authorize.php in core/authorize.php

Administrative script for running authorized file operations.

drupal_maintenance_theme in core/includes/drupal.inc

Enables use of the theme system without requiring database access.

install_begin_request in core/includes/install.core.inc

Begins an installation request, modifying the installation state as needed.

restore.php in core/restore.php

Administrative page for restoring backup database and configuration files.

update.php in core/update.php

Administrative page for handling updates from one Backdrop version to another.

_backdrop_log_error in core/includes/errors.inc

Logs a PHP error or exception and displays an error page in fatal cases.