Backup and restore functionality was added in Backdrop 1.30.0. This documentation is in-progress.
After backing up the site with Backdrop's core backup facility, you can restore any of the backups made to bring the site back to a previous version of the database and configuration.
Point your browser to "http://www.example.com/core/restore.php".
If you are not logged in using either the site maintenance account or an account with the "Restore site backups" permission, you will need to modify the access check statement inside your settings.php file. After finishing the upgrade, be sure to open settings.php again, and change it back to its original state.
The restore process may take several minutes, depending on the size of your database.
Note: only backups made with the Backdrop's core backup facility can be restored. Backups made with a third party host, or with Backup and Migrate module, will not work.