slapd.conf - configuration file for slapd, the stand-alone LDAP daemon




The file /etc/openldap/slapd.conf contains configuration information for the slapd(8) daemon. This configuration file is also used by the SLAPD tools slapacl(8), slapadd(8), slapauth(8), slapcat(8), slapdn(8), slapindex(8), and slaptest(8).

The slapd.conf file consists of a series of global configuration options that apply to slapd as a whole (including all backends), followed by zero or more database backend definitions that contain information specific to a backend instance. The configuration options are case-insensitive; their value, on a case by case basis, may be case-sensitive.

The general format of slapd.conf is as follows:

# comment - these options apply to every database <global configuration options> # first database definition & configuration options database <backend 1 type> <configuration options specific to backend 1> # subsequent database definitions & configuration options ...

As many backend-specific sections as desired may be included. Global options can be overridden in a backend (for options that appear more than once, the last appearance in the slapd.conf file is used).

If a line begins with white space, it is considered a continuation of the previous line. No physical line should be over 2000 bytes long.

Blank lines and comment lines beginning with a ‘#’ character are ignored. Note: continuation lines are unwrapped before comment processing is applied.

Arguments on configuration lines are separated by white space. If an argument contains white space, the argument should be enclosed in double quotes. If an argument contains a double quote (‘"’) or a backslash character (‘#146;), the character should be preceded by a backslash character.

The specific configuration options available are discussed below in the Global Configuration Options, General Backend Options, and General Database Options. Backend-specific options are discussed in the slapd-<backend>(5) manual pages. Refer to the "OpenLDAP Administrator’s Guide" for more details on the slapd configuration file.


Options described in this section apply to all backends, unless specifically overridden in a backend definition. Arguments that should be replaced by actual text are shown in brackets <>.
access to <what> [ by <who> <access> <control> ]+
 Grant access (specified by <access>) to a set of entries and/or attributes (specified by <what>) by one or more requestors (specified by <who>). If no access controls are present, the default policy allows anyone and everyone to read anything but restricts updates to rootdn. (e.g., "access to * by * read"). The rootdn can always read and write EVERYTHING! See slapd.access(5) and the "OpenLDAP’s Administrator’s Guide" for details.
allow <features>
 Specify a set of features (separated by white space) to allow (default none). bind_v2 allows acceptance of LDAPv2 bind requests. Note that slapd(8) does not truly implement LDAPv2 (RFC 1777), now Historic (RFC 3494). bind_anon_cred allows anonymous bind when credentials are not empty (e.g. when DN is empty). bind_anon_dn allows unauthenticated (anonymous) bind when DN is not empty. update_anon allows unauthenticated (anonymous) update operations to be processed (subject to access controls and other administrative limits). proxy_authz_anon allows unauthenticated (anonymous) proxy authorization control to be processed (subject to access controls, authorization and other administrative limits).
argsfile <filename>
 The (absolute) name of a file that will hold the slapd server’s command line (program name and options).
attributeoptions [option-name]...
 Define tagging attribute options or option tag/range prefixes. Options must not end with ‘-’, prefixes must end with ‘-’. The ‘lang-’ prefix is predefined. If you use the attributeoptions directive, ‘lang-’ will no longer be defined and you must specify it explicitly if you want it defined.

An attribute description with a tagging option is a subtype of that attribute description without the option. Except for that, options defined this way have no special semantics. Prefixes defined this way work like the ‘lang-’ options: They define a prefix for tagging options starting with the prefix. That is, if you define the prefix ‘x-foo-’, you can use the option ‘x-foo-bar’. Furthermore, in a search or compare, a prefix or range name (with a trailing ‘-’) matches all options starting with that name, as well as the option with the range name sans the trailing ‘-’. That is, ‘x-foo-bar-’ matches ‘x-foo-bar’ and ‘x-foo-bar-baz’.

RFC 4520 reserves options beginning with ‘x-’ for private experiments. Other options should be registered with IANA, see RFC 4520 section 3.5. OpenLDAP also has the ‘binary’ option built in, but this is a transfer option, not a tagging option.

attributetype ( <oid> [NAME <name>] [DESC <description>] [OBSOLETE] [SUP <oid>] [EQUALITY <oid>] [ORDERING <oid>] [SUBSTR <oid>] [SYNTAX <oidlen>] [SINGLE-VALUE] [COLLECTIVE] [NO-USER-MODIFICATION] [USAGE <attributeUsage>] )"
  Specify an attribute type using the LDAPv3 syntax defined in RFC 4512. The slapd parser extends the RFC 4512 definition by allowing string forms as well as numeric OIDs to be used for the attribute OID and attribute syntax OID. (See the objectidentifier description.)
authz-policy <policy>
 Used to specify which rules to use for Proxy Authorization. Proxy authorization allows a client to authenticate to the server using one user’s credentials, but specify a different identity to use for authorization and access control purposes. It essentially allows user A to login as user B, using user A’s password. The none flag disables proxy authorization. This is the default setting. The from flag will use rules in the authzFrom attribute of the authorization DN. The to flag will use rules in the authzTo attribute of the authentication DN. The any flag, an alias for the deprecated value of both, will allow any of the above, whatever succeeds first (checked in to, from sequence. The all flag requires both authorizations to succeed.

