<s>
Apple	B-Operating_System
Open	I-Operating_System
Directory	I-Operating_System
is	O
the	O
LDAP	B-Protocol
directory	O
service	O
model	O
implementation	O
from	O
Apple	O
Inc	O
.	O
A	O
directory	O
service	O
is	O
software	B-Application
which	O
stores	O
and	O
organizes	O
information	O
about	O
a	O
computer	B-Architecture
network	I-Architecture
's	O
users	O
and	O
network	O
resources	O
and	O
which	O
allows	O
network	O
administrators	O
to	O
manage	O
users	O
 '	O
access	O
to	O
the	O
resources	O
.	O
</s>
<s>
In	O
the	O
context	O
of	O
macOS	B-Operating_System
Server	I-Operating_System
,	O
Open	O
Directory	O
describes	O
a	O
shared	O
LDAPv3	B-Protocol
directory	O
domain	O
and	O
a	O
corresponding	O
authentication	O
model	O
composed	O
of	O
Apple	O
Password	O
Server	O
and	O
Kerberos	B-Protocol
5	I-Protocol
tied	O
together	O
using	O
a	O
modular	O
Directory	O
Services	O
system	O
.	O
</s>
<s>
Apple	B-Operating_System
Open	I-Operating_System
Directory	I-Operating_System
is	O
a	O
fork	B-Application
of	O
OpenLDAP	B-Language
.	O
</s>
<s>
The	O
term	O
Open	O
Directory	O
can	O
also	O
be	O
used	O
to	O
describe	O
the	O
entire	O
directory	O
services	O
framework	O
used	O
by	O
macOS	B-Application
and	O
macOS	B-Operating_System
Server	I-Operating_System
.	O
</s>
<s>
In	O
this	O
context	O
,	O
it	O
describes	O
the	O
role	O
of	O
a	O
macOS	B-Application
or	O
macOS	B-Operating_System
Server	I-Operating_System
system	O
when	O
it	O
is	O
connected	O
to	O
an	O
existing	O
directory	O
domain	O
,	O
in	O
which	O
context	O
it	O
is	O
sometimes	O
referred	O
to	O
as	O
Directory	O
Services	O
.	O
</s>
<s>
Apple	O
,	O
Inc	O
.	O
also	O
publishes	O
an	O
API	B-Application
called	O
the	O
OpenDirectory	O
framework	O
,	O
permitting	O
macOS	B-Application
applications	O
to	O
interrogate	O
and	O
edit	O
the	O
Open	O
Directory	O
data	O
.	O
</s>
<s>
With	O
the	O
release	O
of	O
Mac	B-Application
OS	I-Application
X	I-Application
Leopard	I-Application
(	O
10.5	O
)	O
,	O
Apple	O
chose	O
to	O
move	O
away	O
from	O
using	O
the	O
NetInfo	O
directory	O
service	O
(	O
originally	O
found	O
in	O
NeXTSTEP	B-Application
and	O
OPENSTEP	B-Operating_System
)	O
,	O
which	O
had	O
been	O
used	O
by	O
default	O
for	O
all	O
local	O
accounts	O
and	O
groups	O
in	O
every	O
release	O
of	O
Mac	B-Application
OS	I-Application
X	I-Application
from	O
10.0	O
to	O
10.4	O
.	O
</s>
<s>
Mac	B-Application
OS	I-Application
X	I-Application
10.5	I-Application
now	O
uses	O
Directory	O
Services	O
and	O
its	O
plugins	O
for	O
all	O
directory	O
information	O
.	O
</s>
<s>
macOS	B-Operating_System
Server	I-Operating_System
can	O
host	O
an	O
Open	O
Directory	O
domain	O
when	O
configured	O
as	O
an	O
Open	O
Directory	O
Master	O
.	O
</s>
<s>
In	O
addition	O
to	O
its	O
local	O
directory	O
,	O
this	O
OpenLDAP-based	O
LDAPv3	B-Protocol
domain	O
is	O
designed	O
to	O
store	O
centralized	O
management	O
data	O
,	O
user	O
,	O
group	O
,	O
and	O
computer	O
accounts	O
,	O
which	O
other	O
systems	O
can	O
access	O
.	O
</s>
<s>
The	O
directory	O
domain	O
is	O
paired	O
with	O
the	O
Open	O
Directory	O
Password	O
Server	O
and	O
,	O
optionally	O
,	O
a	O
Kerberos	B-Protocol
realm	O
.	O
</s>
<s>
For	O
Kerberos	B-Protocol
authentication	O
,	O
the	O
