</backingStore>
</backingStore>
</backingStore>
</backingStore>
</backingStore>
</backingStore>
<target dev='vdb' bus='virtio'/>
</disk>
Various disk types and formats can be mixed in one chain. The
<backingStore/> empty element marks the end of the backing chain and it
is there mostly for future support of parsing the chain provided by a
user. If it's missing, we are supposed to probe for the rest of the
chain ourselves, otherwise complete chain was provided by the user. The
index attributes of backingStore elements can be used to unambiguously
identify a specific part of the image chain.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>