If your server is on it's way to being full dead, or your license has expired, you can still create backups via the command line. To do so, run the following command:
echo "action=backup&local%5Fpath=%2Fhome%2Fadmin%2Fadmin%5Fbackups%32&owner=admin&type=admin&value=multiple&when=now&where=local&who=all" >> /usr/local/directadmin/data/task.queue
And make sure that the dataskq is running by checking /var/log/cron. If it isn't you can run the dataskq manually to create the backups:
/usr/local/directadmin/dataskq d200
This will create all backups in /home/admin/admin_backups, assuming there is enough of a system left to do so.
More detail: http://help.directadmin.com/item.php?id=198
