This page describes how to edit a boot.scr file as shipped with the Ubuntu omap images to edit boot commandline options
Obtain the boot.scr from your image (after you dd'ed the image to SD card)
Strip the 72byte long uboot header:
dd if=boot.scr of=boot.script bs=72 skip=1
Open the file in an editor and edit the "setenv bootargs" line to add/remove bootoptions.
If you want to enable a serial console you can for example add the following to that line (if you do that in one of the text based installation images your install will automatically run on the serial tty):
To do a cloneable installation that fires up a personalization and configuration helper on first boot (setting up user, language, timezone, machine name etc) add the string below.
For running the NetBookInstall image in live mode on a serial console add the following, it will give you a serial tty login.
To add the needed uboot header back again use the mkimage command from the uboot-mkimage package:
sudo apt-get install uboot-mkimage mkimage -A arm -T script -C none -n "Ubuntu boot script" -d boot.script boot.scr
Now just copy the newly created boot.scr file on your SD card replacing the existing one and your changes will take effect on boot.