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) Paolo
