2 # Copyright 2007 The OpenLDAP Foundation, All Rights Reserved.
3 # COPYING RESTRICTIONS APPLY, see COPYRIGHT.
7 Overlays are software components that provide hooks to functions analogous to
8 those provided by backends, which can be stacked on top of the backend calls
9 and as callbacks on top of backend responses to alter their behavior.
11 Overlays may be compiled statically into {{slapd}}, or when module support
12 is enabled, they may be dynamically loaded. Most of the overlays
13 are only allowed to be configured on individual databases, but some
14 may also be configured globally.
16 Essentially, they represent a means to:
18 * customize the behavior of existing backends without changing the backend
19 code and without requiring one to write a new custom backend with
20 complete functionality
21 * write functionality of general usefulness that can be applied to
22 different backend types
24 Overlays are usually documented by separate specific man pages in section 5;
25 the naming convention is
27 > slapo-<overlay name>
29 All distributed core overlays have a man page. Feel free to contribute to any,
30 if you think there is anything missing in describing the behavior of the component
31 and the implications of all the related configuration directives.
33 Official overlays are located in
35 > servers/slapd/overlays/
37 That directory also contains the file slapover.txt, which describes the
38 rationale of the overlay implementation, and may serve as guideline for the
39 development of custom overlays.
41 Contribware overlays are located in
43 > contrib/slapd-modules/<overlay name>/
45 along with other types of run-time loadable components; they are officially
46 distributed, but not maintained by the project.
48 They can be stacked on the frontend as well; this means that they can be
49 executed after a request is parsed and validated, but right before the
50 appropriate database is selected. The main purpose is to affect operations
51 regardless of the database they will be handled by, and, in some cases,
52 to influence the selection of the database by massaging the request DN.
54 All the current overlays in 2.4 are listed and described in detail in the
63 This overlay can record accesses to a given backend database on another
66 This allows all of the activity on a given database to be reviewed using arbitrary
67 LDAP queries, instead of just logging to local flat text files. Configuration
68 options are available for selecting a subset of operation types to log, and to
69 automatically prune older log records from the logging database. Log records
70 are stored with audit schema to assure their readability whether viewed as LDIF
73 It is also used for {{SECT:delta-syncrepl replication}}
75 H3: Access Logging Configuration
77 The following is a basic example that implements Access Logging:
80 > suffix dc=example,dc=com
85 > logold (objectclass=person)
92 > by dn.base="cn=admin,dc=example,dc=com" read
94 The following is an example used for {{SECT:delta-syncrepl replication}}:
98 > directory /usr/local/var/openldap-accesslog
101 > index entryCSN,objectClass,reqEnd,reqResult,reqStart
103 Accesslog overlay definitions for the primary db
106 > suffix dc=example,dc=com
112 > # scan the accesslog DB every day, and purge entries older than 7 days
113 > logpurge 07+00:00 01+00:00
115 An example search result against {{B:cn=accesslog}} might look like:
117 > [ghenry@suretec ghenry]# ldapsearch -x -b cn=accesslog
121 > # base <cn=accesslog> with scope subtree
122 > # filter: (objectclass=*)
