https://help.ubuntu.com/12.04/serverguide/openldap-server.html

root@server:~# apt-get install slapd ldap-utils

Administrative password: secret

root@server:~# ldapsearch -x -LLL -H ldap:/// -b dc=corpX,dc=un dn

[server:~] # pkg install openldap-server

[server:~] # pkg_add -r openldap24-server

[server:~] # cat /usr/local/etc/openldap/slapd.conf

...
include         /usr/local/etc/openldap/schema/core.schema
include         /usr/local/etc/openldap/schema/cosine.schema
include         /usr/local/etc/openldap/schema/nis.schema
...
moduleload      back_mdb
...
suffix                "dc=corpX,dc=un"
rootdn                "cn=admin,dc=corpX,dc=un"
...

[server:~] # cat /etc/rc.conf

...
slapd_enable="YES"

[server:~] # /usr/local/etc/rc.d/slapd start

[server:~] # rehash