5. Configuring slapd

Once the software has been built and installed, you are ready to configure slapd(8) for use at your site.

OpenLDAP 2.3 and later have transitioned to using a dynamic runtime configuration engine, slapd-config(5). slapd-config(5)

This chapter describes the general format of the slapd-config(5) configuration system, followed by a detailed description of commonly used settings.

The older style slapd.conf(5) file is still supported, but its use is deprecated and support for it will be withdrawn in a future OpenLDAP release. Configuring slapd(8) via slapd.conf(5) is described in the next chapter.

Refer to slapd(8) for information on how to have slapd automatically convert from slapd.conf(5) to slapd-config(5).

Note: Although the slapd-config(5) system stores its configuration as (text-based) LDIF files, you should never edit any of the LDIF files directly. Configuration changes should be performed via LDAP operations, e.g. ldapadd(1), ldapdelete(1), or ldapmodify(1). For offline modifications (when the server is not running), use slapadd(8) and slapmodify(8).

Note: You will need to continue to use the older slapd.conf(5) configuration system if your OpenLDAP installation requires the use of one or more backends or overlays that have not been updated to use the slapd-config(5) system. As of OpenLDAP 2.4.33, all of the official backends have been updated. There may be additional contributed or experimental overlays that also have not been updated.

5.1. Configuration Layout

The slapd configuration is stored as a special LDAP directory with a predefined schema and DIT. There are specific objectClasses used to carry global configuration options, schema definitions, backend and database definitions, and assorted other items. A sample config tree is shown in Figure 5.1.

Figure 5.1: Sample configuration tree.

Other objects may be part of the configuration but were omitted from the illustration for clarity.

The slapd-config configuration tree has a very specific structure. The root of the tree is named cn=config and contains global configuration settings. Additional settings are contained in separate child entries:

The usual rules for LDIF files apply to the configuration information: Comment lines beginning with a '#' character are ignored. If a line begins with a single space, it is considered a continuation of the previous line (even if the previous line is a comment) and the single leading space is removed. Entries are separated by blank lines.

The general layout of the config LDIF is as follows:

        # global configuration settings
        dn: cn=config
        objectClass: olcGlobal
        cn: config
        <global config settings>

        # schema definitions
        dn: cn=schema,cn=config
        objectClass: olcSchemaConfig
        cn: schema
        <system schema>

        dn: cn={X}core,cn=schema,cn=config
        objectClass: olcSchemaConfig
        cn: {X}core
        <core schema>

        # additional user-specified schema

        # backend definitions
        dn: olcBackend=<typeA>,cn=config
        objectClass: olcBackendConfig
        olcBackend: <typeA>
        <backend-specific settings>

        # database definitions
        dn: olcDatabase={X}<typeA>,cn=config
        objectClass: olcDatabaseConfig
        olcDatabase: {X}<typeA>
        <database-specific settings>

        # subsequent definitions and settings

Some of the entries listed above have a numeric index "{X}" in their names. While most configuration settings have an inherent ordering dependency (i.e., one setting must take effect before a subsequent one may be set), LDAP databases are inherently unordered. The numeric index is used to enforce a consistent ordering in the configuration database, so that all ordering dependencies are preserved. In most cases the index does not have to be provided; it will be automatically generated based on the order in which entries are created.

Configuration directives are specified as values of individual attributes. Most of the attributes and objectClasses used in the slapd configuration have a prefix of "olc" (OpenLDAP Configuration) in their names. Generally there is a one-to-one correspondence between the attributes and the old-style slapd.conf configuration keywords, using the keyword as the attribute name, with the "olc" prefix attached.

A configuration directive may take arguments. If so, the arguments are separated by whitespace. If an argument contains whitespace, the argument should be enclosed in double quotes "like this". In the descriptions that follow, arguments that should be replaced by actual text are shown in brackets <>.

The distribution contains an example configuration file that will be installed in the /usr/local/etc/openldap directory. A number of files containing schema definitions (attribute types and object classes) are also provided in the /usr/local/etc/openldap/schema directory.

5.2. Configuration Directives

This section details commonly used configuration directives. For a complete list, see the slapd-config(5) manual page. This section will treat the configuration directives in a top-down order, starting with the global directives in the cn=config entry. Each directive will be described along with its default value (if any) and an example of its use.

