On Mon, Nov 30, 2015 at 04:34:14PM +0100, Lentes, Bernd wrote: > Stefan wrote: > > > > > Hi Bernd, > > qemu-img cannot be used on the disk image when the VM is running. > > Please use virsh, it communicates with the running QEMU process and > > ensures that the snapshot is crash-consistent. > > > > Hi Stefan, > > thanks for your answer. > > i read that virsh uses internally qemu-img > (http://serverfault.com/questions/692435/qemu-img-snapshot-on-live-vm). > Is that true ?
It's false in the general case. While the VM is running libvirt will use the QEMU monitor to communicate with the QEMU process instead of using qemu-img. While the VM is shut down libvirt can use qemu-img safely. The reason why qemu-img isn't safe is that the image file might be written to by the running VM at the same time as qemu-img reads/writes it. This can corrupt image files. Stefan
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