1 <chapter id="domain-member">
8 <!-- Authors of the ADS-HOWTO -->
13 <title>Domain Membership</title>
16 Domain Membership is a subject of vital concern, Samba must be able to
17 participate as a member server in a Microsoft Domain security context, and
18 Samba must be capable of providing Domain machine member trust accounts,
19 otherwise it would not be capable of offering a viable option for many users.
23 This chapter covers background information pertaining to domain membership,
24 Samba configuration for it, and MS Windows client procedures for joining a
25 domain. Why is this necessary? Because both are areas in which there exists
26 within the current MS Windows networking world and particularly in the
27 Unix/Linux networking and administration world, a considerable level of
28 mis-information, incorrect understanding, and a lack of knowledge. Hopefully
29 this chapter will fill the voids.
33 <title>Features and Benefits</title>
36 MS Windows workstations and servers that want to participate in domain
38 be made Domain members. Participating in Domain security is often called
39 <emphasis>Single Sign On</emphasis> or <acronym>SSO</acronym> for short. This
40 chapter describes the process that must be followed to make a workstation
41 (or another server - be it an <application>MS Windows NT4 / 200x</application>
42 server) or a Samba server a member of an MS Windows Domain security context.
46 Samba-3 can join an MS Windows NT4 style domain as a native member server, an
47 MS Windows Active Directory Domain as a native member server, or a Samba Domain
52 Domain membership has many advantages:
57 MS Windows workstation users get the benefit of SSO
61 Domain user access rights and file ownership / access controls can be set
62 from the single Domain SAM (Security Account Manager) database
63 (works with Domain member servers as well as with MS Windows workstations
64 that are domain members)
68 Only <application>MS Windows NT4 / 200x / XP Professional</application>
69 workstations that are Domain members
70 can use network logon facilities
74 Domain Member workstations can be better controlled through the use of
75 Policy files (<filename>NTConfig.POL</filename>) and Desktop Profiles.
79 Through the use of logon scripts, users can be given transparent access to network
80 applications that run off application servers
84 Network administrators gain better application and user access management
85 abilities because there is no need to maintain user accounts on any network
86 client or server, other than the central Domain database
87 (either NT4/Samba SAM style Domain, NT4 Domain that is back ended with an
88 LDAP directory, or via an Active Directory infrastructure)
95 <title>MS Windows Workstation/Server Machine Trust Accounts</title>
98 A machine trust account is an account that is used to authenticate a client
100 (rather than a user) to the Domain Controller server. In Windows terminology,
101 this is known as a "Computer Account."
105 The password of a machine trust account acts as the shared secret for
106 secure communication with the Domain Controller. This is a security
107 feature to prevent an unauthorized machine with the same NetBIOS name
108 from joining the domain and gaining access to domain user/group
109 accounts. Windows NT, 200x, XP Professional clients use machine trust
110 accounts, but Windows 9x / Me / XP Home clients do not. Hence, a
111 Windows 9x / Me / XP Home client is never a true member of a domain
112 because it does not possess a machine trust account, and thus has no
113 shared secret with the domain controller.
117 A Windows NT4 PDC stores each machine trust account in the Windows Registry.
118 The introduction of MS Windows 2000 saw the introduction of Active Directory,
119 the new repository for machine trust accounts.
123 A Samba PDC, however, stores each machine trust account in two parts,
128 A Domain Security Account (stored in the
129 <parameter>passdb backend</parameter> that has been configured in the
130 &smb.conf; file. The precise nature of the account information that is
131 stored depends on the type of backend database that has been chosen.
135 The older format of this data is the <filename>smbpasswd</filename> database
136 which contains the unix login ID, the Unix user identifier (UID), and the
137 LanMan and NT encrypted passwords. There is also some other information in
138 this file that we do not need to concern ourselves with here.
142 The two newer database types are called <emphasis>ldapsam</emphasis>,
143 <emphasis>tdbsam</emphasis>. Both store considerably more data than the
144 older <filename>smbpasswd</filename> file did. The extra information
145 enables new user account controls to be used.
149 A corresponding Unix account, typically stored in
150 <filename>/etc/passwd</filename>. Work is in progress to allow a
151 simplified mode of operation that does not require Unix user accounts, but
152 this may not be a feature of the early releases of Samba-3.
