[Qemu-discuss] How can I use json format to backup a image by qemu-img tool

[Han Han]

Hi, all
I found qemu-img could use json format to create a backup image, like following:
#  qemu-img create -f qcow2 -b 'json: json: { "file.driver":"file", 
"file.filename":"/nfs/images/v.qcow2"}' /tmp/foo 100M
But I am not clear what is the meaning of these json parameters and if there is 
any other available parameters in the json format? I couldn't find useful info 
from Google or qemu manual. Could you tell the available json parameters or 
where I can find them? 
Thks

Best rewards,
Han