path: root/docs/docbook/projdoc/Samba-PDC-HOWTO.sgml

<chapter id="samba-pdc">


<chapterinfo>
	&author.jerry;
	&author.jht;
	<author>
		<firstname>David</firstname><surname>Bannon</surname>
		<affiliation>
			<orgname>Samba Team</orgname>
			<address><email>dbannon@samba.org</email></address>
		</affiliation>
	</author>
	<pubdate> (26 Apr 2001) </pubdate>
</chapterinfo>

<title>
Samba as an NT4 or Win2k Primary Domain Controller
</title>


<sect1>
<title>Prerequisite Reading</title>

<para>
Before you continue reading in this chapter, please make sure 
that you are comfortable with configuring basic files services
in smb.conf and how to enable and administer password 
encryption in Samba.  Theses two topics are covered in the
&smb.conf; manpage.
</para>


</sect1>



<sect1>
<title>
Background
</title>

<para>
This article outlines the steps necessary for configuring Samba as a PDC.
It is necessary to have a working Samba server prior to implementing the
PDC functionality.
</para>

<itemizedlist>
	<listitem><para>
	Domain logons for Windows NT 4.0 / 200x / XP Professional clients.
	</para></listitem>
	
	<listitem><para>
	Placing Windows 9x / Me clients in user level security
	</para></listitem>
	
	<listitem><para>
	Retrieving a list of users and groups from a Samba PDC to
	Windows 9x / Me / NT / 200x / XP Professional clients
	</para></listitem>
	
	<listitem><para>
	Roaming Profiles
	</para></listitem>
	
	<listitem><para>
	Network/System Policies
	</para></listitem>
</itemizedlist>

<note>
<para>
Roaming Profiles and System/Network policies are advanced network administration topics
that are covered separately in this document.
</para>
</note>

<para>
The following functionalities are new to the Samba 3.0 release:
</para>

<itemizedlist>
	<listitem><para>
	Windows NT 4 domain trusts
	</para></listitem>
	
	<listitem><para>
	Adding users via the User Manager for Domains
	</para></listitem>
</itemizedlist>

<para>
The following functionalities are NOT provided by Samba 3.0:
</para>

<itemizedlist>
	<listitem><para>
	SAM replication with Windows NT 4.0 Domain Controllers
	(i.e. a Samba PDC and a Windows NT BDC or vice versa) 
	</para></listitem>
	
	<listitem><para>
	Acting as a Windows 2000 Domain Controller (i.e. Kerberos and 
	Active Directory)
	</para></listitem>
</itemizedlist>

<para>
Please note that Windows 9x / Me / XP Home clients are not true members of a domain
for reasons outlined in this article.  Therefore the protocol for
support Windows 9x-style domain logons is completely different
from NT4 / Win2k type domain logons and has been officially supported for some 
time.
</para>

<para><emphasis>
MS Windows XP Home edition is NOT able to join a domain and does not permit
the use of domain logons.</emphasis>
</para>


<para>
Implementing a Samba PDC can basically be divided into 3 broad
steps.
</para>

<orderedlist numeration="arabic">
	<listitem><para>
	Configuring the Samba PDC
	</para></listitem>
	
	<listitem><para>
	Creating machine trust accounts	and joining clients to the domain
	</para></listitem>

	<listitem><para>
	Adding and managing domain user accounts
	</para></listitem>
</orderedlist>

<para>
There are other minor details such as user profiles, system
policies, etc...  However, these are not necessarily specific
to a Samba PDC as much as they are related to Windows NT networking
concepts.
</para>

</sect1>


<sect1>
<title>Configuring the Samba Domain Controller</title>

<para>
The first step in creating a working Samba PDC is to 
understand the parameters necessary in smb.conf. Here we
attempt to explain the parameters that are covered in
the &smb.conf; man page.
</para>

<para>
Here is an example &smb.conf; for acting as a PDC:
</para>

<para><programlisting>
[global]
    ; Basic server settings
    <ulink url="smb.conf.5.html#NETBIOSNAME">netbios name</ulink> = <replaceable>POGO</replaceable>
    <ulink url="smb.conf.5.html#WORKGROUP">workgroup</ulink> = <replaceable>NARNIA</replaceable>

