How to boot an Indy without keyboard or mouse (server mode):
  
  http://sprysgi.sghms.ac.uk/~cspry/computing/Indy_admin/configuration.html

Booting an Indy without a keyboard or mouse

 I have read that the following setting is useful if you have a spare Indy 
  that you want to sit in a corner and work for you in conjunction with other 
  computers.
 Use these other computers to telnet to the Indy and administer it. To boot an 
  Indy without a keyboard or mouse, enter in a  shell as 'root', when you have
  keyboard and mouse attached:

 nvram nogfxkbd 1

 Shutdown and remove the mouse and keyboard and restart the computer. 
  Rebooting with the 'nogfxkbd' prom variable set to '1', obviates the need for
  a keyboard or mouse to be connected at boot time. This is also described in 
  the 'man' pages on 'prom' which is where other important variables are set, 
  such as the loudness of the speaker at boot time.