How do I disable USB ports while running from a USB stick?

Question

I want to make a bootable Linux image for a USB stick. For security reasons, I want to disable any other USB ports on the computer.

Is this possible? If so, how can I configure it? Let's assume I'm using Ubuntu 11.10.

In other words: I boot my computer from a USB stick. I want to make it impossible to use another stick at the same time.

Edit: The situation is hypothetical, in a discussion about using computers on exams. We are discussing whether students could bring their own computers, but run an OS from a USB stick handed out at the exam. This approach raises concerns about cheating, for example by bringing disallowed material on a USB stick, so I want to explore options to counter this cheating.

Answer 1

If you avoid using automatic device filesystems, you can use static device files defined by you and omitting creating the ones that would be the additional mountable devices eg sdb. This is an untested idea. I would use something, which is already hardened like http://www.backtrack-linux.org/ instead of reinventing the wheel and definitively no root access to the students.