Another set of validation updates

[Samba.git] / docs / Samba-HOWTO-Collection / DomainMember.xml

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<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
<chapter id="domain-member">

<chapterinfo>
        &author.jht;
        &author.jeremy;
        &author.jerry;
        &author.tridge;
        &author.jelmer;
        <author>&person.gd;<contrib>LDAP updates</contrib></author>
</chapterinfo>

<title>Domain Membership</title>

<para>
Domain Membership is a subject of vital concern. Samba must be able to
participate as a member server in a Microsoft Domain Security context, and
Samba must be capable of providing Domain machine member trust accounts,
otherwise it would not be able to offer a viable option for many users.
</para>

<para>
This chapter covers background information pertaining to Domain Membership,
the Samba configuration for it, and MS Windows client procedures for joining a
domain. Why is this necessary? Because both are areas in which there exists
within the current MS Windows networking world and particularly in the
UNIX/Linux networking and administration world, a considerable level of
misinformation, incorrect understanding and a lack of knowledge. Hopefully
this chapter will fill the voids.
</para>

<sect1>
<title>Features and Benefits</title>

<para>
MS Windows workstations and servers that want to participate in Domain Security need to
be made Domain Members. Participating in Domain Security is often called 
<emphasis>Single Sign On</emphasis> or <acronym>SSO</acronym> for short. This
chapter describes the process that must be followed to make a workstation
(or another server &smbmdash; be it an <application>MS Windows NT4 / 200x</application>
server) or a Samba server a member of an MS Windows Domain Security context.
</para>

<para>
<indexterm><primary>Server Type</primary><secondary>Domain Member</secondary></indexterm>
Samba-3 can join an MS Windows NT4-style domain as a native member server, an 
MS Windows Active Directory Domain as a native member server, or a Samba Domain
Control network. Domain Membership has many advantages:
</para>

<itemizedlist>
        <listitem><para>
<indexterm><primary>SAM</primary></indexterm>
        MS Windows workstation users get the benefit of SSO.
        </para></listitem>

        <listitem><para>
        Domain user access rights and file ownership/access controls can be set
        from the single Domain Security Account Manager (SAM) database 
        (works with Domain Member servers as well as with MS Windows workstations
        that are Domain Members).
        </para></listitem>

        <listitem><para>
        Only <application>MS Windows NT4/200x/XP Professional</application>
        workstations that are Domain Members can use network logon facilities.
        </para></listitem>

        <listitem><para>
        Domain Member workstations can be better controlled through the use of
        Policy files (<filename>NTConfig.POL</filename>) and Desktop Profiles.
        </para></listitem>

        <listitem><para>
        Through the use of logon scripts, users can be given transparent access to network
        applications that run off application servers.
        </para></listitem>

        <listitem><para>
        Network administrators gain better application and user access management
        abilities because there is no need to maintain user accounts on any network
        client or server, other than the central Domain database 
        (either NT4/Samba SAM style Domain, NT4 Domain that is backend-ed with an
        LDAP directory, or via an Active Directory infrastructure).
        </para></listitem>
</itemizedlist>

</sect1>

<sect1 id="machine-trust-accounts">
<title>MS Windows Workstation/Server Machine Trust Accounts</title>

<para>
<indexterm><primary>Machine Trust Accounts</primary></indexterm>
A Machine Trust Account is an account that is used to authenticate a client
machine (rather than a user) to the Domain Controller server. In Windows terminology,
this is known as a <quote>Computer Account.</quote> The purpose of the machine account
is to prevent a rogue user and Domain Controller from colluding to gain access to a 
domain member workstation.
</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 NT4 PDC stores each Machine Trust Account in the Windows Registry.
The introduction of MS Windows 2000 saw the introduction of Active Directory,
the new repository for Machine Trust Accounts. A Samba PDC, however, stores
each Machine Trust Account in two parts,
as follows:

<itemizedlist>
        <listitem><para>
        A Domain Security Account (stored in the 
        <smbconfoption name="passdb backend"/> that has been configured in the
        &smb.conf; file. The precise nature of the account information that is
        stored depends on the type of backend database that has been chosen.
        </para>

        <para>
        The older format of this data is the <filename>smbpasswd</filename> database
        that contains the UNIX login ID, the UNIX user identifier (UID), and the
        LanMan and NT encrypted passwords. There is also some other information in
        this file that we do not need to concern ourselves with here.
        </para>