The rules are mechanisms to specify which identities are allowed to perform proxy authorization. The authzFrom attribute in an entry specifies which other users are allowed to proxy login to this entry. The authzTo attribute in an entry specifies which other users this user can authorize as. Use of authzTo rules can be easily abused if users are allowed to write arbitrary values to this attribute. In general the authzTo attribute must be protected with ACLs such that only privileged users can modify it. The value of authzFrom and authzTo describes an identity or a set of identities; it can take five forms:


The first form is a valid LDAP URI where the <host>:<port>, the <attrs> and the <extensions> portions must be absent, so that the search occurs locally on either authzFrom or authzTo. The second form is a DN, with the optional style modifiers exact, onelevel, children, and subtree for exact, onelevel, children and subtree matches, which cause <pattern> to be normalized according to the DN normalization rules, or the special regex style, which causes the <pattern> to be treated as a POSIX (’’extended’’) regular expression, as discussed in regex(7) and/or re_format(7). A pattern of * means any non-anonymous DN. The third form is a SASL id, with the optional fields <mech> and <realm> that allow to specify a SASL mechanism, and eventually a SASL realm, for those mechanisms that support one. The need to allow the specification of a mechanism is still debated, and users are strongly discouraged to rely on this possibility. The fourth form is a group specification, consisting of the keyword group, optionally followed by the specification of the group objectClass and member attributeType. The group with DN <pattern> is searched with base scope, and in case of match, the values of the member attributeType are searched for the asserted DN. For backwards compatibility, if no identity type is provided, i.e. only <pattern> is present, an exact DN is assumed; as a consequence, <pattern> is subjected to DN normalization. Since the interpretation of authzFrom and authzTo can impact security, users are strongly encouraged to explicitly set the type of identity specification that is being used. A subset of these rules can be used as third arg in the authz-regexp statement (see below); significantly, the URI, provided it results in exactly one entry, and the dn.exact:<dn> forms.

authz-regexp <match> <replace>
 Used by the authentication framework to convert simple user names, such as provided by SASL subsystem, or extracted from certificates in case of cert-based SASL EXTERNAL, or provided within the RFC 4370 "proxied authorization" control, to an LDAP DN used for authorization purposes. Note that the resulting DN need not refer to an existing entry to be considered valid. When an authorization request is received from the SASL subsystem, the SASL USERNAME, REALM, and MECHANISM are taken, when available, and combined into a name of the form

This name is then compared against the match POSIX (’’extended’’) regular expression, and if the match is successful, the name is replaced with the replace string. If there are wildcard strings in the match regular expression that are enclosed in parenthesis, e.g.

then the portion of the name that matched the wildcard will be stored in the numbered placeholder variable $1. If there are other wildcard strings in parenthesis, the matching strings will be in $2, $3, etc. up to $9. The placeholders can then be used in the replace string, e.g.

The replaced name can be either a DN, i.e. a string prefixed by "dn:", or an LDAP URI. If the latter, the server will use the URI to search its own database(s) and, if the search returns exactly one entry, the name is replaced by the DN of that entry. The LDAP URI must have no hostport, attrs, or extensions components, but the filter is mandatory, e.g.

The protocol portion of the URI must be strictly ldap. Note that this search is subject to access controls. Specifically, the authentication identity must have "auth" access in the subject.

Multiple authz-regexp options can be given in the configuration file to allow for multiple matching and replacement patterns. The matching patterns are checked in the order they appear in the file, stopping at the first successful match.

concurrency <integer>
 Specify a desired level of concurrency. Provided to the underlying thread system as a hint. The default is not to provide any hint.
conn_max_pending <integer>
 Specify the maximum number of pending requests for an anonymous session. If requests are submitted faster than the server can process them, they will be queued up to this limit. If the limit is exceeded, the session is closed. The default is 100.
conn_max_pending_auth <integer>
 Specify the maximum number of pending requests for an authenticated session. The default is 1000.
defaultsearchbase <dn>
 Specify a default search base to use when client submits a non-base search request with an empty base DN. Base scoped search requests with an empty base DN are not affected.
disallow <features>
 Specify a set of features (separated by white space) to disallow (default none). bind_anon disables acceptance of anonymous bind requests. Note that this setting does not prohibit anonymous directory access (See "require authc"). bind_simple disables simple (bind) authentication. tls_2_anon disables forcing session to anonymous status (see also tls_authc) upon StartTLS operation receipt. tls_authc disallows the StartTLS operation if authenticated (see also tls_2_anon). proxy_authz_non_critical disables acceptance of the proxied authorization control (RFC4370) when criticality is FALSE. dontusecopy_non_critical disables acceptance of the dontUseCopy control (a work in progress) when criticality is FALSE.
ditcontentrule ( <oid> [NAME <name>] [DESC <description>] [OBSOLETE] [AUX <oids>] [MUST <oids>] [MAY <oids>] [NOT <oids>] )"
  Specify an DIT Content Rule using the LDAPv3 syntax defined in RFC 4512. The slapd parser extends the RFC 4512 definition by allowing string forms as well as numeric OIDs to be used for the attribute OID and attribute syntax OID. (See the objectidentifier description.)
gentlehup { on | off }
 A SIGHUP signal will only cause a ’gentle’ shutdown-attempt: Slapd will stop listening for new connections, but will not close the connections to the current clients. Future write operations return unwilling-to-perform, though. Slapd terminates when all clients have closed their connections (if they ever do), or - as before - if it receives a SIGTERM signal. This can be useful if you wish to terminate the server and start a new slapd server with another database, without disrupting the currently active clients. The default is off. You may wish to use idletimeout along with this option.
idletimeout <integer>
 Specify the number of seconds to wait before forcibly closing an idle client connection. A idletimeout of 0 disables this feature. The default is 0. You may also want to set the writetimeout option.
include <filename>
 Read additional configuration information from the given file before continuing with the next line of the current file.
index_intlen <integer>
 Specify the key length for ordered integer indices. The most significant bytes of the binary integer will be used for index keys. The default value is 4, which provides exact indexing for 31 bit values. A floating point representation is used to index too large values.
index_substr_if_minlen <integer>
 Specify the minimum length for subinitial and subfinal indices. An attribute value must have at least this many characters in order to be processed by the indexing functions. The default is 2.
index_substr_if_maxlen <integer>
 Specify the maximum length for subinitial and subfinal indices. Only this many characters of an attribute value will be processed by the indexing functions; any excess characters are ignored. The default is 4.
index_substr_any_len <integer>
 Specify the length used for subany indices. An attribute value must have at least this many characters in order to be processed. Attribute values longer than this length will be processed in segments of this length. The default is 4. The subany index will also be used in subinitial and subfinal index lookups when the filter string is longer than the index_substr_if_maxlen value.
index_substr_any_step <integer>
 Specify the steps used in subany index lookups. This value sets the offset for the segments of a filter string that are processed for a subany index lookup. The default is 2. For example, with the default values, a search using this filter "cn=*abcdefgh*" would generate index lookups for "abcd", "cdef", and "efgh".

