slapd.overlays - Man Page

overlays for slapd, the stand-alone LDAP daemon


The slapd(8) daemon can use a variety of different overlays to alter or extend the normal behavior of a database backend. Overlays may be compiled statically into slapd, or when module support is enabled, they may be dynamically loaded. Most of the overlays are only allowed to be configured on individual databases, but some may also be configured globally.

Configuration options for each overlay are documented separately in the corresponding slapo-<overlay>(5) manual pages.


Access Logging. This overlay can record accesses to a given backend database on another database.


Audit Logging. This overlay records changes on a given backend database to an LDIF log file. By default it is not built.


Automatic Certificate Authority overlay. This overlay can generate X.509 certificate/key pairs for entries in the directory if slapd is linked to OpenSSL. By default it is not built.


Chaining. This overlay allows automatic referral chasing when a referral would have been returned, either when configured by the server or when  requested by the client.


Collective Attributes. This overlay implements RFC 3671 collective attributes; these attributes share common values over all the members of the collection as inherited from an ancestor entry.


Constraint. This overlay enforces a regular expression constraint on all values of specified attributes. It is used to enforce a more rigorous syntax when the underlying attribute syntax is too general.


Dynamic Directory Services. This overlay supports dynamic objects, which have a limited life after which they expire and are automatically deleted.


Dereference Control. This overlay implements the draft Dereference control. The overlay can be used with any backend or globally for all backends.


Dynamic Group. This is a demo overlay which extends the Compare operation to detect members of a dynamic group. It has no effect on any other operations.


Dynamic List. This overlay allows expansion of dynamic groups and more.


Home Directory Provisioning. This overlay manages creation/deletion of home directories for LDAP-based Unix accounts.


MemberOf. This overlay maintains automatic reverse group membership values, typically stored in an attribute called memberOf. This overlay is deprecated and should be replaced with dynlist.


OATH One-Time Password module. This module allows time-based one-time password, AKA "authenticator-style", and HMAC-based one-time password authentication to be used in conjunction with a standard LDAP password for two factor authentication.


Proxybind. This overlay forwards simple bind requests on a local database to a remote LDAP server.


Proxycache. This overlay allows caching of LDAP search requests in a local database. It is most often used with the slapd-ldap(5) or slapd-meta(5) backends.


Password Policy. This overlay provides a variety of password control mechanisms, e.g. password aging, password reuse and duplication control, mandatory password resets, etc.


Referential Integrity. This overlay can be used with a backend database such as slapd-mdb(5) to maintain the cohesiveness of a schema which utilizes reference attributes.


Remote Authentication. This overlay delegates authentication requests to remote directories.


Return Code. This overlay is useful to test the behavior of clients when server-generated erroneous and/or unusual responses occur.


Rewrite/remap. This overlay is experimental. It performs basic DN/data rewrite and objectClass/attributeType mapping.


Server Side Sorting and Virtual List Views. This overlay implements the RFC2891 server-side sorting control and virtual list view controls, and replaces the RFC2696 paged-results implementation to ensure it works with the sorting technique.


Syncrepl Provider. This overlay implements the provider-side support for syncrepl replication, including persistent search functionality.


Translucent Proxy. This overlay can be used with a backend database such as slapd-mdb(5) to create a "translucent proxy". Content of entries retrieved from a remote LDAP server can be partially overridden by the database.


Attribute Uniqueness. This overlay can be used with a backend database such as slapd-mdb(5) to enforce the uniqueness of some or all attributes within a subtree.


Value Sorting. This overlay can be used to enforce a specific order for the values of an attribute when it is returned in a search.



default slapd configuration file


default slapd configuration directory

See Also

ldap(3), slapo-accesslog(5), slapo-auditlog(5), slapo-autoca(5), slapo-chain(5), slapo-collect(5), slapo-constraint(5), slapo-dds(5), slapo-deref(5), slapo-dyngroup(5), slapo-dynlist(5), slapo-memberof(5), slapo-pbind(5), slapo-pcache(5), slapo-ppolicy(5), slapo-refint(5), slapo-remoteauth(5), slapo-retcode(5), slapo-rwm(5), slapo-sssvlv(5), slapo-syncprov(5), slapo-translucent(5), slapo-unique(5). slapo-valsort(5). slapd-config(5), slapd.conf(5), slapd.backends(5), slapd(8). "OpenLDAP Administrator's Guide" (


OpenLDAP Software is developed and maintained by The OpenLDAP Project <>. OpenLDAP Software is derived from the University of Michigan LDAP 3.3 Release.  

Referenced By

slapd.backends(5), slapd.conf(5), slapd-config(5).

2023/07/31 OpenLDAP 2.6.6