Chapter 5. Domain Control

The Essence of Learning: There are many who approach MS Windows networking with incredible misconceptions. That's OK, because it gives the rest of us plenty of opportunity to be of assistance. Those who really want help would be well advised to become familiar with information @@ -16,7 +15,7 @@ of persistent niggles that may be caused by broken network or system configurati To a great many people however, MS Windows networking starts with a domain controller that in some magical way is expected to solve all ills.

-From the Samba mailing list one can readilly identify many common networking issues. +From the Samba mailing list one can readily identify many common networking issues. If you are not clear on the following subjects, then it will do much good to read the sections of this HOWTO that deal with it. These are the most common causes of MS Windows networking problems: @@ -33,7 +32,7 @@ burden on an organisation. Where is the right place to make mistakes? Only out of harm's way! If you are going to make mistakes, then please do this on a test network, away from users and in such a way as to not inflict pain on others. Do your learning on a test network. -

Features and Benefits

What is the key benefit of Microsoft Domain security?

In a word, Single Sign On, or SSO for short. To many, this is the holy @@ -96,7 +95,7 @@ Samba-3, like an MS Windows NT4 PDC or a Windows 200x Active Directory, needs to user and machine trust account information in a suitable backend data store. With Samba-3 there can be multiple back-ends for this including:

- smbpasswd - the plain ascii file stored used by + smbpasswd - 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 private @@ -105,7 +104,7 @@ there can be multiple back-ends for this including: tdbsam - a binary database backend that will be stored in the private directory in a file called passdb.tdb. The key benefit of this binary format - file is that it can store binary objects that can not be accomodated + file is that it can store binary objects that can not be accommodated in the traditional plain text smbpasswd file. These permit the extended account controls that MS Windows NT4 and later also have.
@@ -131,11 +130,11 @@ per user settings for many parameters, over-riding global settings given in the Thus, with samba-3 it is possible to have a default system configuration for profiles, and on a per user basis to over-ride this for those users who should not be subject to the default configuration. -

Basics of Domain Control

Over the years, public perceptions of what Domain Control really is has taken on an almost mystical nature. Before we branch into a brief overview of Domain Control, there are three basic types of domain controllers: -

Domain Controller Types

Primary Domain Controller
Backup Domain Controller
ADS Domain Controller

Domain Controller Types

Primary Domain Controller
Backup Domain Controller
ADS Domain Controller

The Primary Domain Controller or PDC plays an important role in the MS Windows NT4 and Windows 200x Domain Control architecture, but not in the manner that so many expect. There is folk lore that dictates that because of it's role in the MS Windows @@ -150,7 +149,7 @@ part in NT4 type domain user authentication and in synchronisation of the domain database with Backup Domain Controllers.

With MS Windows 200x Server based Active Directory domains, one domain controller seeds a potential -hierachy of domain controllers, each with their own area of delegated control. The master domain +hierarchy of domain controllers, each with their own area of delegated control. The master domain controller has the ability to override any down-stream controller, but a down-line controller has control only over it's down-line. With Samba-3 this functionality can be implemented using an LDAP based user and machine account back end. @@ -167,10 +166,10 @@ On a network segment that has a BDC and a PDC the BDC will be most likely to ser logon requests. The PDC will answer network logon requests when the BDC is too busy (high load). A BDC can be promoted to a PDC. If the PDC is on line at the time that a BDC is promoted to PDC, the previous PDC is automatically demoted to a BDC. With Samba-3 this is NOT an automatic -operation; the PDB and BDC must be manually configured and changes need to be made likewise. +operation; the PDC and BDC must be manually configured and changes need to be made likewise.

With MS Windows NT4, it is an install time decision what type of machine the server will be. -It is possible to change the promote a BDC to a PDC and vica versa only, but the only way +It is possible to change the promote a BDC to a PDC and vice versa only, but the only way to convert a domain controller to a domain member server or a stand-alone server is to reinstall it. The install time choices offered are:

Primary Domain Controller - The one that seeds the domain SAM
Backup Domain Controller - One that obtains a copy of the domain SAM
Domain Member Server - One that has NO copy of the domain SAM, rather it obtains authentication from a Domain Controller for all access controls.
Stand-Alone Server - One that plays NO part is SAM synchronisation, has it's own authentication database and plays no role in Domain security.

@@ -187,7 +186,7 @@ At this time any appearance that Samba-3 is capable of acting as an This functionality should not be used until the Samba-Team offers formal support for it. At such a time, the documentation will be revised to duly reflect all configuration and management requirements. -

Preparing for Domain Control

There are two ways that MS Windows machines may interact with each other, with other servers, and with Domain Controllers: Either as Stand-Alone systems, more commonly called Workgroup members, or as full participants in a security system, @@ -219,7 +218,7 @@ NT4 / 200x / XP clients. MS Windows network Integration)Domain logons for Windows NT4 / 200x / XP Professional clientsConfiguration of Roaming Profiles or explicit configuration to force local profile usageConfiguration of Network/System PoliciesAdding and managing domain user accountsConfiguring MS Windows client machines to become domain members

The following provisions are required to serve MS Windows 9x / Me Clients:

Configuration of basic TCP/IP and MS Windows Networking

Correct designation of the Server Role (security = user)

Network Logon Configuration (Since Windows 9x / XP Home are not technically domain - members, they do not really particpate in the security aspects of Domain logons as such)

Roaming Profile Configuration

Configuration of System Policy handling

Installation of the Network driver "Client for MS Windows Networks" and configuration + members, they do not really participate in the security aspects of Domain logons as such)

Roaming Profile Configuration

Configuration of System Policy handling

Installation of the Network driver "Client for MS Windows Networks" and configuration to log onto the domain

Placing Windows 9x / Me clients in user level security - if it is desired to allow all client share access to be controlled according to domain user / group identities.

