Knowledgebase
How to disable your Drupal site
If you have to do some important changes to your Drupal site, such as an upgrade for example, you should put it in maintenance mode before that. You can do this from the administration panel. After you log in, click on the Configuration tab in the navigation bar. On the page that opens click on the link Maintenance mode; it's in the section Development. On the next page mark the checkbox for Put site into maintenance mode and click on the Save configuration button. On the same page you can also edit the message that is displayed to visitors when your site is under maintenance.
By default, administrators have the permission to access the site while the frontend is disabled. You can log in by using the URL address of the User account page. If your Drupal is installed directly in the root public_html directory on your Drupal hosting account, the URL would be yourdomain.com/user. After you're ready with whatever you're doing, you can switch off the maintenance mode option.