5. The slapd Configuration File

Once the software has been built and installed, you are ready to configure it for use at your site. All slapd runtime configuration is accomplished through the slapd.conf file, installed in the ETCDIR directory you specified in the Make-common file. An alternate configuration file can be specified via a command-line option to slapd or slurpd (see Sections 5 and 8, respectively). This section describes the general format of the config file, followed by a detailed description of each config file option.

5.1 Configuration File Format

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.

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

# comment - these options apply to every database
<global config options>
# first database definition & config options
database <backend 1 type>
<config options specific to backend 1>
# second database definition & config options
database <backend 2 type>
<config options specific to backend 2>
# subsequent database definitions & config options
Configuration line arguments are separated by white space. If an argument contains white space, the argument should be enclosed in double quotes "like this". If an argument contains a double quote or a backslash character `\', the character should be preceded by a backslash character `\'.

The distribution contains an example configuration file that will be installed in the ETCDIR directory. Also provided are slapd.at.conf, which contains many commonly used attribute definitions, and slapd.oc.conf, which contains many commonly used object class definitions. These files can be included from the slapd configuration file (see below).

5.2 Configuration File Options

This section separates the configuration file options into global and backend-specific categories, describing each option and its default value (if any), and giving an example of its use.

5.2.1 Global Options

Options described in this section apply to all backends, unless specifically overridden in a backend definition. Option arguments that should be replaced by actual text are shown in brackets <>.

access to <what> [ by <who> <accesslevel> ]+

This option 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 Section 5.3 on access control for more details and examples.
attribute <name> [<name2>] { bin | ces | cis | tel | dn }
This option associates a syntax with an attribute name. By default, an attribute is assumed to have syntax cis. An optional alternate name can be given for an attribute. The possible syntaxes and their meanings are
bin binary
ces case exact string (case must match during comparisons)
cis case ignore string (case is ignored during comparisons)
tel telephone number string (like cis but blanks and dashes `- ' are ignored during comparisons)
dn distinguished name
defaultaccess { none | compare | search | read | write }
This option specifies the default access to grant requesters not matched by any other access line (see Section 5.3). Note that an access level implies all lesser access levels (e.g., write access implies read, search and compare).
defaultaccess read
include <filename>
This option specifies that slapd should read additional configuration information from the given file before continuing with the next line of the current file. The included file should follow the normal slapd config file format.
Note: You should be careful when using this option - there is no small limit on the number of nested include options, and no loop detection is done.
loglevel <integer>
This option specifies the level at which debugging statements and operation statistics should be syslogged (currently logged to the syslogd(8) LOG_LOCAL4 facility). You must have compiled slapd with - DLDAP_DEBUG for this to work (except for the two stats levels, which are always enabled). Log levels are additive. To display what numbers correspond to what kind of debugging, invoke slapd with the - ? flag or consult the table below. The possible values for <integer> are:
1 trace function calls
2 debug packet handling
4 heavy trace debugging
8 connection management
16 print out packets sent and received
32 search filter processing
64 configuration file processing
128 access control list processing
256 stats log connections/operations/results
512 stats log entries sent
1024 print communication with shell backends
2048 print entry parsing debugging
loglevel 255
This will cause lots and lots of debugging information to be syslogged.
loglevel 256
objectclass <name>
[ requires <attrs> ]
[ allows <attrs> ]
This option defines the schema rules for the given object class. Used in conjunction with the schemacheck option. See Section 5.4 for more details.
referral <url>
This option specifies the referral to pass back when slapd cannot find a local database to handle a request.
referral ldap://ldap.itd.umich.edu
This will refer non-local queries to the LDAP server at the University of Michigan. 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.
schemacheck { on | off }
This option turns schema checking on or off. If schema checking is on, entries added or modified will be checked to ensure they obey the schema rules implied by their object class(es) as defined by the corresponding objectclass option(s). If schema checking is off this check is not done.
schemacheck off
sizelimit <integer>
This option specifies the maximum number of entries to return from a search operation.
sizelimit 500
srvtab <filename>
This option specifies the srvtab file in which slapd can find the kerberos keys necessary for authenticating clients using kerberos. This option is only meaningful if you are using kerberos authentication, which must be enabled at compile time by including the appropriate definitions in the Make-common file.
srvtab /etc/srvtab
timelimit <integer>
This option specifies the maximum number of seconds (in real time) slapd will spend answering a search request. If a request is not finished in this time, a result indicating an exceeded timelimit will be returned.
timelimit 3600

5.2.2 General Backend Options

Options in this section only apply to the backend in which they are defined. They are supported by every type of backend.

