template cloning:

1 clone a template from template
The user may clone a template from an existing template with different name.     
Later he can customize some parts of the template to save the effort to create a full new template.    
For example, he can update the network of the template cloned to have a new different template.  


2. we should also also user clone a template from vm
I just concern the image volume.
For vm may has no CDROM attribute. 
Then does the template need to copy the image volume.
For VM clone, can we make the the vm image as a backing file(or we can 
call it base image).

Then we can create two new images for this vm and new vm.

All these two new images are a read/write snapshot of the original image,

-- any changes to new images will not be reflected in original image.


http://libvirt.org/formatstorage.html#StorageVolBacking

http://wiki.qemu.org/Documentation/CreateSnapshot

-- 
Thanks and best regards!

Sheldon Feng(冯少合)<shaohef@linux.vnet.ibm.com>
IBM Linux Technology Center