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 [1] 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.

Adding Computer Accounts

To interact in a domain, a Windows NT/2000/XP system must be a member of the domain. Domain membership is implemented using computer accounts, which are similar to user accounts and allow a domain controller to keep information with which to authenticate computers on the network. That is, the domain controller must be able to tell if requests that arrive from a computer are coming from a computer that it "knows" as being part of the domain. Each Windows NT/2000/XP system in the domain has a computer account in the domain controllers' database, which on a Windows NT/2000 hosted domain is the SAM database. Although Samba uses a different method (involving the smbpasswd file), it also treats computer accounts similarly to user accounts.

To create a computer account, an administrator configures a Windows NT/2000/XP system to be part of the domain. For Samba 2.2, the "domain administrator" is the root account on the Samba server, and you will need to run the command:

# smbpasswd -a root

to add the root user to Samba's password database. In this case, do not provide smbpasswd with the same password as the actual root account on the server. Create a different password to be used solely for creating computer accounts. This will reduce the possibility of compromising the root password.

When the computer account is created, two things must happen on the Samba server. An entry is added to the smbpasswd file, with a "username" that is the NetBIOS name of the computer with a dollar sign ($) appended to it. This part is handled by the smbpasswd command, and you do not need to perform any additional action to implement it.

With Samba 2.2, an entry is also required in the /etc/passwd file [2] to give the computer account a user ID (UID) on the Samba server.

This account will never be used to log in to the Unix system, so it should not be given a valid home directory or login shell. To make this part work, you must set the add user script parameter in your Samba configuration file, using a command that adds the entry in the proper manner. On our Red Hat Linux system, we set add user script to:

/usr/sbin/useradd -d /dev/null -g 100 -s /bin/false -M %u

This command adds an entry in /etc/passwd similar to the following:

aztec$:x:505:100::/dev/null:/bin/false

Again, notice that the username ends in a dollar sign. The user account shown has a "home directory" of /dev/null, a group ID (GID) of 100, and a "login shell" of /bin/false. The -M flag in our useradd command prevents it from creating the home directory. Samba replaces the %u variable in the useradd command with the NetBIOS name of the computer, including the trailing dollar sign. The basic idea here is to create an entry with a valid username and UID. These are the only parts that Samba uses. It is important that the UID be unique, not also used for other accounts—especially ones that are associated with Samba users.

If you are using some other variety of Unix, you will need to replace our useradd command with a command that performs the same function on your system. If a command such as useradd does not come with your system, you can write a shell script yourself that performs the same function. In any case, the command should add a password hash that does not correspond to any valid password. For example, in the /etc/shadow file of our Linux server, we find the following two lines:

jay:%1%zQ7j7ok8$D/IubyRAY5ovM3bTrpUCn1:11566:0:99999:7:::
zapotec$:!!:11625:0:99999:7:::

The first line is for jay's user account. The second field is the password hash—the long string between the first and second colons. The second line is for the computer account of zapotec, a domain member server. Its "username" ends with a dollar sign ($), and the second field in this case has been set to "!!", which is an arbitrary string not produced from any password. Therefore, there is no valid password for this account on the Linux host. Just about any ASCII string can be used instead of "!!". For example, you could use "DISABLED" instead.

TIP

It is possible to create the entries for /etc/passwd and smbpasswd manually; however, we suggest this method be used very carefully, and only for initial testing, or as a last resort. The reason for this is to maintain security. After the computer account has been created on the server, the next Windows NT/2000/XP system on the network with a matching NetBIOS name to log on to the domain will be associated with this account. This allows crackers a window of opportunity to take over computer accounts for their own purposes.

Configuring Windows Clients for Domain Logons

The client-side configuration for Windows clients is really simple. All you have to do is switch from workgroup to domain networking by enabling domain logons, and in the case of Windows NT/2000/XP, also provide the root password you gave smbpasswd for creating computer accounts. This results in the Windows NT/2000/XP system becoming a member of the domain.

Windows 95/98/Me

To enable domain logons with Windows 95/98/Me, open the Control Panel and double-click the Network icon. Then click Client for Microsoft Networks, and click the Properties button. At this point, you should see a dialog box similar to Figure 4-1. Select the Logon to Windows Domain checkbox at the top of the dialog box, and enter the name of the domain as you have defined it with the workgroup parameter in the Samba configuration file. Then click OK, and reboot the machine when asked.

Figure 4-1. Configuring a Windows 95/98 client for domain logons

WARNING

If Windows complains that you are already logged into the domain, you probably have an active connection to a share in the workgroup (such as a mapped network drive). Simply disconnect the resource temporarily by right-clicking its icon and choosing the Disconnect pop-up menu item.

When Windows reboots, you should see the standard logon dialog with an addition: a field for a domain. The domain name should already be filled in, so simply enter your password and click the OK button. At this point, Windows should consult the primary domain controller (Samba) to see if the password is correct. (You can check the log files if you want to see this in action.) If it worked, congratulations! You have properly configured Samba to act as a domain controller for Windows 95/98/Me machines, and your client is successfully connected.

User-Level Security for Windows 95/98/Me

Now that you have a primary domain controller to authenticate users, you can implement much better security for shares that reside on Windows 95/98/Me systems.[3] To enable this functionality, open the Control Panel, double-click the Network icon, and click the Access Control tab in the dialog box. The window should now look like Figure 4-2.

Figure 4-2. Setting user-level access control

Click the User-level access control radio button, and type in the name of your domain in the text area. Click the OK button. If you get the dialog box shown in Figure 4-3, it means that shares are already on the system.

Figure 4-3. Error dialog while changing to user-level access control

In that case, you might want to cancel the operation and make a record of each of the computer's shares, making it easier to re-create them, and then redo this part. (To get a list of shares, open an MS-DOS prompt window and run the net view \\computer_name command.) Otherwise, you will get a message asking you to reboot to put the change in configuration into effect.

