If you use file-based guest images, one may have increased the number of configured loop devices (the default allows up to 8 loop devices to become active). If you need more than 8 file-based guests/loop devices, you must modify the /etc/modprobe.conf file. When modifying the modprobe.conf file, you must include this line:

options loop max_loop=64

This example uses 64 but you can specify another number to set the maximum loop value. You may also have to implement loop device backed guests on your system. To employ loop device backed guests for a paravirtual system, use the phy: block device or tap:aio commands. To employ loop device backed guests for a full virtualized system, use the phy: device or file: file commands.