Using qemu-img to modify an image that is in use can corrupt the image
Opening a QEMU disk image from multiple processes at the same time, for example by attempting to take a snapshot of a QEMU image while the guest is running, in some cases corrupts the image. To avoid this problem, never use the qemu-img utility to modify images in use by a running virtual machine or any other process. In addition, be aware that querying an image that is being modified by another process may trigger an inconsistent state error. This update also adds an admonition about the mentioned problem to the qemu-img(1) man page.