After rebooting, you can create shares with user-level access control. To do this, right-click the folder you wish to share, and select Sharing.... This will bring up the Shared Properties dialog box, shown in Figure 4-4.

Click the Change... button, and you should see the dialog box shown in Figure 4-7. In this dialog box, you can choose to have the Windows NT client become a member of the domain by clicking the checkbox marked Domain: in the Member of box. Then type in the name of the domain to which you wish the client to log on; it should be the same as the one you specified using the workgroup parameter in the Samba configuration file. Click the checkbox marked Create a Computer Account in the Domain, and fill in "root" for the text area labeled User Name:. In the Password: text area, fill in the root password you gave smbpasswd for creating computer accounts.

Figure 4-7. Configuring a Windows NT client for domain logons

WARNING

If Windows complains that you are already logged in, you probably have an active connection to a share in the workgroup (such as a mapped network drive). Disconnect the resource temporarily by right-clicking its icon and choosing the Disconnect pop-up menu item.

After you press the OK button, Windows should present you with a small dialog box welcoming you to the domain. Click the Close button in the Network dialog box, and reboot the computer as requested. When the system comes up again, the machine will automatically present you with a logon screen similar to the one for Windows 95/98/Me clients, except that the domain text area has a drop-down menu so that you can opt to log on to either the local system or the domain. Make sure your domain is selected, and log on to the domain using any Samba-enabled user account on the Samba server.

WARNING

Be sure to select the correct domain in the Windows NT logon dialog box. Once it is selected, it might take a moment for Windows NT to build the list of available domains.

After you enter the password, Windows NT should consult the primary domain controller (Samba) to see if the password is correct. Again, you can check the log files if you want to see this in action. If it worked, you have successfully configured Samba to act as a domain controller for Windows NT machines.

Windows 2000

To configure Windows 2000 for domain logons, log in to the computer as Administrator or another user in the Administrators group, open the Control Panel, and double-click the System icon to open the System Properties dialog box. Click the Network Identification tab, and then click the Properties button. You should now see the Identification Changes dialog box shown in Figure 4-8.

Figure 4-8. The Identification Changes dialog

Click the radio button labeled "Domain:" and fill in the name of your domain in the text-entry area. Then click the OK button. This will bring up the Domain Username and Password dialog box. Enter "root" for the username. For the password, use the password that you gave to smbpasswd for the root account.

WARNING

If Windows complains that you are already logged in, you probably have an active connection to a share in the workgroup (such as a mapped network drive). Disconnect the resource temporarily by right-clicking its icon and choosing the Disconnect pop-up menu item.

After you press the OK button, Windows should present you with a small dialog box welcoming you to the domain. When you click the OK button in this dialog box, you will be told that you need to reboot the computer. Click the OK button in the System Properties dialog box, and reboot the computer as requested. When the system comes up again, the machine will automatically present you with a Log On to Windows dialog box similar to the one shown in Figure 4-9.

Figure 4-9. The Windows 2000 logon window

If you do not see the Log on to: drop-down menu, click the Options << button and it will appear. Select your domain, rather than the local computer, from the menu.

WARNING

Be sure to select the correct domain in the logon dialog box. Once it is selected, it might take a moment for Windows to build the list of available domains.

Enter the username and password of any Samba-enabled user in the User name: and Password: fields, and either press the Enter key or click the OK button. If it worked, your Windows session will start up with no error dialogs.

Windows XP Home

You have our condolences if you are trying to use the Home edition of Windows XP in a domain environment! Microsoft has omitted support for Windows NT domains from Windows XP Home, resulting in a product that is ill-suited for use in a domain-based network.

On the client side, Windows XP Home users cannot log on to a Windows NT domain. Although it is still possible to access domain resources, a username and password must be supplied each time the user connects to a resource, rather than the "single signon" of a domain logon. Domain features such as logon scripts and roaming profiles are not supported.

As a server, Windows XP Home cannot join a Windows NT domain as a domain member server. It can serve files and printers, but only using share-mode ("workgroup") security. It can't even use user-mode security, as Windows 95/98/Me can.

Considering these limitations, we do not recommend Windows XP Home for any kind of local area network computing.

Windows XP Professional

To configure Windows XP Professional for domain logons, log in to the computer as Administrator or another user in the Administrators group, open the Control Panel in Classic View, and double-click the System icon to open the System Properties dialog box. Click the Computer Name tab and then click the Change... button. You should now see the Computer Name Changes dialog box shown in Figure 4-10.

Figure 4-10. The Computer Name Changes dialog

Click the radio button labeled "Domain:", and fill in the name of your domain in the text-entry area. Then click the OK button. This will bring up the Domain Username and Password dialog box. Enter "root" for the username. For the password, use the password that you gave to smbpasswd for the root account.

WARNING

If Windows complains that you are already logged in, you probably have an active connection to a share in the workgroup (such as a mapped network drive). Disconnect the resource temporarily by right-clicking its icon and choosing the Disconnect pop-up menu item.

After you press the OK button, Windows should present you with a small dialog box welcoming you to the domain. When you click the OK button in this dialog box, you will be told that you need to reboot the computer to put the changes into effect. Click the OK buttons in the dialog boxes to close them, and reboot the computer as requested. When the system comes up again, the machine will automatically present you with a Log On to Windows dialog box similar to the one shown in Figure 4-11.

Figure 4-11. The Windows XP logon window

If you get a dialog box at this point that tells you the domain controller cannot be found, the solution is to change a registry setting as follows.

