After several tries and a lot of serial console usage I finally got extroot working. I am new to digging in the guts of linux and started my journey about extroot in the openwrt wiki. As this is very technical I got confused and…long story short here is a howto for beginners on how to setup your openwrt box to boot from an external USB stick.
I assume you have a fresh openwrt setup (Attitude Adjustment) without any installed packages. You have set up your network of course (vi /etc/config/network) to match your home network ip/dns/gateway. Your ‘internet is up’ and furthermore you have a USB stick (obviously).
I have an 8 gb verbartim mini stick.
Once the system is booted up type the following