Linuxjournalonline teaches you how to use GRUB to dual-boot Linux and another operating system. You need to go to etc/default/grub and edit that file. Here you can configure the time it needs to start booting a system and what OS to boot. You need to be root to edit this configuration file. Don't forget to run update-grub to force an update of grub.cfg. And this is the end of the short process needed to configure Grub 2 for Linux.