tty auto login

# apt-get install mingetty


Debian :

# vi /etc/inittab
# 1:2345:respawn:/sbin/getty 38400 tty1
1:2345:respawn:/sbin/mingetty --autologin root --noclear tty1

Ubuntu :

# vi /etc/init/tty1.conf

# exec /sbin/getty -8 38400 tty1
exec /sbin/mingetty --autologin root --noclear tty1

References :
Debian User Forums • View topic - auto login and startx without a display manager - lenny
How do I auto-login as root into the TTY upon boot? - Ask Ubuntu