How to lock a linux user from logging into a machine?

In some scenarios its needed to lock a user to login into his own account.  This can be achieved by many ways.

1.  GUI way

 1.1 Go to System -> Administration -> Users and Groups

 1.2 Now select the particular user from the left side, then click on the advanced settings button

 1.3 Click on the Advanced tab then tick the check box with value "Disable Account"

 1.4 To revoke follow the 1.1 & 1.2 now you can see a "Enable account" button click and enable

2. Terminal way

1. As a root user issue the following command in the terminal

    $sudo passwd -l "username of the user to lock"