    ; we should act as the domain and local master browser
    <ulink url="smb.conf.5.html#OSLEVEL">os level</ulink> = 64
    <ulink url="smb.conf.5.html#PERFERREDMASTER">preferred master</ulink> = yes
    <ulink url="smb.conf.5.html#DOMAINMASTER">domain master</ulink> = yes
    <ulink url="smb.conf.5.html#LOCALMASTER">local master</ulink> = yes
    
    ; security settings (must user security = user)
    <ulink url="smb.conf.5.html#SECURITYEQUALSUSER">security</ulink> = user
    
    ; encrypted passwords are a requirement for a PDC
    <ulink url="smb.conf.5.html#ENCRYPTPASSWORDS">encrypt passwords</ulink> = yes
    
    ; support domain logons
    <ulink url="smb.conf.5.html#DOMAINLOGONS">domain logons</ulink> = yes
    
    ; where to store user profiles?
    <ulink url="smb.conf.5.html#LOGONPATH">logon path</ulink> = \\%N\profiles\%u
    
    ; where is a user's home directory and where should it be mounted at?
    <ulink url="smb.conf.5.html#LOGONDRIVE">logon drive</ulink> = H:
    <ulink url="smb.conf.5.html#LOGONHOME">logon home</ulink> = \\homeserver\%u
    
    ; specify a generic logon script for all users
    ; this is a relative **DOS** path to the [netlogon] share
    <ulink url="smb.conf.5.html#LOGONSCRIPT">logon script</ulink> = logon.cmd

; necessary share for domain controller
[netlogon]
    <ulink url="smb.conf.5.html#PATH">path</ulink> = /usr/local/samba/lib/netlogon
    <ulink url="smb.conf.5.html#READONLY">read only</ulink> = yes
    <ulink url="smb.conf.5.html#WRITELIST">write list</ulink> = <replaceable>ntadmin</replaceable>
    
; share for storing user profiles
[profiles]
    <ulink url="smb.conf.5.html#PATH">path</ulink> = /export/smb/ntprofile
    <ulink url="smb.conf.5.html#READONLY">read only</ulink> = no
    <ulink url="smb.conf.5.html#CREATEMASK">create mask</ulink> = 0600
    <ulink url="smb.conf.5.html#DIRECTORYMASK">directory mask</ulink> = 0700
</programlisting></para>

<para>
There are a couple of points to emphasize in the above configuration.
</para>

<itemizedlist>
	<listitem><para>
	Encrypted passwords must be enabled.  For more details on how 
	to do this, refer to <link linkend="passdb">the User Database chapter</link>.
	</para></listitem>
	
	<listitem><para>
	The server must support domain logons and a
	<filename>[netlogon]</filename> share
	</para></listitem>
	
	<listitem><para>
	The server must be the domain master browser in order for Windows 
	client to locate the server as a DC.  Please refer to the various 
	Network Browsing documentation included with this distribution for 
	details.
	</para></listitem>
</itemizedlist>    

<para>
Samba 3.0 offers a complete implementation of group mapping
between Windows NT groups and Unix groups (this is really quite
complicated to explain in a short space).
</para>

</sect1>


<sect1>
<title>Creating Machine Trust Accounts and Joining Clients to the Domain</title>

<para>
A machine trust account is a Samba account that is used to
authenticate a client machine (rather than a user) to the Samba
server.  In Windows terminology, this is known as a "Computer
Account."</para>

<para>
The password of a machine trust account acts as the shared secret for
secure communication with the Domain Controller.  This is a security
feature to prevent an unauthorized machine with the same NetBIOS name
from joining the domain and gaining access to domain user/group
accounts.  Windows NT, 200x, XP Professional clients use machine trust
accounts, but Windows 9x / Me / XP Home clients do not.  Hence, a
Windows 9x / Me / XP Home  client is never a true member of a domain
because it does not possess a machine trust account, and thus has no
shared secret with the domain controller.
</para>

<para>A Windows PDC stores each machine trust account in the Windows
Registry. A Samba-3 PDC also has to stoe machine trust account information
in a suitable back-end data store. With Samba-3 there can be multiple back-ends
for this including:
</para>

<itemizedlist>
	<listitem><para>
	<emphasis>smbpaswd</emphasis> - the plain ascii file stored used by
	earlier versions of Samba. This file configuration option requires
	a Unix/Linux system account for EVERY entry (ie: both for user and for
	machine accounts). This file will be located in the <emphasis>private</emphasis>
	directory (default is /usr/local/samba/lib/private or on linux /etc/samba).
	</para></listitem>

