Do you mean DOS or an NT command prompt? AFAIK, most BIOS updates are done in either DOS or GUI Windows. A command prompt only NT is a bit tricky, and not very useful anyway. A DOS booting USB stick ...
I'm not always next to the cabinet which houses my Xserves and other gear, but use Screen Sharing quite a lot on my local network and TeamViewver when I'm further afield for access. No USB device I've ...