5.2.1. cn=config

Directives contained in this entry generally apply to the server as a whole. Most of them are system or connection oriented, not database related. This entry must have the olcGlobal objectClass. olcIdleTimeout: <integer>

Specify the number of seconds to wait before forcibly closing an idle client connection. A value of 0, the default, disables this feature. olcLogLevel: <level>

This directive specifies the level at which log statements and operation statistics should be sent to syslog (currently logged to the syslogd(8) LOG_LOCAL4 facility). You must have configured OpenLDAP --enable-debug (the default) for this to work, except for the two statistics levels, which are always enabled. Log levels may be specified as integers or by keyword. Multiple log levels may be used and the levels are additive. The possible values for <level> are:

Table 5.1: Logging Levels
Level Keyword Description
-1 any enable all debugging
0   no debugging
1 (0x1 trace) trace function calls
2 (0x2 packets) debug packet handling
4 (0x4 args) heavy trace debugging
8 (0x8 conns) connection management
16 (0x10 BER) print out packets sent and received
32 (0x20 filter) search filter processing
64 (0x40 config) configuration processing
128 (0x80 ACL) access control list processing
256 (0x100 stats) stats log connections/operations/results
512 (0x200 stats2) stats log entries sent
1024 (0x400 shell) print communication with shell backends
2048 (0x800 parse) print entry parsing debugging
16384 (0x4000 sync) syncrepl consumer processing
32768 (0x8000 none) only messages that get logged regardless of configured log level

The desired log level can be input as a single integer that combines the (ORed) desired levels, both in decimal or in hexadecimal notation, as a list of integers (that are ORed internally), or as a list of the names that are shown between brackets, such that

                olcLogLevel 129
                olcLogLevel 0x81
                olcLogLevel 128 1
                olcLogLevel 0x80 0x1
                olcLogLevel acl trace

are equivalent.


 olcLogLevel -1

This will enable all log levels.

 olcLogLevel conns filter

Just log the connection and search filter processing.

 olcLogLevel none

Log those messages that are logged regardless of the configured loglevel. This differs from setting the log level to 0, when no logging occurs. At least the None level is required to have high priority messages logged.


 olcLogLevel stats

Basic stats logging is configured by default. olcReferral <URI>

This directive specifies the referral to pass back when slapd cannot find a local database to handle a request.


        olcReferral: ldap://root.openldap.org

This will refer non-local queries to the global root LDAP server at the OpenLDAP Project. Smart LDAP clients can re-ask their query at that server, but note that most of these clients are only going to know how to handle simple LDAP URLs that contain a host part and optionally a distinguished name part. Sample Entry

dn: cn=config
objectClass: olcGlobal
cn: config
olcIdleTimeout: 30
olcLogLevel: Stats
olcReferral: ldap://root.openldap.org

5.2.2. cn=module

If support for dynamically loaded modules was enabled when configuring slapd, cn=module entries may be used to specify sets of modules to load. Module entries must have the olcModuleList objectClass. olcModuleLoad: <filename>

Specify the name of a dynamically loadable module to load. The filename may be an absolute path name or a simple filename. Non-absolute names are searched for in the directories specified by the olcModulePath directive. olcModulePath: <pathspec>

Specify a list of directories to search for loadable modules. Typically the path is colon-separated but this depends on the operating system. Sample Entries

dn: cn=module{0},cn=config
objectClass: olcModuleList
cn: module{0}
olcModuleLoad: /usr/local/lib/smbk5pwd.la

dn: cn=module{1},cn=config
objectClass: olcModuleList
cn: module{1}
olcModulePath: /usr/local/lib:/usr/local/lib/slapd
olcModuleLoad: accesslog.la
olcModuleLoad: pcache.la

5.2.3. cn=schema

The cn=schema entry holds all of the schema definitions that are hard-coded in slapd. As such, the values in this entry are generated by slapd so no schema values need to be provided in the config file. The entry must still be defined though, to serve as a base for the user-defined schema to add in underneath. Schema entries must have the olcSchemaConfig objectClass. olcAttributeTypes: <RFC4512 Attribute Type Description>

This directive defines an attribute type. Please see the Schema Specification chapter for information regarding how to use this directive. olcObjectClasses: <RFC4512 Object Class Description>

This directive defines an object class. Please see the Schema Specification chapter for information regarding how to use this directive. Sample Entries

dn: cn=schema,cn=config
objectClass: olcSchemaConfig
cn: schema

dn: cn=test,cn=schema,cn=config
objectClass: olcSchemaConfig
cn: test
olcAttributeTypes: ( 1.1.1
  NAME 'testAttr'
  EQUALITY integerMatch
olcAttributeTypes: ( 1.1.2 NAME 'testTwo' EQUALITY caseIgnoreMatch
  SUBSTR caseIgnoreSubstringsMatch SYNTAX )
olcObjectClasses: ( 1.1.3 NAME 'testObject'
  MAY ( testAttr $ testTwo ) AUXILIARY )

5.2.4. Backend-specific Directives

Backend directives apply to all database instances of the same type and, depending on the directive, may be overridden by database directives. Backend entries must have the olcBackendConfig objectClass. olcBackend: <type>

This directive names a backend-specific configuration entry. <type> should be one of the supported backend types listed in Table 5.2.