	<listitem><para>
	<emphasis>smbpasswd_nua</emphasis> - This file is independant of the
	system wide user accounts. The use of this back-end option requires
	specification of the "non unix account range" option also. It is called
	smbpasswd and will be located in the <filename>private</filename> directory.
	</para></listitem>

	<listitem><para>
	<emphasis>tdbsam</emphasis> - a binary database backend that will be
	stored in the <emphasis>private</emphasis> directory in a file called
	<emphasis>passwd.tdb</emphasis>. The key benefit of this binary format
	file is that it can store binary objects that can not be accomodated
	in the traditional plain text smbpasswd file.
	</para></listitem>

	<listitem><para>
	<emphasis>tdbsam_nua</emphasis> like the smbpasswd_nua option above, this
	file allows the creation of arbitrary user and machine accounts without
	requiring that account to be added to the system (/etc/passwd) file. It
	too requires the specification of the "non unix account range" option
	in the [globals] section of the &smb.conf; file.
	</para></listitem>

	<listitem><para>
	<emphasis>ldapsam</emphasis> - An LDAP based back-end. Permits the
	LDAP server to be specified. eg: ldap://localhost or ldap://frodo.murphy.com
	</para></listitem>

	<listitem><para>
	<emphasis>ldapsam_nua</emphasis> - LDAP based back-end with no unix
	account requirement, like smbpasswd_nua and tdbsam_nua above.
	</para></listitem>
</itemizedlist>

<para>Read the chapter about the <link linkend="passdb">User Database</link> 
for details.</para>

<para>
A Samba PDC, however, stores each machine trust account in two parts,
as follows:

<itemizedlist>
    <listitem><para>A Samba account, stored in the same location as user
    LanMan and NT password hashes (currently
    <filename>smbpasswd</filename>). The Samba account 
    possesses and uses only the NT password hash.</para></listitem>

    <listitem><para>A corresponding Unix account, typically stored in
    <filename>/etc/passwd</filename>. (Future releases will alleviate the need to
    create <filename>/etc/passwd</filename> entries.) </para></listitem>
</itemizedlist>
</para>

<para>
There are two ways to create machine trust accounts:
</para>

<itemizedlist>
	<listitem><para> Manual creation. Both the Samba and corresponding
	Unix account are created by hand.</para></listitem>
	
	<listitem><para> "On-the-fly" creation. The Samba machine trust
	account is automatically created by Samba at the time the client
	is joined to the domain. (For security, this is the
	recommended method.) The corresponding Unix account may be
	created automatically or manually. </para>
	</listitem>

</itemizedlist>

<sect2>
<title>Manual Creation of Machine Trust Accounts</title>

<para>
The first step in manually creating a machine trust account is to
manually create the corresponding Unix account in
<filename>/etc/passwd</filename>.  This can be done using
<command>vipw</command> or other 'add user' command that is normally
used to create new Unix accounts.  The following is an example for a
Linux based Samba server:
</para>

<para>
  <prompt>root# </prompt><command>/usr/sbin/useradd -g 100 -d /dev/null -c <replaceable>"machine 
nickname"</replaceable> -s /bin/false <replaceable>machine_name</replaceable>$ </command>
</para>
<para>
<prompt>root# </prompt><command>passwd -l <replaceable>machine_name</replaceable>$</command>
</para>

<para>On *BSD systems, this can be done using the 'chpass' utility:</para>

<para>
<prompt>root# </prompt><command>chpass -a "<replaceable>machine_name</replaceable>$:*:101:100::0:0:Workstation <replaceable>machine_name</replaceable>:/dev/null:/sbin/nologin"</command>
</para>

<para>
The <filename>/etc/passwd</filename> entry will list the machine name 
with a "$" appended, won't have a password, will have a null shell and no 
home directory. For example a machine named 'doppy' would have an 
<filename>/etc/passwd</filename> entry like this:
</para>

<para><programlisting>
doppy$:x:505:501:<replaceable>machine_nickname</replaceable>:/dev/null:/bin/false
</programlisting></para>

