Ubuntu. How to create a fake USB from a folder?

Question

linux

Hello!
The task is interesting, but I have not yet been able to find a solution.
In general, I run a docker container from an ubuntu image. In a running container, do the following:

1. create folder X
   
2. put what files in folder X
   
3. create img/iso image of X folder
   
4. Mount img/iso image under the guise of a removable USB drive
   

Those. eventually some folder should act as the inserted USB. You can even readonly
Here is the last point of the problem.
PS: in fact, physically, no USB media will be inserted. You just need to get this effect.

Answer 1

the file system from the image file is mounted via the loop device.
google "mount -o loop" the topic is long-standing painted in a bunch of places.