What is Grub?
Grub is abbreviaton of “GRand Unified Bootloader”. It is used as a bootloader.The location of grub is in /boot/grub
$ cd /boot/grub
To see the content.
/boot/grub$ ls -l
Always make a back up before you work with a file system.
$ sudo cp menu.lst menu.lst.backup
To Open the menu.lst file.
:/boot/grub$ sudo gedit menu.lst
If you upgrade your kernel, you will get another choice of running Ubuntu. Either you want to go with your old kernel or start with a new one. Automatically added to menu.lst
:/boot/grub$ sudo apt-get update
:/boot/grub$ sudo apt-get upgrade
:/boot/grub$ sudo apt-get dist-upgrade