158 There are three ways to create machine trust accounts:
163 Manual creation from the Unix/Linux command line. Here, both the Samba and
164 corresponding Unix account are created by hand.
168 Using the MS Windows NT4 Server Manager (either from an NT4 Domain member
169 server, or using the Nexus toolkit available from the Microsoft web site.
170 This tool can be run from any MS Windows machine so long as the user is
171 logged on as the administrator account.
175 "On-the-fly" creation. The Samba machine trust account is automatically
176 created by Samba at the time the client is joined to the domain.
177 (For security, this is the recommended method.) The corresponding Unix
178 account may be created automatically or manually.
183 <title>Manual Creation of Machine Trust Accounts</title>
186 The first step in manually creating a machine trust account is to manually
187 create the corresponding Unix account in <filename>/etc/passwd</filename>.
188 This can be done using <command>vipw</command> or another 'add user' command
189 that is normally used to create new Unix accounts. The following is an example for a Linux based Samba server:
193 &rootprompt;<userinput>/usr/sbin/useradd -g 100 -d /dev/null -c <replaceable>"machine nickname"</replaceable> -s /bin/false <replaceable>machine_name</replaceable>$ </userinput>
197 &rootprompt;<userinput>passwd -l <replaceable>machine_name</replaceable>$</userinput>
201 On *BSD systems, this can be done using the <command>chpass</command> utility:
205 &rootprompt;<userinput>chpass -a "<replaceable>machine_name</replaceable>$:*:101:100::0:0:Workstation <replaceable>machine_name</replaceable>:/dev/null:/sbin/nologin"</userinput>
209 The <filename>/etc/passwd</filename> entry will list the machine name
210 with a "$" appended, won't have a password, will have a null shell and no
211 home directory. For example a machine named 'doppy' would have an
212 <filename>/etc/passwd</filename> entry like this:
216 doppy$:x:505:501:<replaceable>machine_nickname</replaceable>:/dev/null:/bin/false
220 Above, <replaceable>machine_nickname</replaceable> can be any
221 descriptive name for the client, i.e., BasementComputer.
222 <replaceable>machine_name</replaceable> absolutely must be the NetBIOS
223 name of the client to be joined to the domain. The "$" must be
224 appended to the NetBIOS name of the client or Samba will not recognize
225 this as a machine trust account.
229 Now that the corresponding Unix account has been created, the next step is to create
230 the Samba account for the client containing the well-known initial
231 machine trust account password. This can be done using the <ulink
232 url="smbpasswd.8.html"><command>smbpasswd(8)</command></ulink> command
238 &rootprompt;<userinput>smbpasswd -a -m <replaceable>machine_name</replaceable></userinput>
243 where <replaceable>machine_name</replaceable> is the machine's NetBIOS
244 name. The RID of the new machine account is generated from the UID of
245 the corresponding Unix account.
249 <title>Join the client to the domain immediately</title>
252 Manually creating a machine trust account using this method is the
253 equivalent of creating a machine trust account on a Windows NT PDC using
254 the <application>Server Manager</application>. From the time at which the
255 account is created to the time which the client joins the domain and
256 changes the password, your domain is vulnerable to an intruder joining
257 your domain using a machine with the same NetBIOS name. A PDC inherently
258 trusts members of the domain and will serve out a large degree of user
259 information to such clients. You have been warned!
265 <title>Using NT4 Server Manager to Add Machine Accounts to the Domain</title>
268 If the machine from which you are trying to manage the domain is an
269 <application>MS Windows NT4 workstation</application>
270 then the tool of choice is the package called <command>SRVTOOLS.EXE</command>.
271 When executed in the target directory this will unpack
272 <command>SrvMge.exe</command> and <command>UsrMgr.exe</command> (both are
273 Domain Management tools for MS Windows NT4 workstation.
277 If your workstation is any other MS Windows product you should download the
278 <command>Nexus.exe</command> package from the Microsoft web site. When executed
279 from the target directory this will unpack the same tools but for use on
280 <application>MS Windows 9x/Me/200x/XP</application>.
