Pdbsql provides three samba passdb backend modules: pdb_mysql, pdb_pgsql, and pdb_multi. pdb_mysql is a MySQL passdb backend. pdb_pgsql is a PostgreSQL passdb backend. pdb_multi is a backend which loads multiple passdb backends. These are provided because support for MySQL and PostGreSQL passdb backends has been removed from the Samba source tree, due to lack of an active maintainer.