Note: Indexing support depends on the particular backend in use. Also, changing these settings will generally require deleting any indices that depend on these parameters and recreating them with slapindex(8).

ldapsyntax ( <oid> [DESC <description>] [X-SUBST <substitute-syntax>] )"
  Specify an LDAP syntax using the LDAPv3 syntax defined in RFC 4512. The slapd parser extends the RFC 4512 definition by allowing string forms as well as numeric OIDs to be used for the syntax OID. (See the objectidentifier description.) The slapd parser also honors the X-SUBST extension (an OpenLDAP-specific extension), which allows to use the ldapsyntax statement to define a non-implemented syntax along with another syntax, the extension value substitute-syntax, as its temporary replacement. The substitute-syntax must be defined. This allows to define attribute types that make use of non-implemented syntaxes using the correct syntax OID. Unless X-SUBST is used, this configuration statement would result in an error, since no handlers would be associated to the resulting syntax structure.

localSSF <SSF>
 Specifies the Security Strength Factor (SSF) to be given local LDAP sessions, such as those to the ldapi:// listener. For a description of SSF values, see sasl-secprops’s minssf option description. The default is 71.
logfile <filename>
 Specify a file for recording debug log messages. By default these messages only go to stderr and are not recorded anywhere else. Specifying a logfile copies messages to both stderr and the logfile.
loglevel <integer> [...]
 Specify the level at which debugging statements and operation statistics should be syslogged (currently logged to the syslogd(8) LOG_LOCAL4 facility). They must be considered subsystems rather than increasingly verbose log levels. Some messages with higher priority are logged regardless of the configured loglevel as soon as any logging is configured. Log levels are additive, and available levels are:
1 (0x1 trace) trace function calls
2 (0x2 packets) debug packet handling
4 (0x4 args) heavy trace debugging (function args)
8 (0x8 conns) connection management
16 (0x10 BER) print out packets sent and received
32 (0x20 filter) search filter processing
64 (0x40 config) configuration file processing
128 (0x80 ACL) access control list processing
256 (0x100 stats) connections, LDAP operations, results (recommended)
512 (0x200 stats2) stats log entries sent
1024 (0x400 shell) print communication with shell backends
2048 (0x800 parse) entry parsing

16384 (0x4000 sync) LDAPSync replication
32768 (0x8000 none) only messages that get logged whatever log level is set
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

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

are equivalent. The keyword any can be used as a shortcut to enable logging at all levels (equivalent to -1). The keyword none, or the equivalent integer representation, causes those messages that are logged regardless of the configured loglevel to be logged. In fact, if loglevel is set to 0, no logging occurs, so at least the none level is required to have high priority messages logged.

The loglevel defaults to stats. This level should usually also be included when using other loglevels, to help analyze the logs.

moduleload <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 modulepath option. This option and the modulepath option are only usable if slapd was compiled with --enable-modules.
modulepath <pathspec>
 Specify a list of directories to search for loadable modules. Typically the path is colon-separated but this depends on the operating system. The default is /usr/lib/openldap/modules, which is where the standard OpenLDAP install will place its modules.
objectclass ( <oid> [NAME <name>] [DESC <description>] [OBSOLETE] [SUP <oids>] [{ ABSTRACT | STRUCTURAL | AUXILIARY }] [MUST <oids>] [MAY <oids>] )"
  Specify an objectclass using the LDAPv3 syntax defined in RFC 4512. The slapd parser extends the RFC 4512 definition by allowing string forms as well as numeric OIDs to be used for the object class OID. (See the objectidentifier description.) Object classes are "STRUCTURAL" by default.
objectidentifier <name> { <oid> | <name>[:<suffix>] }
 Define a string name that equates to the given OID. The string can be used in place of the numeric OID in objectclass and attribute definitions. The name can also be used with a suffix of the form ":xx" in which case the value "oid.xx" will be used.
password-hash <hash> [<hash>...]
 This option configures one or more hashes to be used in generation of user passwords stored in the userPassword attribute during processing of LDAP Password Modify Extended Operations (RFC 3062). The <hash> must be one of {SSHA}, {SHA}, {SMD5}, {MD5}, {CRYPT}, and {CLEARTEXT}. The default is {SSHA}.