Open the Start Menu and click the Run... menu item. In the text area in the dialog box that opens, type in "regedit" and click the OK button to start the Registry Editor. You will be editing the registry, so follow the rest of the directions very carefully. Click the "+" button next to the HKEY_LOCAL_MACHINE folder, and in the contents that open up, click the "+" button next to the SYSTEM folder. Continue in the same manner to open CurrentControlSet, then Services, then Netlogon. (You will have to scroll down many times to find Netlogon in the list of services.) Then click the Parameters folder, and you will see items appear in the right side of the window. Double-click "requiresignorseal", and a dialog box will open. In the Value data: text area, change the "1" to a "0" (zero), and click the OK button, which modifies the registry both in memory and on disk. Now close the Registry Editor and log off and back on again.

If you do not see the Log on to: drop-down menu, click the Options << button and it will appear. Select your domain from the menu, rather than the local computer.

WARNING

Be sure to select the correct domain in the logon dialog box. Once it is selected, it might take a moment for Windows to build the list of available domains.

Logon Scripts

After a Windows client connects with a domain controller (either to authenticate a user, in the case of Windows 95/98/Me, or to log on to the domain, in the case of Windows NT/2000/XP), the client downloads an MS-DOS batch file to run. The domain controller supplies the file assuming one has been made available for it. This batch file is the logon script and is useful in setting up an initial environment for the user.

In a Unix environment, the ability to run such a script might lead to a very complex initialization and deep customization. However, the Windows environment is mainly oriented to the GUI, and the command-line functions are more limited. Most commonly, the logon script is used to run a net command, such as net use, to connect a network drive letter, like this:

net use T: \\toltec\test

This command will make our [test] share (from Chapter 2) show up as the T: drive in My Computer. This will happen automatically, and T: will be available to the user at the beginning of her session, instead of requiring her to run the net use command or connect the T: drive using the Map Network Drive function of Windows Explorer.

Another useful command is:

net use H: /home

which connects the user's home directory to a drive letter (which can be H:, as shown here, or some other letter, as defined by logon drive). For this to work, you must have a [homes] share defined in your smb.conf file.

If you are using roaming profiles, you should definitely have:

net time \\toltec /set /yes

in your logon script. (As usual, replace "toltec" with the name of your Samba PDC.) This will make sure the clocks of the Windows clients are synchronized with the PDC, which is important for roaming profiles to work correctly.

Creating a Logon Script

In our smb.conf file, we have the line:

logon script = logon.bat

This defines the location and name of the logon script batch file on the Samba server. The path is relative to the [netlogon] share, defined later in the file like this:

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

With this example, the logon script is /user/local/samba/lib/netlogon/logon.bat. We include the directives writable = no, to make sure network clients cannot change anything in the [netlogon] share, and also browsable = no, which keeps them from even seeing the share when they browse the contents of the server. Nothing in [netlogon] should ever be modified by nonadministrative users. Also, the permissions on the directory for [netlogon] should be set appropriately (no write permissions for "other" users), as we showed you earlier in this chapter.

Notice also that the extension of our logon script is .bat. Be careful about this—an extension of .cmd will work for Windows NT/2000/XP clients, but will result in errors for Windows 95/98/Me clients, which do not recognize .cmd as an extension for batch files.

Because the logon script will be executed on a Windows system, it must be in MS-DOS text-file format, with the end of line composed of a carriage return followed by a linefeed. The Unix convention is a newline, which is simply a linefeed character, so if you use a Unix text editor to create your logon script, you must somehow make it use the appropriate characters. With vim (a clone of the vi editor that is distributed with Red Hat Linux), the method is to create a new file and use the command:

:se ff=dos

to set the file format to MS-DOS style before typing in any text. With emacs, the same can be done using the command:

^X Enter f dos Enter

where ^X is a Control-X character and Enter is a press of the Enter key. Another method is to create a Unix-format file in any text editor and then convert it to MS-DOS format using the unix2dos program:

$ unix2dos unix_file >logon.bat

If your system does not have unix2dos, don't worry. You can implement it yourself with the following two-line Perl script:

#!/usr/bin/perl
open FILE, $ARGV[0];
while (<FILE>) { s/$/\r/; print }

Or, you can use Notepad on a Windows system to write your script and then drag the logon script over to a folder on the Samba server. In any case, you can check the format of your script using the od command, like this:

$ od -c logon.bat

You should see output resembling this:

0000000   n  e  t     u  s  e      T   :    \  \  t  o  l
0000020   t  e  c  \  t  e  s  t  \r  \n
0000032

The important detail here is that at the end of each line is a \r \n, which is a carriage return followed by a linefeed.

Our example logon script, containing a single net use command, was created and set up in a way that allows it to be run successfully on any Windows client, regardless of which Windows version is installed on the client and which user is authenticating or logging on to the domain. But what if we need to have different users, computers, or Windows versions running different logon scripts?

One method is to use variables inside the logon script that cause commands to be conditionally executed. For details on how to do this, you can consult a reference on batch-file programming for MS-DOS and Windows NT command language. One such reference is Windows NT System Administration, published by O'Reilly.

Windows batch-command language is very limited in functionality. Fortunately, Samba also supports a means by which customization can be handled. The smb.conf file contains variables that can be used to insert (at runtime) the name of the server (%L), the username of the person who is accessing the server's resources (%u), or the computer name of the client system (%m). To give an example, if we set up the path to the logon script as:

logon script = %u/logon.bat

we would then put a directory for each user in the [netlogon] share, with each directory named the same as the user's username, and in each directory we would put a customized logon.bat file. Then each user would have his own custom logon script. We will give you a better example of how to do this kind of thing in the next section, Section 4.5.

TIP

For more information on Samba configuration file variables, such as the %L, %u, and %m variables we just used, see Chapter 6 and Appendix B.

When modifying and testing your logon script, don't just log off of your Windows session and log back on to make your script run. Instead, restart (reboot) your system before logging back on. Because Windows often keeps the [netlogon] share open across logon sessions, the reboot ensures that Windows and Samba have completely released and reconnected the [netlogon] share, and the new version of the logon script is being run while logging on.

