libvirt users - Nov 2019 - virsh snapshot-create --print-xml seems to ignore most arguments

Hi,

I am wondering if the --print-xml option is working correctly. The
output for two snapshot-create commands are the same, even though the
first one includes additional options (no-metadata and atomic).

I want to use the generated XML to create a snapshot via a perl script,
and Sys::Virt only seems to support snapshots using a XML description
of the arguments.


timos@cerberus:~$ sudo virsh snapshot-create-as --domain web guest-
state1 --diskspec hda,file=overlay1.qcow2 --disk-only --atomic --no-
metadata --print-xml
<domainsnapshot>
  <name>guest-state1</name>
  <disks>
    <disk name='hda'>
      <source file='overlay1.qcow2'/>
    </disk>
  </disks>
</domainsnapshot>


timos@cerberus:~$ sudo virsh snapshot-create-as --domain web guest-
state1 --diskspec hda,file=overlay1.qcow2 --disk-only  --print-xml
<domainsnapshot>
  <name>guest-state1</name>
  <disks>
    <disk name='hda'>
      <source file='overlay1.qcow2'/>
    </disk>
  </disks>
</domainsnapshot>

My libvirt version is:

Compiled against library: libvirt 5.6.0
Using library: libvirt 5.6.0
Using API: QEMU 5.6.0
Running hypervisor: QEMU 4.1.0

Regards,
Timo

On 11/20/19 11:14 AM, Timo Schneider wrote:
> Hi,
> 
> I am wondering if the --print-xml option is working correctly. The
> output for two snapshot-create commands are the same, even though the
> first one includes additional options (no-metadata and atomic).
--no-metadata and --atomic merely pass additional flags to the API call; 
they do not affect the XML.  Remember, it is the combination of both the 
XML and the API flags that control what the API will do.
> 
> I want to use the generated XML to create a snapshot via a perl script,
> and Sys::Virt only seems to support snapshots using a XML description
> of the arguments.
Yes, the perl bindings don't have the convenience wrappers like virsh, 
so you'll need the XML; but the perl bindings DO let you also pass in 
flags for the case where virsh has bool options for setting a flag.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org