5. The slapd Configuration File

Once the software has been built and installed, you are ready to configure slapd(8) for use at your site. The slapd runtime configuration is primarily accomplished through the slapd.conf(5) file, normally installed in the /usr/local/etc/openldap directory.

An alternate configuration file can be specified via a command-line option to slapd(8) or slurpd(8). This chapter describes the general format of the config file, followed by a detailed description of commonly used config file directives.

5.1. Configuration File Format

The slapd.conf(5) file consists of three types of configuration information: global, backend specific, and database specific. Global information is specified first, followed by information associated with a particular backend type, which is then followed by information associated with a particular database instance. Global directives can be overridden in backend and/or database directives, and backend directives can be overridden by database directives.

Blank lines and comment lines beginning with a '#' character are ignored. If a line begins with white space, it is considered a continuation of the previous line. The general format of slapd.conf is as follows:

        # global configuration directives
        <global config directives>

        # backend definition
        backend <typeA>
        <backend-specific directives>

        # first database definition & config directives
        database <typeA>
        <database-specific directives>

        # second database definition & config directives
        database <typeB>
        <database-specific directives>

        # second database definition & config directives
        database <typeA>
        <database-specific directives>

        # subsequent backend & database definitions & config directives

A configuration directive may take arguments. If so, they are separated by white space. If an argument contains white space, the argument should be enclosed in double quotes "like this". If an argument contains a double quote or a backslash character `\', the character should be preceded by a backslash character `\'.

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 File Directives

This section details commonly used configuration directives. For a complete list, see the slapd.conf(5) manual page. This section separates the configuration file directives into global, backend-specific and data-specific categories, describing each directive and its default value (if any), and giving an example of its use.

5.2.1. Global Directives

Directives described in this section apply to all backends and databases unless specifically overridden in a backend or database definition. Arguments that should be replaced by actual text are shown in brackets <>. access 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 requesters (specified by <who>). See the Access Control section of this chapter for a summary of basic usage.

Note: If no access directives are specified, the default access control policy, access to * by * read, allows all both authenticated and anonymous users read access. attributetype <RFC2252 Attribute Type Description>

This directive defines an attribute type. Please see the Schema Specification chapter for information regarding how to use this directive. idletimeout <integer>

Specify the number of seconds to wait before forcibly closing an idle client connection. An idletimeout of 0, the default, disables this feature. include <filename>

This directive specifies that slapd should read additional configuration information from the given file before continuing with the next line of the current file. The included file should follow the normal slapd config file format. The file is commonly used to include files containing schema specifications.

Note: You should be careful when using this directive - there is no small limit on the number of nested include directives, and no loop detection is done. loglevel <integer>

This directive specifies the level at which debugging statements and operation statistics should be syslogged (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 are additive. To display what numbers correspond to what kind of debugging, invoke slapd with -? or consult the table below. The possible values for <integer> are:

Table 5.1: Debugging Levels
Level Description
-1 enable all debugging
0 no debugging
1 trace function calls
2 debug packet handling
4 heavy trace debugging
8 connection management
16 print out packets sent and received
32 search filter processing
64 configuration file processing
128 access control list processing
256 stats log connections/operations/results
512 stats log entries sent
1024 print communication with shell backends
2048 print entry parsing debugging


 loglevel -1

This will cause lots and lots of debugging information to be logged.


 loglevel 256 objectclass <RFC2252 Object Class Description>

This directive defines an object class. Please see the Schema Specification chapter for information regarding how to use this directive. referral <URI>

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


        referral 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. sizelimit <integer>

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


        sizelimit 500 timelimit <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.


        timelimit 3600

5.2.2. General Backend Directives

Directives in this section apply only to the backend in which they are defined. They are supported by every type of backend. Backend directives apply to all databases instances of the same type and, depending on the directive, may be overridden by database directives. backend <type>

This directive marks the beginning of a backend declaration. <type> should be one of the supported backend types listed in Table 5.2.

Table 5.2: Database Backends
Types Description
bdb Berkeley DB transactional backend
dnssrv DNS SRV backend
ldap Lightweight Directory Access Protocol (Proxy) backend
ldbm Lightweight DBM backend
meta Meta Directory backend
monitor Monitor backend
passwd Provides read-only access to passwd(5)
perl Perl Programmable backend
shell Shell (extern program) backend
sql SQL Programmable backend


        backend bdb

This marks the beginning of a new BDB backend definition.