128 > objectClass: auditContainer
131 > # 20080110163829.000004Z, accesslog
132 > dn: reqStart=20080110163829.000004Z,cn=accesslog
133 > objectClass: auditModify
134 > reqStart: 20080110163829.000004Z
135 > reqEnd: 20080110163829.000005Z
138 > reqAuthzID: cn=admin,dc=suretecsystems,dc=com
139 > reqDN: uid=suretec-46022f8$,ou=Users,dc=suretecsystems,dc=com
141 > reqMod: sambaPwdCanChange:- ###CENSORED###
142 > reqMod: sambaPwdCanChange:+ ###CENSORED###
143 > reqMod: sambaNTPassword:- ###CENSORED###
144 > reqMod: sambaNTPassword:+ ###CENSORED###
145 > reqMod: sambaPwdLastSet:- ###CENSORED###
146 > reqMod: sambaPwdLastSet:+ ###CENSORED###
147 > reqMod: entryCSN:= 20080110163829.095157Z#000000#000#000000
148 > reqMod: modifiersName:= cn=admin,dc=suretecsystems,dc=com
149 > reqMod: modifyTimestamp:= 20080110163829Z
158 For more information, please see {{slapo-accesslog(5)}} and the {{SECT:delta-syncrepl replication}} section.
163 The Audit Logging overlay can be used to record all changes on a given backend database to a specified log file.
167 If the need arises whereby changes need to be logged as standard LDIF, then the auditlog overlay {{B:slapo-auditlog (5)}}
168 can be used. Full examples are available in the man page {{B:slapo-auditlog (5)}}
170 H3: Audit Logging Configuration
172 If the directory is running vi {{F:slapd.d}}, then the following LDIF could be used to add the overlay to the overlay list
173 in {{B:cn=config}} and set what file the {{TERM:LDIF}} gets logged to (adjust to suit)
175 > dn: olcOverlay=auditlog,olcDatabase={1}hdb,cn=config
177 > objectClass: olcOverlayConfig
178 > objectClass: olcAuditLogConfig
179 > olcOverlay: auditlog
180 > olcAuditlogFile: /tmp/auditlog.ldif
183 In this example for testing, we are logging changes to {{F:/tmp/auditlog.ldif}}
185 A typical {{TERM:LDIF}} file created by {{B:slapo-auditlog (5)}} would look like:
187 > # add 1196797576 dc=suretecsystems,dc=com cn=admin,dc=suretecsystems,dc=com
188 > dn: dc=suretecsystems,dc=com
190 > objectClass: dcObject
191 > objectClass: organization
193 > o: Suretec Systems Ltd.
194 > structuralObjectClass: organization
195 > entryUUID: 1606f8f8-f06e-1029-8289-f0cc9d81e81a
196 > creatorsName: cn=admin,dc=suretecsystems,dc=com
197 > modifiersName: cn=admin,dc=suretecsystems,dc=com
198 > createTimestamp: 20051123130912Z
199 > modifyTimestamp: 20051123130912Z
200 > entryCSN: 20051123130912.000000Z#000001#000#000000
201 > auditContext: cn=accesslog
202 > # end add 1196797576
204 > # add 1196797577 dc=suretecsystems,dc=com cn=admin,dc=suretecsystems,dc=com
205 > dn: ou=Groups,dc=suretecsystems,dc=com
208 > objectClass: organizationalUnit
210 > structuralObjectClass: organizationalUnit
211 > entryUUID: 160aaa2a-f06e-1029-828a-f0cc9d81e81a
212 > creatorsName: cn=admin,dc=suretecsystems,dc=com
213 > modifiersName: cn=admin,dc=suretecsystems,dc=com
214 > createTimestamp: 20051123130912Z
215 > modifyTimestamp: 20051123130912Z
216 > entryCSN: 20051123130912.000000Z#000002#000#000000
217 > # end add 1196797577
225 The chain overlay provides basic chaining capability to the underlying
228 What is chaining? It indicates the capability of a DSA to follow referrals on
229 behalf of the client, so that distributed systems are viewed as a single
230 virtual DSA by clients that are otherwise unable to "chase" (i.e. follow)
231 referrals by themselves.
233 The chain overlay is built on top of the ldap backend; it is compiled by
234 default when {{B:--enable-ldap}}.
237 H3: Chaining Configuration
239 In order to demonstrate how this overlay works, we shall discuss a typical
240 scenario which might be one master server and three Syncrepl slaves.
242 On each replica, add this near the top of the file (global), before any database
246 > chain-uri "ldap://ldapmaster.example.com"
247 > chain-idassert-bind bindmethod="simple"
248 > binddn="cn=Manager,dc=example,dc=com"
249 > credentials="<secret>"
252 > chain-return-error TRUE
254 Add this below your {{syncrepl}} statement:
256 > updateref "ldap://ldapmaster.example.com/"
258 The {{B:chain-tls}} statement enables TLS from the slave to the ldap master.
259 The DITs are exactly the same between these machines, therefore whatever user
260 bound to the slave will also exist on the master. If that DN does not have
261 update privileges on the master, nothing will happen.
