First, install the OpenLDAP server daemon slapd and ldap-utils, a package containing LDAP management utilities:

sudo apt-get install slapd ldap-utils

By default slapd is configured with minimal options needed to run the slapd daemon.

The configuration example in the following sections will match the domain name of the server. For example, if the machine's Fully Qualified Domain Name (FQDN) is ldap.example.com, the default suffix will be dc=example,dc=com.

OpenLDAP uses a separate directory which contains the cn=config Directory Information Tree (DIT). The cn=config DIT is used to dynamically configure the slapd daemon, allowing the modification of schema definitions, indexes, ACLs, etc without stopping the service.

The backend cn=config directory has only a minimal configuration and will need additional configuration options in order to populate the frontend directory. The frontend will be populated with a "classical" scheme that will be compatible with address book applications and with Unix Posix accounts. Posix accounts will allow authentication to various applications, such as web applications, email Mail Transfer Agent (MTA) applications, etc.

	For external applications to authenticate using LDAP they will each need to be specifically configured to do so. Refer to the individual application documentation for details.

	Remember to change dc=example,dc=com in the following examples to match your LDAP configuration.

First, some additional schema files need to be loaded. In a terminal enter:

sudo ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/ldap/schema/cosine.ldif
sudo ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/ldap/schema/nis.ldif
sudo ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/ldap/schema/inetorgperson.ldif

Next, copy the following example LDIF file, naming it backend.example.com.ldif, somewhere on your system:

# Load dynamic backend modules
dn: cn=module,cn=config
objectClass: olcModuleList
cn: module
olcModulepath: /usr/lib/ldap
olcModuleload: back_hdb

# Database settings
dn: olcDatabase=hdb,cn=config
objectClass: olcDatabaseConfig
objectClass: olcHdbConfig
olcDatabase: {1}hdb
olcSuffix: dc=example,dc=com
olcDbDirectory: /var/lib/ldap
olcRootDN: cn=admin,dc=example,dc=com
olcRootPW: secret
olcDbConfig: set_cachesize 0 2097152 0
olcDbConfig: set_lk_max_objects 1500
olcDbConfig: set_lk_max_locks 1500
olcDbConfig: set_lk_max_lockers 1500
olcDbIndex: objectClass eq
olcLastMod: TRUE
olcDbCheckpoint: 512 30
olcAccess: to attrs=userPassword by dn="cn=admin,dc=example,dc=com" write by anonymous auth by self write by * none
olcAccess: to attrs=shadowLastChange by self write by * read
olcAccess: to dn.base="" by * read
olcAccess: to * by dn="cn=admin,dc=example,dc=com" write by * read

	Change olcRootPW: secret to a password of your choosing.

Now add the LDIF to the directory:

sudo ldapadd -Y EXTERNAL -H ldapi:/// -f backend.example.com.ldif

The frontend directory is now ready to be populated. Create a frontend.example.com.ldif with the following contents:

# Create top-level object in domain
dn: dc=example,dc=com
objectClass: top
objectClass: dcObject
objectclass: organization
o: Example Organization
dc: Example
description: LDAP Example 

# Admin user.
dn: cn=admin,dc=example,dc=com
objectClass: simpleSecurityObject
objectClass: organizationalRole
cn: admin
description: LDAP administrator
userPassword: secret

dn: ou=people,dc=example,dc=com
objectClass: organizationalUnit
ou: people

dn: ou=groups,dc=example,dc=com
objectClass: organizationalUnit
ou: groups

dn: uid=john,ou=people,dc=example,dc=com
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: shadowAccount
uid: john
sn: Doe
givenName: John
cn: John Doe
displayName: John Doe
uidNumber: 1000
gidNumber: 10000
userPassword: password
gecos: John Doe
loginShell: /bin/bash
homeDirectory: /home/john
shadowExpire: -1
shadowFlag: 0
shadowWarning: 7
shadowMin: 8
shadowMax: 999999
shadowLastChange: 10877
mail: [email protected]
postalCode: 31000
l: Toulouse
o: Example
mobile: +33 (0)6 xx xx xx xx
homePhone: +33 (0)5 xx xx xx xx
title: System Administrator
postalAddress: 
initials: JD

dn: cn=example,ou=groups,dc=example,dc=com
objectClass: posixGroup
cn: example
gidNumber: 10000

In this example the directory structure, a user, and a group have been setup. In other examples you might see the objectClass: top added in every entry, but that is the default behaviour so you do not have to add it explicitly.

Add the entries to the LDAP directory:

sudo ldapadd -x -D cn=admin,dc=example,dc=com -W -f frontend.example.com.ldif

We can check that the content has been correctly added with the ldapsearch utility. Execute a search of the LDAP directory:

ldapsearch -xLLL -b "dc=example,dc=com" uid=john sn givenName cn

dn: uid=john,ou=people,dc=example,dc=com
cn: John Doe
sn: Doe
givenName: John

Just a quick explanation:

The cn=config tree can be manipulated using the utilities in the ldap-utils package. For example:

LDAP often quickly becomes a highly critical service to the network. Multiple systems will come to depend on LDAP for authentication, authorization, configuration, etc. It is a good idea to setup a redundant system through replication.