5.2.3. General Database Directives

Directives in this section apply only to the database in which they are defined. They are supported by every type of database. database <type>

This directive marks the beginning of a database instance declaration. <type> should be one of the supported backend types listed in Table 5.2.


        database bdb

This marks the beginning of a new BDB database instance declaration. readonly { on | off }

This directive puts the database into "read-only" mode. Any attempts to modify the database will return an "unwilling to perform" error.


        readonly off replica

        replica host=<hostname>[:<port>]
                [bindmethod={ simple | kerberos | sasl }]

This directive specifies a replication site for this database. The host= parameter specifies a host and optionally a port where the slave slapd instance can be found. Either a domain name or IP address may be used for <hostname>. If <port> is not given, the standard LDAP port number (389) is used.

The binddn= parameter gives the DN to bind as for updates to the slave slapd. It should be a DN which has read/write access to the slave slapd's database, typically given as a rootdn in the slave's config file. It must also match the updatedn directive in the slave slapd's config file. Since DNs are likely to contain embedded spaces, the entire "binddn=<DN>" string should be enclosed in double quotes.

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

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

Kerberos authentication is deprecated in favor of SASL authentication mechanisms, in particular the KERBEROS_V4 and GSSAPI mechanisms. Kerberos authentication requires binddn and srvtab parameters.

SASL authentication is generally recommended. SASL authentication requires specification of a mechanism using the mech 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.

See the chapter entitled Replication with slurpd for more information on how to use this directive. replogfile <filename>

This directive specifies the name of the replication log file to which slapd will log changes. The replication log is typically written by slapd and read by slurpd. Normally, this directive is only used if slurpd is being used to replicate the database. However, you can also use it to generate a transaction log, if slurpd is not running. In this case, you will need to periodically truncate the file, since it will grow indefinitely otherwise.

See the chapter entitled Replication with slurpd for more information on how to use this directive. rootdn <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:

        rootdn "cn=Manager,dc=example,dc=com"

SASL-based Example:

        rootdn "uid=root,cn=example.com,cn=digest-md5,cn=auth"

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

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


        rootpw secret

It is also permissible to provide hash of the password in RFC 2307 form. slappasswd(8) may be used to generate the password hash.


        rootpw {SSHA}ZKKuqbEKJfKSXhUbHG3fG8MDn9j1v4QN

The hash was generated using the command slappasswd -s secret. suffix <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 at least one is required for each database definition.


        suffix "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 line(s) in each database definition in the order they appear in the file. Thus, if one database suffix is a prefix of another, it must appear after it in the config file. updatedn <dn>

This directive is only applicable in a slave slapd. It specifies the DN allowed to make changes to the replica. This may be the DN slurpd(8) binds as when making changes to the replica or the DN associated with a SASL identity.

Entry-based Example:

        updatedn "cn=Update Daemon,dc=example,dc=com"

SASL-based Example:

        updatedn "uid=slurpd,cn=example.com,cn=digest-md5,cn=auth"

See the Replication with slurpd chapter for more information on how to use this directive. updateref <URL>

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


        updateref       ldap://master.example.net

5.2.4. BDB Database Directives

Directives in this category only apply to a BDB database. That is, they must follow a "database bdb" line and come before any subsequent "backend" or "database" line. For a complete reference of BDB configuration directives, see slapd-bdb(5). directory <directory>

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


        directory /usr/local/var/openldap-data

5.2.5. LDBM Database Directives

Directives in this category only apply to a LDBM database. That is, they must follow a "database ldbm" line and come before any subsequent "backend" or "database" line. For a complete reference of LDBM configuration directives, see slapd-ldbm(5). cachesize <integer>

This directive specifies the size in entries of the in-memory cache maintained by the LDBM backend database instance.


        cachesize 1000 dbcachesize <integer>

This directive specifies the size in bytes of the in-memory cache associated with each open index file. If not supported by the underlying database method, this directive is ignored without comment. Increasing this number uses more memory but can cause a dramatic performance increase, especially during modifies or when building indices.


        dbcachesize 100000 dbnolocking

This option, if present, disables database locking. Enabling this option may improve performance at the expense of data security. dbnosync

This option causes on-disk database contents to not be immediately synchronized with in memory changes upon change. Enabling this option may improve performance at the expense of data integrity. directory <directory>

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


        directory /usr/local/var/openldap-data index {<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.


        index default pres,eq
        index uid
        index cn,sn pres,eq,sub
        index 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.

