setup hybrid graphic in grub

[zombo fu]

Lenovo Y460 Intel core i3 and ATI Radeon 5650

https://help.ubuntu.com/community/HybridGraphics

there is three steps in the process:


echo ON > /sys/kernel/debug/vgaswitcheroo/switch  # use all graphics
echo IGD > /sys/kernel/debug/vgaswitcheroo/switch  # open IGD
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch  # close DIS

unfortunately, it does not work because /sys could not be write before
it had been mounted with debugfs, so,  I  don't know how to the author
 could make it works.

so, how to make it works?

Thanks help.