Table 5.2: Database Backends
Types Description
asyncmet a Asynchronous Metadirectory backend
config Slapd configuration backend
dnssrv DNS SRV backend
ldap Lightweight Directory Access Protocol (Proxy) backend
ldif Lightweight Data Interchange Format backend
mdb Memory-Mapped DB backend
meta Metadirectory backend
monitor Monitor backend
ndb MySQL NDB backend
null Null backend
passwd Provides read-only access to passwd(5)
perl Perl Programmable backend
relay Relay backend
sock Socket backend
sql SQL Programmable backend
wt WiredTiger backend


        olcBackend: mdb

This marks the beginning of a new MDB backend definition. At present, only back-mdb implements any options of this type, so this setting is not needed for any other backends. Sample Entry

 dn: olcBackend=mdb,cn=config
 objectClass: olcBackendConfig
 olcBackend: mdb
 olcBkMdbIdlExp: 16

5.2.5. Database-specific Directives

Directives in this section are supported by every type of database. Database entries must have the olcDatabaseConfig objectClass. olcDatabase: [{<index>}]<type>

This directive names a specific database instance. The numeric {<index>} may be provided to distinguish multiple databases of the same type. Usually the index can be omitted, and slapd will generate it automatically. <type> should be one of the supported backend types listed in Table 5.2 or the frontend type.

The frontend is a special database that is used to hold database-level options that should be applied to all the other databases. Subsequent database definitions may also override some frontend settings.

The config database is also special; both the config and the frontend databases are always created implicitly even if they are not explicitly configured, and they are created before any other databases.


        olcDatabase: mdb

This marks the beginning of a new MDB database instance. olcAccess: to <what> [ by <who> [<accesslevel>] [<control>] ]+

This directive grants access (specified by <accesslevel>) to a set of entries and/or attributes (specified by <what>) by one or more requestors (specified by <who>). See the Access Control section of this guide for basic usage.

Note: If no olcAccess directives are specified, the default access control policy, to * by * read, allows all users (both authenticated and anonymous) read access.

Note: Access controls defined in the frontend are appended to all other databases' controls. olcReadonly { TRUE | FALSE }

This directive puts the database into "read-only" mode. Any attempts to modify the database will return an "unwilling to perform" error. If set on a consumer, modifications sent by syncrepl will still occur.


        olcReadonly: FALSE olcRootDN: <DN>

This directive specifies the DN that is not subject to access control or administrative limit restrictions for operations on this database. The DN need not refer to an entry in this database or even in the directory. The DN may refer to a SASL identity.

Entry-based Example:

        olcRootDN: cn=Manager,dc=example,dc=com

SASL-based Example:

        olcRootDN: uid=root,cn=example.com,cn=digest-md5,cn=auth

See the SASL Authentication section for information on SASL authentication identities. olcRootPW: <password>

This directive can be used to specify a password for the DN for the rootdn (when the rootdn is set to a DN within the database).


        olcRootPW: secret

It is also permissible to provide a hash of the password in RFC2307 form. slappasswd(8) may be used to generate the password hash.


        olcRootPW: {SSHA}ZKKuqbEKJfKSXhUbHG3fG8MDn9j1v4QN

The hash was generated using the command slappasswd -s secret. olcSizeLimit: <integer>

This directive specifies the maximum number of entries to return from a search operation.


        olcSizeLimit: 500

See the Limits section of this guide and slapd-config(5) for more details. olcSuffix: <dn suffix>

This directive specifies the DN suffix of queries that will be passed to this backend database. Multiple suffix lines can be given, and usually at least one is required for each database definition. (Some backend types, such as frontend and monitor use a hard-coded suffix which may not be overridden in the configuration.)


        olcSuffix: dc=example,dc=com

Queries with a DN ending in "dc=example,dc=com" will be passed to this backend.

