Make Grub2 Boot the Last Operating System You Used
The GRUB2 boot loader can seem confusing at first. Instead of one configuration file, there are several. You run one command update-grub to update the configuration file, another command (grub-install) to write the configuration to the Master Boot Record (MBR) on your hard drive. On the plus side, GRUB2 can make life much easier if you’re running a dual or multiple boot system – say, switching between Linux and Windows, or hopping between multiple distros.