        <para>
        The two newer database types are called ldapsam, and
        tdbsam. Both store considerably more data than the
        older <filename>smbpasswd</filename> file did. The extra information
        enables new user account controls to be implemented.
        </para></listitem>

        <listitem><para>
        A corresponding UNIX account, typically stored in
        <filename>/etc/passwd</filename>. Work is in progress to allow a
        simplified mode of operation that does not require UNIX user accounts, but
        this may not be a feature of the early releases of Samba-3.
        </para></listitem>
</itemizedlist>
</para>

<para>
<indexterm><primary>Machine Trust Accounts</primary><secondary>creating</secondary></indexterm>
There are three ways to create Machine Trust Accounts:
</para>

<itemizedlist>
        <listitem><para>
        Manual creation from the UNIX/Linux command line. Here, both the Samba and
        corresponding UNIX account are created by hand.
        </para></listitem>

        <listitem><para>
        <indexterm><primary>Server Manager</primary></indexterm>
        Using the MS Windows NT4 Server Manager, either from an NT4 Domain Member
        server, or using the Nexus toolkit available from the Microsoft Web site.
        This tool can be run from any MS Windows machine as long as the user is
        logged on as the administrator account.
        </para></listitem>
        
        <listitem><para>
        <quote>On-the-fly</quote> 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 another <quote>add user</quote> command
that is normally used to create new UNIX accounts. The following is an example for
a Linux-based Samba server:
</para>

<para>
<indexterm><primary>useradd</primary></indexterm>
<indexterm><primary>vipw</primary></indexterm>
<screen>
&rootprompt;<userinput>/usr/sbin/useradd -g machines -d /var/lib/nobody -c <replaceable>"machine nickname"</replaceable> \
   -s /bin/false <replaceable>machine_name</replaceable>$ </userinput>

&rootprompt;<userinput>passwd -l <replaceable>machine_name</replaceable>$</userinput>
</screen>
</para>

<para>In the example above there is an existing system group <quote>machines</quote> which is used
as the primary group for all machine accounts. In the following examples the <quote>machines</quote> group has
numeric GID equal 100.</para>

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

<para>
<screen>
&rootprompt;<userinput>chpass -a \
'<replaceable>machine_name</replaceable>$:*:101:100::0:0:Windows <replaceable>machine_name</replaceable>:/dev/null:/sbin/nologin'</userinput>
</screen>
</para>

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

<programlisting>
doppy$:x:505:100:<replaceable>machine_nickname</replaceable>:/dev/null:/bin/false
</programlisting>

<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 <quote>$</quote> 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 
<command>smbpasswd</command> command 
as shown here:
</para>

<para>
<screen>
&rootprompt;<userinput>smbpasswd -a -m <replaceable>machine_name</replaceable></userinput>
</screen>
</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 
<indexterm><primary>Server Manager</primary></indexterm>
the <application>Server Manager</application>. From the time at which the 
account is created to the time the client joins the domain and 
changes the password, your domain is vulnerable to an intruder joining 
your domain using 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>Managing Domain Machine Accounts using NT4 Server Manager</title>

<para>
A working <smbconfoption name="add machine script"/> is essential
for machine trust accounts to be automatically created. This applies no matter whether
one uses automatic account creation, or if one wishes to use the NT4 Domain Server Manager.
</para>

<para>
<indexterm><primary>SRVTOOLS.EXE</primary></indexterm>
If the machine from which you are trying to manage the domain is an 
<application>MS Windows NT4 workstation or MS Windows 200x/XP Professional</application>,
the tool of choice is the package called <command>SRVTOOLS.EXE</command>. 
When executed in the target directory it will unpack <command>SrvMgr.exe</command>
and <command>UsrMgr.exe</command> (both are domain management tools for MS Windows NT4 workstation).
</para>

<para>
<indexterm><primary>Nexus.exe</primary></indexterm>
If your workstation is a <application>Microsoft Windows 9x/Me</application> family product
 you should download the <command>Nexus.exe</command> package from the Microsoft web site.
When executed from the target directory this will unpack the same tools but for use on 
this platform.
</para>

<para>
Further information about these tools may be obtained from the following locations:
</para>

