(written by Haidinger Walter)
Do a "man 8 mount" and search for a section entitled "THE LOOP DEVICE".
Create the device-nodes if they do not exist yet:
mknod /dev/loop0 b 7 0 mknod /dev/loop1 b 7 1 ... mknod /dev/loop9 b 7 9
More information and examples can be found in:
CD Writing HOWTO (which also explains how to mount cdrom-images)
Documentation/ramdisk.txt (in the kernel sources)
Note: To use loop devices, you must have a kernel that supports them.