Configuration of the slapd.conf(5) to support LDAP monitoring is quite simple.
First, ensure core.schema schema configuration file is included by your slapd.conf(5) file. The monitor backend requires it.
Second, instantiate the monitor backend by adding a database monitor directive below your existing database sections. For instance:
Lastly, add additional global or database directives as needed.
Like most other database backends, the monitor backend does honor slapd(8) access and other administrative controls. As some monitor information may be sensitive, it is generally recommend access to cn=monitor be restricted to directory administrators and their monitoring agents. Adding an access directive immediately below the database monitor directive is a clear and effective approach for controlling access. For instance, the addition of the following access directive immediately below the database monitor directive restricts access to monitoring information to the specified directory manager.
access to *
by * none
More information on slapd(8) access controls, see The access Control Directive section of the The slapd Configuration File chapter and slapd.access(5).
After restarting slapd(8), you are ready to start exploring the monitoring information provided in cn=config as discussed in the Accessing Monitoring Information section of this chapter.
One can verify slapd(8) is properly configured to provide monitoring information by attempting to read the cn=monitor object. For instance, if the following ldapsearch(1) command returns the cn=monitor object (with, as requested, no attributes), it's working.
ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W \
-b 'cn=Monitor' -s base 1.1
Note that unlike general purpose database backends, the database suffix is hardcoded. It's always cn=Monitor. So no suffix directive should be provided. Also note that general purpose database backends, the monitor backend cannot be instantiated multiple times. That is, there can only be one (or zero) occurrences of database monitor in the server's configuration.