Disable Guest Session in Ubuntu 15.04 Login Screen

For personal computers you may want to disable or remove the guest session from the login screen in Ubuntu 15.04 Vivid Vervet. This can be easily done by adding a rule into the configuration file of LightDM display manager.
To get started:
1. Open Ubuntu Software Center, search for and install gksu, which allows to run graphical commands as root:

2. Open terminal from the Dash or by pressing Ctrl+Alt+T on keyboard. When it opens, run below command:

gksu gedit /etc/lightdm/lightdm.conf

When the file opens, add below lines if it’s empty or add the third line:

[SeatDefaults] greeter-session=unity-greeter allow-guest=false

so the file looks like:

Save the file and restart your computer to apply changes.