{SHA} and {SSHA} use the SHA-1 algorithm (FIPS 160-1), the latter with a seed.

{MD5} and {SMD5} use the MD5 algorithm (RFC 1321), the latter with a seed.

{CRYPT} uses the crypt(3).

{CLEARTEXT} indicates that the new password should be added to userPassword as clear text.

Note that this option does not alter the normal user applications handling of userPassword during LDAP Add, Modify, or other LDAP operations.

password-crypt-salt-format <format>
 Specify the format of the salt passed to crypt(3) when generating {CRYPT} passwords (see password-hash) during processing of LDAP Password Modify Extended Operations (RFC 3062).

This string needs to be in sprintf(3) format and may include one (and only one) %s conversion. This conversion will be substituted with a string of random characters from [A-Za-z0-9./]. For example, "%.2s" provides a two character salt and "$1$%.8s" tells some versions of crypt(3) to use an MD5 algorithm and provides 8 random characters of salt. The default is "%s", which provides 31 characters of salt.

pidfile <filename>
 The (absolute) name of a file that will hold the slapd server’s process ID (see getpid(2)).
referral <url>
 Specify the referral to pass back when slapd(8) cannot find a local database to handle a request. If specified multiple times, each url is provided.
require <conditions>
 Specify a set of conditions (separated by white space) to require (default none). The directive may be specified globally and/or per-database; databases inherit global conditions, so per-database specifications are additive. bind requires bind operation prior to directory operations. LDAPv3 requires session to be using LDAP version 3. authc requires authentication prior to directory operations. SASL requires SASL authentication prior to directory operations. strong requires strong authentication prior to directory operations. The strong keyword allows protected "simple" authentication as well as SASL authentication. none may be used to require no conditions (useful to clear out globally set conditions within a particular database); it must occur first in the list of conditions.
reverse-lookup on | off
 Enable/disable client name unverified reverse lookup (default is off if compiled with --enable-rlookups).
rootDSE <file>
 Specify the name of an LDIF(5) file containing user defined attributes for the root DSE. These attributes are returned in addition to the attributes normally produced by slapd.

The root DSE is an entry with information about the server and its capabilities, in operational attributes. It has the empty DN, and can be read with e.g.: ldapsearch -x -b "" -s base "+" See RFC 4512 section 5.1 for details.

sasl-auxprops <plugin> [...]
 Specify which auxprop plugins to use for authentication lookups. The default is empty, which just uses slapd’s internal support. Usually no other auxprop plugins are needed.
sasl-host <fqdn>
 Used to specify the fully qualified domain name used for SASL processing.
sasl-realm <realm>
 Specify SASL realm. Default is empty.
sasl-secprops <properties>
 Used to specify Cyrus SASL security properties. The none flag (without any other properties) causes the flag properties default, "noanonymous,noplain", to be cleared. The noplain flag disables mechanisms susceptible to simple passive attacks. The noactive flag disables mechanisms susceptible to active attacks. The nodict flag disables mechanisms susceptible to passive dictionary attacks. The noanonymous flag disables mechanisms which support anonymous login. The forwardsec flag require forward secrecy between sessions. The passcred require mechanisms which pass client credentials (and allow mechanisms which can pass credentials to do so). The minssf=<factor> property specifies the minimum acceptable security strength factor as an integer approximate to effective key length used for encryption. 0 (zero) implies no protection, 1 implies integrity protection only, 56 allows DES or other weak ciphers, 112 allows triple DES and other strong ciphers, 128 allows RC4, Blowfish and other modern strong ciphers. The default is 0. The maxssf=<factor> property specifies the maximum acceptable security strength factor as an integer (see minssf description). The default is INT_MAX. The maxbufsize=<size> property specifies the maximum security layer receive buffer size allowed. 0 disables security layers. The default is 65536.
schemadn <dn>
 Specify the distinguished name for the subschema subentry that controls the entries on this server. The default is "cn=Subschema".
security <factors>
 Specify a set of security strength factors (separated by white space) to require (see sasl-secprops’s minssf option for a description of security strength factors). The directive may be specified globally and/or per-database. ssf=<n> specifies the overall security strength factor. transport=<n> specifies the transport security strength factor. tls=<n> specifies the TLS security strength factor. sasl=<n> specifies the SASL security strength factor. update_ssf=<n> specifies the overall security strength factor to require for directory updates. update_transport=<n> specifies the transport security strength factor to require for directory updates. update_tls=<n> specifies the TLS security strength factor to require for directory updates. update_sasl=<n> specifies the SASL security strength factor to require for directory updates. simple_bind=<n> specifies the security strength factor required for simple username/password authentication. Note that the transport factor is measure of security provided by the underlying transport, e.g. ldapi:// (and eventually IPSEC). It is not normally used.
serverID <integer> [<URL>]
 Specify an integer ID from 0 to 4095 for this server (limited to 3 hexadecimal digits). These IDs are required when using multimaster replication and each master must have a unique ID. Note that this requirement also applies to separate masters contributing to a glued set of databases. If the URL is provided, this directive may be specified multiple times, providing a complete list of participating servers and their IDs. The fully qualified hostname of each server should be used in the supplied URLs. The IDs are used in the "replica id" field of all CSNs generated by the specified server. The default value is zero. Example:
        serverID 1
sizelimit {<integer>|unlimited}
sizelimit size[.{soft|hard|unchecked}]=<integer> [...]
 Specify the maximum number of entries to return from a search operation. The default size limit is 500. Use unlimited to specify no limits. The second format allows a fine grain setting of the size limits. Extra args can be added on the same line. See limits for an explanation of the different flags.
sockbuf_max_incoming <integer>
 Specify the maximum incoming LDAP PDU size for anonymous sessions. The default is 262143.
sockbuf_max_incoming_auth <integer>
 Specify the maximum incoming LDAP PDU size for authenticated sessions. The default is 4194303.
sortvals <attr> [...]
 Specify a list of multi-valued attributes whose values will always be maintained in sorted order. Using this option will allow Modify, Compare, and filter evaluations on these attributes to be performed more efficiently. The resulting sort order depends on the attributes’ syntax and matching rules and may not correspond to lexical order or any other recognizable order.
threads <integer>
 Specify the maximum size of the primary thread pool. The default is 16; the minimum value is 2.
timelimit {<integer>|unlimited}
timelimit time[.{soft|hard}]=<integer> [...]
 Specify the maximum number of seconds (in real time) slapd will spend answering a search request. The default time limit is 3600. Use unlimited to specify no limits. The second format allows a fine grain setting of the time limits. Extra args can be added on the same line. See limits for an explanation of the different flags.
tool-threads <integer>
 Specify the maximum number of threads to use in tool mode. This should not be greater than the number of CPUs in the system. The default is 1.
writetimeout <integer>
 Specify the number of seconds to wait before forcibly closing a connection with an outstanding write. This allows recovery from various network hang conditions. A writetimeout of 0 disables this feature. The default is 0.


