To temporarily take your Drupal site offline to anonymous and authenticated users, you can place your site into Maintenance Mode.
Maintenance Mode functionality is located at admin > Configuration > Development.
|Click the link to enter maintenance mode.|
On the maintenance mode page, you can update the message that is displayed when your site is in maintenance mode.
From the this page, by clicking the check box, you can place your site in maintenance mode.
|The red arrow indicates the checkbox to put your site into maintenance mode and the blue arrow indicates where you can place your custom message.|
Click the save configuration button at the bottom of the page.
To take your site out of maintenance mode, uncheck the box and click save.