If var/.maintenance.flag does not exist, the maintenance mode is off and This file will make some exceptions so the Magento 2 maintenance mode can be off
500 Internal Server errors in Magento Community – common causes The maintenance.flag file in the root directory causes the site to display a maintenance mode page to visitors. In the cart’s download directory (usually found as downloader, change the permissions for index.php from 666 to 755) Magento has built-in Maintenance mode which is ready to use with simple minimalistic approach. For advanced features, like switching maintenance mode on per-store-view basis from Magento Backend, please skip to the next section.Magento maintenance mode is controlled by maintenance.flag file under Magento’s root and coded in Magento’s index.php file: How to show maintenance mode page in magento (website under construction) Create a file name maintenance.flag in your magento root directory. Contents under this file doesn’t matter, you can keep it empty. Download and open original index.php file. On line 47 put the following code: 1. 2 $ ip = $ _SERVER ['REMOTE When you implement your new updates, maintenance mode enabled on Magento. Permission in index. php file is changed by Maintenance flag to 666 which makes it unable to execute by web browsers. After that, Magento can not change permissions of index. php file or remove the maintenance. flag. You can see “500 error” in this case. 500 Internal Server errors in Magento Community – common causes The maintenance.flag file in the root directory causes the site to display a maintenance mode page to visitors. In the cart’s download directory (usually found as downloader, change the permissions for index.php from 666 to 755)
/path/backup.sql-将数据库还原为gzip压缩文件（Linux）gunzip
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