note that not all backends and overlays support runtime configuration (I guess we...

[openldap] / doc / guide / admin / slapdconf2.sdf

# $OpenLDAP$
# Copyright 2005, The OpenLDAP Foundation, All Rights Reserved.
# COPYING RESTRICTIONS APPLY, see COPYRIGHT.

H1: Configuring slapd

Once the software has been built and installed, you are ready
to configure {{slapd}}(8) for use at your site. Unlike previous
OpenLDAP releases, the slapd runtime configuration in 2.3 is
fully LDAP-enabled and can be managed using the standard LDAP
operations with data in {{TERM:LDIF}}. The LDAP configuration engine
allows all of slapd's configuration options to be changed on the fly,
generally without requiring a server restart for the changes
to take effect. The old style {{slapd.conf}}(5) file is still
supported, but must be converted to the new {{slapd.d}}(5) format
to allow runtime changes to be saved. While the old style
configuration uses a single file, normally installed as
{{F:/usr/local/etc/openldap/slapd.conf}}, the new style
uses a slapd backend database to store the configuration. The
configuration database normally resides in the
{{F:/usr/local/etc/openldap/slapd.d}} directory.

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

Note: some of the backends and of the distributed overlays
do not support runtime configuration yet.  In those cases,
the old style {{slapd.conf}}(5) file must be used.

Note: the current version of {{slurpd}} has not been updated for
compatibility with this new configuration engine. If you must use
slurpd for replication at your site, you will have to maintain an
old-style {{slapd.conf}} file for slurpd to use.


H2: 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.

!import "config_dit.gif"; align="center"; title="Sample configuration tree"
FT[align="Center"] Figure 5.1: Sample configuration tree.

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

The {{slapd.d}} configuration tree has a very specific structure. The
root of the tree is named {{EX:cn=config}} and contains global configuration
settings. Additional settings are contained in separate child entries:
* Include files
.. Usually these are just pathnames left over from a converted
{{EX:slapd.conf}} file.
.. Otherwise use of Include files is deprecated.
* Dynamically loaded modules
.. These may only be used if the {{EX:--enable-modules}} option was
used to configure the software.
* Schema definitions
.. The {{EX:cn=schema,cn=config}} entry contains the system schema (all
the schema that is hard-coded in slapd).
.. Child entries of {{EX:cn=schema,cn=config}} contain user schema as
loaded from config files or added at runtime.
* Backend-specific configuration 
* Database-specific configuration
.. Overlays are defined in children of the Database entry.
.. Databases and Overlays may also have other miscellaneous children.

The usual rules for LDIF files apply to the configuration information:
Comment lines beginning with a '{{EX:#}}' character
are ignored.  If a line begins with white space, it is considered a
continuation of the previous line (even if the previous line is a
comment). 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 {{EX:"{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 {{EX:"olc"}} (OpenLDAP Configuration)
in their names. Generally there is a one-to-one correspondence
between the attributes and the old-style {{EX: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 white space.  If an argument contains white space,
the argument should be enclosed in double quotes {{EX:"like this"}}. If
an argument contains a double quote or a backslash character `{{EX:\}}',
the character should be preceded by a backslash character `{{EX:\}}'.
In the descriptions that follow, arguments that should be replaced
by actual text are shown in brackets {{EX:<>}}.

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


H2: Configuration Directives

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


H3: 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 {{EX:olcGlobal}} objectClass.


H4: 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.