263 You will need to restart the slave after these changes. Then, if you are using
264 {{loglevel 256}}, you can monitor an {{ldapmodify}} on the slave and the master.
266 Now start an {{ldapmodify}} on the slave and watch the logs. You should expect
269 > Sep 6 09:27:25 slave1 slapd[29274]: conn=11 fd=31 ACCEPT from IP=143.199.102.216:45181 (IP=143.199.102.216:389)
270 > Sep 6 09:27:25 slave1 slapd[29274]: conn=11 op=0 STARTTLS
271 > Sep 6 09:27:25 slave1 slapd[29274]: conn=11 op=0 RESULT oid= err=0 text=
272 > Sep 6 09:27:25 slave1 slapd[29274]: conn=11 fd=31 TLS established tls_ssf=256 ssf=256
273 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 op=1 BIND dn="uid=user1,ou=people,dc=example,dc=com" method=128
274 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 op=1 BIND dn="uid=user1,ou=People,dc=example,dc=com" mech=SIMPLE ssf=0
275 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 op=1 RESULT tag=97 err=0 text=
276 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 op=2 MOD dn="uid=user1,ou=People,dc=example,dc=com"
277 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 op=2 MOD attr=mail
278 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 op=2 RESULT tag=103 err=0 text=
279 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 op=3 UNBIND
280 > Sep 6 09:27:28 slave1 slapd[29274]: conn=11 fd=31 closed
281 > Sep 6 09:27:28 slave1 slapd[29274]: syncrepl_entry: LDAP_RES_SEARCH_ENTRY(LDAP_SYNC_MODIFY)
282 > Sep 6 09:27:28 slave1 slapd[29274]: syncrepl_entry: be_search (0)
283 > Sep 6 09:27:28 slave1 slapd[29274]: syncrepl_entry: uid=user1,ou=People,dc=example,dc=com
284 > Sep 6 09:27:28 slave1 slapd[29274]: syncrepl_entry: be_modify (0)
286 And on the master you will see this:
288 > Sep 6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 PROXYAUTHZ dn="uid=user1,ou=people,dc=example,dc=com"
289 > Sep 6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 MOD dn="uid=user1,ou=People,dc=example,dc=com"
290 > Sep 6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 MOD attr=mail
291 > Sep 6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 RESULT tag=103 err=0 text=
293 Note: You can clearly see the PROXYAUTHZ line on the master, indicating the
294 proper identity assertion for the update on the master. Also note the slave
295 immediately receiving the Syncrepl update from the master.
297 H3: Handling Chaining Errors
299 By default, if chaining fails, the original referral is returned to the client
300 under the assumption that the client might want to try and follow the referral.
302 With the following directive however, if the chaining fails at the provider
303 side, the actual error is returned to the client.
305 > chain-return-error TRUE
313 This overlay enforces a regular expression constraint on all values
314 of specified attributes during an LDAP modify request that contains add or modify
315 commands. It is used to enforce a more rigorous syntax when the underlying attribute
316 syntax is too general.
319 H3: Constraint Configuration
321 Configuration via {{slapd.conf}}(5) would look like:
324 > constraint_attribute mail regex ^[:alnum:]+@mydomain.com$
325 > constraint_attribute title uri
326 > ldap:///dc=catalog,dc=example,dc=com?title?sub?(objectClass=titleCatalog)
328 A specification like the above would reject any {{mail}} attribute which did not
329 look like {{<alpha-numeric string>@mydomain.com}}.
331 It would also reject any title attribute whose values were not listed in the
332 title attribute of any {{titleCatalog}} entries in the given scope.
334 An example for use with {{cn=config}}:
336 > dn: olcOverlay=constraint,olcDatabase={1}hdb,cn=config
338 > objectClass: olcOverlayConfig
339 > objectClass: olcConstraintConfig
340 > olcOverlay: constraint
341 > olcConstraintAttribute: mail regex ^[:alnum:]+@mydomain.com$
342 > olcConstraintAttribute: title uri ldap:///dc=catalog,dc=example,dc=com?title?sub?(objectClass=titleCatalog)
345 H2: Dynamic Directory Services
350 This overlay supports dynamic objects, which have a limited life after
351 which they expire and are automatically deleted.