Replication is achieved using the Syncrepl engine. Syncrepl allows the changes to be synced using a consumer, provider model. A provider sends directory changes to consumers.

Consumer Configuration

1. On the Consumer server configure it the same as the Provider except for the Syncrepl configuration steps.

   Add the additional schema files:

   sudo ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/ldap/schema/cosine.ldif
   sudo ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/ldap/schema/nis.ldif
   sudo ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/ldap/schema/inetorgperson.ldif
   

   Also, create, or copy from the provider server, the backend.example.com.ldif

   # Load dynamic backend modules
   dn: cn=module,cn=config
   objectClass: olcModuleList
   cn: module
   olcModulepath: /usr/lib/ldap
   olcModuleload: back_hdb
   
   # Database settings
   dn: olcDatabase=hdb,cn=config
   objectClass: olcDatabaseConfig
   objectClass: olcHdbConfig
   olcDatabase: {1}hdb
   olcSuffix: dc=example,dc=com
   olcDbDirectory: /var/lib/ldap
   olcRootDN: cn=admin,dc=example,dc=com
   olcRootPW: secret
   olcDbConfig: set_cachesize 0 2097152 0
   olcDbConfig: set_lk_max_objects 1500
   olcDbConfig: set_lk_max_locks 1500
   olcDbConfig: set_lk_max_lockers 1500
   olcDbIndex: objectClass eq
   olcLastMod: TRUE
   olcDbCheckpoint: 512 30
   olcAccess: to attrs=userPassword by dn="cn=admin,dc=example,dc=com" write by anonymous auth by self write by * none
   olcAccess: to attrs=shadowLastChange by self write by * read
   olcAccess: to dn.base="" by * read
   olcAccess: to * by dn="cn=admin,dc=example,dc=com" write by * read
   

   And add the LDIF by entering:

   sudo ldapadd -Y EXTERNAL -H ldapi:/// -f backend.example.com.ldif
   

2. Do the same with the frontend.example.com.ldif file listed above, and add it:

   sudo ldapadd -x -D cn=admin,dc=example,dc=com -W -f frontend.example.com.ldif
   

   The two severs should now have the same configuration except for the Syncrepl options.

3. Now create a file named consumer_sync.ldif containing:

   #Load the syncprov module.
   dn: cn=module{0},cn=config
   changetype: modify
   add: olcModuleLoad
   olcModuleLoad: syncprov
   
   # syncrepl specific indices
   dn: olcDatabase={1}hdb,cn=config
   changetype: modify
   add: olcDbIndex
   olcDbIndex: entryUUID eq
   -
   add: olcSyncRepl
   olcSyncRepl: rid=0 provider=ldap://ldap01.example.com bindmethod=simple binddn="cn=admin,dc=example,dc=com" 
    credentials=secret searchbase="dc=example,dc=com" logbase="cn=accesslog" 
    logfilter="(&(objectClass=auditWriteObject)(reqResult=0))" schemachecking=on 
    type=refreshAndPersist retry="60 +" syncdata=accesslog
   -
   add: olcUpdateRef
   olcUpdateRef: ldap://ldap01.example.com
   

   You will probably want to change the following attributes:

   • ldap01.example.com to your server's hostname.

   • binddn

   • credentials

   • searchbase

   • olcUpdateRef:

4. Add the LDIF file to the configuration tree:

   sudo ldapadd -c -Y EXTERNAL -H ldapi:/// -f consumer_sync.ldif
   

The frontend database should now sync between servers. You can add additional servers using the steps above as the need arises.

	The slapd daemon will send log information to /var/log/syslog by default. So if all does not go well check there for errors and other troubleshooting information. Also, be sure that each server knows it's Fully Qualified Domain Name (FQDN). This is configured in /etc/hosts with a line similar to: 127.0.0.1 ldap01.example.com ldap01 .

Authentication requires access to the password field, that should be not accessible by default. Also, in order for users to change their own password, using passwd or other utilities, shadowLastChange needs to be accessible once a user has authenticated.

To view the Access Control List (ACL), use the ldapsearch utility:

ldapsearch -xLLL -b cn=config -D cn=admin,cn=config -W olcDatabase=hdb olcAccess

Enter LDAP Password: 
dn: olcDatabase={1}hdb,cn=config
olcAccess: {0}to attrs=userPassword,shadowLastChange by dn="cn=admin,dc=exampl
 e,dc=com" write by anonymous auth by self write by * none
olcAccess: {1}to dn.base="" by * read
olcAccess: {2}to * by dn="cn=admin,dc=example,dc=com" write by * read

When authenticating to an OpenLDAP server it is best to do so using an encrypted session. This can be accomplished using Transport Layer Security (TLS) and/or Secure Sockets Layer (SSL).

The first step in the process is to obtain or create a certificate. Because slapd is compiled using the gnutls library, the certtool utility will be used to create certificates.