<para>
Above, <replaceable>machine_nickname</replaceable> can be any
descriptive name for the client, i.e., BasementComputer.
<replaceable>machine_name</replaceable> absolutely must be the NetBIOS
name of the client to be joined to the domain.  The "$" must be
appended to the NetBIOS name of the client or Samba will not recognize
this as a machine trust account.
</para>


<para>
Now that the corresponding Unix account has been created, the next step is to create 
the Samba account for the client containing the well-known initial 
machine trust account password.  This can be done using the <ulink 
url="smbpasswd.8.html"><command>smbpasswd(8)</command></ulink> command 
as shown here:
</para>

<para>
<prompt>root# </prompt><userinput>smbpasswd -a -m <replaceable>machine_name</replaceable></userinput>
</para>

<para>
where <replaceable>machine_name</replaceable> is the machine's NetBIOS
name.  The RID of the new machine account is generated from the UID of 
the corresponding Unix account.
</para>

<warning>
	<title>Join the client to the domain immediately</title>

	<para>
	Manually creating a machine trust account using this method is the 
	equivalent of creating a machine trust account on a Windows NT PDC using 
	the "Server Manager".  From the time at which the account is created
	to the time which the client joins the domain and changes the password,
	your domain is vulnerable to an intruder joining your domain using a
	a machine with the same NetBIOS name.  A PDC inherently trusts
	members of the domain and will serve out a large degree of user 
	information to such clients.  You have been warned!
	</para>
</warning>
</sect2>


<sect2>
<title>"On-the-Fly" Creation of Machine Trust Accounts</title>

<para>
The second (and recommended) way of creating machine trust accounts is
simply to allow the Samba server to create them as needed when the client
is joined to the domain. </para>

<para>Since each Samba machine trust account requires a corresponding
Unix account, a method for automatically creating the
Unix account is usually supplied; this requires configuration of the
<ulink url="smb.conf.5.html#ADDUSERSCRIPT">add user script</ulink> 
option in <filename>smb.conf</filename>.  This
method is not required, however; corresponding Unix accounts may also
be created manually.
</para>


<para>Below is an example for a RedHat 6.2 Linux system.
</para>

<para><programlisting>
[global]
   # &lt;...remainder of parameters...&gt;
   add user script = /usr/sbin/useradd -d /dev/null -g 100 -s /bin/false -M %u 
</programlisting></para>

</sect2>


<sect2><title>Joining the Client to the Domain</title>

<para>
The procedure for joining a client to the domain varies with the
version of Windows.
</para>

<itemizedlist>
<listitem><para><emphasis>Windows 2000</emphasis></para>

	<para> When the user elects to join the client to a domain, Windows prompts for
	an account and password that is privileged to join the domain.  A
	Samba administrative account (i.e., a Samba account that has root
	privileges on the Samba server) must be entered here; the
	operation will fail if an ordinary user account is given. 
	The password for this account should be
	set to a different password than the associated
	<filename>/etc/passwd</filename> entry, for security
	reasons. </para>

	<para>The session key of the Samba administrative account acts as an
	encryption key for setting the password of the machine trust
	account. The machine trust account will be created on-the-fly, or
	updated if it already exists.</para>
</listitem>

<listitem><para><emphasis>Windows NT</emphasis></para>

    <para> If the machine trust account was created manually, on the
	Identification Changes menu enter the domain name, but do not
	check the box "Create a Computer Account in the Domain."  In this case,
	the existing machine trust account is used to join the machine to
	the domain.</para>

    <para> If the machine trust account is to be created
	on-the-fly, on the Identification Changes menu enter the domain
	name, and check the box "Create a Computer Account in the Domain."  In
	this case, joining the domain proceeds as above for Windows 2000
	(i.e., you must supply a Samba administrative account when
	prompted).</para>
</listitem>

<listitem><para><emphasis>Samba</emphasis</para>
	<para>Joining a samba client to a domain is documented in 
	the <link linkend="domain-member">Domain Member</link> chapter.
</para></listitem>
</itemizedlist>

</sect2>
</sect1>

<sect1>
<title>Common Problems and Errors</title>

<sect2>
<title>I cannot include a '$' in a machine name</title>
<para>
A 'machine name' in (typically) <filename>/etc/passwd</filename> 	
of the machine name with a '$' appended. FreeBSD (and other BSD 
systems?) won't create a user with a '$' in their name.
</para>