Note: When the backend to pass a query to is selected, slapd looks at the suffix value(s) in each database definition in the order in which they were configured. Thus, if one database suffix is a prefix of another, it must appear after it in the configuration. olcSyncrepl

        olcSyncrepl: rid=<replica ID>
                [retry=[<retry interval> <# of retries>]+]
                searchbase=<base DN>
                [filter=<filter str>]
                [attrs=<attr list>]
                [exattrs=<attr list>]
                [logbase=<base DN>]
                [logfilter=<filter str>]

This directive specifies the current database as a consumer of the provider content by establishing the current slapd(8) as a replication consumer site running a syncrepl replication engine. The provider database is located at the provider site specified by the provider parameter. The consumer database is kept up-to-date with the provider content using the LDAP Content Synchronization protocol. See RFC4533 for more information on the protocol.

The rid parameter is used for identification of the current syncrepl directive within the replication consumer server, where <replica ID> uniquely identifies the syncrepl specification described by the current syncrepl directive. <replica ID> is non-negative and is no more than three decimal digits in length.

The provider parameter specifies the replication provider site containing the provider content as an LDAP URI. The provider parameter specifies a scheme, a host and optionally a port where the provider slapd instance can be found. Either a domain name or IP address may be used for <hostname>. Examples are ldap://provider.example.com:389 or ldaps:// If <port> is not given, the standard LDAP port number (389 or 636) is used. Note that the syncrepl uses a consumer-initiated protocol, and hence its specification is located on the consumer.

The content of the syncrepl consumer is defined using a search specification as its result set. The consumer slapd will send search requests to the provider slapd according to the search specification. The search specification includes searchbase, scope, filter, attrs, exattrs, attrsonly, sizelimit, and timelimit parameters as in the normal search specification. The searchbase parameter has no default value and must always be specified. The scope defaults to sub, the filter defaults to (objectclass=*), attrs defaults to "*,+" to replicate all user and operational attributes, and attrsonly is unset by default. Both sizelimit and timelimit default to "unlimited", and only positive integers or "unlimited" may be specified. The exattrs option may also be used to specify attributes that should be omitted from incoming entries.

The LDAP Content Synchronization protocol has two operation types: refreshOnly and refreshAndPersist. The operation type is specified by the type parameter. In the refreshOnly operation, the next synchronization search operation is periodically rescheduled at an interval time after each synchronization operation finishes. The interval is specified by the interval parameter. It is set to one day by default. In the refreshAndPersist operation, a synchronization search remains persistent in the provider slapd instance. Further updates to the provider will generate searchResultEntry to the consumer slapd as the search responses to the persistent synchronization search.

If an error occurs during replication, the consumer will attempt to reconnect according to the retry parameter which is a list of the <retry interval> and <# of retries> pairs. For example, retry="60 10 300 3" lets the consumer retry every 60 seconds for the first 10 times and then retry every 300 seconds for the next three times before stop retrying. + in <# of retries> means indefinite number of retries until success.

The schema checking can be enforced at the LDAP Sync consumer site by turning on the schemachecking parameter. If it is turned on, every replicated entry will be checked for its schema as the entry is stored on the consumer. Every entry in the consumer should contain those attributes required by the schema definition. If it is turned off, entries will be stored without checking schema conformance. The default is off.

The binddn parameter gives the DN to bind as for the syncrepl searches to the provider slapd. It should be a DN which has read access to the replication content in the provider database.

The bindmethod is simple or sasl, depending on whether simple password-based authentication or SASL authentication is to be used when connecting to the provider slapd instance.

Simple authentication should not be used unless adequate data integrity and confidentiality protections are in place (e.g. TLS or IPsec). Simple authentication requires specification of binddn and credentials parameters.

SASL authentication is generally recommended. SASL authentication requires specification of a mechanism using the saslmech parameter. Depending on the mechanism, an authentication identity and/or credentials can be specified using authcid and credentials, respectively. The authzid parameter may be used to specify an authorization identity.

The realm parameter specifies a realm which a certain mechanisms authenticate the identity within. The secprops parameter specifies Cyrus SASL security properties.

The starttls parameter specifies use of the StartTLS extended operation to establish a TLS session before authenticating to the provider. If the critical argument is supplied, the session will be aborted if the StartTLS request fails. Otherwise the syncrepl session continues without TLS. The tls_reqcert setting defaults to "demand" and the other TLS settings default to the same as the main slapd TLS settings.

