Hi all,
I'm currently in the process of migrating LDAP data from a really outdated system to something a bit fresher. So, I started with the OpenLDAP as provided by Debian, and learned that a good part of the system management knowledge I had is outdated. So, I stared reading TFM.
... and stumbled over the section where I wanted to learn how to set up monitoring with the cn=config configuration scheme.
Naturally, that was exactly the incentive I needed to actually start giving back something to the community. So, I ended up playing around a bit and googling a bit and scratching my head a lot, taking notes, and came up with something you might want to add into the manual -- see below.
Unfortunately, the whole thing did not exactly work out as I intended, because the crucial step insists on failing. Namely, trying to create a monitor database fails, indicating there already is one in existence. However, I can't find any such beast:
root@host:~/ldap# ldapsearch -Q -LLL -H ldapi:/// -Y EXTERNAL -b 'cn=config' '(|(olcDatabase=monitor)(objectClass=olcMonitorConfig))' root@host:~/ldap#
I have actually tried to add the above data using slapadd, with slapd shut down, and got an even more confusing error message: root@host:~/ldap# slapadd -n 0 -l addMonitorDB.ldif slapadd: could not add entry dn="olcDatabase=Monitor,cn=config" (line=1): autocreation of "olcDatabase={-1}frontend" failed _######### 46.91% eta none elapsed none spd 1.3 M/s Closing DB...
So, what do I need to do to get my manual suggestion into working condition? (And also allow me to monitor my all fresh LDAP instance :-)
Cheers,
Arno
-----8<--------------cut here... manual text below ------------->8------
20.1. Monitor configuration via cn=config(5)
To enable monitoring an OpenLDAP server, the "monitor" database needs to be available and configured, also allowing read acces to it.
20.1.1. Ensure the monitor backend is available
The first step is to ensure the monitor database is part of the running slapd process. As database backends can be build into the main binary, or loaded dynamically, as configured, the initial step is to check if the module is built in, is already loaded, or, if not, add it to the configuration.
20.1.2. Check the binary for built-in modules
By running
root@host:~/ldap# slapd -VVV @(#) $OpenLDAP: slapd (May 23 2018 04:25:19) $ Debian OpenLDAP Maintainers pkg-openldap-devel@lists.alioth.debian.org
Included static backends: config ldif root@host:~/ldap#
it is easy to check if the monitor backend database is built-in; in the above case, it is not. If it already is part of the slapd binary, the process goes to section 20.1.5 further below.
20.1.3. Check module loader configuration
*Note* that the below examples use one particular scheme to access LDAP with administrative, i.e. full, privileges; things may be configured differently in other environments. (The example is correct for a stock Debian 9 installation, by the way.)
Checking if the monitor backend is already configured to be loaded requires querying the LDAP configuration, in particular the module loader configuration:
root@host:~/ldap# ldapsearch -LLL -H ldapi:/// -Y EXTERNAL -b 'cn=config' '(objectClass=olcModuleList)' olcModuleLoad SASL/EXTERNAL authentication started SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth SASL SSF: 0 dn: cn=module{0},cn=config olcModuleLoad: {0}back_mdb olcModuleLoad: {1}back_monitor
root@host:~/ldap#
In this example, we see the back_monitor module to be loaded. If a line referencing this module was not shown, the next step is described below. Otherwise, proceed at section 20.1.5.
20.1.4. Add the monitor module to the module loader configuration
20.1.4.1. Verify the necessary module exists.
A careful administrator will ensure the needed module is actually available to be loaded. This is done by checking the needed file exists in the module loader's path.
We assume the path to be correctly set up in the loaders configuration in the first place, trusting that the package builder prepared this step. Thus:
root@host:~/ldap# ldapsearch -LLL -H ldapi:/// -Y EXTERNAL -b 'cn=config' '(objectClass=olcModuleList)' olcModulePath SASL/EXTERNAL authentication started SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth SASL SSF: 0 dn: cn=module{0},cn=config olcModulePath: /usr/lib/ldap
root@host:~/ldap# ls -l /usr/lib/ldap/*monitor* lrwxrwxrwx 1 root root 26 May 23 2018 /usr/lib/ldap/back_monitor-2.4.so.2 -> back_monitor-2.4.so.2.10.7 -rw-r--r-- 1 root root 109408 May 23 2018 /usr/lib/ldap/back_monitor-2.4.so.2.10.7 -rw-r--r-- 1 root root 976 May 23 2018 /usr/lib/ldap/back_monitor.la lrwxrwxrwx 1 root root 26 May 23 2018 /usr/lib/ldap/back_monitor.so -> back_monitor-2.4.so.2.10.7 root@host:~/ldap#
and voilà, things look good, the module shared object file is available, and things are prepared for different versions coexisting in the usual Unix/Linux way. (The author has no idea what to expect on a windows system.)
If things did *not* look good, it would be time to check the distribution repositories for packages with OpenLDAP modules, or verify the build and installation process, both of which is out of scope of this chapter.
20.1.4.2. Adding the monitor backend to the loader configuration
Assuming paths and binaries are all correct, it's now merely a matter of adding some attributes to the module loader's configuration. This can be done with just a few lines of LDIF:
root@host:~/ldap# cat loadMonitor.ldif dn: cn=config,cn=module changetype: modify add: olcModuleLoad olcModuleLoad: back_monitor
root@host:~/ldap# ldapmodify -H ldapi:/// -Y EXTERNAL -f loadMonitor.ldif
should do all that is necessary. Error messages hopefully provide an indication of what went wrong in case there is a problem.
20.1.5. Verifying the monitor backend needs to be configured
Of course, we start out being extra-careful, by checking that no monitor backend is already configured:
root@host:~/ldap# ldapsearch -LLL -H ldapi:/// -Y EXTERNAL -b 'cn=config' '(objectClass=olcDataBaseConfig)' olcDatabase objectClass SASL/EXTERNAL authentication started SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth SASL SSF: 0 dn: olcDatabase={-1}frontend,cn=config objectClass: olcDatabaseConfig objectClass: olcFrontendConfig olcDatabase: {-1}frontend
dn: olcDatabase={0}config,cn=config objectClass: olcDatabaseConfig olcDatabase: {0}config
dn: olcDatabase={1}mdb,cn=config objectClass: olcDatabaseConfig objectClass: olcMdbConfig olcDatabase: {2}mdb
root@host:~/ldap#
Carefully checking the output, it becomes clear no monitor database is available as yet, so we need to continue.
20.1.6. Adding a "monitor" database Again, a simple LDAP add operation will be sufficient:
root@host:~/ldap# cat addMonitorDB.ldif dn: olcDatabase=monitor,cn=config objectClass: olcDatabaseConfig objectClass: olcMonitorConfig olcDatabase: monitor olcAccess: to dn.subtree=cn=monitor by users read
root@host:~/ldap#
Naturally, the ACL(s) may be adjusted as needed.
root@host:~/ldap# ldapadd -H ldapi:/// -Y EXTERNAL -f addMonitorDB.ldif SASL/EXTERNAL authentication started SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth SASL SSF: 0 adding new entry "olcDatabase=monitor,cn=config" ldap_add: Other (e.g., implementation specific) error (80) additional info: only one monitor database allowed
(BETTER NOT PUBLISH THE FINAL TWO LINES...)