More information regarding logon scripts can be found in the O'Reilly book, Managing Windows NT Logons.

Roaming Profiles

One benefit of the centralized authentication of Windows NT domains is that a user can log on from more than just one computer. To help users feel more "at home" when logged on at a computer other than their usual one, Microsoft has added the ability for users' personal settings to "roam" from one computer to another.

All Windows versions can be configured individually for each user of the computer. Windows NT/2000/XP supports the ability to handle multiple user accounts, and Windows 95/98/Me can be configured for use by multiple users, keeping the configuration settings for each user separate. Each user can configure the computer's settings to her liking, and the system saves these settings as the user's profile, such that upon logging on to the system, the user is presented with her familiar desktop.

Some of the settings, such as folder options or the image used for the desktop background, are held in the registry. Others, including the documents and folders appearing on the desktop and the contents of the Start menu, are stored as folders and files in the filesystem.

When the profile is stored on the local system, it is called a local profile. On Windows NT, local profiles are stored in C:\winnt\profiles. On Windows 2000/XP, they can be found in C:\Documents and Settings. On Windows 95/98/Me, when configured for a single user (the default case), the local profile is scattered in places such as the registry and directories such as C:\Windows\Desktop and C:\Windows\Start Menu. When Windows 95/98/Me is configured for multiple users, the local profile of the preexisting user is moved to a folder in C:\Windows\Profiles that has the same name as the user, and any users that are subsequently added to the computer have their local profiles created in that directory as well. You can browse through the local profiles to see their structure—each has a registry file (USER.DAT for Windows 95/98/Me and NTUSER.DAT for Windows NT/2000/XP) and some folders that contain shortcuts and documents.

A roaming profile is a user profile that is stored on a server and "follows" its owner around the network so that when the user logs on to the domain from another computer, his profile is downloaded from the server and his familiar desktop appears on that computer as well.

WARNING

Samba can support roaming profiles, and it is a fairly simple matter to configure it for them. However, this is one feature that we recommend you do not use, at least until you are sure you understand roaming profiles well and are very confident that you can implement them with no harm incurred. If you want to (or are required to) implement roaming profiles for your Windows clients, we suggest you first set up a small domain with a Samba server and a few Windows clients exclusively for the purposes of research and testing. Under no circumstances should you attempt to implement roaming profiles in a careless or frivolous manner.

How Roaming Profiles work

We will start out by explaining to you how roaming profiles work when set up correctly. You will need a clear understanding of them to tell the difference between when they are working as they are designed and when they are not. In addition, roaming profiles can be a source of confusion for your users in many ways, and you should know how to detect when a problem with a client is related to roaming profile function or dysfunction.

TIP

A definitive source of documentation on Windows NT roaming profiles is the Microsoft white paper Implementing Policies and Profiles for Windows NT 4.0, which can be found at http://www.microsoft.com/ntserver/techresources/management/prof_policies.asp.

During the domain logon process, the roaming profile is copied from the domain controller and used as a local profile during the user's logon session. When the user logs off the domain, the local profile is copied back to the domain controller and stored as the new roaming profile. When the local profile is changed, the server does not receive an update until the user logs off the domain or shuts down or reboots the client. The client does not send an update to the server during the logon session, and a client does not receive an update of a setting changed on another client during a logon session. When the user does log off, changes in the configuration settings in the local profile are sent to the server, and the updates of the roaming profile are available for the next logon session.

This simple behavior can lead to unexpected results when users are logged on to the domain on more than one client at a time. If a user makes a change to the configuration settings on one client and then logs off, the settings can result in the roaming profile being modified accordingly. But the next client that logs off might cause those changes to be overwritten, and if so, the settings from the first client will be lost. The behavior of different Windows versions varies with regard to this, and we've seen a wide variety of behaviors—not always in alignment with Microsoft's documentation or even working the same way on separate occasions. Sometimes Windows will refuse to overwrite a profile, perhaps giving an "access denied" error, and at other times it will seem to work while producing odd side effects. A common source of confusion is what happens if a file is added to or deleted from the desktop, which is by default configured to be part of the profile. A deleted file might later reappear, and it is even possible for a file to irrecoverably disappear without warning (on Windows 95/98). Or maybe a file that is added to the desktop on one client never gets added to the roaming profile and fails to propagate to other clients. This behavior is somewhat improved on Windows 2000/XP, which attempts to merge items into the profile that are added on concurrently logged-on clients.

One factor that comes into play is that Windows compares the timestamps of the local and roaming profiles and can refuse to overwrite a roaming profile if it is newer than the local profile on the client, or vice versa. For this reason, it is important to keep the clocks of the Windows clients and the Samba PDC synchronized. We have already shown you how to do this, using the net time \\server /set /yes command in the logon script.

Even when the server and clients are correctly configured, a number of things that can happen make things seem "broken." The most common occurrence is that some shortcuts on clients other than the one that created the roaming profile will not work. These shortcuts can exist on the desktop or as items in the Start menu. This behavior is a result of applications or files that exist on one computer but not others. Windows will display these shortcuts, but if they appear on the desktop, they will have a generic icon and will bring up an error message if a user double-clicks them.

TIP

Because profiles can and usually do include the contents of the desktop and other folders, it is possible for the roaming profile to grow to a huge size due to actions of a user, such as creating new files on the desktop or copying files there. By default, Internet Explorer keeps its disk cache in the Temporary Internet Files folder in the profile and has been known to populate this directory with thousands of files. This can result in a huge roaming profile that causes network congestion and very large delays while users are logging on to the domain. (A fix for this can be found in article Q185255 in the Microsoft Knowledge Base.)

One behavior we've seen a few times is that if, for some reason (e.g., a network error or misconfiguration), the roaming profile is not available during the logon process, Windows will use the local profile on the client instead. When this happens, the user might receive an unfamiliar profile, and all the benefits of roaming profiles are lost for that logon session.