database <databasetype>

This option marks the beginning of a new database instance definition. <databasetype> should be one of ldbm, shell, or passwd, depending on which backend will serve the database.
database ldbm
This marks the beginning of a new LDBM backend database instance definition.
lastmod { on | off }
This option controls whether slapd will automatically maintain the modifiersName, modifyTimestamp, creatorsName, and createTimestamp attributes for entries.
lastmod off
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.
readonly off
replica host=<hostname>[:<port>]
bindmethod={ simple | kerberos }
This option specifies a replication site for this database. The host= parameter specifies a host and optionally a port where the slave slapd instance can be found. Either a domain name or IP address may be used for <hostname>. If <port> is not given, the standard LDAP port number (389) is used.
The binddn= parameter gives the DN to bind as for updates to the slave slapd. It should be a DN which has read/write access to the slave slapd's database, typically given as a "rootdn" in the slave's config file. It must also match the updatedn option in the slave slapd's config file. Since DNs are likely to contain embedded spaces, the entire "binddn=<DN>" string should be enclosed in quotes.
bindmethod is either simple or kerberos, depending on whether simple password-based authentication or kerberos authentication is to be used when connecting to the slave slapd. Simple authentication requires a valid password be given. Kerberos authentication requires a valid srvtab file.
The credentials= parameter, which is only required if using simple authentication, gives the password for binddn on the slave slapd.
The srvtab= parameter, which is only required if using kerberos, specifies the filename which holds the kerberos key for the slave slapd. If omitted, /etc/srvtab is used.
See Section 10 for more details on replication.
replogfile <filename>
This option 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 option 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 Section 10 for more details on replication.
rootdn <dn>
This option specifies the DN of an entry that is not subject to access control or administrative limit restrictions for operations on this database.
rootdn "cn=Manager, o=U of M, c=US"
rootkrbname <kerberosname>
This option specifies a kerberos name for the DN given above that will always work, regardless of whether an entry with the given DN exists or has a krbName attribute. This option is useful when creating a database and also when using slurpd to provide replication service (see Section 10).
rootkrbname admin@umich.edu
rootpw <password>
This option specifies a password for the DN given above that will always work, regardless of whether an entry with the given DN exists or has a password. This option is useful when creating a database and also when using slurpd to provide replication service (see Section 10).
rootpw secret
suffix <dn suffix>
This option specifies the DN suffix of queries that will be passed to this backend database. Multiple suffix lines can be given, and at least one is required for each database definition.
suffix "o=University of Michigan, c=US"
Queries with a DN ending in "o=University of Michigan, c=US" will be passed to this backend.
Note: when the backend to pass a query to is selected, slapd looks at the suffix line(s) in each database definition in the order they appear in the file. Thus, if one database suffix is a prefix of another, it must appear after it in the config file.
updatedn <dn>
This option is only applicable in a slave slapd. It specifies the DN allowed to make changes to the replica (typically, this is the DN slurpd binds as when making changes to the replica).

5.2.3 LDBM Backend-Specific Options

Options in this category only apply to the LDBM backend database. That is, they must follow a "database ldbm" line and come before any other "database" line.

cachesize <integer>

This option specifies the size in entries of the in-memory cache maintained by the LDBM backend database instance.
cachesize 1000
dbcachesize <integer>
This option specifies the size in bytes of the in-memory cache associated with each open index file. If not supported by the underlying database method, this option is ignored without comment. Increasing this number uses more memory but can cause a dramatic performance increase, especially during modifies or when building indexes.
dbcachesize 100000
directory <directory>
This option specifies the directory where the LDBM files containing the database and associated indexes live.
directory /usr/tmp
index {<attrlist> | default} [pres,eq,approx,sub,none]
This option specifies the indexes to maintain for the given attribute. If only an <attrlist> is given, all possible indexes are maintained.
index cn
index sn,uid eq,sub,approx
index default none
This example causes all indexes to be maintained for the cn attribute; equality, substring, and approximate indexes for the sn and uid attributes; and no indexes for all other attributes.
mode <integer>
This option specifies the file protection mode that newly created database index files should have.
mode 0600

5.2.4 Shell Backend-Specific Options

bind <pathname>
unbind <pathname>
search <pathname>
compare <pathname>
modify <pathname>
modrdn <pathname>
add <pathname>
delete <pathname>
abandon <pathname>
These options specify the pathname of the command to execute in response to the given LDAP operation. The command given should understand and follow the input/output conventions described in Appendix B.
search /usr/local/bin/search.sh
Note that you need only supply those commands you want the backend to handle. Operations for which a command is not supplied will be refused with an "unwilling to perform" error.