<para>
<simplelist>
<member><ulink noescape="1" url="http://support.microsoft.com/default.aspx?scid=kb;en-us;173673"/></member>
<member><ulink noescape="1" url="http://support.microsoft.com/default.aspx?scid=kb;en-us;172540"/></member>
</simplelist>
</para>

<para>
Launch the <command>srvmgr.exe</command> (Server Manager for Domains) and follow these steps:
</para>

<procedure>
<title>Server Manager Account Machine Account Management</title>
        <step><para>
        From the menu select <guimenu>Computer</guimenu>.
        </para></step>

        <step><para>
        Click <guimenuitem>Select Domain</guimenuitem>.
        </para></step>

        <step><para>
        Click the name of the domain you wish to administer in the
        <guilabel>Select Domain</guilabel> panel and then click 
        <guibutton>OK</guibutton>.
        </para></step>

        <step><para>
        Again from the menu select <guimenu>Computer</guimenu>.
        </para></step>

        <step><para>
        Select <guimenuitem>Add to Domain</guimenuitem>.
        </para></step>

        <step><para>
        In the dialog box, click the radio button to 
        <guilabel>Add NT Workstation of Server</guilabel>, then
        enter the machine name in the field provided, and click the 
        <guibutton>Add</guibutton> button.
        </para></step>
</procedure>

</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
add machine script option in &smb.conf;. This method is not required, however, corresponding UNIX
accounts may also be created manually.
</para>


<para>
Here is an example for a Red Hat Linux system.
</para>

<para><smbconfblock>
<smbconfsection>[global]</smbconfsection>
<smbconfcomment>&lt;...remainder of parameters...&gt;</smbconfcomment>
<smbconfoption name="add machine script">/usr/sbin/useradd -d /var/lib/nobody -g 100 \</smbconfoption>
<member><parameter>  -s /bin/false -M %u</parameter></member>
</smbconfblock></para>


</sect2>


<sect2><title>Making an MS Windows Workstation or Server a Domain Member</title>

<para>
The procedure for making an MS Windows workstation or server a member of the domain varies
with the version of Windows.
</para>

<sect3>
        <title>Windows 200x/XP Professional Client</title>

        <para>
        When the user elects to make the client a Domain Member, Windows 200x prompts for
        an account and password that has privileges to create  machine accounts in the domain.
        A Samba Administrator Account (i.e., a Samba account that has <constant>root</constant> privileges on the
        Samba server) must be entered here; the operation will fail if an ordinary user
        account is given. 
        </para>

        <para>
        For security reasons, the password for this Administrator Account should be set
        to a password that is other than that used for the root user in <filename>/etc/passwd</filename>.
        </para>

        <para>
        The name of the account that is used to create Domain Member machine accounts can be
        anything the network administrator may choose. If it is other than <constant>root</constant>
        then this is easily mapped to <constant>root</constant> in the file named in the &smb.conf; parameter
        <smbconfoption name="username map">/etc/samba/smbusers</smbconfoption>.
        </para>

        <para>
        The session key of the Samba Administrator 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>
</sect3>

<sect3>
        <title>Windows NT4 Client</title>

        <para>
        If the Machine Trust Account was created manually, on the
        Identification Changes menu enter the domain name, but do not
        check the box <guilabel>Create a Computer Account in the Domain</guilabel>.
        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 <guilabel>Create a Computer Account in the Domain</guilabel>. In this case, joining
        the domain proceeds as above for Windows 2000 (i.e., you must supply a Samba Administrator Account when
        prompted).
        </para>
</sect3>

<sect3>
        <title>Samba Client</title>

        <para>Joining a Samba client to a domain is documented in 
        <link linkend="domain-member-server">Domain Member Server</link>.
        </para>
</sect3>

</sect2>
</sect1>

<sect1 id="domain-member-server">
<title>Domain Member Server</title>

<para>
This mode of server operation involves the Samba machine being made a member
of a domain security context. This means by definition that all user
authentication will be done from a centrally defined authentication regime. 
The authentication regime may come from an NT3/4-style (old domain technology)
server, or it may be provided from an Active Directory server (ADS) running on
MS Windows 2000 or later.
</para>

<para>
<emphasis>
Of course it should be clear that the authentication backend itself could be
from any distributed directory architecture server that is supported by Samba.
This can be LDAP (from OpenLDAP), or Sun's iPlanet, or NetWare Directory
Server, and so on.
</emphasis>
</para>

