Loop device information

You can see what is being used by a loop device with losetup:
# losetup /dev/loop0
/dev/loop0: [fd06]:234921356 (/linux/isos/backtrack.iso)

To detach an image from loop device
losetup -d /dev/loop0 ## to detach image associate with loop0

It is possible to increase the number of available loop devices. Free
all loop devices, and add a line with the following to
/etc/modprobe.conf:
options loop max_loop=64

(maximum is 256)

Then, do: rmmod loop && modprobe loop

If you get an error that the module couldn't be removed, you still have
loop devices in use.

Newer kernels (2.6.21 or 2.6.22) use a dynamic allocation of loop
devices, so you will only have to create the filesystem representation
of the devices:
for ((i=8;i<64;i++)); do
[ -e /dev/loop$i ] || mknod -m 0600 /dev/loop$i b 7 $i
done