Rather than replicating whole entries, the consumer can query logs of data modifications. This mode of operation is referred to as delta syncrepl. In addition to the above parameters, the logbase and logfilter parameters must be set appropriately for the log that will be used. The syncdata parameter must be set to either "accesslog" if the log conforms to the slapo-accesslog(5) log format, or "changelog" if the log conforms to the obsolete changelog format. If the syncdata parameter is omitted or set to "default" then the log parameters are ignored.

The syncrepl replication mechanism is supported by the mdb backend.

See the LDAP Sync Replication chapter of this guide for more information on how to use this directive. olcTimeLimit: <integer>

This directive specifies the maximum number of seconds (in real time) slapd will spend answering a search request. If a request is not finished in this time, a result indicating an exceeded timelimit will be returned.


        olcTimeLimit: 3600

See the Limits section of this guide and slapd-config(5) for more details. olcUpdateref: <URL>

This directive is only applicable in a replica (or shadow) slapd(8) instance. It specifies the URL to return to clients which submit update requests upon the replica. If specified multiple times, each URL is provided.


        olcUpdateref:   ldap://provider.example.net Sample Entries

dn: olcDatabase=frontend,cn=config
objectClass: olcDatabaseConfig
objectClass: olcFrontendConfig
olcDatabase: frontend
olcReadOnly: FALSE

dn: olcDatabase=config,cn=config
objectClass: olcDatabaseConfig
olcDatabase: config
olcRootDN: cn=Manager,dc=example,dc=com

5.2.6. MDB Backend Directives

Directives in this category only apply to the MDB database backend. They will apply to all "database mdb" instances in the configuration. For a complete reference of MDB backend configuration directives, see slapd-mdb(5). olcBkMdbIdlExp <exponent>

Specify a power of 2 for the maximum size of an index slot. The default is 16, yielding a maximum slot size of 2^16 or 65536. The specified value must be in the range of 16-30.

This setting helps with the case where certain search filters are slow to return results due to an index slot having collapsed to a range value. This occurs when the number of candidate entries that match the filter for the index slot exceed the configured slot size.

If this setting is decreased on a server with existing MDB databases, each db will immediately need its indices to be rebuilt while slapd is offline with the "slapindex -q -t" command.

If this setting is increased on a server with existing MDB databases, each db will need its indices rebuilt to take advantage of the change for indices that have already been converted to ranges.

5.2.7. MDB Database Directives

Directives in this category apply to the MDB database backend. They are used in an olcDatabase entry in addition to the generic database directives defined above. For a complete reference of MDB configuration directives, see slapd-mdb(5). In addition to the olcDatabaseConfig objectClass, MDB database entries must have the olcMdbConfig objectClass. olcDbDirectory: <directory>

This directive specifies the directory where the MDB files containing the database and associated indices live.


        olcDbDirectory: /usr/local/var/openldap-data olcDbCheckpoint: <kbyte> <min>

This directive specifies the frequency for flushing the database disk buffers. This directive is only needed if the olcDbNoSync option is TRUE. The checkpoint will occur if either <kbyte> data has been written or <min> minutes have passed since the last checkpoint. Both arguments default to zero, in which case they are ignored. When the <min> argument is non-zero, an internal task will run every <min> minutes to perform the checkpoint. Note: currently the _kbyte_ setting is unimplemented.


        olcDbCheckpoint: 1024 10 olcDbEnvFlags: {nosync,nometasync,writemap,mapasync,nordahead}

This option specifies flags for finer-grained control of the LMDB library's operation. olcDbIndex: {<attrlist> | default} [pres,eq,approx,sub,none]

This directive specifies the indices to maintain for the given attribute. If only an <attrlist> is given, the default indices are maintained. The index keywords correspond to the common types of matches that may be used in an LDAP search filter.


        olcDbIndex: default pres,eq
        olcDbIndex: uid
        olcDbIndex: cn,sn pres,eq,sub
        olcDbIndex: objectClass eq

The first line sets the default set of indices to maintain to present and equality. The second line causes the default (pres,eq) set of indices to be maintained for the uid attribute type. The third line causes present, equality, and substring indices to be maintained for cn and sn attribute types. The fourth line causes an equality index for the objectClass attribute type.

There is no index keyword for inequality matches. Generally these matches do not use an index. However, some attributes do support indexing for inequality matches, based on the equality index.

A substring index can be more explicitly specified as subinitial, subany, or subfinal, corresponding to the three possible components of a substring match filter. A subinitial index only indexes substrings that appear at the beginning of an attribute value. A subfinal index only indexes substrings that appear at the end of an attribute value, while subany indexes substrings that occur anywhere in a value.