354 H3: Dynamic Directory Service Configuration
362 This overlay extends the Compare operation to detect
363 members of a dynamic group. This overlay is now deprecated
364 as all of its functions are available using the
365 {{SECT:Dynamic Lists}} overlay.
368 H3: Dynamic Group Configuration
376 This overlay allows expansion of dynamic groups and lists. Instead of having the
377 group members or list attributes hard coded, this overlay allows us to define
378 an LDAP search whose results will make up the group or list.
380 H3: Dynamic List Configuration
382 This module can behave both as a dynamic list and dynamic group, depending on
383 the configuration. The syntax is as follows:
386 > dynlist-attrset <group-oc> <URL-ad> [member-ad]
388 The parameters to the {{F:dynlist-attrset}} directive have the following meaning:
389 * {{F:<group-oc>}}: specifies which object class triggers the subsequent LDAP search.
390 Whenever an entry with this object class is retrieved, the search is performed.
391 * {{F:<URL-ad>}}: is the name of the attribute which holds the search URI. It
392 has to be a subtype of {{F:labeledURI}}. The attributes and values present in
393 the search result are added to the entry unless {{F:member-ad}} is used (see
395 * {{F:member-ad}}: if present, changes the overlay behavior into a dynamic group.
396 Instead of inserting the results of the search in the entry, the distinguished name
397 of the results are added as values of this attribute.
399 Here is an example which will allow us to have an email alias which automatically
400 expands to all user's emails according to our LDAP filter:
402 In {{slapd.conf}}(5):
404 > dynlist-attrset nisMailAlias labeledURI
406 This means that whenever an entry which has the {{F:nisMailAlias}} object class is
407 retrieved, the search specified in the {{F:labeledURI}} attribute is performed.
409 Let's say we have this entry in our directory:
410 > cn=all,ou=aliases,dc=example,dc=com
412 > objectClass: nisMailAlias
413 > labeledURI: ldap:///ou=People,dc=example,dc=com?mail?one?(objectClass=inetOrgPerson)
415 If this entry is retrieved, the search specified in {{F:labeledURI}} will be
416 performed and the results will be added to the entry just as if they have always
417 been there. In this case, the search filter selects all entries directly
418 under {{F:ou=People}} that have the {{F:inetOrgPerson}} object class and retrieves
419 the {{F:mail}} attribute, if it exists.
421 This is what gets added to the entry when we have two users under {{F:ou=People}}
422 that match the filter:
423 !import "allmail-en.png"; align="center"; title="Dynamic list for email aliases"
424 FT[align="Center"] Figure X.Y: Dynamic List for all emails
426 The configuration for a dynamic group is similar. Let's see an example which would
427 automatically populate an {{F:allusers}} group with all the user accounts in the
430 In {{F:slapd.conf}}(5):
432 > dynlist-attrset groupOfNames labeledURI member
434 Let's apply it to the following entry:
435 > cn=allusers,ou=group,dc=example,dc=com
437 > objectClass: groupOfNames
438 > labeledURI: ldap:///ou=people,dc=example,dc=com??one?(objectClass=inetOrgPerson)
440 The behavior is similar to the dynamic list configuration we had before:
441 whenever an entry with the {{F:groupOfNames}} object class is retrieved, the
442 search specified in the {{F:labeledURI}} attribute is performed. But this time,
443 only the distinguished names of the results are added, and as values of the
444 {{F:member}} attribute.
447 !import "allusersgroup-en.png"; align="center"; title="Dynamic group for all users"
448 FT[align="Center"] Figure X.Y: Dynamic Group for all users
450 Note that a side effect of this scheme of dynamic groups is that the members
451 need to be specified as full DNs. So, if you are planning in using this for
452 {{F:posixGroup}}s, be sure to use RFC2307bis and some attribute which can hold
453 distinguished names. The {{F:memberUid}} attribute used in the {{F:posixGroup}}
454 object class can hold only names, not DNs, and is therefore not suitable for
457 H2: Reverse Group Membership Maintenance
461 In some scenarios, it may be desirable for a client to be able to determine
462 which groups an entry is a member of, without performing an additional search.