5.2.5 Password Backend-Specific Options

Options in this category only apply to the PASSWD backend database. That is, they must follow a "database passwd" line and come before any other "database" line.

file <filename>

This option specifies an alternate passwd file to use.
file /etc/passwd

5.3 Access Control

Access to slapd entries and attributes is controlled by the access configuration file directive. The general form of an access line is:
<access directive> ::= access to <what>
[ by <who> <access> ]+
<what> ::= * | [ dn=<regex> ] [ filter=<ldapfilter> ]
[ attrs=<attrlist> ]
<who> ::= * | self | dn=<regex> | addr=<regex> |
domain=<regex> | dnattr=<dn attribute>
<access> ::= [self]none | [self]compare | [self]search
| [self]read | [self]write
where the <what> part selects the entries and/or attributes to which the access applies, the <who> part specifies which entities are granted access, and the <access> part specifies the access granted. Multiple <who> <access> pairs are supported, allowing many entities to be granted different access to the same set of entries and attributes.

5.3.1 What to control access to

The <what> part of an access specification determines the entries and attributes to which the access control applies. Entries can be selected in two ways: by a regular expression matching the entry's distinguished name:
dn=<regular expression>
NOTE: The DN pattern specified should be "normalized", meaning that there should be no extra spaces, and commas should be used to separate components. An example normalized DN is "cn=Babs Jensen,o=University of Michigan,c=US". An example of a non-normalized DN is "cn =Babs Jensen; o=University of Michigan, c=US".

Or, entries may be selected by a filter matching some attribute(s) in the entry:

filter=<ldap filter>
where <ldap filter> is a string representation of an LDAP search filter, as described in RFC 1588. The special entry selector "*" is used to select any entry, and is a convenient shorthand for the equivalent "dn=.*" selector.

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

attrs=<attribute list>
Access to the entry itself must be granted or denied using the special attribute name "entry". Note that giving access to an attribute is not enough; access to the entry itself through the "entry" attribute is also required. The complete examples at the end of this section should help clear things up.

5.3.2 Who to grant access to

The <who> part identifies the entity or entities being granted access. Note that access is granted to "entities" not "entries." Entities can be specified by the special "*" identifier, matching any entry, the keyword "self" matching the entry protected by the access, or by a regular expression matching an entry's distinguished name:
dn=<regular expression>
NOTE: The DN pattern specified should be "normalized", meaning that there should be no extra spaces, and commas should be used to separate components.

Or entities can be specified by a regular expression matching the client's IP address or domain name:

addr=<regular expression>
domain=<regular expression>
or by an entry listed in a DN-valued attribute in the entry to which the access applies:
dnattr=<dn-valued attribute name>
The dnattr specification is used to give access to an entry whose DN is listed in an attribute of the entry (e.g., give access to a group entry to whoever is listed as the owner of the group entry).

5.3.3 The access to grant

The kind of <access> granted can be one of the following:
none | compare | search | read | write
Note that each level implies all lower levels of access. So, for example, granting someone write access to an entry also grants them read, search, and compare access.

5.3.4 Access Control Evaluation

When evaluating whether some requester should be given access to an entry and/or attribute, slapd compares the entry and/or attribute to the <what> selectors given in the configuration file. Access directives local to the current database are examined first, followed by global access directives. Within this priority, access directives are examined in the order in which they appear in the config file. Slapd stops with the first <what> selector that matches the entry and/or attribute. The corresponding access directive is the one slapd will use to evaluate access.

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

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

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

5.3.5 Access Control Examples

The access control facility described above is quite powerful. This section shows some examples of its use. First, some simple examples:
access to * by * read
This access directive grants read access to everyone. If it appears alone it is the same as the following defaultaccess line.
defaultaccess read
The following example shows the use of a regular expression to select the entries by DN in two access directives where ordering is significant.
access to dn=".*, o=U of M, c=US"
by * search
access to dn=".*, c=US"
by * read
Read access is granted to entries under the c=US subtree, except for those entries under the "o=University of Michigan, c=US" subtree, to which search access is granted. If the order of these access directives was reversed, the U-M-specific directive would never be matched, since all U-M entries are also c=US entries.

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

access to dn=".*, o=U of M, c=US" attr=homePhone
by self write
by dn=".*, o=U of M, c=US" search
by domain=.*\.umich\.edu read
by * compare
access to dn=".*, o=U of M, c=US"
by self write
by dn=".*, o=U of M, c=US" search
by * none
This example applies to entries in the "o=U of M, c=US" subtree. To all attributes except homePhone, the entry itself can write them, other U-M entries can search by them, anybody else has no access. The homePhone attribute is writable by the entry, searchable by other U-M entries, readable by clients connecting from somewhere in the umich.edu domain, and comparable by everybody else.

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 too add and remove only their own DN from the member attribute, you could accomplish it with an access directive like this:

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

Note that the attr=member construct in the <what> clause is a shorthand for the clause "dn=* attr=member" (i.e., it matches the member attribute in all entries).

