It's qcow2 and increasing size is not what the problem is. The problem is, if the forked image is smaller than the base image. In that case, qemu-img should not create the image in first place.
It's qcow2 and increasing size is not what the problem is. The problem is, if the forked image is smaller than the base image. In that case, qemu-img should not create the image in first place.