This is a weird one. Allow me to clarify, I have a Debian Linux file server - and I need to access some files from it. Usually, I would just use a network for this (wifi, ethernet, etc) but unfortunately the client computer can only access files over USB (the client is designed so that you can insert a USB flash drive, from which it reads).
Is there a way of making a USB drive pretend that it is a flash drive (or similar)? Perhaps that's phrased badly; to put it another way -- how do I make a USB port provide a file system instead of using it to access one?
Update: I forgot to mention that I'm using Debian Linux for the file system.
I'm glad I didn't try this:
http://en.wikipedia.org/wiki/Direct_cable_connection#DCC_with_USB
EDIT
If this works, it would be the easiest method; depending on how much you value your time, spending $30-40 bucks on something like this would be the first route I'd take:
http://ca.startech.com/product/PCMACLINK2-USB-to-USB-Data-Transfer-Cable-for-Windows-and-Mac
...and this site references other data transfer USB cables/devices that are (likely) more Linux friendly:
http://www.linux-usb.org/usbnet/
More digging produced this; I've seen this referenced in several other forum threads: http://www.linux-usb.org/gadget/
It's an API that appears to put your host (server) into USB slave mode to emulate a mass storage device. Looks like it's non-trivial to implement (see "how much do you value your time").
After digesting all of this, is there any reason why you can't do the obvious and copy the files you need from the server to a USB pendrive/harddrive?
I dont have a resolution for you. But it looks like this thread is on the right track.
Every Android phone can do something like this. Plug it in a USB port, hit the unmount option, and it looks like a USB stick to the host computer. Some more digging around this area might turn up the answer you are looking for.