1.计算grub的MD5加密密码：
#grub-md5-crypt
Password:
Retype password:
输入两遍密码进行确认以后，就会计算出你所输入密码的MD5加密值，如：$1$pFddV1$3X/XnIzEySuSF7fL9BUUj/
复制该密码进行MD5加密后的值。
2.配置grub
[root@server5 ~]# cat /boot/grub/grub.conf
# 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/sda2
# initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
password --md5 $1$pFddV1$3X/XnIzEySuSF7fL9BUUj/
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux Server (2.6.18-308.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-308.el5 ro root=LABEL=/ rhgb quiet
initrd /initrd-2.6.18-308.el5.img
3.重启后生效