If slapd is built with support for Transport Layer Security, there are more options you can specify.
TLSCipherSuite <cipher-suite-spec>
 Permits configuring what ciphers will be accepted and the preference order. <cipher-suite-spec> should be a cipher specification for OpenSSL. Example:


To check what ciphers a given spec selects, use:

        openssl ciphers -v <cipher-suite-spec>

To obtain the list of ciphers in GNUtls use:

        gnutls-cli -l

TLSCACertificateFile <filename>
 Specifies the file that contains certificates for all of the Certificate Authorities that slapd will recognize.
TLSCACertificatePath <path>
 Specifies the path of a directory that contains Certificate Authority certificates in separate individual files. Usually only one of this or the TLSCACertificateFile is used. This directive is not supported when using GNUtls.
TLSCertificateFile <filename>
 Specifies the file that contains the slapd server certificate.
TLSCertificateKeyFile <filename>
 Specifies the file that contains the slapd server private key that matches the certificate stored in the TLSCertificateFile file. Currently, the private key must not be protected with a password, so it is of critical importance that it is protected carefully.
TLSDHParamFile <filename>
 This directive specifies the file that contains parameters for Diffie-Hellman ephemeral key exchange. This is required in order to use a DSA certificate on the server. If multiple sets of parameters are present in the file, all of them will be processed. Note that setting this option may also enable Anonymous Diffie-Hellman key exchanges in certain non-default cipher suites. You should append "!ADH" to your cipher suites if you have changed them from the default, otherwise no certificate exchanges or verification will be done. When using GNUtls these parameters are always generated randomly so this directive is ignored.
TLSRandFile <filename>
 Specifies the file to obtain random bits from when /dev/[u]random is not available. Generally set to the name of the EGD/PRNGD socket. The environment variable RANDFILE can also be used to specify the filename. This directive is ignored with GNUtls.
TLSVerifyClient <level>
 Specifies what checks to perform on client certificates in an incoming TLS session, if any. The <level> can be specified as one of the following keywords:
never This is the default. slapd will not ask the client for a certificate.
allow The client certificate is requested. If no certificate is provided, the session proceeds normally. If a bad certificate is provided, it will be ignored and the session proceeds normally.
try The client certificate is requested. If no certificate is provided, the session proceeds normally. If a bad certificate is provided, the session is immediately terminated.
demand | hard | true
 These keywords are all equivalent, for compatibility reasons. The client certificate is requested. If no certificate is provided, or a bad certificate is provided, the session is immediately terminated.

Note that a valid client certificate is required in order to use the SASL EXTERNAL authentication mechanism with a TLS session. As such, a non-default TLSVerifyClient setting must be chosen to enable SASL EXTERNAL authentication.

TLSCRLCheck <level>
 Specifies if the Certificate Revocation List (CRL) of the CA should be used to verify if the client certificates have not been revoked. This requires TLSCACertificatePath parameter to be set. This directive is ignored with GNUtls. <level> can be specified as one of the following keywords:
none No CRL checks are performed
peer Check the CRL of the peer certificate
all Check the CRL for a whole certificate chain
TLSCRLFile <filename>
 Specifies a file containing a Certificate Revocation List to be used for verifying that certificates have not been revoked. This directive is only valid when using GNUtls.


Options in this section only apply to the configuration file section for the specified backend. They are supported by every type of backend.
backend <databasetype>
 Mark the beginning of a backend definition. <databasetype> should be one of bdb, config, dnssrv, hdb, ldap, ldif, meta, monitor, null, passwd, perl, relay, shell, or sql, depending on which backend will serve the database.


