Virtual Console

Add the following lines into /etc/inittab: 

# Run Gettys in standard run level
1:2345:respawn:/sbin/mingetty tty1
2:2345:respawn:/sbin/mingetty tty2
3:2345:respawn:/sbin/mingetty tty3

You can also add the following CTRL-ALT-DEL, but be carefull if you are on a graphical switch with Windows machine, if a Windows user do this key combination and he do it on a linux machine it will reboot ! 

#Trap CTRL-ALT-DELETE
ca::ctrlaltdel:/sbin/shutown -t3 -r now

Serial Console

Install the package named minicom

If you use a converter USB-serial, you can check into /var/log/message, when you plug you will see a new device like ttyUSB0

Start: minicom -s Change the settings to adapt the right tty, and speed. Save it as default and exit. Now you are connected on the serial port. To exit <CTRL+A>-<Z> and <X>