GNU/Linux system provides means for using the terminal devices namely tty1,tty2,…As a part of gnu/linux general security we can enable/disable root login on these devices. Each of the tty devices can be accessed by pressing Ctrl+Alt+F1 or Ctrl+Alt+F2… The /etc/securetty file allows you to specify which tty devices the root user is allowed to login on. The /etc/securetty file is read by the login program. Its format is a list of the tty devices names allowed, and on all others tty that are commented out or doesn’t appear in this file, root login is disallowed.To allow root access in a particular tty we just need to uncomment that line.

Edit the securetty file (sudo nano /etc/securetty) and comment out the following lines

tty1
#tty2
#tty3
#tty4
#tty5
#tty6
#tty7
#tty8

which means root is only allowed to login on tty1.