H4: olcLogLevel: <level>

This directive specifies the level at which debugging statements
and operation statistics should be syslogged (currently logged to
the {{syslogd}}(8) {{EX:LOG_LOCAL4}} facility). You must have
configured OpenLDAP {{EX:--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.
To display what levels
correspond to what kind of debugging, invoke slapd with {{EX:-?}}
or consult the table below. The possible values for <level> are:

!block table; colaligns="RL"; align=Center; \
        title="Table 5.1: Debugging Levels"
Level   Keyword Description
-1      Any     enable all debugging
0               no debugging
1       Trace   trace function calls
2       Packets debug packet handling
4       Args    heavy trace debugging
8       Conns   connection management
16      BER     print out packets sent and received
32      Filter  search filter processing
64      Config  configuration processing
128     ACL     access control list processing
256     Stats   stats log connections/operations/results
512     Stats2  stats log entries sent
1024    Shell   print communication with shell backends
2048    Parse   print entry parsing debugging
4096    Cache   database cache processing
8192    Index   database indexing
16384   Sync    syncrepl consumer processing
!endblock

\Example:

E: olcLogLevel: -1

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

E: olcLogLevel: Conns Filter

Just log the connection and search filter processing.

\Default:

E: olcLogLevel: Stats


H4: olcReferral <URI>

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

\Example:

>       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.


H4: Sample Entry

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



H3: cn=include

An include entry holds the pathname of one include file. Include files
are part of the old style slapd.conf configuration system and must be in
slapd.conf format. Include files were commonly used to load schema
specifications. While they are still supported, their use is deprecated.
Include entries must have the {{EX:olcIncludeFile}} objectClass.


H4: olcInclude: <filename>

This directive specifies that slapd should read additional
configuration information from the given file. 

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.


H4: Sample Entries

>dn: cn=include{0},cn=config
>objectClass: olcIncludeFile
>cn: include{0}
>olcInclude: ./schema/core.schema
>
>dn: cn=include{1},cn=config
>objectClass: olcIncludeFile
>cn: include{1}
>olcInclude: ./schema/cosine.schema


H3: cn=module

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


H4: 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 {{EX:olcModulePath}}
directive.


H4: 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.


H4: 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


H3: 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 {{EX:olcSchemaConfig}}
objectClass.


H4: olcAttributeTypes: <{{REF:RFC2252}} Attribute Type Description>

This directive defines an attribute type.
Please see the {{SECT:Schema Specification}} chapter
for information regarding how to use this directive.


H4: olcObjectClasses: <{{REF:RFC2252}} Object Class Description>

This directive defines an object class.
Please see the {{SECT:Schema Specification}} chapter for
information regarding how to use this directive.


H4: 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
> SYNTAX 1.3.6.1.4.1.1466.115.121.1.27 )
>olcAttributeTypes: ( 1.1.2 NAME 'testTwo' EQUALITY caseIgnoreMatch
> SUBSTR caseIgnoreSubstringsMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.44 )
>olcObjectClasses: ( 1.1.3 NAME 'testObject'
> MAY ( testAttr $ testTwo ) AUXILIARY )


H3: 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
{{EX:olcBackendConfig}} objectClass.

H4: olcBackend: <type>

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

!block table; align=Center; coltags="EX,N"; \
        title="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
ldif    Lightweight Data Interchange Format 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
!endblock

\Example:

>       olcBackend: bdb

There are no other directives defined for this entry, so generally
it will not be needed. However, specific backend types may define
additional attributes for their particular use.


H4: Sample Entry

> dn: olcBackend=bdb,cn=config
> objectClass: olcBackendConfig
> olcBackend: bdb


H3: Database-specific Directives

Directives in this section are supported by every type of database.
Database entries must have the {{EX:olcDatabaseConfig}} objectClass.

H4: 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.
{{EX:<type>}} should be one of the
supported backend types listed in Table 5.2 or the {{EX:frontend}} type.

The {{EX: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.

\Example:

>       olcDatabase: bdb

This marks the beginning of a new {{TERM:BDB}} database instance.


H4: 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 requesters (specified by <who>).
See the {{SECT:Access Control}} section of this chapter for a
summary of basic usage.

!if 0
More detailed discussion of this directive can be found in the
{{SECT:Advanced Access Control}} chapter.
!endif

Note: If no {{EX:olcAccess}} directives are specified, the default
access control policy, {{EX: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.


H4: 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.