284 Launch the <command>srvmgr.exe</command> (Server Manager for Domains) and follow these steps:
288 <title>Server Manager Account Machine Account Management</title>
290 From the menu select <guimenu>Computer</guimenu>
294 Click on <guimenuitem>Select Domain</guimenuitem>
298 Click on the name of the domain you wish to administer in the
299 <guilabel>Select Domain</guilabel> panel and then click
300 <guibutton>OK</guibutton>.
304 Again from the menu select <guimenu>Computer</guimenu>
308 Select <guimenuitem>Add to Domain</guimenuitem>
312 In the dialog box, click on the radio button to
313 <guilabel>Add NT Workstation of Server</guilabel>, then
314 enter the machine name in the field provided, then click the
315 <guibutton>Add</guibutton> button.
322 <title>"On-the-Fly" Creation of Machine Trust Accounts</title>
325 The second (and recommended) way of creating machine trust accounts is
326 simply to allow the Samba server to create them as needed when the client
327 is joined to the domain.
330 <para>Since each Samba machine trust account requires a corresponding Unix account, a method
331 for automatically creating the Unix account is usually supplied; this requires configuration of the
332 <ulink url="smb.conf.5.html#ADDMACHINESCRIPT">add machine script</ulink> option in
333 <filename>smb.conf</filename>. This method is not required, however; corresponding Unix
334 accounts may also be created manually.
339 Below is an example for a RedHat Linux system.
342 <para><programlisting>
344 # <...remainder of parameters...>
345 add machine script = /usr/sbin/useradd -d /dev/null -g 100 -s /bin/false -M %u
346 </programlisting></para>
352 <sect2><title>Making an MS Windows Workstation or Server a Domain Member</title>
355 The procedure for making an MS Windows workstation of server a member of the domain varies
356 with the version of Windows:
360 <title>Windows 200x XP Professional</title>
363 When the user elects to make the client a domain member, Windows 200x prompts for
364 an account and password that has privileges to create machine accounts in the domain.
365 A Samba administrative account (i.e., a Samba account that has root privileges on the
366 Samba server) must be entered here; the operation will fail if an ordinary user
371 Note: For security reasons the password for this administrative account should be set
372 to a password that is other than that used for the root user in the
373 <filename>/etc/passwd</filename>.
377 The name of the account that is used to create domain member machine accounts can be
378 anything the network administrator may choose. If it is other than <emphasis>root</emphasis>
379 then this is easily mapped to root using the file pointed to be the &smb.conf; parameter
380 <parameter>username map = /etc/samba/smbusers</parameter>.
384 The session key of the Samba administrative account acts as an
385 encryption key for setting the password of the machine trust
386 account. The machine trust account will be created on-the-fly, or
387 updated if it already exists.
392 <title>Windows NT4</title>
395 If the machine trust account was created manually, on the
396 Identification Changes menu enter the domain name, but do not
397 check the box <guilabel>Create a Computer Account in the Domain</guilabel>.
398 In this case, the existing machine trust account is used to join the machine
403 If the machine trust account is to be created
404 on-the-fly, on the Identification Changes menu enter the domain
405 name, and check the box <guilabel>Create a Computer Account in the
406 Domain</guilabel>. In this case, joining the domain proceeds as above
407 for Windows 2000 (i.e., you must supply a Samba administrative account when
415 <para>Joining a Samba client to a domain is documented in
416 the <link linkend="domain-member-server">Domain Member Server</link> section of this chapter chapter.
423 <sect1 id="domain-member-server">
424 <title>Domain Member Server</title>
427 This mode of server operation involves the Samba machine being made a member
428 of a domain security context. This means by definition that all user
429 authentication will be done from a centrally defined authentication regime.
430 The authentication regime may come from an NT3/4 style (old domain technology)
431 server, or it may be provided from an Active Directory server (ADS) running on
432 MS Windows 2000 or later.
437 Of course it should be clear that the authentication back end itself could be
438 from any distributed directory architecture server that is supported by Samba.
439 This can be LDAP (from OpenLDAP), or Sun's iPlanet, of NetWare Directory
445 Please refer to the <link linkend="samba-pdc">Domain Control chapter</link>
446 for more information regarding how to create a domain
447 machine account for a domain member server as well as for information
448 regarding how to enable the Samba domain member machine to join the domain and
449 to be fully trusted by it.
