Enabling Magento Maintenance Mode
Magento 1.4 introduced a method for quickly enabling maintenance mode on a running store. To enabled maintenance mode simply create a file called maintenance.flag file in your Magento root.
The maintenance mode template is found in the errors/default/503.phtml. Integration with the “Allowed IPs” in the developer section of the configuration section would be nice but, of course, there is a way you can hack it. Without this hack maintenance mode is enabled for everyone, even if you have an admin session.
Thanks for this great info. The next question that arose for me was how to customise the 'maintenance page' that shows to the public. I tried changing the errors/default/503.phtml page and that worked but it kept the default magento theme (logo, colors, header and footer etc). Does anyone know how to just pop a blank html page there that can be fully customised? Thanks!
Dear Nick, I need some help on the maintenance mode.