\Default:

>       olcReadonly: FALSE


H4: olcReplica

>       olcReplica: uri=ldap[s]://<hostname>[:<port>] | host=<hostname>[:<port>]
>               [bindmethod={simple|sasl}]
>               ["binddn=<DN>"]
>               [saslmech=<mech>]
>               [authcid=<identity>]
>               [authzid=<identity>]
>               [credentials=<password>]

This directive specifies a replication site for this database for
use with slurpd. The
{{EX:uri=}} parameter specifies a scheme, 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 or 636) is used.

{{EX:host}} is deprecated in favor of the {{EX:uri}} parameter.

{{EX:uri}} allows the replica LDAP server to be specified as an LDAP 
URI such as {{EX:ldap://slave.example.com:389}} or
{{EX:ldaps://slave.example.com:636}}.

The {{EX: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.  It must also match the {{EX:updatedn}}
directive in the slave slapd's config file.  Generally, this DN
{{should not}} be the same as the {{EX:rootdn}} of the master
database.  Since DNs are likely to contain embedded spaces, the
entire {{EX:"binddn=<DN>"}} string should be enclosed in double
quotes.

The {{EX:bindmethod}} is {{EX:simple}} or {{EX:sasl}},
depending on whether simple password-based authentication
or {{TERM:SASL}} authentication is to be used when connecting
to the slave slapd.

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
{{EX:binddn}} and {{EX:credentials}} parameters.

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

See the chapter entitled {{SECT:Replication with slurpd}} for more
information on how to use this directive.


H4: olcReplogfile: <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 {{SECT:Replication with slurpd}} for more
information on how to use this directive.


H4: 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 {{SECT:SASL Authentication}} section for information on
SASL authentication identities.


H4: 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).

\Example:

>       olcRootPW: secret

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

\Example:

>       olcRootPW: {SSHA}ZKKuqbEKJfKSXhUbHG3fG8MDn9j1v4QN

The hash was generated using the command {{EX:slappasswd -s secret}}.


H4: olcSizeLimit: <integer>

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

\Default:

>       olcSizeLimit: 500



H4: 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 {{EX:frontend}} and
{{EX:monitor}} use a hard-coded suffix which may not be overridden
in the configuration.)

\Example:

>       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.


H4: olcSyncrepl

>       olcSyncrepl: rid=<replica ID>
>               provider=ldap[s]://<hostname>[:port]
>               [type=refreshOnly|refreshAndPersist]
>               [interval=dd:hh:mm:ss]
>               [retry=[<retry interval> <# of retries>]+]
>               [searchbase=<base DN>]
>               [filter=<filter str>]
>               [scope=sub|one|base]
>               [attrs=<attr list>]
>               [attrsonly]
>               [sizelimit=<limit>]
>               [timelimit=<limit>]
>               [schemachecking=on|off]
>               [bindmethod=simple|sasl]
>               [binddn=<DN>]
>               [saslmech=<mech>]
>               [authcid=<identity>]
>               [authzid=<identity>]
>               [credentials=<passwd>]
>               [realm=<realm>]
>               [secprops=<properties>]


This directive specifies the current database as a replica of the
master content by establishing the current {{slapd}}(8) as a
replication consumer site running a syncrepl replication engine.
The master database is located at the replication provider site
specified by the {{EX:provider}} parameter. The replica database is
kept up-to-date with the master content using the LDAP Content
Synchronization protocol. See {{EX:draft-zeilenga-ldup-sync-xx.txt}}
({{a work in progress}}) for more information on the protocol.

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

The {{EX:provider}} parameter specifies the replication provider site
containing the master content as an LDAP URI. The {{EX: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
{{EX:ldap://provider.example.com:389}} or {{EX:ldaps://192.168.1.1:636}}.
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 at the consumer site, whereas the {{EX:replica}}
specification is located at the provider site. {{EX:syncrepl}} and
{{EX:replica}} directives define two independent replication
mechanisms. They do not represent the replication peers of each other.