Kerberos	B-Protocol
realm	O
can	O
either	O
be	O
hosted	O
by	O
a	O
Kerberos	B-Protocol
key	O
distribution	O
center	O
(	O
KDC	O
)	O
running	O
on	O
the	O
server	O
system	O
,	O
or	O
the	O
server	O
can	O
participate	O
in	O
an	O
existing	O
Kerberos	B-Protocol
realm	O
.	O
</s>
<s>
For	O
services	O
that	O
are	O
not	O
Kerberized	B-Protocol
,	O
the	O
Password	O
Server	O
provides	O
the	O
following	O
Simple	O
Authentication	O
and	O
Security	O
Layer-based	O
authentication	O
methods	O
:	O
</s>
<s>
Any	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
Server	I-Operating_System
system	O
prior	O
to	O
10.7	O
(	O
Lion	O
)	O
configured	O
as	O
an	O
Active	B-Protocol
Directory	I-Protocol
Master	O
can	O
act	O
as	O
a	O
Windows	O
Primary	O
Domain	O
Controller	O
(	O
PDC	O
)	O
,	O
providing	O
domain	O
authentication	O
services	O
to	O
Microsoft	B-Application
Windows	I-Application
clients	O
.	O
</s>
<s>
In	O
a	O
more	O
general	O
sense	O
,	O
Open	O
Directory	O
can	O
describe	O
the	O
plugins	O
model	O
used	O
by	O
Directory	O
Utility	O
and	O
the	O
directory	O
services	O
framework	O
in	O
macOS	B-Application
and	O
macOS	B-Operating_System
Server	I-Operating_System
.	O
</s>
<s>
This	O
could	O
be	O
thought	O
of	O
as	O
analogous	O
to	O
the	O
Name	B-Protocol
Service	I-Protocol
Switch	I-Protocol
systems	O
of	O
some	O
other	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
When	O
connected	O
to	O
a	O
directory	O
system	O
,	O
a	O
macOS	B-Application
client	O
or	O
Server	O
can	O
authenticate	O
users	O
,	O
lookup	O
contacts	O
,	O
perform	O
service	B-Protocol
discovery	I-Protocol
and	O
name	O
resolution	O
with	O
the	O
following	O
types	O
of	O
directories	O
:	O
</s>
<s>
Open	O
Directory	O
began	O
with	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
Server	I-Operating_System
10.2	O
.	O
</s>
<s>
Version	O
10.2	O
also	O
included	O
support	O
for	O
Kerberos	B-Protocol
.	O
</s>
<s>
Mac	B-Application
OS	I-Application
X	I-Application
versions	O
10.1	O
and	O
10.0	O
stored	O
user	O
password	O
information	O
within	O
the	O
directory	O
domain	O
using	O
crypt	O
password	O
authentication	O
authorities	O
,	O
but	O
version	O
10.2	O
paved	O
the	O
way	O
for	O
the	O
current	O
Shadow	O
Hash	O
and	O
Password	O
Server	O
mechanisms	O
.	O
</s>
<s>
Password	O
Server	O
is	O
the	O
successor	O
to	O
Authentication	O
Manager	O
,	O
and	O
was	O
introduced	O
in	O
Open	O
Directory	O
2	O
in	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
Server	I-Operating_System
10.3	O
.	O
</s>
<s>
Open	O
Directory	O
2	O
was	O
also	O
the	O
first	O
version	O
to	O
use	O
LDAPv3	B-Protocol
as	O
the	O
directory	O
domain	O
.	O
</s>
<s>
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
Server	I-Operating_System
10.4	O
includes	O
Open	O
Directory	O
3	O
,	O
which	O
introduced	O
Active	B-Protocol
Directory	I-Protocol
domain	O
member	O
support	O
,	O
trusted	O
directory	O
binding	O
,	O
and	O
increased	O
robustness	O
.	O
</s>
<s>
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
Server	I-Operating_System
10.5	O
features	O
Open	O
Directory	O
4	O
with	O
support	O
for	O
cross-domain	O
authorization	O
and	O
a	O
built-in	O
RADIUS	B-Protocol
server	I-Protocol
for	O
managing	O
AirPort	O
base	O
stations	O
.	O
</s>