5.4 Schema Enforcement

The objectclass and schemacheck configuration file options can be used to enforce schema rules on entries in the directory. The schema rules are defined by one or more objectclass lines, and enforcement is turned on or off via the schemacheck option. The format of an objectclass line is:
objectclass <name>
[ requires <attrs> ]
[ allows <attrs> ]
This option defines the schema rules for the object class given by <name>. Schema rules consist of the attributes the entry is required to have (given by the requires <attrs> clause) and those attributes that it may optionally have (given by the allows <attrs> clause). In both clauses, <attrs> is a comma-separated list of attribute names.

Note that object class inheritance (that is, defining one object class in terms of another) is not supported directly. All of an object class's required and allowed attributes must be listed in the objectclass definition.

For example, to define an objectclass called myPerson, you might include a definition like this:

objectclass myperson
requires cn, sn, objectclass
allows mail, phone, fax
To then enforce this rule (i.e., to make sure an entry with an objectclass of myperson contains the cn, sn and objectclass attributes, and that it contains no other attributes besides mail, phone, and fax), turn on schema checking with a line like this:
schemacheck on

5.5 Configuration File Example

The following is an example configuration file, interspersed with explanatory text. It defines two databases to handle different parts of the X.500 tree; both are LDBM database instances. The line numbers shown are provided for reference only and are not included in the actual file. First, the global configuration section:
1. # example config file - global configuration section
2. include /usr/local/etc/slapd.at.conf
3. include /usr/local/etc/slapd.oc.conf
4. schemacheck on
5. referral ldap://ldap.itd.umich.edu
Line 1 is a comment. Lines 2 and 3 include other config files containing attribute and object class definitions, respectively. Line 4 turns on schema checking. The referral option 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 ldap.itd.umich.edu.

The next section of the configuration file defines an LDBM backend that will handle queries for things in the "o=University of Michigan, c=US" portion of the tree. The database is to be replicated to two slave slapds, one on truelies, the other on judgmentday. Indexes are to be maintained for several attributes, and the userPassword attribute is to be protected from unauthorized access.

1. # ldbm definition for the U-M database
2. database ldbm
3. suffix "o=University of Michigan, c=US"
4. directory /usr/local/ldbm-umich
6. rootdn "cn=Manager, o=University of Michigan, c=US"
7. rootpw secret
8. replogfile /usr/local/ldbm-umich/slapd.replog
9. replica host=truelies.rs.itd.umich.edu:389
10. binddn="cn=Replicator, o=U of M, c=US"
11. bindmethod=simple credentials=secret
12.replica host=judgmentday.rs.itd.umich.edu
13. binddn="cn=Replicator, o=U of M, c=US"
14. bindmethod=kerberos
15. srvtab=/etc/srvtab.judgmentday
16.# ldbm indexed attribute definitions
17.index cn,sn,uid pres,eq,approx,sub
18.index objectclass pres,eq
19.index default none
20.# ldbm access control definitions
21.defaultaccess read
22.access to attr=userpassword
23. by self write
24. by dn="cn=Admin, o=University of Michigan, c=US" write
25. by * compare
Line 1 is a comment. The start of the database definition is marked by the database keyword on line 2. Line 3 specifies the DN suffix for queries to pass to this database. Line 4 specifies the directory in which the database files will live

Lines 6 and 7 identify the database "super user" entry and associated password. This entry is not subject to access control or size or time limit restrictions.

Lines 8 through 15 are for replication. Line 8 specifies the replication log file (where changes to the database are logged - this file is written by slapd and read by slurpd). Lines 9 through 11 specify the hostname and port for a replicated host, the DN to bind as when performing updates, the bind method (simple) and the credentials (password) for the binddn. Lines 12 through 15 specify a second replication site, using kerberos instead of simple authentication. See Section 10 on slurpd for more information on these options.

Lines 16 through 19 indicate the indexes to maintain for various attributes. The default is not to maintain any indexes (line 19).

Lines 20 through 25 specify access control for entries in the database. For all entries, the userPassword attribute is writable by the entry and the "admin" entry, comparable by everyone else. All other attributes allow read access by default (line 21). Note that the special "entry" attribute is not required in the access directive beginning on line 22. This is because the default access is read.

The next section of the example configuration file defines another LDBM database. This one handles queries involving the "o="Babs, Inc.", c=US" subtree.

1. # ldbm definition for Babs, Inc. database
2. database ldbm
3. suffix "o=\"Babs, Inc.\", c=US"
4. directory /usr/local/ldbm-babs
5. rootdn "cn=Babs, o=\"Babs, Inc.\", c=US"
6. index default
Note the use of `\' to escape the quotes necessary in the distinguished names given on lines 3 and 5. By default, all indexes are maintained for every attribute in an entry.
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