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 {{EX:searchbase}},
{{EX:scope}}, {{EX:filter}}, {{EX:attrs}}, {{EX:attrsonly}},
{{EX:sizelimit}}, and {{EX:timelimit}} parameters as in the normal
search specification. The syncrepl search specification has
the same value syntax and the same default values as in the
{{ldapsearch}}(1) client search tool.

The LDAP Content Synchronization protocol has two operation
types: {{EX:refreshOnly}} and {{EX:refreshAndPersist}}.
The operation type is specified by the {{EX:type}} parameter.
In the {{EX: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 {{EX:interval}} parameter. It is set to one day by default.
In the {{EX:refreshAndPersist}} operation, a synchronization search
remains persistent in the provider slapd. Further updates to the
master replica will generate {{EX: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 {{EX:schemachecking}} parameter.
If it is turned on, every replicated entry will be checked for its
schema as the entry is stored into the replica content.
Every entry in the replica 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 {{EX: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
master database. 

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

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 {{EX:binddn}}
and {{EX:credentials}} parameters.

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

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

The syncrepl replication mechanism is supported by the
three native backends: back-bdb, back-hdb, and back-ldbm.

See the {{SECT:LDAP Sync Replication}} chapter of the admin guide
for more information on how to use this directive.


H4: 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.

\Default:

>       olcTimeLimit: 3600


H4: olcUpdateDN: <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:

>       olcUpdateDN: "cn=Update Daemon,dc=example,dc=com"

SASL-based Example:

>       olcUpdateDN: "uid=slurpd,cn=example.com,cn=digest-md5,cn=auth"

See the {{SECT:Replication with slurpd}} chapter for more information
on how to use this directive.

H4: olcUpdateref: <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 {{TERM:URL}} is provided.

\Example:

>       olcUpdateref:   ldap://master.example.net


H4: Sample Entry

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

H3: BDB and HDB Database Directives

Directives in this category apply to both the {{TERM:BDB}}
and the {{TERM:HDB}} database.
They are used in an olcDatabase entry in addition to the generic
database directives defined above.  For a complete reference
of BDB/HDB configuration directives, see {{slapd-bdb}}(5). In
addition to the {{EX:olcDatabaseConfig}} objectClass, BDB and HDB
database entries must have the {{EX:olcBdbConfig}} and
{{EX:olcHdbConfig}} objectClass, respectively.


H4: olcDbDirectory: <directory>

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

\Default:

>       olcDbDirectory: /usr/local/var/openldap-data


H4: olcDbCachesize: <integer>

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

\Default:

>       olcDbCachesize: 1000


H4: olcDbCheckpoint: <kbyte> <min>

This directive specifies how often to checkpoint the BDB transaction log.
A checkpoint operation flushes the database buffers to disk and writes a
checkpoint record in the log.
The checkpoint will occur if either <kbyte> data has been written or
<min> minutes have passed since the last checkpont. 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. See the Berkeley DB reference guide for more details.

\Example:

>       olcDbCheckpoint: 1024 10


H4: olcDbConfig: <DB_CONFIG setting>

This attribute specifies a configuration directive to be placed in the
{{EX:DB_CONFIG}} file of the database directory. At server startup time, if
no such file exists yet, the {{EX:DB_CONFIG}} file will be created and the
settings in this attribute will be written to it. If the file exists,
its contents will be read and displayed in this attribute. The attribute
is multi-valued, to accomodate multiple configuration directives. No default
is provided, but it is essential to use proper settings here to get the
best server performance.

\Example:

>       olcDbConfig: set_cachesize 0 10485760 0
>       olcDbConfig: set_lg_bsize 2097512
>       olcDbConfig: set_lg_dir /var/tmp/bdb-log
>       olcDbConfig: set_flags DB_LOG_AUTOREMOVE

In this example, the BDB cache is set to 10MB, the BDB transaction log
buffer size is set to 2MB, and the transaction log files are to be stored
in the /var/tmp/bdb-log directory. Also a flag is set to tell BDB to
delete transaction log files as soon as their contents have been
checkpointed and they are no longer needed. Without this setting the
transaction log files will continue to accumulate until some other
cleanup procedure removes them. See the SleepyCat documentation for the
{{EX:db_archive}} command for details.

