LDAP means Lightweight Directory Access Protocol, it is a simplified version of X500 protocol. You will find a more detailed presentation [http://en.wikipedia.org/wiki/LDAP on Wikipedia].
To describe quickly, all informations are stored in a tree. You have to determine by yourself the directory arborescence (the Directory Information Tree: the DIT). We will begin with a basic tree with two nodes above the root :
- "People" node where your users will be stored
- "Groups" node where your groups will be stored
You have to first determine what the root of your LDAP will be. By default, your tree will be determined by your internet domain. If your domain is example.com (we will use it in the above example), your root will be dc=example,dc=com.
First of all, install ldap daemon on the server ; install the following packages: slapd (see InstallingSoftware).
Enter your domain as asked and the password that you want for the directory administrator.
Only few changes will be operated on the default configuration. First set the root password in the configuration file (instead of in the directory):
8<-------------------------------------------- suffix "dc=example,dc=com" directory "/var/lib/ldap" rootdn "cn=admin,dc=example,dc=com" rootpw secret 8<--------------------------------------------
The directory has been created at the installation, now it is time to populate. It will be populated with a "classical" entry that will be compatible with directory (for example for a shared directory), with classical accounts (for a web application) and with Unix accounts (posix).
LDAP directory can be feed with a ldif file (ldif means ldap directory interchange format). Here is an exemple :
dn: dc=example,dc=com dc= example dn: ou=people,dc=example,dc=com objectClass: top objectClass: organizationalUnit ou: people dn: ou=groups,dc=example,dc=com objectClass: top objectClass: organizationalUnit ou: groups dn: ou=admin,dc=example,dc=com objectClass: top objectClass: organizationalUnit ou: admin dn: uid=lionel,ou=people,dc=example,dc=com objectClass: top objectClass: inetOrgPerson objectClass: posixAccount objectClass: shadowAccount uid: lionel sn: Porcheron givenName: Lionel cn: Lionel Porcheron displayName: Lionel Porcheron uidNumber: 1000 gidNumber: 10000 gecos: Lionel Porcheron loginShell: /bin/bash homeDirectory: /home/lionel shadowExpire: -1 shadowFlag: 0 shadowWarning: 7 shadowMin: 8 shadowMax: 999999 shadowLastChange: 10877 mail: firstname.lastname@example.org 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: LP dn: cn=example,ou=groups,dc=example,dc=com objectClass: top objectClass: posixGroup cn: exemple gidNumber: 10000 displayName: Exemple group
In the example above, the directory structure, a user and group have been setup. Now, add it to the LDAP :
stop LDAP daemon: sudo /etc/init.d/slapd stop
delete the content that has been automaticaly added: sudo rm -rf /var/lib/ldap/*
add the content sudo slapadd -l init.ldif
We can check that the content has been correctly added, but first add the ldap-utils package in order to execute search in the LDAP directory :
sudo apt-get install ldap-utils ldapsearch -xLLL uid=lionel sn givenName cn dn: uid=lionel,ou=people,dc=example,dc=com cn: Lionel Porcheron sn: Porcheron givenName: Lionel
Just a quick explanation :
-x is because we do not use SASL authentication method (by default)
-LLL disable printing LDIF informations
You have setup your LDAP directory, and now you have to use it.
- You can authenticate your users on the directory as explained in ["LDAPClientAuthentication"]
- You can authenticate your users in a web application.
- You can use it as a shared address directory for your mail agent.
Use of LDAP are infinite !
LDAP service often becore quickly a hightly critical service in an information system: all is depending of LDAP: autentication, authorization, mail system, etc. It can be a good idea to setup a redundant system. It is easy to setup, here is a quick howto.
With OpenLDAP 2.2 (on Breezy and Dapper), replication is based on a master-slave relation.
attachment:IconsPage/IconWarning3.png You will have to remember that modifications should ALWAYS be done on the master ! If you modifies the slave, modifications will get lost.
On the master, you have to modify the database section of the /etc/ldap/slapd.conf to add a replica instruction. The following example shows a replica on ldap-2.example.com with the Manager user with secret as password. The replication logfile is the place modifications are stored before to be send to the LDAP slave.
replica uri=ldap://ldap-2.example.com:389 binddn="cn=Manager,dc=example,dc=com" bindmethod=simple credentials=secret replogfile /var/lib/ldap/replog
Restart your LDAP server.
On the slave, you have to authorize your master to update LDAP database. Add the following lines to your /etc/ldap/slapd.conf file in the database section:
updatedn cn=Manager,dc=example,dc=com updateref ldap://ldap-1.example.com
Restart your LDAP server.
[http://www.openldap.org OpenLDAP website] give you lot of informations
[http://www.tldp.org/HOWTO/html_single/LDAP-HOWTO/ LDAP HOWTO]