Manual:DefaultSettings.php

DefaultSettings.php contains default configuration settings.

DefaultSettings.php should never be edited, since any changes made to it will be lost at every upgrade of MediaWiki. Rather, changes should be made to LocalSettings.php .

As of Mediawiki 1.38, including DefaultSettings.php in your LocalSettings.php will result in the error described at Phrabicator T311966:

PHP Fatal error:  Uncaught FatalError: $wgBaseDirectory must not be modified in settings files! Use the MW_INSTALL_PATH environment variable to override the installation root directory. in /var/www/html/w/includes/Setup.php:237
Stack trace:
#0 /var/www/html/w/maintenance/doMaintenance.php(96): require_once()
#1 /var/www/html/w/maintenance/update.php(264): require_once('/var/www/html/w...')
#2 {main}
  thrown in /var/www/html/w/includes/Setup.php on line 237

Fatal error: Uncaught FatalError: $wgBaseDirectory must not be modified in settings files! Use the MW_INSTALL_PATH environment variable to override the installation root directory. in /var/www/html/w/includes/Setup.php:237
Stack trace:
#0 /var/www/html/w/maintenance/doMaintenance.php(96): require_once()
#1 /var/www/html/w/maintenance/update.php(264): require_once('/var/www/html/w...')
#2 {main}
  thrown in /var/www/html/w/includes/Setup.php on line 237