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

        index objectClass eq mode <integer>

This directive specifies the file protection mode that newly created database index files should have.


        mode 0600

5.3. Access Control

Access to slapd entries and attributes is controlled by the access configuration file directive. The general form of an access line is:

        <access directive> ::= access to <what>
                [by <who> <access> <control>]+
        <what> ::= * |
                [dn[.<basic-style>]=<regex> | dn.<scope-style>=<DN>]
                [filter=<ldapfilter>] [attrs=<attrlist>]
        <basic-style> ::= regex | exact
        <scope-style> ::= base | one | subtree | children
        <attrlist> ::= <attr> | <attr> , <attrlist>
        <attr> ::= <attrname> | entry | children
        <who> ::= * | [anonymous | users | self
                        | dn[.<basic-style>]=<regex> | dn.<scope-style>=<DN>]
        <access> ::= [self]{<level>|<priv>}
        <level> ::= none | auth | compare | search | read | write
        <priv> ::= {=|+|-}{w|r|s|c|x}+
        <control> ::= [stop | continue | break]

where the <what> part selects the entries and/or attributes to which the access applies, the <who> part specifies which entities are granted access, and the <access> part specifies the access granted. Multiple <who> <access> <control> triplets are supported, allowing many entities to be granted different access to the same set of entries and attributes. Not all of these access control options are described here; for more details see the slapd.access(5) man page.

5.3.1. What to control access to

The <what> part of an access specification determines the entries and attributes to which the access control applies. Entries are commonly selected in two ways: by DN and by filter. The following qualifiers select entries by DN:

        by *
        by dn[.<basic-style>]=<regex>
        by dn.<scope-style>=<DN>

The first form is used to select all entries. The second form may be used to select entries by matching a regular expression against the target entry's normalized DN. (The second form is not discussed further in this document.) The third form is used to select entries which are within the requested scope of DN. The <DN> is a string representation of the Distinguished Name, as described in RFC2253.

The scope can be either base, one, subtree, or children. Where base matches only the entry with provided DN, one matches the entries whose parent is the provided DN, subtree matches all entries in the subtree whose root is the provided DN, and children matches all entries under the DN (but not the entry named by the DN).

For example, if the directory contained entries named:

        0: o=suffix
        1: cn=Manager,o=suffix
        2: ou=people,o=suffix
        3: uid=kdz,ou=people,o=suffix
        4: cn=addresses,uid=kdz,ou=people,o=suffix
        5: uid=hyc,ou=people,o=suffix


Entries may also be selected using a filter:

        by filter=<ldap filter>

where <ldap filter> is a string representation of an LDAP search filter, as described in RFC2254. For example:

        by filter=(objectClass=person)

Note that entries by be select by both DN and filter by include both qualifiers in the <what> clause.

        by dn.one="ou=people,o=suffix" filter=(objectClass=person)

Attributes within an entry are selected by including a comma-separated list of attribute names in the <what> selector:

        attrs=<attribute list>

There are two special psuedo attributes entry and children. To read (and hence return) an target entry, the subject must have read access to the target's entry attribute. To add or delete an entry, the subject must have write access to the entry's entry attribute AND must have write access to the entry's parent's children attribute. To rename an entry, the subject must have write access to entry's entry attribute AND have write access to both the old parent's and new parent's children attributes. The complete examples at the end of this section should help clear things up.

Lastly, there is a special entry selector "*" that is used to select any entry. It is used when no other <what> selector has been provided. It's equivalent to "dn=.*"

5.3.2. Who to grant access to

The <who> part identifies the entity or entities being granted access. Note that access is granted to "entities" not "entries." The following table summarizes entity specifiers:

Table 5.3: Access Entity Specifiers
Specifier Entities
* All, including anonymous and authenticated users
anonymous Anonymous (non-authenticated) users
users Authenticated users
self User associated with target entry
dn[.<basic-style>]=<regex> Users matching a regular expression
dn.<scope-style>=<DN> Users within scope of a DN

The DN specifier behaves much like <what> clause DN specifiers.