Ideally the BDB cache must be
at least as large as the working set of the database, the log buffer size
should be large enough to accomodate most transactions without overflowing,
and the log directory must be on a separate physical disk from the main
database files. And both the database directory and the log directory
should be separate from disks used for regular system activities such as
the root, boot, or swap filesystems. See the FAQ-o-Matic and the SleepyCat
documentation for more details.


H4: olcDbNosync: { TRUE | FALSE }

This option causes on-disk database contents to not be immediately
synchronized with in memory changes upon change.  Setting this option
to {{EX:TRUE}} may improve performance at the expense of data integrity. This
directive has the same effect as using
>       olcDbConfig: set_flags DB_TXN_NOSYNC


H4: olcDbIDLcacheSize: <integer>

Specify the size of the in-memory index cache, in index slots. The
default is zero. A larger value will speed up frequent searches of
indexed entries. The optimal size will depend on the data and search
characteristics of the database, but using a number three times
the entry cache size is a good starting point.

\Example:

>       olcDbIDLcacheSize: 3000


H4: olcDbIndex: {<attrlist> | default} [pres,eq,approx,sub,none]

This directive specifies the indices to maintain for the given
attribute. If only an {{EX:<attrlist>}} is given, the default
indices are maintained.

\Example:

>       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 {{EX:uid}} attribute type.
The third line causes present, equality, and substring indices to
be maintained for {{EX:cn}} and {{EX:sn}} attribute types.  The
fourth line causes an equality index for the {{EX:objectClass}}
attribute type.

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

>       olcDbindex: objectClass eq

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.


H4: olcDbLinearIndex: { TRUE | FALSE }

If this setting is {{EX:TRUE}} slapindex will index one attribute
at a time. The default settings is {{EX:FALSE}} in which case all
indexed attributes of an entry are processed at the same time. When
enabled, each indexed attribute is processed individually, using
multiple passes through the entire database. This option improves
slapindex performance when the database size exceeds the BDB cache
size. When the BDB cache is large enough, this option is not needed
and will decrease performance. Also by default, slapadd performs
full indexing and so a separate slapindex run is not needed. With
this option, slapadd does no indexing and slapindex must be used.


H4: olcDbMode: <integer>

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

\Default:

>       olcDbMode: 0600


H4: olcDbSearchStack: <integer>

Specify the depth of the stack used for search filter evaluation.
Search filters are evaluated on a stack to accomodate nested {{EX:AND}} /
{{EX: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.

\Default:

>       olcDbSearchStack: 16


H4: olcDbShmKey: <integer>

Specify a key for a shared memory BDB environment. By default the BDB
environment uses memory mapped files. If a non-zero value is specified,
it will be used as the key to identify a shared memory region that will
house the environment.

\Example:

>       olcDbShmKey: 42


H4: Sample Entry

>dn: olcDatabase=hdb,cn=config
>objectClass: olcDatabaseConfig
>objectClass: olcHdbConfig
>olcDatabase: hdb
>olcSuffix: "dc=example,dc=com"
>olcDbDirectory: /usr/local/var/openldap-data
>olcDbCacheSize: 1000
>olcDbCheckpoint: 1024 10
>olcDbConfig: set_cachesize 0 10485760 0
>olcDbConfig: set_lg_bsize 2097152
>olcDbConfig: set_lg_dir /var/tmp/bdb-log
>olcDbConfig: set_flags DB_LOG_AUTOREMOVE
>olcDbIDLcacheSize: 3000
>olcDbIndex: objectClass eq


