i couldnt get u actually but if u are asking that how to prevent booting form linux single then go to /etc/lilo.conf file and the say image=<the kernel image>eg /boot/vmlinuz-2.2.12 root=</where the root is mounted> eq /dev/hda1 read-only password="the passowrd u want' restricted after the u come out of the file and say /sbin/lilo and then boot it will do the blocking of single user mode.