# yum  install openldap-clients nss-pam-ldapd

passwd:     files ldap
shadow:     files ldap
group:      files ldap 

hosts:      files dns

bootparams: nisplus [NOTFOUND=return] files

ethers:     files
netmasks:   files
networks:   files
protocols:  files
rpc:        files
services:   files ldap

netgroup:   files ldap

publickey:  nisplus

automount:  files ldap
aliases:    files nisplus

RHEL6/CentOS6 : /etc/pam_ldap.conf
RHEL5/CentOS5 : /etc/ldap.conf

LDAP pluggable authentication module

lrwxrwxrwx 1 root root    14 Apr 23  2014 system-auth -> system-auth-ac

After RHEL6/CentOS6

configuration file for LDAP nameservice daemon
After RHEL6/CentOS6

# getent passwd

# getent group

# id USER