目的是禁用red hat/Centos/Oracle linux的单用户模式：可以用grub-md5-crypt生成md5加密码，把生成的密码放在/etc/grub/grub.conf文件的splashimage参数下一行就可以禁用单用户模式了，这时进入单用户的时候需要输入加密码.
[root@rac02 grub]# grub-md5-crypt
Password:
Retype password:
$1$VS9Dl0$TX1ITOn.LnqG50/T3Df9v1
[root@rac02 grub]# vi 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/mapper/vg_rac01-lv_root
# initrd /initrd-[generic-]version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
password --md5 $1$VS9Dl0$TX1ITOn.LnqG50/T3Df9v1
hiddenmenu
title Oracle Linux Server (2.6.32-71.el6.i686)
root (hd0,0)
kernel /vmlinuz-2.6.32-71.el6.i686 ro root=/dev/mapper/vg_rac01-lv_root rd_LVM_LV=vg_rac01/lv_root rd_LVM_LV=vg_rac01/lv_swap rd_NO_LUKS 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
"grub.conf" 18L, 870C written
[root@rac02 grub]# reboot
[root@rac02 grub]#
Broadcast message from root@rac02
(/dev/pts/0) at 23:50 ...
The system is going down for reboot NOW!