Options in this section only apply to the configuration file section for the database in which they are defined. They are supported by every type of backend. Note that the database and at least one suffix option are mandatory for each database.
database <databasetype>
 Mark the beginning of a new database instance definition. <databasetype> should be one of bdb, config, dnssrv, hdb, ldap, ldif, meta, monitor, null, passwd, perl, relay, shell, or sql, depending on which backend will serve the database.

LDAP operations, even subtree searches, normally access only one database. That can be changed by gluing databases together with the subordinate keyword. Access controls and some overlays can also involve multiple databases.

add_content_acl on | off
 Controls whether Add operations will perform ACL checks on the content of the entry being added. This check is off by default. See the slapd.access(5) manual page for more details on ACL requirements for Add operations.
hidden on | off
 Controls whether the database will be used to answer queries. A database that is hidden will never be selected to answer any queries, and any suffix configured on the database will be ignored in checks for conflicts with other databases. By default, hidden is off.
lastmod on | off
 Controls whether slapd will automatically maintain the modifiersName, modifyTimestamp, creatorsName, and createTimestamp attributes for entries. It also controls the entryCSN and entryUUID attributes, which are needed by the syncrepl provider. By default, lastmod is on.
limits <selector> <limit> [<limit> [...]]
 Specify time and size limits based on the operation’s initiator or base DN. The argument <selector> can be any of
anonymous | users | [<dnspec>=]<pattern> | group[/oc[/at]]=<pattern>

<dnspec> ::= dn[.<type>][.<style>]
<type> ::= self | this
<style> ::= exact | base | onelevel | subtree | children | regex | anonymous

DN type self is the default and means the bound user, while this means the base DN of the operation. The term anonymous matches all unauthenticated clients. The term users matches all authenticated clients; otherwise an exact dn pattern is assumed unless otherwise specified by qualifying the (optional) key string dn with exact or base (which are synonyms), to require an exact match; with onelevel, to require exactly one level of depth match; with subtree, to allow any level of depth match, including the exact match; with children, to allow any level of depth match, not including the exact match; regex explicitly requires the (default) match based on POSIX (’’extended’’) regular expression pattern. Finally, anonymous matches unbound operations; the pattern field is ignored. The same behavior is obtained by using the anonymous form of the <selector> clause. The term group, with the optional objectClass oc and attributeType at fields, followed by pattern, sets the limits for any DN listed in the values of the at attribute (default member) of the oc group objectClass (default groupOfNames) whose DN exactly matches pattern.

The currently supported limits are size and time.

The syntax for time limits is time[.{soft|hard}]=<integer>, where integer is the number of seconds slapd will spend answering a search request. If no time limit is explicitly requested by the client, the soft limit is used; if the requested time limit exceeds the hard limit, the value of the limit is used instead. If the hard limit is set to the keyword soft, the soft limit is used in either case; if it is set to the keyword unlimited, no hard limit is enforced. Explicit requests for time limits smaller or equal to the hard limit are honored. If no limit specifier is set, the value is assigned to the soft limit, and the hard limit is set to soft, to preserve the original behavior.

The syntax for size limits is size[.{soft|hard|unchecked}]=<integer>, where integer is the maximum number of entries slapd will return answering a search request. If no size limit is explicitly requested by the client, the soft limit is used; if the requested size limit exceeds the hard limit, the value of the limit is used instead. If the hard limit is set to the keyword soft, the soft limit is used in either case; if it is set to the keyword unlimited, no hard limit is enforced. Explicit requests for size limits smaller or equal to the hard limit are honored. The unchecked specifier sets a limit on the number of candidates a search request is allowed to examine. The rationale behind it is that searches for non-properly indexed attributes may result in large sets of candidates, which must be examined by slapd(8) to determine whether they match the search filter or not. The unchecked limit provides a means to drop such operations before they are even started. If the selected candidates exceed the unchecked limit, the search will abort with Unwilling to perform. If it is set to the keyword unlimited, no limit is applied (the default). If it is set to disabled, the search is not even performed; this can be used to disallow searches for a specific set of users. If no limit specifier is set, the value is assigned to the soft limit, and the hard limit is set to soft, to preserve the original behavior.

In case of no match, the global limits are used. The default values are the same as for sizelimit and timelimit; no limit is set on unchecked.

If pagedResults control is requested, the hard size limit is used by default, because the request of a specific page size is considered an explicit request for a limitation on the number of entries to be returned. However, the size limit applies to the total count of entries returned within the search, and not to a single page. Additional size limits may be enforced; the syntax is{<integer>|noEstimate|unlimited}, where integer is the max page size if no explicit limit is set; the keyword noEstimate inhibits the server from returning an estimate of the total number of entries that might be returned (note: the current implementation does not return any estimate). The keyword unlimited indicates that no limit is applied to the pagedResults control page size. The syntax size.prtotal={<integer>|unlimited|disabled} allows to set a limit on the total number of entries that a pagedResults control allows to return. By default it is set to the hard limit. When set, integer is the max number of entries that the whole search with pagedResults control can return. Use unlimited to allow unlimited number of entries to be returned, e.g. to allow the use of the pagedResults control as a means to circumvent size limitations on regular searches; the keyword disabled disables the control, i.e. no paged results can be returned. Note that the total number of entries returned when the pagedResults control is requested cannot exceed the hard size limit of regular searches unless extended by the prtotal switch.

