Thanks for your answer, I am trying to make a snapshot of whole virtual machine (disk, CPU state, memory). But I need to make this snapshot in matter of seconds. I have already try to create snapshot of disk, which is not problem. I use qcow2 format, and create new disk image using original disk image as backing file. But still I am not able to assign state of vm with new disk. I have found some commands for creating snapshots in libvirt API, so in my opinion one way how to accomplish my task is to create utility using theese commands, and create snapshot of vm in RAM - I hope it would be faster. But I wonder whether virsh contains similar functionality, so I won't need to programm it again. Dne 2.12.2013 19:32, Eric Blake napsal(a): On 12/02/2013 09:04 AM, Juraj Melo wrote: What are you trying to copy-on-write? Is it just disk state, or VM memory state? Do you have corresponding qemu commands that you are trying to figure out if virsh maps to those same commands? There's a lot of flexibility in the virsh snapshot XML, but not all of it has been wired up yet (in part because it's still a moving target for what upstream qemu supports), so knowing more details about what you are trying to do will help us better answer whether it can be done now and if so with which commands.