Using Samba, Second Edition

Chapter 4. Windows NT Domains

In previous chapters, we’ve focused on workgroup networking to keep things simple and introduce you to networking with Samba in the most painless manner we could find. However, workgroup computing has its drawbacks, and for many computing environments, the greater security and single logon of the Windows NT domain make it worthwhile to spend the extra effort to implement a domain.

In addition to the domain features of that we discussed in Chapter 1, having a domain makes it possible to use logon scripts and roaming profiles (also called roving profiles ). A logon script is a text file of commands that are run during startup, and a profile is a collection of information regarding the desktop environment, including the contents of the Start menu, icons that appear on the desktop, and other characteristics about the GUI environment that users are allowed to customize. A roaming profile can follow its owner from computer to computer, allowing her to have the same familiar interface appear wherever she logs on.

A Windows NT domain offers centralized control over the network. Policies can be set up by an administrator to define aspects of the users’ environment and limit the amount of control they have over the network and their computers. It is also possible for administrators to perform remote administration of the domain controllers from any Windows NT/2000/XP workstation.

Samba 2.2 has the ability to act as a primary domain controller, supporting domain logons from Windows 95/98/Me/NT/2000/XP computers and allowing Windows NT/2000/XP^[21] systems to join the domain as domain member servers. Samba can also join a domain as a member server, allowing the primary domain controller to be a Windows NT/2000 system or another Samba server.

Tip

Samba 2.2 does not support LDAP and Kerberos authentication of Active Directory, so it cannot act as a Windows 2000 Active Directory domain controller. However, Samba can be added to an Active Directory domain as a member server, with the Windows 2000 domain controllers running in either mixed or native mode. The Windows 2000 server (even if it is running in native mode) supports the Samba server by acting as a PDC emulator, using the Windows NT style of authentication rather than the Kerberos style.

If you’re adding a Samba server to a network that has already been set up, you won’t have to decide whether to use a workgroup or a domain; you will simply have to be compatible with what’s already in place. If you do have a choice, we suggest you evaluate both workgroup and domain computing carefully before rolling out a big installation. You will have a lot of work to do if you later need to convert one to the other. One last thought on this matter is that Microsoft is developing Windows in the direction of increased use of domains and is intending that eventually Windows networks be composed solely of Active Directory domains. If you implement a Windows NT domain now, you’ll be in a better position to transition to Active Directory later, after Samba has better support for it.

In this chapter, we cover various topics directly related to using Samba in a Windows NT domain, including:

• Configuring and using Samba as the primary domain controller

• Setting up Windows 95/98/Me systems to log on to the domain

• Implementing user-level security on Windows 95/98/Me

• Adding Windows NT/2000/XP systems to the domain

• Configuring logon scripts, roaming profiles, and system policies

• Adding a Samba server to a domain as a member server

Samba as the Primary Domain Controller

Samba 2.2 is able to handle the most desired functions of a primary domain controller in a Windows NT domain, handling domain logons and authentication for accessing shared resources, as well as supporting logon scripts, roaming profiles, and system policies.

Tip

You will need to use at least Samba 2.2 to ensure that PDC functionality for Windows NT/2000/XP clients is present. Prior to Samba 2.2, only limited user authentication for NT clients was present.

In this section, we will show you how to configure Samba as a PDC for use with Windows 95/98/Me and Windows NT/2000/XP clients. The two groups of Windows versions interact differently within domains, and in some cases are supported in slightly different ways. If you know you are going to be using only Windows 95/98/Me or Windows NT/2000/XP, you can set up Samba to support only that group. However, there isn’t any harm in supporting both at the same time.

Tip

If you would like more information on how to set up domains, see the file Samba-PDC-HOWTO.html in the docs/htmldocs directory of the Samba source distribution.

Samba must be the only domain controller for the domain. Make sure that a PDC isn’t already active, and that there are no backup domain controllers. Samba 2.2 is not able to communicate with backup domain controllers, and having domain controllers in your domain with unsynchronized data would result in a very dysfunctional network.

