If you encounter this error while trying to mount a loop device (cd-image and such):

$ sudo mount -o loop -t squashfs /media/disk/casper/filesystem.squashfs /home/tdd/No-rsync-stuff/usb
mount: could not find any free loop device

you have run out of loop devices.

Here's a script to create from loop8 to loop63:

for ((i=8;i<64;i++)); do
  [ -e /dev/loop$i ] || mknod -m 0600 /dev/loop$i b 7 $i
done