H2: Access Control

Access to slapd entries and attributes is controlled by the
olcAccess attribute, whose values are a sequence of access directives.
The general form of the olcAccess configuration is:

>       olcAccess: <access directive>
>       <access directive> ::= 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> [val[.<basic-style>]=<regex>] | <attr> , <attrlist>
>       <attr> ::= <attrname> | entry | children
>       <who> ::= * | [anonymous | users | self
>                       | dn[.<basic-style>]=<regex> | dn.<scope-style>=<DN>] 
>               [dnattr=<attrname>]
>               [group[/<objectclass>[/<attrname>][.<basic-style>]]=<regex>]
>               [peername[.<basic-style>]=<regex>]
>               [sockname[.<basic-style>]=<regex>]
>               [domain[.<basic-style>]=<regex>]
>               [sockurl[.<basic-style>]=<regex>]
>               [set=<setspec>]
>               [aci=<attrname>]
>       <access> ::= [self]{<level>|<priv>}
>       <level> ::= none | auth | compare | search | read | write
>       <priv> ::= {=|+|-}{w|r|s|c|x|0}+
>       <control> ::= [stop | continue | break]

where the <what> part selects the entries and/or attributes to which
the access applies, the {{EX:<who>}} part specifies which entities
are granted access, and the {{EX:<access>}} part specifies the
access granted. Multiple {{EX:<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.


H3: 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:

>       to *
>       to dn[.<basic-style>]=<regex>
>       to 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 {{REF:RFC2253}}.

The scope can be either {{EX:base}}, {{EX:one}}, {{EX:subtree}},
or {{EX:children}}.  Where {{EX:base}} matches only the entry with
provided DN, {{EX:one}} matches the entries whose parent is the
provided DN, {{EX:subtree}} matches all entries in the subtree whose
root is the provided DN, and {{EX: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

\Then:
. {{EX:dn.base="ou=people,o=suffix"}} match 2;
. {{EX:dn.one="ou=people,o=suffix"}} match 3, and 5;
. {{EX:dn.subtree="ou=people,o=suffix"}} match 2, 3, 4, and 5; and
. {{EX:dn.children="ou=people,o=suffix"}} match 3, 4, and 5.


Entries may also be selected using a filter:

>       to filter=<ldap filter>

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

>       to filter=(objectClass=person)

Note that entries may be selected by both DN and filter by
including both qualifiers in the <what> clause.

>       to 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>

A specific value of an attribute is selected by using a single
attribute name and also using a value selector:

>       attrs=<attribute> val[.<style>]=<regex>

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

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


H3: 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:

!block table; align=Center; coltags="EX,N"; \
        title="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
!endblock

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

Other control factors are also supported.  For example, a {{EX:<who>}}
can be restricted 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).

Some factors may not be appropriate in all environments (or any).
For example, the domain factor relies on IP to domain name lookups.
As these can easily spoofed, the domain factor should not be avoided.


H3: The access to grant


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


!block table; colaligns="LRL"; coltags="EX,EX,N"; align=Center; \
        title="Table 5.4: Access Levels"
Level   Privileges      Description
none    =0              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
!endblock

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


H3: 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 {{EX:<what>}} selectors given in the configuration.
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 (which are held in
the {{EX:frontend}} database definition).  Within this
priority, access directives are examined in the order in which they
appear in the configuration attribute.  Slapd stops with the first {{EX:<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 {{EX:<who>}}
selectors within the access directive selected above in the order
in which they appear. It stops with the first {{EX:<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
{{EX:<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 configuration. Similarly, if one {{EX:<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.



H3: Access Control Examples

The access control facility described above is quite powerful.  This
section shows some examples of its use for descriptive purposes.

A simple example:

>       olcAccess: to * by * read

This access directive grants read access to everyone.

>       olcAccess: to *
>               by self write
>               by anonymous auth
>               by * read

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

>       olcAccess: 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 of strength 128 or better have been established,
allows authentication access to anonymous users, and read access
when strength 64 or better security protections have been established.  If
the client has not establish sufficient security protections, the
implicit {{EX:by * none}} clause would be applied.