<para>
The problem is only in the program used to make the entry, once 
made, it works perfectly. So create a user without the '$' and 
use <command>vipw</command> to edit the entry, adding the '$'. Or create 
the whole entry with vipw if you like, make sure you use a 
unique User ID !
</para>
</sect2>

<sect2>
<title>I get told "You already have a connection to the Domain...." 
or "Cannot join domain, the credentials supplied conflict with an 
existing set.." when creating a machine trust account.</title>

<para>
This happens if you try to create a machine trust account from the 
machine itself and already have a connection (e.g. mapped drive) 
to a share (or IPC$) on the Samba PDC.  The following command
will remove all network drive connections:
</para>

<para>
<prompt>C:\WINNT\></prompt> <command>net use * /d</command>
</para>

<para>
Further, if the machine is a already a 'member of a workgroup' that 
is the same name as the domain you are joining (bad idea) you will 
get this message.  Change the workgroup name to something else, it 
does not matter what, reboot, and try again.
</para>
</sect2>

<sect2>
<title>The system can not log you on (C000019B)....</title>

<para>I joined the domain successfully but after upgrading 
to a newer version of the Samba code I get the message, "The system 
can not log you on (C000019B), Please try again or consult your 
system administrator" when attempting to logon.
</para>

<para>
This occurs when the domain SID stored in the secrets.tdb database
is changed. The most common cause of a change in domain SID is when
the domain name and/or the server name (netbios name) is changed.
The only way to correct the problem is to restore the original domain 
SID or remove the domain client from the domain and rejoin. The domain
SID may be reset using either the smbpasswd or rpcclient utilities.
</para>
</sect2>

<sect2>
<title>The machine trust account for this computer either does not 
exist or is not accessible.</title>

<para>
When I try to join the domain I get the message "The machine account 
for this computer either does not exist or is not accessible". What's 
wrong?
</para>

<para>
This problem is caused by the PDC not having a suitable machine trust account. 
If you are using the <parameter>add user script</parameter> method to create 
accounts then this would indicate that it has not worked. Ensure the domain 
admin user system is working.
</para>

<para>
Alternatively if you are creating account entries manually then they 
have not been created correctly. Make sure that you have the entry 
correct for the machine trust account in smbpasswd file on the Samba PDC. 
If you added the account using an editor rather than using the smbpasswd 
utility, make sure that the account name is the machine NetBIOS name 
with a '$' appended to it ( i.e. computer_name$ ). There must be an entry 
in both /etc/passwd and the smbpasswd file. Some people have reported 
that inconsistent subnet masks between the Samba server and the NT 
client have caused this problem.   Make sure that these are consistent 
for both client and server.
</para>
</sect2>

<sect2>
<title>When I attempt to login to a Samba Domain from a NT4/W2K workstation,
I get a message about my account being disabled.</title>

<para>
At first be ensure to enable the useraccounts with <command>smbpasswd -e 
%user%</command>, this is normally done, when you create an account.
</para>

</sect2>

</sect1>

<sect1>
<title>Domain Control for Windows 9x/ME</title>

<para>
A domain and a workgroup are exactly the same thing in terms of network
browsing.  The difference is that a distributable authentication
database is associated with a domain, for secure login access to a
network.  Also, different access rights can be granted to users if they
successfully authenticate against a domain logon server. Samba-3 does this
now in the same way that MS Windows NT/2K.
</para>

<para>
The SMB client logging on to a domain has an expectation that every other
server in the domain should accept the same authentication information.
Network browsing functionality of domains and workgroups is identical and
is explained in this documentation under the browsing discussions.
It should be noted, that browsing is totally orthogonal to logon support.
</para>

<para>
Issues related to the single-logon network model are discussed in this
section.  Samba supports domain logons, network logon scripts, and user
profiles for MS Windows for workgroups and MS Windows 9X/ME clients
which are the focus of this section.
</para>


<para>
When an SMB client in a domain wishes to logon it broadcast requests for a
logon server.  The first one to reply gets the job, and validates its
password using whatever mechanism the Samba administrator has installed.
It is possible (but very stupid) to create a domain where the user
database is not shared between servers, i.e. they are effectively workgroup
servers advertising themselves as participating in a domain.  This
demonstrates how authentication is quite different from but closely
involved with domains.
</para>