Tip

Although Samba 2.2 cannot function as, or work with, a Windows NT BDC, it is possible to set up another Samba server to act as a backup for a Samba PDC. For further information, see the file Samba-BDC-HOWTO.html in the docs/htmldocs directory of the Samba source distribution.

Configuring Samba to be a PDC is a matter of modifying the smb.conf file, creating some directories, and restarting the server.

Modifying smb.conf

First you will need to start with an smb.conf file that correctly configures Samba for workgroup computing, such as the one we created in Chapter 2, and insert the following lines into the [global] section:

[global]
    ; use the name of your Samba server instead of toltec
    ; and your own workgroup instead of METRAN
    netbios name = toltec
    workgroup = METRAN
    encrypt passwords = yes
        
    domain master = yes
    local master = yes
    preferred master = yes
    os level = 65

    security = user
    domain logons = yes
    
    ; logon path tells Samba where to put Windows NT/2000/XP roaming profiles
    logon path = \\%L\profiles\%u\%m
    logon script = logon.bat

    logon drive = H:
    ; logon home is used to specify home directory and
    ; Windows 95/98/Me roaming profile location
    logon home = \\%L\%u\.win_profile\%m
    
    time server = yes

    ; instead of jay, use the names of all users in the Windows NT/2000/XP
    ; Administrators group who log on to the domain
    domain admin group = root jay

    ; the below works on Red Hat Linux - other OSs might need a different command
    add user script = /usr/sbin/useradd -d /dev/null -g 100 -s /bin/false -M %u

And after the [global] section, add these three new shares:

[netlogon]
    path = /usr/local/samba/lib/netlogon
    writable = no
    browsable = no

[profiles]
    ; you might wish to use a different directory for your
    ; Windows NT/2000/XP roaming profiles
    path = /home/samba-ntprof
    browsable = no
    writable = yes
    create mask = 0600
    directory mask = 0700

[homes]
    read only = no
    browsable = no
    guest ok = no
    map archive = yes

Now for the explanation. If you are comparing this example to the configuration file presented in Chapter 2, you will notice that the first three parameter settings are similar. We start out in the [global] section by setting the NetBIOS name of the Samba server. We are using the default, which is the DNS hostname, but are being explicit because the NetBIOS name is used in UNCs that appear later in smb.conf. The next two lines, setting the workgroup name and choosing to use encrypted passwords, are identical to our smb.conf file from Chapter 2. However, things are now a little different: even though it still reads “workgroup”, we are actually setting the name of the domain. For a workgroup, using encrypted passwords is optional; when using a domain, they are required.

The next four lines set up our Samba PDC to handle browsing services. The line domain master = yes causes Samba to be the domain master browser, which handles browsing services for the domain across multiple subnets if necessary. Although it looks very similar, local master = yes does not cause Samba to be the master browser on the subnet, but merely tells it to participate in browser elections and allow itself to win. (These two lines are yet more default settings that we include to be clear.) The next two lines ensure that Samba wins the elections. Setting the preferred master parameter makes Samba force an election when it starts up. The os level parameter is set higher than that of any other system, which results in Samba winning that election. (At the time of this writing, an os level of 65 was sufficient to win over all versions of Windows—but make sure no other Samba server is set higher!) We make sure Samba is both the domain and local master browser because Windows NT/2000 PDCs always reserve the domain master browser role for themselves and because Windows clients require things to be that way to find the primary domain controller. It is possible to allow another computer on the network to win the role of local master browser, but having the same server act as both domain and local masters is simpler and more efficient.

The next two lines in the [global] section set up Samba to handle the actual domain logons. We set security = user so that Samba will require a username and password. This is actually the same as in the workgroup setup we covered in Chapter 1 and Chapter 2 because it is the default. The only reason we’re including it explicitly is to avoid confusion: another valid setting is security = domain, but that is for having another (Windows or Samba) domain controller handle the logons and should never be found in the smb.conf of a Samba PDC. The next line, domain logons = yes, is what tells Samba we want this server to handle domain logons.