<note><para>
When Samba is configured to use an LDAP, or other identity management and/or
directory service, it is Samba that continues to perform user and machine
authentication. It should be noted that the LDAP server does not perform
authentication handling in place of what Samba is designed to do.
</para></note>

<para>
Please refer to <link linkend="samba-pdc">Domain Control</link>, for more information regarding
how to create a domain machine account for a Domain Member server as well as for
information on how to enable the Samba Domain Member machine to join the domain
and be fully trusted by it.
</para>

<sect2>
<title>Joining an NT4-type Domain with Samba-3</title>

<para><link linkend="assumptions">Next table</link> lists names that have been used in the remainder of this chapter.</para>

<table frame="all" id="assumptions"><title>Assumptions</title>
        <tgroup cols="2">
                <colspec align="right"/>
                <colspec align="left"/>
        <tbody>
                        <row>
                                <entry>NetBIOS name:</entry><entry>SERV1</entry>
                        </row>
                        <row>
                                <entry>Windows 200x/NT domain name:</entry><entry>&example.workgroup;</entry>
                        </row>
                        <row>
                                <entry>Domain's PDC NetBIOS name:</entry><entry>DOMPDC</entry>
                        </row>
                        <row>
                                <entry>Domain's BDC NetBIOS names:</entry><entry>DOMBDC1 and DOMBDC2</entry>
                        </row>
        </tbody>
        </tgroup>
</table>

<para>
First, you must edit your &smb.conf; file to tell Samba it should now use domain security.
</para>

<para>
        Change (or add) your 
        <smbconfoption name="security"/> line in the [global] section 
of your &smb.conf; to read:
</para>

<para>
<smbconfblock>
<smbconfoption name="security">domain</smbconfoption>
</smbconfblock>
</para>

<para>
Next change the <smbconfoption name="workgroup"/> line in the <smbconfsection>[global]</smbconfsection>
section to read: 
</para>

<para>
<smbconfblock>
<smbconfoption name="workgroup">&example.workgroup;</smbconfoption>
</smbconfblock>
</para>

<para>
This is the name of the domain we are joining.
</para>

<para>
You must also have the parameter <smbconfoption name="encrypt passwords"/>
set to <constant>yes</constant> in order for your users to authenticate to the NT PDC.
This is the default setting if this parameter is not specified. There is no need to specify this
parameter, but if it is specified in the &smb.conf; file, it must be set to <constant>Yes</constant>.
</para>

<para>
Finally, add (or modify) a <smbconfoption name="password server"/> line in the [global]
section to read: 
</para>

<para>
<smbconfblock>
<smbconfoption name="password server">DOMPDC DOMBDC1 DOMBDC2</smbconfoption>
</smbconfblock>
</para>

<para>
These are the primary and backup Domain Controllers Samba 
will attempt to contact in order to authenticate users. Samba will 
try to contact each of these servers in order, so you may want to 
rearrange this list in order to spread out the authentication load 
among Domain Controllers.
</para>

<para>
Alternately, if you want smbd to automatically determine 
the list of Domain Controllers to use for authentication, you may 
set this line to be:
</para>

<para>
<smbconfblock>
<smbconfoption name="password server">*</smbconfoption>
</smbconfblock>
</para>

<para>
This method allows Samba to use exactly the same mechanism that NT does. The 
method either uses broadcast-based name resolution, performs a WINS database
lookup in order to find a Domain Controller against which to authenticate,
or locates the Domain Controller using DNS name resolution.
</para>

<para>
To join the domain, run this command:
</para>

<para>
<screen>
&rootprompt;<userinput>net join -S DOMPDC -U<replaceable>Administrator%password</replaceable></userinput>
</screen>
</para>

<para>
If the <option>-S DOMPDC</option> argument is not given, the domain name will be obtained from &smb.conf;.
</para>

<para>
The machine is joining the domain DOM, and the PDC for that domain (the only machine
that has write access to the domain SAM database) is DOMPDC, therefore use the <option>-S</option>
option. The <replaceable>Administrator%password</replaceable> is the login name and
password for an account that has the necessary privilege to add machines to the
domain. If this is successful, you will see the message in your terminal window the
text shown below. Where the older NT4 style domain architecture is used:
<screen>
<computeroutput>Joined domain DOM.</computeroutput>
</screen>
</para>

