The idmap alloc backend provides a plugin interface for Winbind to use when allocating Unix uids/gids for Windows SIDs. This option is to be used in conjunction with the parameter and refers to the name of the idmap module which will provide the id allocation functionality. Please refer to the man page for each idmap plugin to determine whether or not the module implements the allocation feature. The most common plugins are the tdb ( idmap_tdb8) and ldap (idmap_ldap 8) libraries. Also refer to the option. tdb