453 <title>Joining an NT4 type Domain with Samba-3</title>
456 <table frame="all"><title>Assumptions</title>
457 <tgroup align="left" cols="2">
459 <row><entry>NetBIOS name:</entry><entry>SERV1</entry></row>
460 <row><entry>Win2K/NT domain name:</entry><entry>DOM</entry></row>
461 <row><entry>Domain's PDC NetBIOS name:</entry><entry>DOMPDC</entry></row>
462 <row><entry>Domain's BDC NetBIOS names:</entry><entry>DOMBDC1 and DOMBDC2</entry></row>
469 First, you must edit your &smb.conf; file to tell Samba it should
470 now use domain security.
474 Change (or add) your <ulink url="smb.conf.5.html#SECURITY">
475 <parameter>security</parameter></ulink> line in the [global] section
476 of your &smb.conf; to read:
486 Next change the <ulink url="smb.conf.5.html#WORKGROUP"><parameter>
487 workgroup</parameter></ulink> line in the <parameter>[global]</parameter>
498 as this is the name of the domain we are joining.
502 You must also have the parameter <ulink url="smb.conf.5.html#ENCRYPTPASSWORDS">
503 <parameter>encrypt passwords</parameter></ulink> set to <constant>yes
504 </constant> in order for your users to authenticate to the NT PDC.
508 Finally, add (or modify) a <ulink url="smb.conf.5.html#PASSWORDSERVER">
509 <parameter>password server</parameter></ulink> line in the [global]
515 password server = DOMPDC DOMBDC1 DOMBDC2
520 These are the primary and backup domain controllers Samba
521 will attempt to contact in order to authenticate users. Samba will
522 try to contact each of these servers in order, so you may want to
523 rearrange this list in order to spread out the authentication load
524 among domain controllers.
528 Alternatively, if you want smbd to automatically determine
529 the list of Domain controllers to use for authentication, you may
540 This method allows Samba to use exactly the same mechanism that NT does. This
541 method either broadcasts or uses a WINS database in order to
542 find domain controllers to authenticate against.
546 In order to actually join the domain, you must run this command:
551 <prompt>root# </prompt><userinput>net join -S DOMPDC -U<replaceable>Administrator%password</replaceable></userinput>
556 If the <option>-S DOMPDC</option> argument is not given then
557 the domain name will be obtained from &smb.conf;.
561 As we are joining the domain DOM and the PDC for that domain
562 (the only machine that has write access to the domain SAM database)
563 is DOMPDC, we use it for the <option>-S</option> option.
564 The <replaceable>Administrator%password</replaceable> is
565 the login name and password for an account which has the necessary
566 privilege to add machines to the domain. If this is successful
567 you will see the message:
571 <computeroutput>Joined domain DOM.</computeroutput>
572 or <computeroutput>Joined 'SERV1' to realm 'MYREALM'</computeroutput>
576 in your terminal window. See the <ulink url="net.8.html">
577 net(8)</ulink> man page for more details.
581 This process joins the server to the domain without having to create the machine
582 trust account on the PDC beforehand.
586 This command goes through the machine account password
587 change protocol, then writes the new (random) machine account
588 password for this Samba server into a file in the same directory
589 in which an smbpasswd file would be stored - normally:
593 <filename>/usr/local/samba/private/secrets.tdb</filename>
597 This file is created and owned by root and is not
598 readable by any other user. It is the key to the domain-level
599 security for your system, and should be treated as carefully
600 as a shadow password file.
604 Finally, restart your Samba daemons and get ready for
605 clients to begin using domain security!
611 <title>Why is this better than security = server?</title>
614 Currently, domain security in Samba doesn't free you from
615 having to create local Unix users to represent the users attaching
616 to your server. This means that if domain user <constant>DOM\fred
617 </constant> attaches to your domain security Samba server, there needs
618 to be a local Unix user fred to represent that user in the Unix
619 filesystem. This is very similar to the older Samba security mode
620 <ulink url="smb.conf.5.html#SECURITYEQUALSSERVER">security = server</ulink>,
621 where Samba would pass through the authentication request to a Windows
622 NT server in the same way as a Windows 95 or Windows 98 server would.
626 Please refer to the <link linkend="winbind">Winbind</link> chapter
627 for information on a system to automatically
628 assign UNIX uids and gids to Windows NT Domain users and groups.