Note that by default, setting an index for an attribute also affects every subtype of that attribute. E.g., setting an equality index on the name attribute causes cn, sn, and every other attribute that inherits from name to be indexed.

By default, no indices are maintained. It is generally advised that minimally an equality index upon objectClass be maintained.

        olcDbIndex: objectClass eq

Additional indices should be configured corresponding to the most common searches that are used on the database. Presence indexing should not be configured for an attribute unless the attribute occurs very rarely in the database, and presence searches on the attribute occur very frequently during normal use of the directory. Most applications don't use presence searches, so usually presence indexing is not very useful.

If this setting is changed while slapd is running, an internal task will be run to generate the changed index data. All server operations can continue as normal while the indexer does its work. If slapd is stopped before the index task completes, indexing will have to be manually completed using the slapindex tool. olcDbMaxEntrySize: <bytes>

Specify the maximum size of an entry in bytes. Attempts to store an entry larger than this size will be rejected with the error LDAP_ADMINLIMIT_EXCEEDED. The default is 0, which is unlimited. olcDbMaxReaders: <integer>

This directive specifies the maximum number of threads that may have concurrent read access to the database. Tools such as slapcat count as a single thread, in addition to threads in any active slapd processes. The default is 126. olcDbMaxSize: <bytes>

This directive specifies the maximum size of the database in bytes. A memory map of this size is allocated at startup time and the database will not be allowed to grow beyond this size. The default is 10485760 bytes (10MB). This setting may be changed upward if the configured limit needs to be increased.

Note: It is important to set this to as large a value as possible, (relative to anticipated growth of the actual data over time) since growing the size later may not be practical when the system is under heavy load. olcDbMode: { <octal> | <symbolic> }

This directive specifies the file protection mode that newly created database index files should have. This can be in the form 0600 or -rw-------


        olcDbMode: 0600 olcDbMultival: { <attrlist> | default } <integer> hi,<integer> lo

Specify the number of values for which a multivalued attribute is stored in a separate table. Normally entries are stored as a single blob inside the database. When an entry gets very large or contains attributes with a very large number of values, modifications on that entry may get very slow. Splitting the large attributes out to a separate table can improve the performance of modification operations. The threshold is specified as a pair of integers. If the number of values exceeds the hi threshold the values will be split out. If a modification deletes enough values to bring an attribute below the lo threshold the values will be removed from the separate table and merged back into the main entry blob. The threshold can be set for a specific list of attributes, or the default can be configured for all other attributes. The default value for both hi and lo thresholds is UINT_MAX, which keeps all attributes in the main blob.

In addition to increasing write performance of operations the use of multival can also decrease fragmentation of the primary MDB database. olcDbRtxnsize: <entries>

This directive specifies the maximum number of entries to process in a single read transaction when executing a large search. Long-lived read transactions prevent old database pages from being reused in write transactions, and so can cause significant growth of the database file when there is heavy write traffic. This setting causes the read transaction in large searches to be released and reacquired after the given number of entries has been read, to give writers the opportunity to reclaim old database pages. The default is 10000. olcDbSearchStack: <integer>

Specify the depth of the stack used for search filter evaluation. Search filters are evaluated on a stack to accommodate nested AND / OR clauses. An individual stack is allocated for each server thread. The depth of the stack determines how complex a filter can be evaluated without requiring any additional memory allocation. Filters that are nested deeper than the search stack depth will cause a separate stack to be allocated for that particular search operation. These separate allocations can have a major negative impact on server performance, but specifying too much stack will also consume a great deal of memory. Each search uses 512K bytes per level on a 32-bit machine, or 1024K bytes per level on a 64-bit machine. The default stack depth is 16, thus 8MB or 16MB per thread is used on 32 and 64 bit machines, respectively. Also the 512KB size of a single stack slot is set by a compile-time constant which may be changed if needed; the code must be recompiled for the change to take effect.


        olcDbSearchStack: 16 olcDbNosync: { TRUE | FALSE }

This directive causes on-disk database contents to not be immediately synchronized with in memory changes upon change. Setting this option to TRUE may improve performance at the expense of data integrity. Sample Entry

dn: olcDatabase=mdb,cn=config
objectClass: olcDatabaseConfig
objectClass: olcMdbConfig
olcDatabase: mdb
olcSuffix: dc=example,dc=com
olcDbDirectory: /usr/local/var/openldap-data
olcDbIndex: objectClass eq