<para>
Using these features you can make your clients verify their logon via
the Samba server; make clients run a batch file when they logon to
the network and download their preferences, desktop and start menu.
</para>

<para>
Before launching into the configuration instructions, it is 
worthwhile lookingat how a Windows 9x/ME client performs a logon:
</para>

<orderedlist>
<listitem>
	<para>
	The client broadcasts (to the IP broadcast address of the subnet it is in)
	a NetLogon request. This is sent to the NetBIOS name DOMAIN&lt;1c&gt; at the
	NetBIOS layer.  The client chooses the first response it receives, which
	contains the NetBIOS name of the logon server to use in the format of 
	\\SERVER.
	</para>
</listitem>

<listitem>
	<para>
	The client then connects to that server, logs on (does an SMBsessetupX) and
	then connects to the IPC$ share (using an SMBtconX).
	</para>
</listitem>

<listitem>
	<para>
	The client then does a NetWkstaUserLogon request, which retrieves the name
	of the user's logon script. 
	</para>
</listitem>

<listitem>
	<para>
	The client then connects to the NetLogon share and searches for this 	
	and if it is found and can be read, is retrieved and executed by the client.
	After this, the client disconnects from the NetLogon share.
	</para>
</listitem>

<listitem>
	<para>
	The client then sends a NetUserGetInfo request to the server, to retrieve
	the user's home share, which is used to search for profiles. Since the
	response to the NetUserGetInfo request does not contain much more 	
	the user's home share, profiles for Win9X clients MUST reside in the user
	home directory.
	</para>
</listitem>

<listitem>
	<para>
	The client then connects to the user's home share and searches for the 
	user's profile. As it turns out, you can specify the user's home share as
	a sharename and path. For example, \\server\fred\.profile.
	If the profiles are found, they are implemented.
	</para>
</listitem>

<listitem>
	<para>
	The client then disconnects from the user's home share, and reconnects to
	the NetLogon share and looks for CONFIG.POL, the policies file. If this is
	found, it is read and implemented.
	</para>
</listitem>
</orderedlist>


<sect2>
<title>Configuration Instructions:	Network Logons</title>

<para>
The main difference between a PDC and a Windows 9x logon 
server configuration is that
</para>

<itemizedlist>

<listitem><para>
Password encryption is not required for a Windows 9x logon server.
</para></listitem>

<listitem><para>
Windows 9x/ME clients do not possess machine trust accounts.
</para></listitem>

</itemizedlist>

<para>
Therefore, a Samba PDC will also act as a Windows 9x logon 
server.
</para>


<warning>
<title>security mode and master browsers</title>

<para>
There are a few comments to make in order to tie up some 
loose ends.  There has been much debate over the issue of whether
or not it is ok to configure Samba as a Domain Controller in security
modes other than <constant>USER</constant>.  The only security mode 
which  will not work due to technical reasons is <constant>SHARE</constant>
mode security.  <constant>DOMAIN</constant> and <constant>SERVER</constant>
mode security is really just a variation on SMB user level security.
</para>

<para>
Actually, this issue is also closely tied to the debate on whether 
or not Samba must be the domain master browser for its workgroup
when operating as a DC.  While it may technically be possible
to configure a server as such (after all, browsing and domain logons
are two distinctly different functions), it is not a good idea to
so.  You should remember that the DC must register the DOMAIN#1b NetBIOS 
name.  This is the name used by Windows clients to locate the DC.
Windows clients do not distinguish between the DC and the DMB.
For this reason, it is very wise to configure the Samba DC as the DMB.
</para>

<para>
Now back to the issue of configuring a Samba DC to use a mode other
than "security = user".  If a Samba host is configured to use 
another SMB server or DC in order to validate user connection 
requests, then it is a fact that some other machine on the network 
(the "password server") knows more about user than the Samba host.
99% of the time, this other host is a domain controller.  Now 
in order to operate in domain mode security, the "workgroup" parameter
must be set to the name of the Windows NT domain (which already 
has a domain controller, right?)
</para>

<para>
Therefore configuring a Samba box as a DC for a domain that 
already by definition has a PDC is asking for trouble.
Therefore, you should always configure the Samba DC to be the DMB
for its domain.
</para>
</warning>

</sect2>
</sect1>
</chapter>