<para>
Where Active Directory is used:
<screen>
<computeroutput>Joined SERV1 to realm MYREALM.</computeroutput>
</screen>
</para>

<para>
Refer to the <command>net</command> man page for further information.
</para>

<para>
This process joins the server to the domain without having to create the machine
trust account on the PDC beforehand.
</para>

<para>
This command goes through the machine account password change protocol, then writes
the new (random) machine account password for this Samba server into a file in the
same directory in which a smbpasswd file would be normally stored:
<screen>
<filename>/usr/local/samba/private/secrets.tdb</filename>
or 
<filename>/etc/samba/secrets.tdb</filename>.
</screen>
</para>

<para>
This file is created and owned by root and is not readable by any other user. It is
the key to the Domain-level security for your system, and should be treated as carefully 
as a shadow password file.
</para>

<para>
Finally, restart your Samba daemons and get ready for clients to begin using domain
security. The way you can restart your Samba daemons depends on your distribution,
but in most cases the following will suffice:
<screen>
&rootprompt;/etc/init.d/samba restart
</screen>
</para>

</sect2>

<sect2>
<title>Why Is This Better Than <parameter>security = server</parameter>?</title>

<para>
Currently, domain security in Samba does not free you from 
having to create local UNIX users to represent the users attaching 
to your server. This means that if Domain user <constant>DOM\fred
</constant> attaches to your Domain Security Samba server, there needs 
to be a local UNIX user fred to represent that user in the UNIX 
file system. This is similar to the older Samba security mode 
<smbconfoption name="security">server</smbconfoption>,
where Samba would pass through the authentication request to a Windows 
NT server in the same way as a Windows 95 or Windows 98 server would.
</para>

<para>
Please refer to <link linkend="winbind">Winbind: Use of Domain Accounts</link> chapter, for information on a system
to automatically assign UNIX UIDs and GIDs to Windows NT Domain users and groups.
</para>

<para>
The advantage to Domain-level security is that the 
authentication in Domain-level security is passed down the authenticated 
RPC channel in exactly the same way that an NT server would do it. This 
means Samba servers now participate in domain trust relationships in 
exactly the same way NT servers do (i.e., you can add Samba servers into 
a resource domain and have the authentication passed on from a resource
domain PDC to an account domain PDC).
</para>

<para>
In addition, with <smbconfoption name="security">server</smbconfoption>, every Samba 
daemon on a server has to keep a connection open to the 
authenticating server for as long as that daemon lasts. This can drain 
the connection resources on a Microsoft NT server and cause it to run 
out of available connections. With <smbconfoption name="security">domain</smbconfoption>, 
however, the Samba daemons connect to the PDC/BDC only for as long 
as is necessary to authenticate the user and then drop the connection, 
thus conserving PDC connection resources.
</para>

<para>
And finally, acting in the same manner as an NT server 
authenticating to a PDC means that as part of the authentication 
reply, the Samba server gets the user identification information such 
as the user SID, the list of NT groups the user belongs to, and so on. 
</para>

<note>
<para>
Much of the text of this document was first published in the Web magazine 
<ulink url="http://www.linuxworld.com">LinuxWorld</ulink> as the article <ulink
url="http://www.linuxworld.com/linuxworld/lw-1998-10/lw-10-samba.html"/>
<emphasis>Doing the NIS/NT Samba</emphasis>.
</para>
</note>

</sect2>
</sect1>

<sect1 id="ads-member">
<title>Samba ADS Domain Membership</title>

<para>
<indexterm significance="preferred"><primary>Active Directory</primary></indexterm>
<indexterm significance="preferred"><primary>ADS</primary><see>Active Directory</see></indexterm>
<indexterm><primary>KDC</primary></indexterm>
<indexterm><primary>Kerberos</primary></indexterm>
This is a rough guide to setting up Samba-3 with Kerberos authentication against a
Windows 200x KDC. A familiarity with Kerberos is assumed.
</para> 