463 Examples of this are applications using the {{TERM:DIT}} for access control
464 based on group authorization.
466 The {{B:memberof}} overlay updates an attribute (by default {{B:memberOf}}) whenever
467 changes occur to the membership attribute (by default {{B:member}}) of entries of the
468 objectclass (by default {{B:groupOfNames}}) configured to trigger updates.
470 Thus, it provides maintenance of the list of groups an entry is a member of,
471 when usual maintenance of groups is done by modifying the members on the group
474 H3: Member Of Configuration
476 The typical use of this overlay requires just enabling the overlay for a
477 specific database. For example, with the following minimal slapd.conf:
479 > include /usr/share/openldap/schema/core.schema
480 > include /usr/share/openldap/schema/cosine.schema
481 > modulepath /usr/lib/openldap
482 > moduleload memberof.la
483 > authz-regexp "gidNumber=0\\\+uidNumber=0,cn=peercred,cn=external,cn=auth"
484 > "cn=Manager,dc=example,dc=com"
486 > suffix "dc=example,dc=com"
487 > rootdn "cn=Manager,dc=example,dc=com"
489 > directory /var/lib/ldap2.4
491 > index objectClass eq
496 adding the following ldif:
499 > dn: dc=example,dc=com
500 > objectclass: domain
503 > dn: ou=Group,dc=example,dc=com
504 > objectclass: organizationalUnit
507 > dn: ou=People,dc=example,dc=com
508 > objectclass: organizationalUnit
511 > dn: uid=test1,ou=People,dc=example,dc=com
512 > objectclass: account
515 > dn: cn=testgroup,ou=Group,dc=example,dc=com
516 > objectclass: groupOfNames
518 > member: uid=test1,ou=People,dc=example,dc=com
520 Results in the following output from a search on the test1 user:
522 > # ldapsearch -LL -Y EXTERNAL -H ldapi:/// "(uid=test1)" -b dc=example,dc=com memberOf
523 > SASL/EXTERNAL authentication started
524 > SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
528 > dn: uid=test1,ou=People,dc=example,dc=com
529 > memberOf: cn=testgroup,ou=Group,dc=example,dc=com
531 Note that the {{B:memberOf}} attribute is an operational attribute, so it must be
532 requested explicitly.
535 H2: The Proxy Cache Engine
537 {{TERM:LDAP}} servers typically hold one or more subtrees of a
538 {{TERM:DIT}}. Replica (or shadow) servers hold shadow copies of
539 entries held by one or more master servers. Changes are propagated
540 from the master server to replica (slave) servers using LDAP Sync
541 replication. An LDAP cache is a special type of replica which holds
542 entries corresponding to search filters instead of subtrees.
546 The proxy cache extension of slapd is designed to improve the
547 responsiveness of the ldap and meta backends. It handles a search
549 by first determining whether it is contained in any cached search
550 filter. Contained requests are answered from the proxy cache's local
551 database. Other requests are passed on to the underlying ldap or
552 meta backend and processed as usual.
554 E.g. {{EX:(shoesize>=9)}} is contained in {{EX:(shoesize>=8)}} and
555 {{EX:(sn=Richardson)}} is contained in {{EX:(sn=Richards*)}}
557 Correct matching rules and syntaxes are used while comparing
558 assertions for query containment. To simplify the query containment
559 problem, a list of cacheable "templates" (defined below) is specified
560 at configuration time. A query is cached or answered only if it
561 belongs to one of these templates. The entries corresponding to
562 cached queries are stored in the proxy cache local database while
563 its associated meta information (filter, scope, base, attributes)
564 is stored in main memory.
566 A template is a prototype for generating LDAP search requests.
567 Templates are described by a prototype search filter and a list of
568 attributes which are required in queries generated from the template.