Other control factors are also supported. For example, a <who> can be restricted by a regular expression matching the client's domain name:

        domain=<regular expression>

or by an entry listed in a DN-valued attribute in the entry to which the access applies:

        dnattr=<dn-valued attribute name>

The dnattr specification is used to give access to an entry whose DN is listed in an attribute of the entry (e.g., give access to a group entry to whoever is listed as the owner of the group entry).

5.3.3. The access to grant

The kind of <access> granted can be one of the following:

Table 5.4: Access Levels
Level Privileges Description
none   no access
auth =x needed to bind
compare =cx needed to compare
search =scx needed to apply search filters
read =rscx needed to read search results
write =wrscx needed to modify/rename

Each level implies all lower levels of access. So, for example, granting someone write access to an entry also grants them read, search, compare, and auth access. However, one may use the privileges specifier to grant specific permissions.

5.3.4. Access Control Evaluation

When evaluating whether some requester should be given access to an entry and/or attribute, slapd compares the entry and/or attribute to the <what> selectors given in the configuration file. For each entry, access controls provided in the database which holds the entry (or the first database if not held in any database) apply first, followed by the global access directives. Within this priority, access directives are examined in the order in which they appear in the config file. Slapd stops with the first <what> selector that matches the entry and/or attribute. The corresponding access directive is the one slapd will use to evaluate access.

Next, slapd compares the entity requesting access to the <who> selectors within the access directive selected above in the order in which they appear. It stops with the first <who> selector that matches the requester. This determines the access the entity requesting access has to the entry and/or attribute.

Finally, slapd compares the access granted in the selected <access> clause to the access requested by the client. If it allows greater or equal access, access is granted. Otherwise, access is denied.

The order of evaluation of access directives makes their placement in the configuration file important. If one access directive is more specific than another in terms of the entries it selects, it should appear first in the config file. Similarly, if one <who> selector is more specific than another it should come first in the access directive. The access control examples given below should help make this clear.

5.3.5. Access Control Examples

The access control facility described above is quite powerful. This section shows some examples of its use. First, some simple examples:

        access to * by * read

This access directive grants read access to everyone.

        access to *
                by self write
                by anonymous auth
                by * read

This directive allows users to modify their own entries, allows authenticate, and allows all others to read. Note that only the first by <who> clause which matches applies. Hence, the anonymous users are granted auth, not read. The last clause could just as well have been "by users read".

It is often desirable to restrict operations based upon the level of protection in place. The following shows how security strength factors (SSF) can be used.

        access to *
                by ssf=128 self write
                by ssf=64 anonymous auth
                by ssf=64 users read

This directive allows users to modify their own entries if security protections have of strength 128 or better have been established, allows simple authentication and read access when 64 or better security protections have been established.

The following example shows the use of a regular expression to select the entries by DN in two access directives where ordering is significant.

        access to dn.children="dc=example,dc=com"
                by * search
        access to dn.children="dc=com"
                by * read

Read access is granted to entries under the dc=com subtree, except for those entries under the dc=example,dc=com subtree, to which search access is granted. No access is granted to dc=com as neither access directive matches this DN. If the order of these access directives was reversed, the trailing directive would never be reached, since all entries under dc=example,dc=com are also under dc=com entries.

Also note that if no access to directive matches or no by <who> clause, access is denied. That is, every access to directive ends with an implicit by * none clause and every access list ends with an implicit access to * by * none directive.