632 The advantage to domain-level security is that the
633 authentication in domain-level security is passed down the authenticated
634 RPC channel in exactly the same way that an NT server would do it. This
635 means Samba servers now participate in domain trust relationships in
636 exactly the same way NT servers do (i.e., you can add Samba servers into
637 a resource domain and have the authentication passed on from a resource
638 domain PDC to an account domain PDC).
642 In addition, with <parameter>security = server</parameter> every Samba
643 daemon on a server has to keep a connection open to the
644 authenticating server for as long as that daemon lasts. This can drain
645 the connection resources on a Microsoft NT server and cause it to run
646 out of available connections. With <parameter>security = domain</parameter>,
647 however, the Samba daemons connect to the PDC/BDC only for as long
648 as is necessary to authenticate the user, and then drop the connection,
649 thus conserving PDC connection resources.
653 And finally, acting in the same manner as an NT server
654 authenticating to a PDC means that as part of the authentication
655 reply, the Samba server gets the user identification information such
656 as the user SID, the list of NT groups the user belongs to, etc.
661 Much of the text of this document
662 was first published in the Web magazine
663 <ulink url="http://www.linuxworld.com">LinuxWorld</ulink> as the article <ulink
664 url="http://www.linuxworld.com/linuxworld/lw-1998-10/lw-10-samba.html">Doing
665 the NIS/NT Samba</ulink>.
672 <sect1 id="ads-member">
673 <title>Samba ADS Domain Membership</title>
676 This is a rough guide to setting up Samba 3.0 with Kerberos authentication against a
677 Windows2000 KDC. A familiarity with Kerberos is assumed.
681 <title>Setup your <filename>smb.conf</filename></title>
684 You must use at least the following 3 options in &smb.conf;:
687 <para><programlisting>
688 realm = your.kerberos.REALM
690 encrypt passwords = yes
691 </programlisting></para>
694 In case samba can't figure out your ads server using your realm name, use the
695 <parameter>ads server</parameter> option in <filename>smb.conf</filename>:
697 ads server = your.kerberos.server
702 You do <emphasis>not</emphasis> need a smbpasswd file, and older clients will be authenticated as
703 if <parameter>security = domain</parameter>, although it won't do any harm and
704 allows you to have local users not in the domain. It is expected that the above
705 required options will change soon when active directory integration will get
712 <title>Setup your <filename>/etc/krb5.conf</filename></title>
715 The minimal configuration for <filename>krb5.conf</filename> is:
718 <para><programlisting>
720 default_realm = YOUR.KERBEROS.REALM
723 YOUR.KERBEROS.REALM = {
724 kdc = your.kerberos.server
726 </programlisting></para>
729 Test your config by doing a <userinput>kinit
730 <replaceable>USERNAME</replaceable>@<replaceable>REALM</replaceable></userinput> and
731 making sure that your password is accepted by the Win2000 KDC.
735 The realm must be uppercase or you will get <errorname>Cannot find KDC for
736 requested realm while getting initial credentials</errorname> error.
740 Time between the two servers must be synchronized. You will get a
741 <errorname>kinit(v5): Clock skew too great while getting initial credentials</errorname>
742 if the time difference is more than five minutes.
746 You also must ensure that you can do a reverse DNS lookup on the IP
747 address of your KDC. Also, the name that this reverse lookup maps to
748 must either be the NetBIOS name of the KDC (ie. the hostname with no
749 domain attached) or it can alternatively be the NetBIOS name
750 followed by the realm.
754 The easiest way to ensure you get this right is to add a
755 <filename>/etc/hosts</filename> entry mapping the IP address of your KDC to
756 its NetBIOS name. If you don't get this right then you will get a
757 <errorname>local error</errorname> when you try to join the realm.
761 If all you want is Kerberos support in &smbclient; then you can skip
762 straight to <link linkend="ads-test-smbclient">Test with &smbclient;</link> now.
763 <link linkend="ads-create-machine-account">Creating a computer account</link>
764 and <link linkend="ads-test-server">testing your servers</link>
765 is only needed if you want Kerberos support for &smbd; and &winbindd;.