Defining a logon path is necessary for supporting roaming profiles for Windows NT/2000/XP clients. The UNC \\%L\profiles\%u refers to a share held on the Samba server where the profiles are kept. The variables %L and %u are replaced by Samba with the name of the server and the username of the logged on user, respectively. The section in smb.conf defining the [profiles] share contains the definition of exactly where the profiles are kept on the server. We’ll get back to this topic a bit later in this chapter.

The logon script = logon.bat line specifies the name of an MS-DOS batch file that will be executed when the client logs on to the domain. The path specified here is relative to the [netlogon] share that is defined later in the smb.conf file.

The settings of logon drive and logon home have a couple of purposes. Setting logon drive = H: allows the home directory of the user to be connected to drive letter H on the client. The logon home parameter is set to the location of the home directory on the server, and again, %u is replaced at runtime by the logged on user’s username. The home directory is used to store roaming profiles for Windows 95/98/Me clients. These parameters tie into the [homes] share that we are adding, as we will explain a bit later.

Setting time server = yes causes Samba to advertise itself as a time service for the network. This is optional.

The domain admin group parameter exists as a short-term measure in Samba 2.2 to give Samba a list of users who have administrative privileges in the domain. The list should contain any Samba users who log on from Windows NT/2000/XP systems and are members of the Administrators or Domain Admins groups, if roaming profiles are to work correctly.

The last parameter to add to the [global] section is add user script, and you will need it only if one or more of your clients is a Windows NT/2000/XP system. We will tell you more about this in Section 4.2 later in this chapter.

The rest of the additions to smb.conf are the definitions for three shares. The [netlogon] share is necessary for Samba to handle domain logons because Windows clients need to connect to it during the logon process and will fail if the share does not exist. Other than that, the only function of [netlogon] is to be a repository for logon scripts and system-policy files, which we shall cover in detail later in this chapter. The path to a directory on the Samba server is given, and because the clients only read logon scripts and system-policy files from the share, the writable = no definition is used to make the share read-only. Users do not need to see the share, so we set browsable = no to make the share invisible.

The [profiles] share is needed for use with Windows NT/2000/XP roaming profiles. The path points to a directory on the Samba server where the profiles are kept, and in this case, the clients must be able to read and write the profile data. The create mask (read and write permitted for the owner only) and directory mask (read, write, and search permitted for the owner only) are set up such that a user’s profile data can be read and written only by the user and not accessed or modified by anyone else.

The [homes] share is necessary for our definitions of logon drive and logon home to work. Samba uses the [homes] share to add the home directory of the user (found in /etc/passwd ) as a share. Instead of appearing as “homes”, the share will be accessible on the client through a folder having the same name as the user’s username. We will cover this topic in more detail in Chapter 9.

At this point, you might want to run testparm to check your smb.conf file.

Creating Directories on the Samba Server

The [netlogon] and [profiles] shares defined in our new smb.conf file reference directories on the Samba server, and it is necessary to create those directories with the proper permissions:

# mkdir /usr/local/samba/lib/netlogon
# chmod 775 /usr/local/samba/lib/netlogon
# mkdir /home/samba-ntprof
# chmod 777 /home/samba-ntprof

The directory names we use are just examples. You are free to choose your own.

Restarting the Samba Server

At this point, the only thing left to do is restart the Samba server, and the changes will be put into effect:

# /etc/rc.d/init.d/smb restart

(or use whatever method works on your system, as discussed in Chapter 2.) The server is now ready to accept domain logons.

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^[21] When we include Windows XP in discussions of Windows NT domains in this book, we are referring to Windows XP Professional and not to the Home edition. The reason for this is explained in the section on Windows XP later in this chapter.