Adding and managing domain user accounts

Note

Roaming Profiles and System/Network policies are advanced network administration topics @@ -248,7 +247,7 @@ domain/workgroup. Local master browsers in the same domain/workgroup on broadcas then ask for a complete copy of the browse list for the whole wide area network. Browser clients will then contact their local master browser, and will receive the domain-wide browse list, instead of just the list for their broadcast-isolated subnet. -

Domain Control - Example Configuration

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. @@ -302,20 +301,20 @@ Here is an example smb.conf for acting as a PDC: read only = no create mask = 0600 directory mask = 0700 -

Note

The above parameters make for a full set of parameters that may define the server's mode of operation. The following parameters are the essentials alone: -

+
 	workgroup = NARNIA
 	domain logons = Yes
 	domain master = Yes
 	security = User
-

+

The additional parameters shown in the longer listing above just makes for a more complete environment. -

There are a couple of points to emphasize in the above configuration.

Encrypted passwords must be enabled. For more details on how @@ -328,23 +327,23 @@ There are a couple of points to emphasize in the above configuration. client to locate the server as a DC. Please refer to the various Network Browsing documentation included with this distribution for details. -

Samba ADS Domain Control

Samba-3 is not and can not act as an Active Directory Server. It can not truly function as an Active Directory Primary Domain Controller. The protocols for some of the functionality the Active Directory Domain Controllers is have been partially implemented on an experimental only basis. Please do NOT expect Samba-3 to support these protocols - nor should you depend on any such functionality either now or in the future. The Samba-Team may well remove such -experiemental features or may change their behaviour. -

Domain and Network Logon Configuration

+experimental features or may change their behaviour. +

Domain and Network Logon Configuration

The subject of Network or Domain Logons is discussed here because it rightly forms an integral part of the essential functionality that is provided by a Domain Controller. -

Domain Network Logon Service

All Domain Controllers must run the netlogon service (domain logons in Samba). One Domain Controller must be configured with domain master = Yes (the Primary Domain Controller); on ALL Backup Domain Controllers domain master = No must be set. -

Example Configuration

-	[globals]
+
Example Configuration
+	[global]
 		domain logons = Yes
 		domain master = (Yes on PDC, No on BDCs)
 
@@ -353,7 +352,7 @@ must be set.
 		path = /var/lib/samba/netlogon
 		guest ok = Yes
 		browseable = No
-
The Special Case of MS Windows XP Home Edition
Note

+

The Special Case of MS Windows XP Home Edition

Note

MS Windows XP Home Edition does not have the ability to join any type of Domain security facility. Unlike, MS Windows 9x / Me, MS Windows XP Home Edition also completely lacks the ability to log onto a network. @@ -365,7 +364,7 @@ MS Windows XP Professional.

Now that this has been said, please do NOT ask the mailing list, or email any of the Samba-Team members with your questions asking how to make this work. It can't be done. -

The Special Case of Windows 9x / Me

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 @@ -445,7 +444,7 @@ The main difference between a PDC and a Windows 9x logon server configuration is

A Samba PDC will act as a Windows 9x logon server; after all, it does provide the network logon services that MS Windows 9x / Me expect to find. -

Security Mode and Master Browsers

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 @@ -479,7 +478,7 @@ 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 and set security = user. This is the only officially supported mode of operation. -

Common Problems and Errors

I cannot include a '$' in a machine name

Common Problems and Errors

I cannot include a '$' in a machine name

A 'machine account', (typically) stored in /etc/passwd, takes the form of the machine name with a '$' appended. FreeBSD (and other BSD systems?) won't create a user with a '$' in their name. @@ -487,7 +486,7 @@ systems?) won't create a user with a '$' in their name. The problem is only in the program used to make the entry. Once made, it works perfectly. Create a user without the '$'. Then use vipw to edit the entry, adding the '$'. Or create the whole entry with vipw if you like; make sure you use a unique User ID! -

I get told "You already have a connection to the Domain...." +

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.

This happens if you try to create a machine trust account from the @@ -501,7 +500,7 @@ Further, if the machine is 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. -

The system can not log you on (C000019B)....

I joined the domain successfully but after upgrading +

The system can not log you on (C000019B)....

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. @@ -512,14 +511,14 @@ 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 net or rpcclient utilities. -

The reset or change the domain SID you can use the net command as follows: -

 root# net getlocalsid 'OLDNAME'
 root# net setlocalsid 'SID'
-

The machine trust account for this computer either does not +
+

The machine trust account for this computer either does not exist or is not accessible.

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 @@ -532,7 +531,7 @@ admin user system is working.

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. +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 @@ -542,10 +541,10 @@ Some people have also reported that inconsistent subnet masks between the Samba server and the NT client can cause this problem. Make sure that these are consistent for both client and server. -

When I attempt to login to a Samba Domain from a NT4/W2K workstation, +

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

Enable the user accounts with smbpasswd -e username, this is normally done as an account is created. -

Until a few minutes after Samba has started, clients get the error "Domain Controller Unavailable"

A domain controller has to announce on the network who it is. This usually takes a while.

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