The limits statement is typically used to let an unlimited number of entries be returned by searches performed with the identity used by the consumer for synchronization purposes by means of the RFC 4533 LDAP Content Synchronization protocol (see syncrepl for details).

maxderefdepth <depth>
 Specifies the maximum number of aliases to dereference when trying to resolve an entry, used to avoid infinite alias loops. The default is 15.
mirrormode on | off
 This option puts a replica database into "mirror" mode. Update operations will be accepted from any user, not just the updatedn. The database must already be configured as a syncrepl consumer before this keyword may be set. This mode also requires a serverID (see above) to be configured. By default, mirrormode is off.
monitoring on | off
 This option enables database-specific monitoring in the entry related to the current database in the "cn=Databases,cn=Monitor" subtree of the monitor database, if the monitor database is enabled. Currently, only the BDB and the HDB databases provide database-specific monitoring. The default depends on the backend type.
overlay <overlay-name>
 Add the specified overlay to this database. An overlay is a piece of code that intercepts database operations in order to extend or change them. Overlays are pushed onto a stack over the database, and so they will execute in the reverse of the order in which they were configured and the database itself will receive control last of all. See the slapd.overlays(5) manual page for an overview of the available overlays. Note that all of the database’s regular settings should be configured before any overlay settings.
readonly on | off
 This option puts the database into "read-only" mode. Any attempts to modify the database will return an "unwilling to perform" error. By default, readonly is off.
restrict <oplist>
 Specify a whitespace separated list of operations that are restricted. If defined inside a database specification, restrictions apply only to that database, otherwise they are global. Operations can be any of add, bind, compare, delete, extended[=<OID>], modify, rename, search, or the special pseudo-operations read and write, which respectively summarize read and write operations. The use of restrict write is equivalent to readonly on (see above). The extended keyword allows to indicate the OID of the specific operation to be restricted.
rootdn <dn>
 Specify the distinguished name that is not subject to access control or administrative limit restrictions for operations on this database. This DN may or may not be associated with an entry. An empty root DN (the default) specifies no root access is to be granted. It is recommended that the rootdn only be specified when needed (such as when initially populating a database). If the rootdn is within a namingContext (suffix) of the database, a simple bind password may also be provided using the rootpw directive. Many optional features, including syncrepl, require the rootdn to be defined for the database.
rootpw <password>
 Specify a password (or hash of the password) for the rootdn. The password can only be set if the rootdn is within the namingContext (suffix) of the database. This option accepts all RFC 2307 userPassword formats known to the server (see password-hash description) as well as cleartext. slappasswd(8) may be used to generate a hash of a password. Cleartext and {CRYPT} passwords are not recommended. If empty (the default), authentication of the root DN is by other means (e.g. SASL). Use of SASL is encouraged.
suffix <dn suffix>
 Specify 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.

If the suffix of one database is "inside" that of another, the database with the inner suffix must come first in the configuration file. You may also want to glue such databases together with the subordinate keyword.

subordinate [advertise]
 Specify that the current backend database is a subordinate of another backend database. A subordinate database may have only one suffix. This option may be used to glue multiple databases into a single namingContext. If the suffix of the current database is within the namingContext of a superior database, searches against the superior database will be propagated to the subordinate as well. All of the databases associated with a single namingContext should have identical rootdns. Behavior of other LDAP operations is unaffected by this setting. In particular, it is not possible to use moddn to move an entry from one subordinate to another subordinate within the namingContext.

If the optional advertise flag is supplied, the naming context of this database is advertised in the root DSE. The default is to hide this database context, so that only the superior context is visible.

If the slap tools slapcat(8), slapadd(8), or slapindex(8) are used on the superior database, any glued subordinates that support these tools are opened as well.

Databases that are glued together should usually be configured with the same indices (assuming they support indexing), even for attributes that only exist in some of these databases. In general, all of the glued databases should be configured as similarly as possible, since the intent is to provide the appearance of a single directory.

Note that the subordinate functionality is implemented internally by the glue overlay and as such its behavior will interact with other overlays in use. By default, the glue overlay is automatically configured as the last overlay on the superior backend. Its position on the backend can be explicitly configured by setting an overlay glue directive at the desired position. This explicit configuration is necessary e.g. when using the syncprov overlay, which needs to follow glue in order to work over all of the glued databases. E.g.         database bdb         suffix dc=example,dc=com         ...         overlay glue         overlay syncprov

syncrepl rid=<replica ID> provider=ldap[s]://<hostname>[:port] searchbase=<base DN> [type=refreshOnly|refreshAndPersist] [interval=dd:hh:mm:ss] [retry=[<retry interval> <# of retries>]+] [filter=<filter str>] [scope=sub|one|base|subord] [attrs=<attr list>] [attrsonly] [sizelimit=<limit>] [timelimit=<limit>] [schemachecking=on|off] [network-timeout=<seconds>] [timeout=<seconds>] [bindmethod=simple|sasl] [binddn=<dn>] [saslmech=<mech>] [authcid=<identity>] [authzid=<identity>] [credentials=<passwd>] [realm=<realm>] [secprops=<properties>] [starttls=yes|critical] [tls_cert=<file>] [tls_key=<file>] [tls_cacert=<file>] [tls_cacertdir=<path>] [tls_reqcert=never|allow|try|demand] [tls_ciphersuite=<ciphers>] [tls_crlcheck=none|peer|all] [logbase=<base DN>] [logfilter=<filter str>] [syncdata=default|accesslog|changelog]
  Specify the current database as a replica which is kept up-to-date with the master content by establishing the current slapd(8) as a replication consumer site running a syncrepl replication engine. The replica content is kept synchronized to the master content using the LDAP Content Synchronization protocol. Refer to the "OpenLDAP Administrator’s Guide" for detailed information on setting up a replicated slapd directory service using the syncrepl replication engine.

rid identifies the current syncrepl directive within the replication consumer site. It is a non-negative integer not greater than 4095 (limited to three hexadecimal digits).

provider specifies the replication provider site containing the master content as an LDAP URI. If <port> is not given, the standard LDAP port number (389 or 636) is used.