Configuring Samba for Roaming Profiles

In an ideal world, different Windows versions would share the same roaming profile, allowing users to log on to the domain from any Windows client system, ranging from Windows 95 to Windows XP, and enjoy their familiar settings. It would even be possible to be logged on concurrently from multiple clients, and a change made to the profile on any of them would quickly propagate to all the others. Settings in a roaming profile made on a client that didn't apply to another would be handled sanely.

Unfortunately, this scenario does not work in reality, and it is important to maintain separate roaming profiles to prevent different Windows versions from using or modifying a roaming profile created by, and/or in use by, another version.

We do this by using configuration file variables to point to different profile directories. If you look at Table B-1 in Appendix B, which shows the variables that can be used, you might be tempted to use the %a variable, which is replaced by the name of the operating system the client is running. However, this does not work because all of Windows 95/98/Me will be seen as the same operating system, and likewise for Windows 2000/XP. So, we use %m to get the NetBIOS name of the client, and combine that with a symbolic link to point to the directory containing the profile for the Windows version that particular client is running.

Our additions to smb.conf that appeared earlier in this chapter included the two lines:

logon path = \\%L\profiles\%u\%m
logon home = \\%L\%u\.win_profile\%m

The first line specifies where the roaming profiles for Windows NT/2000/XP clients are kept, and the second line performs the same function for Windows 95/98/Me clients. In both cases, the location is specified as a UNC, but logon path (for Windows NT/2000/XP) is specified relative to the [profiles] share, while logon home (for Windows 95/98/Me) is specified relative to the user's home directory. This is done to comply with Samba's emulation of Windows NT/2000 PDC behavior.

The logon home UNC must begin by specifying the user's home directory, which in our previous example would be \\%L\%u. The variable %L expands to the NetBIOS name of the server (in this case, toltec), and %u expands to the name of the user. This must be done to allow the command:

C:\>net use h: /home

to function correctly to connect the user's home directory to drive letter H: on all Windows clients. (The drive letter used for this purpose is defined by logon drive.) We add the directory .win_profile to the UNC to put the Windows 95/98/Me roaming profile in a subdirectory of the user's home directory.

WARNING

Note that in both logon path and logon home, we absolutely avoid making the profile directory the same as the user's home directory, and the directory that contains the profile is not used for any other purpose. This is because when the roaming profile is updated, all directories and files in the roaming-profile directory that are not part of the roaming profile are deleted.

In the logon path line in smb.conf, we use %u to put the profiles directory in a subdirectory in the [profiles] share, such that each user gets her own directory that holds her roaming profiles.

We define the [profiles] share like this:

[profiles]
    writable = yes
    create mask = 0600
    directory mask = 0700
    browsable = no
    path = /home/samba-ntprof

The first four parameters in the previous share definition specify to allow roaming profiles to be written with the users' permissions, to create files with read and write permissions for the owner, and to create directories with read, write, and search permissions for the owner and no access allowed for other users. As with the [netlogon] share, we set browsable = no so that the share will not show up on the clients in Windows Explorer.

We've decided to put our Windows NT/2000/XP profiles in /home, the default location of the home directories on Linux. This will make it simple to include the roaming profiles in backups of the home directories. You can use another directory if you like.

Notice that in both logon path and logon home, the directory we specify ends in %m, which Samba replaces with the NetBIOS name of the client. We are using the client's computer name to identify indirectly which version of Windows it is running.

Initially, the directories you specify to hold the roaming profiles will be empty and will become populated as clients log off for the first time. (Samba will even create the directories if they do not already exist.) At first, the directories will simply contain profiles that are identical to the clients' local profiles, and we highly recommend that you make a backup at this point before things get complicated. A listing of the roaming profile directory for user iman, after she has logged off from Windows 98 clients mixtec and pueblo and Windows Me clients huastec and navajo, might look something like the following:

$ ls -l /home/iman/.win_profile
total 4
drwx------    6 iman      iman          4096 Dec  8 18:09 huastec
drwx------    9 iman      iman          4096 Dec  7 03:47 mixtec
drwx------   11 iman      iman          4096 Dec  7 03:05 navajo
drwx------   11 iman      iman          4096 Dec  7 03:05 pueblo

If things were left like this, the clients would not share their roaming profiles, so next we change from using separate directories to having symbolic links point to common directories:

# mv mixtec Win98
# mv navajo WinMe
# rm huastec pueblo
# ln -s Win98 pueblo
# ln -s WinMe huastec
# chown iman:iman *
# ls -l /home/iman/.win_profile
total 6
lrwxrwxrwx    1 iman      iman             5 Nov 16 01:40 huastec -> WinMe
lrwxrwxrwx    1 iman      iman             5 Nov 16 01:40 mixtec -> Win98
lrwxrwxrwx    1 iman      iman             5 Nov 21 17:24 navajo -> WinMe
lrwxrwxrwx    1 iman      iman             5 Nov 23 01:16 pueblo -> Win98
drwx------    9 iman      iman          4096 Dec  7 03:47 Win98
drwx------   11 iman      iman          4096 Dec  7 03:05 WinMe

Now when iman logs on to the domain from either Windows 98 system, the client from which she is logging on will get the profile stored in the Win98 directory (that started out as her local profile on mixtec). This works likewise for the Windows Me clients.

