Mastering Drupal 8

Override system

Configuration in Drupal is stored in the database and can be imported from and exported to the filesystem. But there are times when it is necessary to apply a set of changes to the existing configuration outside of this system. A common reason is to set attributes on a specific environment. In Drupal 7, there was the global $conf variable, which could be manipulated in the settings.php file to provide this functionality.

A major challenge with the approach in Drupal 7 is that any overrides could not be distinguished from other settings. From the point of view of a configuration form, there was no distinction between attributes coming from the database or from the override. This means that if the configuration form were submitted, ...