Clone a vm sharing disk

[Valerio Pachera <sirio81@xxxxxxxxx>]

Hi, I have a vm with a qcow2 disk hosted on a btrfs file system.

Looking at the documentation it seems always possibile to create a clone and share the source disk:

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/virtualization_administration_guide/cloning_vms_with_virt-manager

But I can't do it!

The options is "grey".

What am I missing?

Virt-manager 2.2.1