To show a more complete example, here is a listing of a fully operational Windows 95/98/Me profiles directory:

$ ls -l /home/jay/.win_profile
total 12
lrwxrwxrwx    1 jay      jay             9 Nov 16 22:14 aztec -> /home/jay
lrwxrwxrwx    1 jay      jay             5 Nov 16 01:40 hopi -> Win95
lrwxrwxrwx    1 jay      jay             5 Nov 16 01:40 huastec -> WinMe
lrwxrwxrwx    1 jay      jay             5 Nov 16 01:38 maya -> Win98
lrwxrwxrwx    1 jay      jay             5 Nov 16 01:40 mixtec -> Win98
lrwxrwxrwx    1 jay      jay             5 Nov 21 17:24 navajo -> WinMe
lrwxrwxrwx    1 jay      jay             5 Nov 23 01:16 pueblo -> Win98
lrwxrwxrwx    1 jay      jay             5 Nov 22 02:06 ute -> Win95
drwx------    6 jay      jay          4096 Dec  8 18:09 Win95
drwx------    9 jay      jay          4096 Dec  7 03:47 Win98
drwx------   11 jay      jay          4096 Dec  7 03:05 WinMe
lrwxrwxrwx    1 jay      jay             5 Nov 21 22:48 yaqui -> Win98
lrwxrwxrwx    1 jay      jay             9 Nov 16 22:14 zuni -> /home/jay

Again, the computer name of each client exists in this directory as a symbolic link that points to the directory containing the actual roaming profile. For example, maya, a client that runs Windows 98, has a symbolic link named maya to the Win98 directory. A listing of Win98 shows:

$ ls -l Win98
total 148
drwxr-xr-x    3 jay      jay          4096 Nov 23 01:30 Application Data
drwxr-xr-x    2 jay      jay          4096 Nov 23 01:30 Cookies
drwxr-xr-x    3 jay      jay          4096 Dec  7 03:47 Desktop
drwxr-xr-x    3 jay      jay          4096 Nov 23 01:30 History
drwxr-xr-x    2 jay      jay          4096 Nov 23 01:30 NetHood
drwxr-xr-x    2 jay      jay          4096 Dec  7 03:47 Recent
drwxr-xr-x    3 jay      jay          4096 Nov 23 01:30 Start Menu
-rw-r--r--    1 jay      jay        114720 Dec  7 03:46 USER.DAT

The contents of the Win95 and WinMe directories appear similar and contain roaming profiles that work exactly as they should on their respective operating systems.

Notice in the previous listing that aztec and zuni are symbolic links to /home/jay. We've cautioned you never to configure a roaming profile directory to be a user's home directory, but this is to handle something different. The clients aztec and zuni are Windows XP systems, which handle logon home differently than other versions of Windows. We have set logon home = \\%L\%u\.win profile, and all versions of Windows except for Windows XP strip off everything after \\%L\%u and correctly locate the home directory—in this case, /home/jay. Windows XP uses the full UNC, so we simply add a symbolic link to redirect it to the correct directory to get the net use H: /home command to work as it should. The roaming profiles for Windows XP systems are not affected by this and are kept with the other roaming profiles in the Windows NT/2000/XP family, as shown in this listing:

$ ls -l /home/samba-ntprof/jay
total 16
lrwxrwxrwx    1 jay      jay             5 Nov 20 03:45 apache -> Win2K
lrwxrwxrwx    1 jay      jay             5 Nov 13 12:35 aztec -> WinXP
lrwxrwxrwx    1 jay      jay             5 Nov 13 12:34 dine -> WinNT
lrwxrwxrwx    1 jay      jay             5 Nov 24 03:44 inca -> Win2K
lrwxrwxrwx    1 jay      jay             5 Nov 13 12:34 pima -> Win2K
drwx------   13 jay      jay          4096 Dec  3 15:24 qero
drwx------   13 jay      jay          4096 Dec  1 20:31 Win2K
drwx------   12 jay      jay          4096 Nov 30 17:04 WinNT
drwx------   13 jay      jay          4096 Nov 20 01:23 WinXP
lrwxrwxrwx    1 jay      jay             5 Nov 20 06:09 yavapai -> WinXP
lrwxrwxrwx    1 jay      jay             5 Nov 13 12:34 zapotec -> Win2K
lrwxrwxrwx    1 jay      jay             5 Nov 13 12:35 zuni -> WinXP

As you can see, we are using a similar method for the Windows NT/2000/XP roaming profiles. In the listing, qero is not a symbolic link, but rather a directory that holds the roaming profile for qero, a Windows 2000 client that has recently been added. We had not created a symbolic link called qero before installing Windows 2000, so when jay logged off for the first time, Samba created a directory named qero and copied the roaming profile received from the client to the new directory. Because this is a separate directory from Win2K, which all other Windows 2000 clients are using to share their roaming profiles, the roaming profile for qero works like a local profile, except that it is stored on the primary domain controller.

This might seem like an odd thing to do, but it has some purpose. Sometimes you might wish to isolate a client in this manner, especially while the operating system is being installed and initially configured. Remember, if that client, with its default local profile, is logged off the domain, the local profile will be written to the roaming profile directory. If the client were using the shared roaming profile directory, the effect could be undesirable, to say the least. Using our method, the qero directory can later be renamed to make it into an archival backup, or it can just be deleted. Then a new symlink named qero can be created to point to the Win2K directory, and qero will share the roaming profile in Win2K with the other Windows 2000 clients.

An alternative method is simply to create the symbolic links before the clients are added to the network. After you become more comfortable with the way roaming profiles work, you might find this method to be simpler and quicker.

Again, we urge you to be careful about letting different versions of Windows share the same roaming profile. The method of configuring roaming profiles we've shown you here allows you to test a configuration for a few clients at a time without affecting your whole network of clients. For example, we could install a small number of Windows 2000 and Windows XP systems in the domain for testing purposes and then create symlinks for them that point to a directory called Win2KXP to find out if sharing roaming profiles between our Windows 2000 and Windows XP systems meets our expectations. The Win2KXP directory could be created as an empty directory, in which case it would have a roaming profile written to it by the first of the clients to log off. Or, Win2KXP could simply be a renamed roaming profile directory that was created by one of the clients when it was added to the domain.

Configuring Windows 95/98/Me for Roaming Profiles

For roaming profiles to work on Windows 95/98/Me clients, all you need to do is change one setting to allow each user to have a separate local profile. This has the side effect of enabling roaming profiles as well.

