General configuration
completely new command line interface. With new commands used to manage Grub2, things can be cumbersome at times. To make things easier for new users, I will try to cover the general Grub2 commands that will come handy.
Updating Grub: The update-grub command lets you directories.
Switching menu entries: Since it is not recommended order to make changes. To make a boot entry default, edit / etc/default/grub /etc/default directory has many useful customisation parameters for editing menus.
To make an entry default, change the numerical value of the entry GRUB_DEFAULT=0 to whichever entry you wish to boot into automatically. Similarly, you can change TIMEOUT=10 value.
Recovering Grub 2: The most important aspect of installation of some other operating system, Grub could get lost or replaced with some other boot loader. In that case, you have to re-install Grub. In order to do that, a bootable Linux medium with Grub2 as the main boot loader is required. Once booted into the live environment, open a terminal. As the root user, issue the following commands: