Sometimes we need to make update on live running site. We may have to update module, add new module or update changes. Updating the magento site can be risky when the site is running live. So, the solution is to temporarily put the site in maintenance mode and do the necessary changes. In magento, we can put the site in maintenance mode by adding the 'maintenance.flag' file at the root of the site. Now, when we browse the site, we will see the screen as shown below: We can also update the look and content of the above page. For that, we need to update the content of 503.phtml page found at 'errors/default/' folder at root. The header and footer template can be found at 'errors/default/page.phtml'. After we make the changes, we have to remove the maintenace.flag file from the root. Then the site will be live again.
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