Command line:

Edit LightDM’s configuration File

sudo vim /etc/lightdm/lightdm.conf

Add the following line in the [SeatDefaults] section, save and exit from file.

allow-guest=false

The changes will take effect when you restart your computer.

sudo shutdown -r now

or

sudo reboot

You can also restart LightDM

sudo restart lightdm

GUI:

System Settings > Login Screen(LightDM) > General

uncheck Allow guest login , and click the Apply button

• Linux
• Ubuntu