more info at https://help.ubuntu.com/lts/serverguide/openldap-server.html

Server

apt-get install slapd ldap-utils

initial configuration

dpkg-reconfigure slapd

Client

Install

apt-get install libnss-ldap ldapscripts

Configure

dpkg-reconfigure ldap-auth-config
auth-client-config -t nss -p lac_ldap
pam-auth-update