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

>       olcAccess: to dn.children="dc=example,dc=com"
>               by * search
>       olcAccess: to dn.children="dc=com"
>               by * read

Read access is granted to entries under the {{EX:dc=com}} subtree,
except for those entries under the {{EX:dc=example,dc=com}} subtree,
to which search access is granted.  No access is granted to
{{EX: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 {{EX:dc=example,dc=com}}
are also under {{EX:dc=com}} entries.

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

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

>       olcAccess: to dn.subtree="dc=example,dc=com" attr=homePhone
>               by self write
>               by dn.children=dc=example,dc=com" search
>               by peername.regex=IP:10\..+ read
>       olcAccess: 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 "{{EX:dc=example,dc=com}}"
subtree. To all attributes except {{EX:homePhone}}, an entry can
write to itself, entries under {{EX:example.com}} entries can search
by them, anybody else has no access (implicit {{EX:by * none}})
excepting for authentication/authorization (which is always done
anonymously).  The {{EX:homePhone}} attribute is writable by the
entry, searchable by entries under {{EX:example.com}}, readable by
clients connecting from network 10, and otherwise not readable
(implicit {{EX:by * none}}).  All other access is denied by the
implicit {{EX: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:

>       olcAccess: to attr=member,entry
>               by dnattr=member selfwrite

The dnattr {{EX:<who>}} selector says that the access applies to
entries listed in the {{EX:member}} attribute. The {{EX: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.



H3: Access Control Ordering

Since the ordering of {{EX:olcAccess}} directives is essential to their
proper evaluation, but LDAP attributes normally do not preserve the
ordering of their values, OpenLDAP uses a custom schema extension to
maintain a fixed ordering of these values. This ordering is maintained
by prepending a {{EX:"{X}"}} numeric index to each value, similarly to
the approach used for ordering the configuration entries. These index
tags are maintained automatically by slapd and do not need to be specified
when originally defining the values. For example, when you create the
settings

>       olcAccess: to attr=member,entry
>               by dnattr=member selfwrite
>       olcAccess: to dn.children="dc=example,dc=com"
>               by * search
>       olcAccess: to dn.children="dc=com"
>               by * read

when you read them back using slapcat or ldapsearch they will contain

>       olcAccess: {0}to attr=member,entry
>               by dnattr=member selfwrite
>       olcAccess: {1}to dn.children="dc=example,dc=com"
>               by * search
>       olcAccess: {2}to dn.children="dc=com"
>               by * read

The numeric index may be used to specify a particular value to change
when using ldapmodify to edit the access rules. This index can be used
instead of (or in addition to) the actual access value. Using this 
numeric index is very helpful when multiple access rules are being managed.

For example, if we needed to change the second rule above to grant
write access instead of search, we could try this LDIF:

>       changetype: modify
>       delete: olcAccess
>       olcAccess: to dn.children="dc=example,dc=com" by * search
>       -
>       add: olcAccess
>       olcAccess: to dn.children="dc=example,dc=com" by * write
>       -

But this example {{B:will not}} guarantee that the existing values remain in
their original order, so it will most likely yield a broken security
configuration. Instead, the numeric index should be used:

>       changetype: modify
>       delete: olcAccess
>       olcAccess: {1}
>       -
>       add: olcAccess
>       olcAccess: {1}to dn.children="dc=example,dc=com" by * write
>       -

This example deletes whatever rule is in value #1 of the {{EX:olcAccess}}
attribute (regardless of its value) and adds a new value that is
explicitly inserted as value #1. The result will be

>       olcAccess: {0}to attr=member,entry
>               by dnattr=member selfwrite
>       olcAccess: {1}to dn.children="dc=example,dc=com"
>               by * write
>       olcAccess: {2}to dn.children="dc=com"
>               by * read

which is exactly what was intended.