569 The representation for prototype filter is similar to {{REF:RFC4515}},
570 except that the assertion values are missing. Examples of prototype
571 filters are: (sn=),(&(sn=)(givenname=)) which are instantiated by
572 search filters (sn=Doe) and (&(sn=Doe)(givenname=John)) respectively.
574 The cache replacement policy removes the least recently used (LRU)
575 query and entries belonging to only that query. Queries are allowed
576 a maximum time to live (TTL) in the cache thus providing weak
577 consistency. A background task periodically checks the cache for
578 expired queries and removes them.
580 The Proxy Cache paper
581 ({{URL:http://www.openldap.org/pub/kapurva/proxycaching.pdf}}) provides
582 design and implementation details.
585 H3: Proxy Cache Configuration
587 The cache configuration specific directives described below must
588 appear after a {{EX:overlay proxycache}} directive within a
589 {{EX:"database meta"}} or {{EX:database ldap}} section of
590 the server's {{slapd.conf}}(5) file.
592 H4: Setting cache parameters
594 > proxyCache <DB> <maxentries> <nattrsets> <entrylimit> <period>
596 This directive enables proxy caching and sets general cache
597 parameters. The <DB> parameter specifies which underlying database
598 is to be used to hold cached entries. It should be set to
599 {{EX:bdb}} or {{EX:hdb}}. The <maxentries> parameter specifies the
600 total number of entries which may be held in the cache. The
601 <nattrsets> parameter specifies the total number of attribute sets
602 (as specified by the {{EX:proxyAttrSet}} directive) that may be
603 defined. The <entrylimit> parameter specifies the maximum number of
604 entries in a cacheable query. The <period> specifies the consistency
605 check period (in seconds). In each period, queries with expired
608 H4: Defining attribute sets
610 > proxyAttrset <index> <attrs...>
612 Used to associate a set of attributes to an index. Each attribute
613 set is associated with an index number from 0 to <numattrsets>-1.
614 These indices are used by the proxyTemplate directive to define
617 H4: Specifying cacheable templates
619 > proxyTemplate <prototype_string> <attrset_index> <TTL>
621 Specifies a cacheable template and the "time to live" (in sec) <TTL>
622 for queries belonging to the template. A template is described by
623 its prototype filter string and set of required attributes identified
629 An example {{slapd.conf}}(5) database section for a caching server
630 which proxies for the {{EX:"dc=example,dc=com"}} subtree held
631 at server {{EX:ldap.example.com}}.
634 > suffix "dc=example,dc=com"
635 > rootdn "dc=example,dc=com"
636 > uri ldap://ldap.example.com/
638 > proxycache bdb 100000 1 1000 100
639 > proxyAttrset 0 mail postaladdress telephonenumber
640 > proxyTemplate (sn=) 0 3600
641 > proxyTemplate (&(sn=)(givenName=)) 0 3600
642 > proxyTemplate (&(departmentNumber=)(secretary=*)) 0 3600
645 > directory ./testrun/db.2.a
646 > index objectClass eq
647 > index cn,sn,uid,mail pres,eq,sub
650 H5: Cacheable Queries
652 A LDAP search query is cacheable when its filter matches one of the
653 templates as defined in the "proxyTemplate" statements and when it references
654 only the attributes specified in the corresponding attribute set.
655 In the example above the attribute set number 0 defines that only the
656 attributes: {{EX:mail postaladdress telephonenumber}} are cached for the following
661 > Filter: (&(sn=Richard*)(givenName=jack))
662 > Attrs: mail telephoneNumber
664 is cacheable, because it matches the template {{EX:(&(sn=)(givenName=))}} and its
665 attributes are contained in proxyAttrset 0.
667 > Filter: (&(sn=Richard*)(telephoneNumber))
670 is not cacheable, because the filter does not match the template,
671 nor is the attribute givenName stored in the cache
673 > Filter: (|(sn=Richard*)(givenName=jack))
674 > Attrs: mail telephoneNumber
676 is not cacheable, because the filter does not match the template ( logical
677 OR "|" condition instead of logical AND "&" )
680 H2: Password Policies
685 This overlay provides a variety of password control mechanisms,
686 e.g. password aging, password reuse and duplication control, mandatory
687 password resets, etc.