The next example again shows the importance of ordering, both of the access directives and the by <who> clauses. It also shows the use of an attribute selector to grant access to a specific attribute and various <who> selectors.

        access to dn.subtree="dc=example,dc=com" attr=homePhone
                by self write
                by dn.children=dc=example,dc=com" search
                by domain=.*\.example\.com read
        access to dn.subtree="dc=example,dc=com"
                by self write
                by dn.children="dc=example,dc=com" search
                by anonymous auth

This example applies to entries in the "dc=example,dc=com" subtree. To all attributes except homePhone, an entry can write to itself, entries under example.com entries can search by them, anybody else has no access (implicit by * none) excepting for authentication/authorization (which is always done anonymously). The homePhone attribute is writable by the entry, searchable by entries under example.com, readable by clients connecting from somewhere in the example.com domain, and otherwise not readable (implicit by * none). All other access is denied by the implicit access to * by * none.

Sometimes it is useful to permit a particular DN to add or remove itself from an attribute. For example, if you would like to create a group and allow people to add and remove only their own DN from the member attribute, you could accomplish it with an access directive like this:

        access to attr=member,entry
                by dnattr=member selfwrite

The dnattr <who> selector says that the access applies to entries listed in the member attribute. The selfwrite access selector says that such members can only add or delete their own DN from the attribute, not other values. The addition of the entry attribute is required because access to the entry is required to access any of the entry's attributes.

5.4. Configuration File Example

The following is an example configuration file, interspersed with explanatory text. It defines two databases to handle different parts of the X.500 tree; both are BDB 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 section
  2.    include /usr/local/etc/schema/core.schema
  3.    referral ldap://root.openldap.org
  4.    access to * by * read

Line 1 is a comment. Line 2 includes another config file which contains core schema definitions. The referral directive on line 3 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 4 is a global access control. It applies to all entries (after any applicable database-specific access controls).

The next section of the configuration file defines a BDB backend that will handle queries for things in the "dc=example,dc=com" portion of the tree. The database is to be replicated to two slave slapds, one on truelies, the other on judgmentday. Indices are to be maintained for several attributes, and the userPassword attribute is to be protected from unauthorized access.

  5.    # BDB definition for the example.com
  6.    database bdb
  7.    suffix "dc=example,dc=com"
  8.    directory /usr/local/var/openldap-data
  9.    rootdn "cn=Manager,dc=example,dc=com"
 10.    rootpw secret
 11.    # replication directives
 12.    replogfile /usr/local/var/openldap/slapd.replog
 13.    replica host=slave1.example.com:389
 14.            binddn="cn=Replicator,dc=example,dc=com"
 15.            bindmethod=simple credentials=secret
 16.    replica host=slave2.example.com
 17.            binddn="cn=Replicator,dc=example,dc=com"
 18.            bindmethod=simple credentials=secret
 19.    # indexed attribute definitions
 20.    index uid pres,eq
 21.    index cn,sn,uid pres,eq,approx,sub
 22.    index objectClass eq
 23.    # database access control definitions
 24.    access to attr=userPassword
 25.            by self write
 26.            by anonymous auth
 27.            by dn.base="cn=Admin,dc=example,dc=com" write
 28.            by * none
 29.    access to *
 30.            by self write
 31.            by dn.base="cn=Admin,dc=example,dc=com" write
 32.            by * read

Line 5 is a comment. The start of the database definition is marked by the database keyword on line 6. Line 7 specifies the DN suffix for queries to pass to this database. Line 8 specifies the directory in which the database files will live.

Lines 9 and 10 identify the database super-user entry and associated password. This entry is not subject to access control or size or time limit restrictions.

Lines 11 through 18 are for replication. Line 12 specifies the replication log file (where changes to the database are logged - this file is written by slapd and read by slurpd). Lines 13 through 15 specify the hostname and port for a replicated host, the DN to bind as when performing updates, the bind method (simple) and the credentials (password) for the binddn. Lines 16 through 18 specify a second replication site. See the Replication with slurpd chapter for more information on these directives.

Lines 20 through 22 indicate the indices to maintain for various attributes.

Lines 24 through 32 specify access control for entries in this database. As this is the first database, the controls also apply to entries not held in any database (such as the Root DSE). 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).

The next section of the example configuration file defines another BDB 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 39, the read access would be allowed due to the global access rule at line 4.

 33.    # BDB definition for example.net
 34.    database bdb
 35.    suffix "dc=example,dc=net"
 36.    directory /usr/local/var/openldap-data-net
 37.    rootdn "cn=Manager,dc=example,dc=com"
 38.    index objectClass eq
 39.    access to * by users read