GRUB (GRand Unified Bootloader) is a boot loader package from the GNU Project. GRUB provides a user the choice to boot one of multiple operating systems installed on a computer or select a specific kernel configuration available on a particular operating system's partitions.
Step:1 Command To Generate Password for GRUB
Now Copy this encrypted password and add the password entry in the grub.conf file as shown below :
[root@localhost ~]# vi /boot/grub/grub.conf
Step:2 Now Reboot Linux Machine and Go To Boot Loader Screen as show below where you can not go to grub prompt unless you press p and type the correct boot loader Password