grub config for ubuntu 10.04 ~ 13.04,
steps to edit:
* sudo cp /etc/default/grub /etc/default/grub.bak
* sudo vi /etc/default/grub
do changes
* sudo update-grub
this will re-generate /boot/grub/grub.cfg automatically,
*
* ok
*
tip:
"/boot/grub/grub.cfg" can't be edited directly,