How to set grub Password..!!

How to set GRUB password after Linux installed

Login to the your machine as root from there type ‘grub’
#grub

As the user root, proceed as follows to set a boot password:

At the root prompt, encrypt the password using grub-md5-crypt:

# grub-md5-crypt
Password: ****
Retype password: ****
Encrypted: $1$lS2dv/$JOcHkLosIn7CJk9xShzzJVw/

[root@tecmint ~]# vi /boot/grub/menu.lst

OR

[root@tecmint ~]# vi /boot/grub/grub.conf

Note : I advise you to take backup of the files before making any changes to it, if in case something goes wrong you can revert it.

STEP 3: Add the newly created MD5 password in GRUB configuration file. Please paste copied password below timeout line and save it and exit. For example, Enter the line password –md5 <add the copied md5 string

[root@tecmint ~]# vi /boot/grub/grub.conf or [root@tecmint ~]# vi /boot/grub/menu.lst

# grub.conf generated by anaconda

#

# Note that you do not have to rerun grub after making changes to this file

# NOTICE:  You have a /boot partition.  This means that

#          all kernel and initrd paths are relative to /boot/, eg.

#          root (hd0,0)

#          kernel /vmlinuz-version ro root=/dev/sda3

#          initrd /initrd-[generic-]version.img

#boot=/dev/sda

default=0

timeout=5

password --md5 $1$TNUb/1$TwroGJn4eCd4xsYeGiBYq.

splashimage=(hd0,0)/grub/splash.xpm.gz

hiddenmenu

title CentOS (2.6.32-279.5.2.el6.i686)

        root (hd0,0)

        kernel /vmlinuz-2.6.32-279.5.2.el6.i686 ro root=UUID=d06b9517-8bb3-44db-b8c5-7710e183edb7 rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us crashkernel=auto rhgb quiet

        initrd /initramfs-2.6.32-279.5.2.el6.i686.img

title centos (2.6.32-71.el6.i686)

        root (hd0,0)

        kernel /vmlinuz-2.6.32-71.el6.i686 ro root=UUID=d06b9517-8bb3-44db-b8c5-7710e183edb7 rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us crashkernel=auto rhgb quiet

        initrd /initramfs-2.6.32-71.el6.i686.img

Reboot system and try it pressing ‘p‘ to enter password to unlock and enable next features

After rebooting the system and selecting the Linux entry from the boot menu, the following error message is displayed:

Error 32: Must be authenticated
Press Enter to enter the menu. Then press P to get a password prompt. After entering the password and pressing Enter, the selected operating system (Linux in this case) should boot.