Once you have a certificate, key, and CA cert installed, use ldapmodify to add the new configuration options:

sudo ldapmodify -Y EXTERNAL -H ldapi:///

Enter LDAP Password:
dn: cn=config
add: olcTLSCACertificateFile
olcTLSCACertificateFile: /etc/ssl/certs/cacert.pem
-
add: olcTLSCertificateFile
olcTLSCertificateFile: /etc/ssl/certs/ldap01_slapd_cert.pem
-
add: olcTLSCertificateKeyFile
olcTLSCertificateKeyFile: /etc/ssl/private/ldap01_slapd_key.pem

modifying entry "cn=config"

	Adjust the ldap01_slapd_cert.pem, ldap01_slapd_key.pem, and cacert.pem names if yours are different.

Next, edit /etc/default/slapd uncomment the SLAPD_SERVICES option:

SLAPD_SERVICES="ldap:/// ldapi:/// ldaps:///"

Now the openldap user needs access to the certificate:

sudo adduser openldap ssl-cert
sudo chgrp ssl-cert /etc/ssl/private/ldap01_slapd_key.pem
sudo chmod g+r /etc/ssl/private/ldap01_slapd_key.pem

	If the /etc/ssl/private and /etc/ssl/private/server.key have different permissions, adjust the commands appropriately.

Finally, restart slapd:

sudo /etc/init.d/slapd restart

The slapd daemon should now be listening for LDAPS connections and be able to use STARTTLS during authentication.

	If you run into troubles with the server not starting, check the /var/log/syslog. If you see errors like main: TLS init def ctx failed: -1, it is likely there is a configuration problem. Check that the certificate is signed by the authority from in the files configured, and that the ssl-cert group has read permissions on the private key.

sudo ldapmodify -Y EXTERNAL -H ldapi:///

SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0

dn: olcDatabase={1}hdb,cn=config
replace: olcSyncrepl
olcSyncrepl: {0}rid=0 provider=ldap://ldap01.example.com bindmethod=simple binddn="cn=ad
 min,dc=example,dc=com" credentials=secret searchbase="dc=example,dc=com" logbas
 e="cn=accesslog" logfilter="(&(objectClass=auditWriteObject)(reqResult=0))" s
 chemachecking=on type=refreshAndPersist retry="60 +" syncdata=accesslog starttls=yes

modifying entry "olcDatabase={1}hdb,cn=config"

TLS_CERT /etc/ssl/certs/ldap02_slapd_cert.pem
TLS_KEY /etc/ssl/private/ldap02_slapd_key.pem
TLS_CACERT /etc/ssl/certs/cacert.pem

sudo /etc/init.d/slapd restart

Once you have a working LDAP server, the auth-client-config and libnss-ldap packages take the pain out of configuring an Ubuntu client to authenticate using LDAP. To install the packages from, a terminal prompt enter:

sudo apt-get install libnss-ldap

During the install a menu dialog will ask you connection details about your LDAP server.

If you make a mistake when entering your information you can execute the dialog again using:

sudo dpkg-reconfigure ldap-auth-config

The results of the dialog can be seen in /etc/ldap.conf. If your server requires options not covered in the menu edit this file accordingly.

Now that libnss-ldap is configured enable the auth-client-config LDAP profile by entering:

sudo auth-client-config -t nss -p lac_ldap

Using the pam-auth-update utility, configure the system to use LDAP for authentication:

sudo pam-auth-update

From the pam-auth-update menu, choose LDAP and any other authentication mechanisms you need.

You should now be able to login using user credentials stored in the LDAP directory.

	If you are going to use LDAP to store Samba users you will need to configure the server to authenticate using LDAP. See the section called “Samba and LDAP” for details.

The ldap-utils package comes with multiple utilities to manage the directory, but the long string of options needed, can make them a burden to use. The ldapscripts package contains configurable scripts to easily manage LDAP users and groups.

To install the package, from a terminal enter:

sudo apt-get install ldapscripts

Next, edit the config file /etc/ldapscripts/ldapscripts.conf uncommenting and changing the following to match your environment:

SERVER=localhost
BINDDN='cn=admin,dc=example,dc=com'
BINDPWDFILE="/etc/ldapscripts/ldapscripts.passwd"
SUFFIX='dc=example,dc=com'
GSUFFIX='ou=Groups'
USUFFIX='ou=People'
MSUFFIX='ou=Computers'
GIDSTART=10000
UIDSTART=10000
MIDSTART=10000

Now, create the ldapscripts.passwd file to allow authenticated access to the directory:

sudo sh -c "echo -n 'secret' > /etc/ldapscripts/ldapscripts.passwd"
sudo chmod 400 /etc/ldapscripts/ldapscripts.passwd

	Replace “secret” with the actual password for your LDAP admin user.

The ldapscripts are now ready to help manage your directory. The following are some examples of how to use the scripts:

There are more useful scripts in the package, to see a full list enter: dpkg -L ldapscripts | grep bin