The idmap backend provides a plugin interface for Winbind to use varying backends to store SID/uid/gid mapping tables. This option specifies the default backend that is used when no special configuration set by matches the specific request. This default backend also specifies the place where winbind-generated idmap entries will be stored. So it is highly recommended that you specify a writable backend like idmap_tdb 8 or idmap_ldap 8 as the idmap backend. The idmap_rid 8 and idmap_ad 8 backends are not writable and thus will generate unexpected results if set as idmap backend. To use the rid and ad backends, please specify them via the parameter, possibly also for the domain your machine is member of, specified by . Examples of SID/uid/gid backends include tdb ( idmap_tdb8), ldap (idmap_ldap 8), rid ( idmap_rid8), and ad (idmap_ad 8). tdb