I'm trying to boot Ubuntu using PXE from U-Boot on the Samsung XE303C12-A01US Chromebook. I would like to understand better the point 5 of the tutorial here :

https://wiki.linaro.org/Boards/Arndale/Setup/PXEBoot

it says : "At the u-boot prompt, set the environmental variables "serverip" and "ipaddr" as per the board and host PC configuration. Now set the following environmental variables as mentioned..."

the problem is that the Samsung XE303C12-A01US does not have a serial port and I can't stop the u-boot booting and set the enviromental variables manually. I would like to know how can I embed them inside u-boot. Also because there is not a configuration file like boot.cmd/boot.scr like there is on the pandaboard that can be used to pass the parameters. Thanks.