Ho trovato questo, non so se può aiutarti:

" If you don't get a login prompt, or you see a console message like: "respawning too fast....
disabled for five minutes" (check your /var/log/messages file for this and similar errors
from init and/or from any 'getty' that you happen to be using), you should double-check the
syntax of your entry, double-check which serial port you're plugged into (remember Linux' numbering of
serial and printer ports sometimes doesn't correspond to DOS/BIOS extensions --- some crufty hardware
may cause confusion), and check for IRQ conflicts and cabling errors. "