<sect2>
<title>Configure &smb.conf;</title>

<para>
You must use at least the following three options in &smb.conf;:
</para>

<para><smbconfblock>
<smbconfoption name="realm">your.kerberos.REALM</smbconfoption>
<smbconfoption name="security">ADS</smbconfoption>
<smbconfcomment>The following parameter need only be specified if present.</smbconfcomment>
<smbconfcomment>The default setting is not present is Yes.</smbconfcomment>
<smbconfoption name="encrypt passwords">yes</smbconfoption>
</smbconfblock></para>

<para>
In case samba cannot correctly identify the appropriate ADS server using the realm name, use the 
<smbconfoption name="password server"/> option in &smb.conf;:
<smbconfblock>
<smbconfoption name="password server">your.kerberos.server</smbconfoption>
</smbconfblock>
</para>

<note><para>
You do <emphasis>not</emphasis> need a smbpasswd file, and older clients will be authenticated as 
if <smbconfoption name="security">domain</smbconfoption>, although it will not do any harm and 
allows you to have local users not in the domain.
</para></note>

</sect2>
  
<sect2>
<title>Configure <filename>/etc/krb5.conf</filename></title>

<para>
<indexterm><primary>/etc/krb5.conf</primary></indexterm>
<indexterm><primary>Kerberos</primary><secondary>/etc/krb5.conf</secondary></indexterm>
With both MIT and Heimdal Kerberos, it is unnecessary to configure the 
<filename>/etc/krb5.conf</filename>, and it may be detrimental.
</para>

<para>
Microsoft Active Directory servers automatically create SRV records in the DNS zone 
<parameter>_kerberos.REALM.NAME</parameter> for each KDC in the realm. This is part
of the installation and configuration process used to create an Active Directory Domain.
</para>

<para>
MIT's, as well as Heimdal's, recent KRB5 libraries default to checking for SRV records, so they will 
automatically find the KDCs. In addition, <filename>krb5.conf</filename> only allows specifying 
a single KDC, even there if there may be more than one. Using the DNS lookup allows the KRB5 
libraries to use whichever KDCs are available.
</para>

<para>
When manually configuring <filename>krb5.conf</filename>, the minimal configuration is:
</para>

<para>
        <smbfile name="krb5.conf">
        <programlisting>
[libdefaults]
        default_realm = YOUR.KERBEROS.REALM

[realms]
        YOUR.KERBEROS.REALM = {
        kdc = your.kerberos.server
        }

[domain_realms]
        .kerberos.server = YOUR.KERBEROS.REALM
</programlisting></smbfile></para>

<para>
When using Heimdal versions before 0.6 use the following configuration settings:
<screen>
[libdefaults]
        default_realm      = YOUR.KERBEROS.REALM
        default_etypes     = des-cbc-crc des-cbc-md5
        default_etypes_des = des-cbc-crc des-cbc-md5

[realms]
        YOUR.KERBEROS.REALM = {
        kdc = your.kerberos.server
        }

[domain_realms]
        .kerberos.server = YOUR.KERBEROS.REALM
</screen>
</para>

<para>
<indexterm><primary>kinit</primary></indexterm>
Test your config by doing a <userinput>kinit
<replaceable>USERNAME</replaceable>@<replaceable>REALM</replaceable></userinput> and
making sure that your password is accepted by the Win2000 KDC.
</para>

<para>
With Heimdal versions earlier than 0.6.x you only can use newly created accounts
in ADS or accounts that have had the password changed once after migration, or
in case of <constant>Administrator</constant> after installation. At the
moment, a Windows 2003 KDC can only be used with a Heimdal releases later than 0.6
(and no default etypes in krb5.conf). Unfortunately this whole area is still
in a state of flux.
</para>

<note><para>
The realm must be in uppercase or you will get <quote><errorname>Cannot find KDC for
requested realm while getting initial credentials</errorname></quote> error (Kerberos
is case-sensitive!).
</para></note>

<note><para>
Time between the two servers must be synchronized. You will get a
<quote><errorname>kinit(v5): Clock skew too great while getting initial credentials</errorname></quote>
if the time difference is more than five minutes. 
</para></note>

<para>
Clock skew limits are configurable in the Kerberos protocols. The default setting is
five minutes.
</para>

<para>
You also must ensure that you can do a reverse DNS lookup on the IP
address of your KDC. Also, the name that this reverse lookup maps to
must either be the NetBIOS name of the KDC (i.e., the hostname with no
domain attached) or it can alternately be the NetBIOS name followed by the realm. 
</para>

