On 20/09/2016 15:51, Pavel Dovgalyuk wrote: >> From: Paolo Bonzini [mailto:pbonz...@redhat.com] >> On 20/09/2016 15:37, Pavel Dovgalyuk wrote: >>>> c) no rrsnapshot implies -snapshot: >>>> without overlay: >>>> -drive file=disk.raw,if=none,id=img-direct >>>> -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay >>>> >>>> with overlay: >>>> -drive file=foo.qcow2,if=none,id=img-direct >>>> -drive driver=blkreplay,if=none,image=img-direct,id=img-blkreplay >>>> -icount ...,rrsnapshot=snapname >>> >>> But how record will create this overlay? >>> This method requires creating overlay manually, because backing file is >>> not specified at all. >> >> You create it manually, or you just use a .qcow2 file to begin with for >> your image. Then: >> >> 1) if you specify no snapshot, a temporary .qcow2 file is created on top >> so data is not destroyed >> >> 2) if you specify a snapshot, that snapshot is preserved (so you don't >> lose the base state even though the file changes) > > Now I see. > This seems ok, but: > - this approach adds some garbage to original disk image > - won't work with raw images
Yes, for raw images or if you want to keep the pristine image you have to do a "qemu-img create -f qcow2 -b disk.raw foo.qcow2". Paolo