690 H3: Password Policy Configuration
693 H2: Referential Integrity
698 This overlay can be used with a backend database such as slapd-bdb(5)
699 to maintain the cohesiveness of a schema which utilizes reference
702 Whenever a {{modrdn}} or {{delete}} is performed, that is, when an entry's DN
703 is renamed or an entry is removed, the server will search the directory for
704 references to this DN (in selected attributes: see below) and update them
705 accordingly. If it was a {{delete}} operation, the reference is deleted. If it
706 was a {{modrdn}} operation, then the reference is updated with the new DN.
708 For example, a very common administration task is to maintain group membership
709 lists, specially when users are removed from the directory. When an
710 user account is deleted or renamed, all groups this user is a member of have to be
711 updated. LDAP administrators usually have scripts for that. But we can use the
712 {{F:refint}} overlay to automate this task. In this example, if the user is
713 removed from the directory, the overlay will take care to remove the user from
714 all the groups he/she was a member of. No more scripting for this.
716 H3: Referential Integrity Configuration
718 The configuration for this overlay is as follows:
720 > refint_attributes <attribute [attribute ...]>
721 > refint_nothing <string>
723 * {{F:refint_attributes}}: this parameter specifies a space separated list of
724 attributes which will have the referential integrity maintained. When an entry is
725 removed or has its DN renamed, the server will do an internal search for any of the
726 {{F:refint_attributes}} that point to the affected DN and update them accordingly. IMPORTANT:
727 the attributes listed here must have the {{F:distinguishedName}} syntax, that is,
729 * {{F:refint_nothing}}: some times, while trying to maintain the referential
730 integrity, the server has to remove the last attribute of its kind from an
731 entry. This may be prohibited by the schema: for example, the
732 {{F:groupOfNames}} object class requires at least one member. In these cases,
733 the server will add the attribute value specified in {{F:refint_nothing}}
736 To illustrate this overlay, we will use the group membership scenario.
740 > refint_attributes member
741 > refint_nothing "cn=admin,dc=example,dc=com"
743 This configuration tells the overlay to maintain the referential integrity of the {{F:member}}
744 attribute. This attribute is used in the {{F:groupOfNames}} object class which always needs
745 a member, so we add the {{F:refint_nothing}} directive to fill in the group with a standard
746 member should all the members vanish.
748 If we have the following group membership, the refint overlay will
749 automatically remove {{F:john}} from the group if his entry is removed from the
752 !import "refint.png"; align="center"; title="Group membership"
753 FT[align="Center"] Figure X.Y: Maintaining referential integrity in groups
755 Notice that if we rename ({{F:modrdn}}) the {{F:john}} entry to, say, {{F:jsmith}}, the refint
756 overlay will also rename the reference in the {{F:member}} attribute, so the group membership
759 If we removed all users from the directory who are a member of this group, then the end result
760 would be a single member in the group: {{F:cn=admin,dc=example,dc=com}}. This is the
761 {{F:refint_nothing}} parameter kicking into action so that the schema is not violated.
768 This overlay is useful to test the behavior of clients when
769 server-generated erroneous and/or unusual responses occur.
772 H3: Return Code Configuration
780 It performs basic DN/data rewrite and
781 objectClass/attributeType mapping.
784 H3: Rewrite/Remap Configuration
792 This overlay implements the provider-side support for syncrepl
793 replication, including persistent search functionality
796 H3: Sync Provider Configuration
799 H2: Translucent Proxy
804 This overlay can be used with a backend database such as slapd-bdb (5)
805 to create a "translucent proxy".
807 Content of entries retrieved from a remote LDAP server can be partially
808 overridden by the database.
811 H3: Translucent Proxy Configuration
814 H2: Attribute Uniqueness
819 This overlay can be used with a backend database such as slapd-bdb (5)
820 to enforce the uniqueness of some or all attributes within a subtree.
823 H3: Attribute Uniqueness Configuration
831 This overlay can be used to enforce a specific order for the values
832 of an attribute when it is returned in a search.
835 H3: Value Sorting Configuration
844 H3: Example Scenarios