<para>
The easiest way to ensure you get this right is to add a 
<filename>/etc/hosts</filename> entry mapping the IP address of your KDC to 
its NetBIOS name. If you do not get this correct then you will get a 
<errorname>local error</errorname> when you try to join the realm.
</para>

<para>
If all you want is Kerberos support in &smbclient; then you can skip
directly to <link linkend="ads-test-smbclient">Testing with &smbclient;</link> now. 
<link linkend="ads-create-machine-account">Create the Computer Account</link> and 
<link linkend="ads-test-server">Testing Server Setup</link>
are needed only if you want Kerberos support for &smbd; and &winbindd;.
</para>

</sect2>

<sect2 id="ads-create-machine-account">
<title>Create the Computer Account</title>

<para>
As a user who has write permission on the Samba private directory (usually root), run:
<screen>
&rootprompt; <userinput>net ads join -U Administrator%password</userinput>
</screen>
</para>

<para>
When making a Windows client a member of an ADS domain within a complex organization, you
may want to create the machine account within a particular organizational unit. Samba-3 permits
this to be done using the following syntax:
<screen>
&rootprompt; <userinput>kinit Administrator@your.kerberos.REALM</userinput>
&rootprompt; <userinput>net ads join "organizational_unit"</userinput>
</screen>
</para>

<para>
For example, you may want to create the machine account in a container called <quote>Servers</quote>
under the organizational directory <quote>Computers\BusinessUnit\Department</quote> like this:
<screen>
&rootprompt; <userinput>net ads join "Computers\BusinessUnit\Department\Servers"</userinput>
</screen>
</para>

<?latex \newpage ?>

<sect3>
<title>Possible Errors</title>

<para>
<variablelist>
        <varlistentry><term><errorname>ADS support not compiled in</errorname></term>
        <listitem><para>Samba must be reconfigured (remove config.cache) and recompiled
        (make clean all install) after the Kerberos libraries and headers files are installed.
        </para></listitem></varlistentry>

        <varlistentry><term><errorname>net ads join prompts for user name</errorname></term>
        <listitem><para>You need to login to the domain using <userinput>kinit
        <replaceable>USERNAME</replaceable>@<replaceable>REALM</replaceable></userinput>.
        <replaceable>USERNAME</replaceable> must be a user who has rights to add a machine
        to the domain. </para></listitem></varlistentry>

        <varlistentry><term>Unsupported encryption/or checksum types</term>
        <listitem><para>
        Make sure that the <filename>/etc/krb5.conf</filename> is correctly configured
        for the type and version of Kerberos installed on the system.
        </para></listitem></varlistentry>
</variablelist>
</para>

</sect3>

</sect2>

<sect2 id="ads-test-server">
<title>Testing Server Setup</title>

<para>
If the join was successful, you will see a new computer account with the
NetBIOS name of your Samba server in Active Directory (in the <quote>Computers</quote>
folder under Users and Computers.
</para>

<para>
On a Windows 2000 client, try <userinput>net use * \\server\share</userinput>. You should
be logged in with Kerberos without needing to know a password. If this fails then run
<userinput>klist tickets</userinput>. Did you get a ticket for the server? Does it have
an encryption type of DES-CBC-MD5? 
</para>

<note><para>
Samba can use both DES-CBC-MD5 encryption as well as ARCFOUR-HMAC-MD5 encoding.
</para></note>

</sect2>

<sect2 id="ads-test-smbclient">
<title>Testing with &smbclient;</title>


<para>
<indexterm><primary>smbclient</primary></indexterm>
On your Samba server try to login to a Win2000 server or your Samba
server using &smbclient; and Kerberos. Use &smbclient; as usual, but
specify the <option>-k</option> option to choose Kerberos authentication.
</para>

</sect2>

<sect2>
<title>Notes</title>

<para>
You must change administrator password at least once after DC 
install, to create the right encryption types.
</para>

<para>
Windows 200x does not seem to create the <parameter>_kerberos._udp</parameter> and <parameter>_ldap._tcp</parameter> in
the default DNS setup. Perhaps this will be fixed later in service packs.
</para>