5.3. Configuration Example

The following is an example configuration, interspersed with explanatory text. It defines two databases to handle different parts of the X.500 tree; both are MDB database instances. The line numbers shown are provided for reference only and are not included in the actual file. First, the global configuration section:

  1.    # example config file - global configuration entry
  2.    dn: cn=config
  3.    objectClass: olcGlobal
  4.    cn: config
  5.    olcReferral: ldap://root.openldap.org

Line 1 is a comment. Lines 2-4 identify this as the global configuration entry. The olcReferral: directive on line 5 means that queries not local to one of the databases defined below will be referred to the LDAP server running on the standard port (389) at the host root.openldap.org. Line 6 is a blank line, indicating the end of this entry.

  7.    # internal schema
  8.    dn: cn=schema,cn=config
  9.    objectClass: olcSchemaConfig
 10.    cn: schema

Line 7 is a comment. Lines 8-10 identify this as the root of the schema subtree. The actual schema definitions in this entry are hardcoded into slapd so no additional attributes are specified here. Line 11 is a blank line, indicating the end of this entry.

 12.    # include the core schema
 13.    include: file:///usr/local/etc/openldap/schema/core.ldif

Line 12 is a comment. Line 13 is an LDIF include directive which accesses the core schema definitions in LDIF format. Line 14 is a blank line.

Next comes the database definitions. The first database is the special frontend database whose settings are applied globally to all the other databases.

 15.    # global database parameters
 16.    dn: olcDatabase=frontend,cn=config
 17.    objectClass: olcDatabaseConfig
 18.    olcDatabase: frontend
 19.    olcAccess: to * by * read

Line 15 is a comment. Lines 16-18 identify this entry as the global database entry. Line 19 is a global access control. It applies to all entries (after any applicable database-specific access controls). Line 20 is a blank line.

The next entry defines the config backend.

 21.    # set a rootpw for the config database so we can bind.
 22.    # deny access to everyone else.
 23.    dn: olcDatabase=config,cn=config
 24.    objectClass: olcDatabaseConfig
 25.    olcDatabase: config
 26.    olcRootPW: {SSHA}XKYnrjvGT3wZFQrDD5040US592LxsdLy
 27.    olcAccess: to * by * none

Lines 21-22 are comments. Lines 23-25 identify this entry as the config database entry. Line 26 defines the super-user password for this database. (The DN defaults to "cn=config".) Line 27 denies all access to this database, so only the super-user will be able to access it. (This is already the default access on the config database. It is just listed here for illustration, and to reiterate that unless a means to authenticate as the super-user is explicitly configured, the config database will be inaccessible.)

Line 28 is a blank line.

The next entry defines an MDB backend that will handle queries for things in the "dc=example,dc=com" portion of the tree. Indices are to be maintained for several attributes, and the userPassword attribute is to be protected from unauthorized access.

 29.    # MDB definition for example.com
 30.    dn: olcDatabase=mdb,cn=config
 31.    objectClass: olcDatabaseConfig
 32.    objectClass: olcMdbConfig
 33.    olcDatabase: mdb
 34.    olcSuffix: dc=example,dc=com
 35.    olcDbDirectory: /usr/local/var/openldap-data
 36.    olcRootDN: cn=Manager,dc=example,dc=com
 37.    olcRootPW: secret
 38.    olcDbIndex: uid pres,eq
 39.    olcDbIndex: cn,sn pres,eq,approx,sub
 40.    olcDbIndex: objectClass eq
 41.    olcAccess: to attrs=userPassword
 42.      by self write
 43.      by anonymous auth
 44.      by dn.base="cn=Admin,dc=example,dc=com" write
 45.      by * none
 46.    olcAccess: to *
 47.      by self write
 48.      by dn.base="cn=Admin,dc=example,dc=com" write
 49.      by * read

Line 29 is a comment. Lines 30-33 identify this entry as a MDB database configuration entry. Line 34 specifies the DN suffix for queries to pass to this database. Line 35 specifies the directory in which the database files will live.

Lines 36 and 37 identify the database super-user entry and associated password. This entry is not subject to access control or size or time limit restrictions.

Lines 38 through 40 indicate the indices to maintain for various attributes.

Lines 41 through 49 specify access control for entries in this database. For all applicable entries, the userPassword attribute is writable by the entry itself and by the "admin" entry. It may be used for authentication/authorization purposes, but is otherwise not readable. All other attributes are writable by the entry and the "admin" entry, but may be read by all users (authenticated or not).