Open the Control Panel and double-click the Passwords icon to open the Passwords Properties dialog box. Click the User Profiles tab, and the dialog box will appear as shown in Figure 4-12.

Figure 4-12. The Windows 98 Passwords Properties dialog

Click the button labeled "Users can customize their preferences and desktop settings." In the User profile settings box, you can check the options you prefer. When done, click the OK button and reboot as requested. During this first reboot, Windows will copy the local profile data to C:\windows\profiles but will not attempt to copy the roaming profile from the server. The next time the system is shut down, the local profile will be copied to the server, and when Windows reboots, it will copy the roaming profile from the server.

Configuring Windows NT/2000/XP for Roaming Profiles

Roaming profiles are enabled by default on Windows NT/2000/XP. In case you would like to check or modify your settings, follow these directions.

Make sure you are logged in to the local system as Administrator or another user in the Administrators group. Open the Control Panel and double-click the System icon. On Windows NT/2000, click the User Profiles tab, or on Windows XP, click the Advanced tab and then the Settings button in the User Profiles box. You should see the dialog box in Figure 4-13.

Figure 4-13. The Windows 2000 System Properties, User Profiles tab

Notice in the figure that there are two entries for the username jay. The entry ZAPOTEC\jay refers to the account on the local system, and METRAN\jay refers to the domain account. Recall that when a user logs on, a drop-down menu in the dialog box allows him to log on to a domain or log in to the local system. When jay logs in to the local machine, only the local profile is used. When logged on to the domain, the configuration shown will use the roaming profile. To switch a user's profile type for a domain logon account, click the account name to select it, then click the Change Type... button near the bottom of the dialog box. The Change Profile Type dialog box will appear. Click the radio button for either roaming or local profile, and then click the OK buttons for each dialog box.

Mandatory Profiles

With a simple modification, a roaming profile can be made into a mandatory profile, which has the quality of being unmodifiable by its owner. Mandatory profiles are used in some computing environments to simplify administration. The theory is that if users cannot modify their profiles, less can go wrong, and it is also possible to use the same standardized profile for all users.

In practice, some issues come up. Because the users can still modify the configuration settings in their local profile during their logon session, confusion can result the next time they log on to the domain and discover their changes have been "lost." If the user of a client reinstalls an application in a different place, the shortcuts to the program on the desktop, in the Start menu, or in a Quick Launch bar cannot be permanently deleted. They will reappear every time the user logs back on to the domain. Essentially, a mandatory profile is a roaming profile that always fails to update to the server upon logging off!

Another complication is that different versions of Windows behave differently with mandatory profiles. If a user who has a mandatory profile creates a new file on her desktop, the file might be missing the next time the user logs off and on again or reboots. Some Windows versions preserve desktop files in the local profile (even if the file does not exist in the mandatory profile), whereas others do not.

To change a roaming profile to a mandatory profile, all you have to do is rename the .dat file in the roaming profile directory on the server to have a .man extension instead. For a Windows 95/98/Me roaming profile, you would rename USER.DAT to USER.MAN, and for a Windows NT/2000/XP roaming profile, you would rename NTUSER.DAT to NTUSER.MAN. Also, you might want to make the roaming-profile directory and its contents read-only, to make sure that a user can't change it by logging into his Unix user account on the Samba host system.

If you want to have all your users share a mandatory profile, you can change the definitions of logon path and logon home in your smb.conf file to point to a shared mandatory profile on the server and adjust your directory structure and symbolic links accordingly. For example, logon path and logon home might be defined like this:

logon path = \\%L\profiles\%m
logon home = \\%L\%u\.win_profile\%m

Notice that we've removed the %u part of the path for logon path, and we would also change the directory structure on the server to do away with the separation of the profiles by username and have just one profile for each Windows NT/2000/XP version.

We cannot use the same treatment for logon home because it is also used to specify the home directory. In this case, we would change the symbolic links in each user's .win_profile directory to point to a common mandatory profile directory containing the mandatory profiles for each of Windows 95/98/Me. Again, check the ownership and permissions on the files in the directory, and modify them if necessary to make sure a user can't modify any files by logging into her Unix account on the Samba host system.

Logon Script and Roaming-Profile Options

Table 4-1 summarizes the options commonly used in association with Windows NT domain logon scripts and roaming profiles.

Table 4-1. Logon-script options

Option	Parameters	Function	Default	Scope
`logon` `script`	string (MS-DOS path)	Name of logon script batch file	None	Global
`logon` `path`	string (UNC server and share name)	Location of roaming profile	`\\%N\%U\profile`	Global
`logon` `drive`	string (drive letter)	Specifies the logon drive for a home directory	`Z`:	Global
`logon` `home`	string (UNC server and share name)	Specifies a location for home directories for clients logging on to the domain	`\\%N\%U`	Global

logon script

This option specifies a Windows batch file that will be executed on the client after a user has logged on to the domain. Each logon script should be stored in the root directory of the [netlogon] share or a subdirectory. This option frequently uses the %U or %m variables (user or NetBIOS name) to point to an individual script. For example:

[global]
    logon script = %U.bat

will execute a script based on the username. If the user who is connecting is fred and the path of the [netlogon] share maps to the directory /export/samba/netlogon, the script should be /export/samba/netlogon/fred.bat. Because these scripts are downloaded to the client and executed on the Windows side, they must have MS-DOS-style newline characters rather than Unix newlines.

logon path

This option specifies the location where roaming profiles are kept. When the user logs on, a roaming profile will be downloaded from the server to the client and used as the local profile during the logon session. When the user logs off, the contents of the local profile will be uploaded back to the server until the next time the user connects.

