As the title, I'm on RHEL 4.
Currently, there are /dev/loop0 ~ /dev/loop7 (eight devices) created that seems to work fine.
When I try to create a new device, loop8, by calling
mknod /dev/loop8 b 7 8
chown --reference=/dev/loop0 /dev/loop8
chmod --reference=/dev/loop0 /dev/loop8
loop: can't get info on device /dev/loop0: No such device or address
loop: can't open device /dev/loop8: No such device or address
8 is the default number of loop devices. You need to pass an option to the loop module to increase this:
Also, mounting a file via loop device is not persistent, just like mounting anything is not persistent, unless you add it to