770 <sect2 id="ads-create-machine-account">
771 <title>Create the computer account</title>
774 As a user that has write permission on the Samba private directory
777 &rootprompt;<userinput>net join -U Administrator%password</userinput>
782 <title>Possible errors</title>
786 <varlistentry><term><errorname>ADS support not compiled in</errorname></term>
787 <listitem><para>Samba must be reconfigured (remove config.cache) and recompiled
788 (make clean all install) after the Kerberos libs and headers are installed.
789 </para></listitem></varlistentry>
791 <varlistentry><term><errorname>net join prompts for user name</errorname></term>
792 <listitem><para>You need to login to the domain using <userinput>kinit
793 <replaceable>USERNAME</replaceable>@<replaceable>REALM</replaceable></userinput>.
794 <replaceable>USERNAME</replaceable> must be a user who has rights to add a machine
795 to the domain. </para></listitem></varlistentry>
803 <sect2 id="ads-test-server">
804 <title>Test your server setup</title>
807 If the join was successful, you will see a new computer account with the
808 NetBIOS name of your Samba server in Active Directory (in the "Computers"
809 folder under Users and Computers.
813 On a Windows 2000 client try <userinput>net use * \\server\share</userinput>. You should
814 be logged in with Kerberos without needing to know a password. If
815 this fails then run <userinput>klist tickets</userinput>. Did you get a ticket for the
816 server? Does it have an encoding type of DES-CBC-MD5 ?
821 <sect2 id="ads-test-smbclient">
822 <title>Testing with &smbclient;</title>
825 On your Samba server try to login to a Win2000 server or your Samba
826 server using &smbclient; and Kerberos. Use &smbclient; as usual, but
827 specify the <parameter>-k</parameter> option to choose Kerberos authentication.
836 You must change administrator password at least once after DC
837 install, to create the right encoding types
841 W2k doesn't seem to create the _kerberos._udp and _ldap._tcp in
842 their defaults DNS setup. Maybe fixed in service packs?
849 <title>Common Errors</title>
852 In the process of adding / deleting / re-adding domain member machine accounts there are
853 many traps for the unwary player and there are many <quote>little</quote> things that can go wrong.
854 It is particularly interesting how often subscribers on the samba mailing list have concluded
855 after repeated failed attempts to add a machine account that it is necessary to "re-install"
856 MS Windows on t he machine. In truth, it is seldom necessary to reinstall because of this type
857 of problem. The real solution is often very simple, and with understanding of how MS Windows
858 networking functions. easily overcome.
862 <title>Can Not Add Machine Back to Domain</title>
865 <emphasis>Problem:</emphasis> A Windows workstation was reinstalled. The original domain machine
866 account was deleted and added immediately. The workstation will not join the domain if I use
867 the same machine name. Attempts to add the machine fail with a message that the machine already
868 exists on the network - I know it doesn't. Why is this failing?
872 The original name is still in the NetBIOS name cache and must expire after machine account
873 deletion BEFORE adding that same name as a domain member again. The best advice is to delete
874 the old account and then to add the machine with a new name.
880 <title>Adding Machine to Domain Fails</title>
883 Adding a Windows 200x or XP Professional machine to the Samba PDC Domain fails with a
884 message that, <errorname>The machine could not be added at this time, there is a network problem.
885 Please try again later.</errorname> Why?
889 You should check that there is an <parameter>add machine script</parameter> in your &smb.conf;
890 file. If there is not, please add one that is appropriate for your OS platform. If a script
891 has been defined you will need to debug it's operation. Increase the <parameter>log level</parameter>
892 in the &smb.conf; file to level 10, then try to rejoin the domain. Check the logs to see which
893 operation is failing.
897 Possible causes include:
902 The script does not actually exist, or could not be located in the path specified.
906 <emphasis>Corrective Action:</emphasis> Fix it. Make sure that when run manually
907 that the script will add both the Unix system account _and_ the Samba SAM account.
911 The machine could not be added to the Unix system accounts file <filename>/etc/passwd</filename>
915 <emphasis>Corrective Action:</emphasis> Check that the machine name is a legal Unix
916 system account name. ie: If the Unix utility <command>useradd</command> is called
917 then make sure that the machine name you are trying to add can be added using this
918 tool. <command>Useradd</command> on some systems will not allow any upper case characters
919 nor will it allow spaces in the name.