linux box without a keyboard

[Alexei V. Ovsiannikov]

About an hour ago I had to work directly with a mail server running Linux
without monitor and keyboard. When I attached monitor and keyboard without
rebooting the machine, video card was working OK (i.e. I could see some
messages on the screen , but no promt), but the keyboard seemed not to be
working at all. What i did wrong and what should I do to be able to work on
a machine like that?