This is how to make a SQL only back-up via commandline in DirectAdmin. The first line puts the command in the task.queue. The second line runs the task queue and will show the output. The d400 means debug level 400.
echo "action=backup&append%5Fto%5Fpath=nothing&database%5Fdata%5Faware=yes&email%5Fdata%5Faware=yes&local%5Fpath=%2Fhome%2Fadmin%2Fmysql%5Fbackups&option%30=database&option%31=database%5Fdata&owner=admin&type=admin&value=multiple&what=select&when=now&where=local&who=all" >> /usr/local/directadmin/data/task.queue /usr/local/directadmin/dataskq d400
When the back-up is completed you will receive an e-mail via the normal DirectAdmin message system.
The back-ups will be stored in /home/admin/mysql_backups