How to use GPIO on Ubuntu OS not Angstrom OS?

Hello everybody,
I’m newbie in Beagleboard-xM, I had installed Ubuntu OS on bbxm, but I can’t configure GPIO on it.
On Angstrom, I can change mode at

but on Ubuntu OS, omap_mux directory just have 1 empty “board” folder. I just want using GPIO on Ubuntu OS
I also change file beagle.h and rebuild bootloader but it’s still not working.
When I build kernel, I don’t know how to config and after I cross compile into KIT, It’s can’t boot into Ubuntu.
Please help me step by step.

Sorry because my English is not well,

Thank you so much!
— Truong