!if 0
For more details on how to use the {{EX:access}} directive,
consult the {{Advanced Access Control}} chapter.
!endif


H2: Configuration Example

The following is an example configuration, interspersed
with explanatory text. It defines two databases to handle
different parts of the {{TERM:X.500}} tree; both are {{TERM: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:

E:  1.  # example config file - global configuration entry
E:  2.  dn: cn=config
E:  3.  objectClass: olcGlobal
E:  4.  cn: config
E:  5.  olcReferral: ldap://root.openldap.org
E:  6.  

Line 1 is a comment. Lines 2-4 identify this as the global
configuration entry.
The {{EX: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 {{EX:root.openldap.org}}.
Line 6 is a blank line, indicating the end of this entry.

E:  7.  # internal schema
E:  8.  dn: cn=schema,cn=config
E:  9.  objectClass: olcSchemaConfig
E: 10.  cn: schema
E: 11.  

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.

E: 12.  # include the core schema
E: 13.  include: file:///usr/local/etc/openldap/schema/core.ldif
E: 14.  

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 {{EX:frontend}} database whose settings are applied globally
to all the other databases.

E: 15.  # global database parameters
E: 16.  dn: olcDatabase=frontend,cn=config
E: 17.  objectClass: olcDatabaseConfig
E: 18.  olcDatabase: frontend
E: 19.  olcAccess: to * by * read
E: 20.  

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).

The next entry defines a BDB 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 {{EX:userPassword}} attribute is to be
protected from unauthorized access.

E: 21.  # BDB definition for example.com
E: 22.  dn: olcDatabase=bdb,cn=config
E: 23.  objectClass: olcDatabaseConfig
E: 24.  objectClass: olcBdbConfig
E: 25.  olcDatabase: bdb
E: 26.  olcSuffix: "dc=example,dc=com"
E: 27.  olcDbDirectory: /usr/local/var/openldap-data
E: 28.  olcRootDN: "cn=Manager,dc=example,dc=com"
E: 29.  olcRootPW: secret
E: 30.  olcDbIndex: uid pres,eq
E: 31.  olcDbIndex: cn,sn,uid pres,eq,approx,sub
E: 32.  olcDbIndex: objectClass eq
E: 33.  olcAccess: to attr=userPassword
E: 34.    by self write
E: 35.    by anonymous auth
E: 36.    by dn.base="cn=Admin,dc=example,dc=com" write
E: 37.    by * none
E: 38.  olcAccess: to *
E: 39.    by self write
E: 40.    by dn.base="cn=Admin,dc=example,dc=com" write
E: 41.    by * read
E: 42.  

Line 21 is a comment. Lines 22-25 identify this entry as a BDB database
configuration entry.  Line 26 specifies the DN suffix
for queries to pass to this database. Line 27 specifies the directory
in which the database files will live.

Lines 28 and 29 identify the database {{super-user}} entry and associated
password. This entry is not subject to access control or size or
time limit restrictions.

Lines 30 through 32 indicate the indices to maintain for various
attributes.

Lines 33 through 41 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 {{EX: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 42 is a blank line, indicating the end of this entry.

The next section of the example configuration file defines another
BDB database. This one handles queries involving the
{{EX:dc=example,dc=net}} subtree but is managed by the same entity
as the first database.  Note that without line 51, the read access
would be allowed due to the global access rule at line 19.

E: 42.  # BDB definition for example.net
E: 43.  dn: olcDatabase=bdb,cn=config
E: 44.  objectClass: olcDatabaseConfig
E: 45.  objectClass: olcBdbConfig
E: 46.  olcDatabase: bdb
E: 47.  olcSuffix: "dc=example,dc=net"
E: 48.  olcDbDirectory: /usr/local/var/openldap-data-net
E: 49.  olcRootDN: "cn=Manager,dc=example,dc=com"
E: 50.  olcDbIndex: objectClass eq
E: 51.  olcAccess: to * by users read