I am not 100% sure whether this is the right place to raise this issue. Maybe you can forward this to right person

 

          I have the feeling this wikipage >>> http://wiki.qemu.org/Documentation/CreateSnapshot 
          is wrong. I think the decription and the posted command for
          creating snapshots [

qemu-img create -f qcow2
            -b centos-cleaninstall.img snapshot.img] is
          actually describing copy-on-write (or overlay) images. And I
          think this is not the same thing

As far as I know such a command
            would creat a copy-on-write image and not a snapshot.
          On the german debianforum.de I got another suggestion to
          vreate snaptshots which I have not tested yet, but sounds more
          likely to be correct to me

          

              qemu-img snapshot -c [snapshot_name] [base_name]