Line 50 is a blank line, indicating the end of this entry.

The next entry defines another MDB database. This one handles queries involving the dc=example,dc=net subtree but is managed by the same entity as the first database. Note that without line 60, the read access would be allowed due to the global access rule at line 19.

 51.    # MDB definition for example.net
 52.    dn: olcDatabase=mdb,cn=config
 53.    objectClass: olcDatabaseConfig
 54.    objectClass: olcMdbConfig
 55.    olcDatabase: mdb
 56.    olcSuffix: dc=example,dc=net
 57.    olcDbDirectory: /usr/local/var/openldap-data-net
 58.    olcRootDN: cn=Manager,dc=example,dc=com
 59.    olcDbIndex: objectClass eq
 60.    olcAccess: to * by users read

5.4. Converting old style slapd.conf(5) file to cn=config format

Before converting to the cn=config format you should make sure that the config backend is properly configured in your existing config file. While the config backend is always present inside slapd, by default it is only accessible by its rootDN, and there are no default credentials assigned so unless you explicitly configure a means to authenticate to it, it will be unusable.

If you do not already have a database config section, add something like this to the end of slapd.conf

 database config
 rootpw VerySecret

Note: Since the config backend can be used to load arbitrary code into the slapd process, it is extremely important to carefully guard whatever credentials are used to access it. Since simple passwords are vulnerable to password guessing attacks, it is usually better to omit the rootpw and only use SASL authentication for the config rootDN.

An existing slapd.conf(5) file can be converted to the new format using slaptest(8) or any of the slap tools:

        slaptest -f /usr/local/etc/openldap/slapd.conf -F /usr/local/etc/openldap/slapd.d

Test that you can access entries under cn=config using the default rootdn and the rootpw configured above:

        ldapsearch -x -D cn=config -w VerySecret -b cn=config

You can then discard the old slapd.conf(5) file. Make sure to launch slapd(8) with the -F option to specify the configuration directory if you are not using the default directory path.

Note: When converting from the slapd.conf format to slapd.d format, any included files will also be integrated into the resulting configuration database.

5.5. Recovering from a broken configuration

If the server using cn=config does not start, either because the configuration does not represent the current version or because it has been corrupted, these actions are available, in the order of decreasing preference.

Make sure you have made a backup of the "broken" version before you attempt any of these:

5.5.1. Generate an ldif version of the configuration database and reload from that

Most of the time, the configuration can be parsed and a text version generated with slapcat(8):

 slapcat -F /usr/local/etc/openldap/slapd.d -n0 -l extracted_config.ldif

After you have backed up and removed the old configuration database contents, this output ldif can be hand-edited to adjust or remove the offending entries and imported again:

 slapadd -F /usr/local/etc/openldap/slapd.d -l updated_config.ldif
 slaptest -F /usr/local/etc/openldap/slapd.d

5.5.2. Modify config in-place

If the configuration can be parsed and you know exactly what you need to do, you can use slapmodify(8) to effect the required changes directly:

 slapmodify -F /usr/local/etc/openldap/slapd.d
 dn: ..., cn=config
 changetype: ...

5.5.3. Recover with plain back-ldif

If the configuration contains items that slapd(8) cannot process as a cn=config database at all, the last resort is to disable schema checking and operate on it as a regular back-ldif database. This might cease to work with future versions of OpenLDAP without notice, attempt this only when all of the above fail.

First, create a directory to serve as the hosting DB and create the structure:

 mkdir ./recovery ./recovery/cn=recovery
 cp /usr/local/etc/openldap/slapd.d/cn=config.ldif ./recovery/cn=recovery
 cp -r /usr/local/etc/openldap/slapd.d/cn=config ./recovery/cn=recovery

Or, if you have already backed up your old configuration, you can symlink it into place:

 mkdir ./recovery
 ln -s /usr/local/etc/openldap/slapd.d ./recovery/cn=recovery

Next, create a trivial slapd.conf(5) to access the new database:

 database ldif
 suffix cn=recovery
 directory ./recovery/

Note the change of suffix, cn=config is hardcoded to correspond to an active config database, so we have to home it one level deeper - at cn=config,cn=recovery.

Now you can use slapmodify(8) to modify the database, it is most likely you will need to run with schema checking disabled:

 slapmodify -f ./recovery.conf -s

You can test the validity of your config with slaptest(8):

 slaptest -F ./recovery/cn=recovery

And generate a full ldif with slapcat(8):

 slapcat -F ./recovery/cn=recovery -n0