Locking down single-user mode in RHEL5 requires editing /boot/grub/grub.conf and /etc/inittab files.
1. Define the single user login shell in /etc/inittab by adding a the below line :
# vi /etc/inittab ... su:S:wait:/sbin/sulogin
Or you can also use output redirection to have the entry placed in the file /etc/inittab :
# echo "su:S:wait:/sbin/sulogin" >>/etc/inittab
2. Doing the above results in single-user mode showing the same login prompt normally seen in emergency (maintenance) mode :