===How to remove automatic login===
Open the file ///etc/inittab//:
//::sysinit:/etc/rc.d/rc.sysinit 
 tty1::respawn:/sbin/getty -n -l /bin/autologinroot 38400 tty1 
 tty2::respawn:/sbin/getty 38400 tty2 
 tty3::respawn:/sbin/getty 38400 tty3 
 ::ctrlaltdel:/sbin/reboot//

Edit the second line to become like this:
//tty1::respawn:/sbin/getty 38400 tty1//

Henceforth, a username and password will be asked for.

Use [[passwd]] to change the password.