This is why planning is the #1 forgotten thing when setting up a machine/network. Get a monitor. That is about your only option.
This script may work, please correct me linux gurus!
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#!/bin/sh
ifconfig eth0 192.168.0.1 255.255.255.0 media 100baseTX
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I have no clue what you were planning on doing in a situation like this (obviously nothing) and I have no clue how to get this to run off of a floppy on startup. You should be able to plug a keyboard in (pray it just works) type your login wait a second, type your password, wait a couple seconds and run the ifconfig command (if I have syntax correct for linux). This will have to be as root of course. Go to a used computer store and pick up a 14" b/w monitor or setup the system to work with your serial connection like was previously stated. Simple solutions for simple people. Plan ahead. always be prepared, just do it, your way right away, and all that.