При появлении в логе ошибок подобных:
   Feb 25 20:23:53 dc02 slapd[5677]: bdb_equality_candidates: (gidNumber) not indexed
   Feb 25 20:23:53 dc02 slapd[5677]: bdb_equality_candidates: (sambaSID) not indexed
   Feb 25 20:23:53 dc02 slapd[5677]: bdb_equality_candidates: (sambaSID) not indexed
   Feb 25 20:23:55 dc02 slapd[5677]: bdb_equality_candidates: (uid) not indexed
   Feb 25 20:23:55 dc02 slapd[5677]: bdb_equality_candidates: (uid) not indexed

необходимо в файл конфигурации /etc/ldap/slapd.conf в раздел с директивами
"database" добавить следующее:

   # Indices to maintain for this database
   index objectClass                       eq,pres
   index ou,cn,sn,mail,givenname           eq,pres,sub
   index uidNumber,gidNumber,memberUid     eq,pres
   index loginShell                        eq,pres
   # I also added this line to stop warning in syslog ..
   index uniqueMember                      eq,pres
   ## required to support pdb_getsampwnam
   index uid                               pres,sub,eq
   ## required to support pdb_getsambapwrid()
   index displayName                       pres,sub,eq
   # These attributes don't exist in this database ..
   #index nisMapName,nisMapEntry            eq,pres,sub
   index sambaSID                          eq
   index sambaPrimaryGroupSID              eq
   index sambaDomainName                   eq
   index default                           sub
  
После этого:

   # /etc/init.d/slapd stop

   # slapindex
   WARNING!
    Runnig as root!
    There's a fair chance slapd will fail to start.
    Check file permissions!

   # chown openldap:openldap /var/lib/ldap/*

   # /etc/init.d/slapd start
    Starting OpenLDAP: slapd

Добавляемые в slapd.conf строки примерны, поскольку наличие дополнительных
строк или их отсутствие зависит от конфигурации.