The content of the syncrepl replica 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, attrsonly, sizelimit, and timelimit parameters as in the normal search specification. The scope defaults to sub, the filter defaults to (objectclass=*), while there is no default searchbase. The attrs list defaults to "*,+" to return all user and operational attributes, and attrsonly is unset by default. The sizelimit and timelimit only accept "unlimited" and positive integers, and both default to "unlimited". The sizelimit and timelimit parameters define a consumer requested limitation on the number of entries that can be returned by the LDAP Content Synchronization operation; as such, it is intended to implement partial replication based on the size of the replicated database and on the time required by the synchronization. Note, however, that any provider-side limits for the replication identity will be enforced by the provider regardless of the limits requested by the LDAP Content Synchronization operation, much like for any other search operation.

The LDAP Content Synchronization protocol has two operation types. In the refreshOnly operation, the next synchronization search operation is periodically rescheduled at an interval time (specified by interval parameter; 1 day by default) after each synchronization operation finishes. In the refreshAndPersist operation, a synchronization search remains persistent in the provider slapd. Further updates to the master replica 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 3 times before stop retrying. The ‘+’ in <# of retries> means indefinite number of retries until success. If no retry was specified, by default syncrepl retries every hour forever.

The schema checking can be enforced at the LDAP Sync consumer site by turning on the schemachecking parameter. The default is off. Schema checking on means that replicated entries must have a structural objectClass, must obey to objectClass requirements in terms of required/allowed attributes, and that naming attributes and distinguished values must be present. As a consequence, schema checking should be off when partial replication is used.

The network-timeout parameter sets how long the consumer will wait to establish a network connection to the provider. Once a connection is established, the timeout parameter determines how long the consumer will wait for the initial Bind request to complete. The defaults for these parameters come from ldap.conf(5).

A bindmethod of simple requires the options binddn and credentials and should only be used when adequate security services (e.g. TLS or IPSEC) are in place. REMEMBER: simple bind credentials must be in cleartext! A bindmethod of sasl requires the option saslmech. Depending on the mechanism, an authentication identity and/or credentials can be specified using authcid and credentials. The authzid parameter may be used to specify an authorization identity. Specific security properties (as with the sasl-secprops keyword above) for a SASL bind can be set with the secprops option. A non default SASL realm can be set with the realm option. The identity used for synchronization by the consumer should be allowed to receive an unlimited number of entries in response to a search request. The provider, other than allow authentication of the syncrepl identity, should grant that identity appropriate access privileges to the data that is being replicated (access directive), and appropriate time and size limits. This can be accomplished by either allowing unlimited sizelimit and timelimit, or by setting an appropriate limits statement in the consumer’s configuration (see sizelimit and limits for details).

The starttls parameter specifies use of the StartTLS extended operation to establish a TLS session before Binding 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.

updatedn <dn>
 This option is only applicable in a slave database. It specifies the DN permitted to update (subject to access controls) the replica. It is only needed in certain push-mode replication scenarios. Generally, this DN should not be the same as the rootdn used at the master.
updateref <url>
 Specify the referral to pass back when slapd(8) is asked to modify a replicated local database. If specified multiple times, each url is provided.


Each database may allow specific configuration options; they are documented separately in the backends’ manual pages. See the slapd.backends(5) manual page for an overview of available backends.


Here is a short example of a configuration file:

include /etc/openldap/schema/core.schema pidfile /var/run/slapd/run/

# Subtypes of "name" (e.g. "cn" and "ou") with the # option ";x-hidden" can be searched for/compared, # but are not shown. See slapd.access(5). attributeoptions x-hidden lang- access to attrs=name;x-hidden by * =cs

# Protect passwords. See slapd.access(5). access to attrs=userPassword by * auth # Read access to other attributes and entries. access to * by * read

database bdb suffix "dc=our-domain,dc=com" # The database directory MUST exist prior to # running slapd AND should only be accessible # by the slapd/tools. Mode 0700 recommended. directory /var/run/slapd/openldap-data # Indices to maintain index objectClass eq index cn,sn,mail pres,eq,approx,sub

# We serve small clients that do not handle referrals, # so handle remote lookups on their behalf. database ldap suffix "" uri ldap:// lastmod off

"OpenLDAP Administrator’s Guide" contains a longer annotated example of a configuration file. The original /etc/openldap/slapd.conf is another example.


 default slapd configuration file


ldap(3), slapd-config(5), slapd.access(5), slapd.backends(5), slapd.overlays(5), slapd.plugin(5), slapd.replog(5), slapd(8), slapacl(8), slapadd(8), slapauth(8), slapcat(8), slapdn(8), slapindex(8), slappasswd(8), slaptest(8).

"OpenLDAP Administrator’s Guide" (


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

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