secure your grub with md5 password

1.create md5 password with grub
#grub-md5-crypt
Password:
Retype password:
$1$hQxw5/$VV.DSdXzWeHQjwrumXB9D/

2.modify the grub config
#vi /boot/grub/grub.conf
add new line below
password --md5 $1$hQxw5/$VV.DSdXzWeHQjwrumXB9D/

3.reboot system to confirm password