</sect2>
</sect1>

<sect1>
<title>Sharing User ID Mappings between Samba Domain Members</title>

<para>
Samba maps UNIX users and groups (identified by UIDs and GIDs) to Windows users and groups (identified by SIDs).
These mappings are done by the <parameter>idmap</parameter> subsystem of Samba.
</para>

<para>
In some cases it is useful to share these mappings between Samba Domain Members,
so <emphasis>name->id</emphasis> mapping is identical on all machines.
This may be needed in particular when sharing files over both CIFS and NFS.
</para>

<para>To use the <emphasis>LDAP</emphasis> <parameter>ldap idmap suffix</parameter>, set:</para>

<smbconfblock>
<smbconfoption name="ldap idmap suffix">ou=Idmap,dc=quenya,dc=org</smbconfoption>
</smbconfblock>

<para>See the &smb.conf; man page entry for the <smbconfoption name="ldap idmap suffix"></smbconfoption>
parameter for further information.</para>

<para>
Do not forget to specify also the <smbconfoption name="ldap admin dn"/>
and to make certain to set the LDAP administrative password into the <filename>secrets.tdb</filename> using:
<screen>
&rootprompt; smbpasswd -w ldap-admin-password
</screen></para>

</sect1>

<sect1>
<title>Common Errors</title>

<para>
In the process of adding/deleting/re-adding Domain Member machine accounts, there are
many traps for the unwary player and many <quote>little</quote> things that can go wrong.
It is particularly interesting how often subscribers on the Samba mailing list have concluded
after repeated failed attempts to add a machine account that it is necessary to <quote>re-install</quote>
MS Windows on the machine. In truth, it is seldom necessary to reinstall because of this type
of problem. The real solution is often quite simple and with an understanding of how MS Windows
networking functions, it is easy to overcome.
</para>

<sect2>
<title>Cannot Add Machine Back to Domain</title>

<para>
<quote>A Windows workstation was re-installed. The original domain machine
account was deleted and added immediately. The workstation will not join the domain if I use 
the same machine name. Attempts to add the machine fail with a message that the machine already
exists on the network &smbmdash; I know it does not. Why is this failing?</quote>
</para>

<para>
The original name is still in the NetBIOS name cache and must expire after machine account
deletion before adding that same name as a Domain Member again. The best advice is to delete
the old account and then add the machine with a new name.
</para>

</sect2>

<sect2>
<title>Adding Machine to Domain Fails</title>

<para>
<quote>Adding a Windows 200x or XP Professional machine to the Samba PDC Domain fails with a
message that, <errorname>`The machine could not be added at this time, there is a network problem.
Please try again later.'</errorname> Why?</quote>
</para>

<para>
You should check that there is an <smbconfoption name="add machine script"/> in your &smb.conf;
file. If there is not, please add one that is appropriate for your OS platform. If a script
has been defined, you will need to debug its operation. Increase the <smbconfoption name="log level"></smbconfoption>
in the &smb.conf; file to level 10, then try to rejoin the domain. Check the logs to see which
operation is failing.
</para>

<para>
Possible causes include:
</para>

<itemizedlist>
        <listitem><para>
        The script does not actually exist, or could not be located in the path specified.
        </para>

        <para>
        <emphasis>Corrective action:</emphasis> Fix it. Make sure when run manually
        that the script will add both the UNIX system account and the Samba SAM account.
        </para></listitem>

        <listitem><para>
        The machine could not be added to the UNIX system accounts file <filename>/etc/passwd</filename>.
        </para>

        <para>
        <emphasis>Corrective action:</emphasis> Check that the machine name is a legal UNIX
        system account name. If the UNIX utility <command>useradd</command> is called,
        then make sure that the machine name you are trying to add can be added using this
        tool. <command>Useradd</command> on some systems will not allow any upper case characters
        nor will it allow spaces in the name.
        </para></listitem>
</itemizedlist>

<para>
The <smbconfoption name="add machine script"/> does not create the
machine account in the Samba backend database, it is there only to create a UNIX system
account to which the Samba backend database account can be mapped.
</para>

</sect2>

<sect2>
        <title>I Can't Join a Windows 2003 PDC</title>

        <para>Windows 2003 requires SMB signing. Client side SMB signing has been implemented in Samba-3.0.
        Set <smbconfoption name="client use spnego">yes</smbconfoption> when communicating 
        with a Windows 2003 server.</para>
</sect2>

</sect1>
</chapter>