It is often more secure to create a separate share exclusively for storing user profiles:

[global]
    logon path = \\hydra\profile\%U

For more information on this option, see Section 4.5 earlier in this chapter.

logon drive

This option specifies the drive letter on a Windows NT/2000/XP client to which the home directory specified with the logon home option will be mapped. Note that this option will work with Windows NT/2000/XP clients only. For example:

[global]
    logon drive = I:

You should always use drive letters that will not conflict with fixed drives on the client machine. The default is Z:, which is a good choice because it is as far away from A:, C:, and D: as possible.

logon home

This option specifies the location of a user's home directory for use by the MS-DOS net commands. For example, to specify a home directory as a share on a Samba server, use the following:

[global]
    logon home = \\hydra\%U

Note that this works nicely with the [homes] service, although you can specify any directory you wish. Home directories can be mapped with a logon script using the following command:

C:\>net use i: /home

System Policies

A system policy can be used in a Windows NT domain as a remote administration tool for implementing a similar computing environment on all clients and limiting the abilities of users to change configuration settings on their systems or allowing them to run only a limited set of programs. One application of system policies is to use them along with mandatory profiles to implement a collection of computers for public use, such as in a library, school, or Internet cafe.

A system policy is a collection of registry settings that is stored in a file on the PDC and is automatically downloaded to the clients when users log on to the domain. The file containing the settings is created on a Windows system using the System Policy Editor. Because the format of the registry is different between Windows 95/98/Me and Windows NT/2000/XP, it is necessary to make sure that the file that is created is in the proper format. This is a very simple matter because when the System Policy Editor runs on Windows 95/98/Me, it will create a file in the format for Windows 95/98/Me, and if it is run on Windows NT/2000/XP, it will use the format needed by those versions. After the policy file is created with the System Policy Editor, it is stored on the primary domain controller and is automatically downloaded by the clients during the logon process, and the policies are applied to the client system.

On Windows NT 4.0 Server, you can run the System Policy Editor by logging in to the system as Administrator or another user in the Administrators group, opening the Start menu, and selecting Programs, then Administrative Tools, then System Policy Editor. On Windows 2000 Advanced Server, open the Start menu and click Run . . . . In the dialog box that comes up, type in C:\winnt\poledit.exe, and click the OK button.

If you are using a Windows version other than NT Server or Windows 2000 Advanced Server, you must install the System Policy Editor, and getting a copy of it can be a little tricky. If you are running Windows NT 4.0 Workstation or Windows 2000 Professional and have a Windows NT 4.0 Server installation CD-ROM, you can run the file \Clients\Svrtools\Winnt\Setup.bat from that CD to install the Client-based Network Administration Tools, which includes poledit.exe. Then open the Start menu, click Run..., type C:\winnt\system32\poledit.exe into the text area, and click the OK button.

If you are using Windows 95/98, insert a Windows 95 or Windows 98 distribution CD-ROM [4] into your CD-ROM drive, then open the Control Panel and double-click the Add/Remove Programs button.

Click the Windows Setup tab, and then click the Have Disk... button. In the new dialog box that appears, click the Browse... button, then select the CD-ROM drive from the Drives drop-down menu. Then:

If you are using a Windows 95 installation CD-ROM, double-click the admin, then apptools, then poledit folder icons.
If you are using a Windows 98 installation CD-ROM, double-click the tools, then reskit, then netadmin, then poledit folder icons.

You should see "grouppol.inf" appear in the File name: text area on the left of the dialog box. Click the OK buttons in two dialog boxes, and you will be presented with a dialog box in which you should select both the Group Policies and System Policy Editor checkboxes. Then click the Install button. Close the remaining dialog box, and you can now run the System Policy Editor by opening the Start menu and selecting Programs, then Accessories, then System Tools, then System Policy Editor. Or click the Run... item in the Start Menu, and enter C:\Windows\Poledit.

When the System Policy Editor starts up, select New Policy from the File menu, and you will see a window similar to that in Figure 4-14.

Figure 4-14. The System Policy Editor window

The next step is to make a selection from the File menu to add policies for users, groups, and computers. For each item you add, you will be asked for the username, or name of the group or computer, and a new icon will appear in the window. Double-clicking one of the icons will bring up the Properties dialog box, such as the one shown in Figure 4-15.

Figure 4-15. The Properties dialog of System Policy Editor

The upper window in the dialog shows the registry settings that can be modified as part of the system policy, and the lower window shows descriptive information or more settings pertaining to the one selected in the upper window. Notice in the figure that there are three checkboxes and that they are all in different states:

Checked: Meaning that the registry setting is enabled in the policy
White (unchecked): Which clears the registry setting
Gray: Which causes the registry setting on the client to be unmodified

Basically, if all the items are left gray (the default), the system policy will have no effect. The registry of the logged-on client will not be modified. However, if any of the items are either checked or unchecked (white), the registry on the client will be modified to enable the setting or clear it.

WARNING

In this section, we are giving you enough information on using the System Policy Editor to get you started—or, should we say, enough rope with which to hang yourself. Remember that a system policy, once put into action, will be modifying the registries of all clients who log on to the domain. The usual warnings about editing a Windows registry apply here with even greater importance. Consider how difficult (or even impossible) it will be for you to restore the registries on all those clients if anything happens to go wrong. As with roaming profiles, casual or careless implementation of system policies can easily lead to domain-wide disaster.

Creating a good system policy file is a complex topic, which we cannot cover in detail here. It would take a whole book, and yes, there happens to be an O'Reilly book on the subject, Windows System Policy Editor. Another definitive source of documentation on Windows NT system policies and the System Policy Editor is the Microsoft white paper Implementing Policies and Profiles for Windows NT 4.0, which can be found at http://www.microsoft.com/ntserver/techresources/management/prof_policies.asp.

Once you have created a policy, click the OK button and use the Save As... item from the File menu to save it. Use the filename config.pol for a Windows 95/98 system policy and ntconfig.pol for a policy that will be used on Windows NT/2000/XP clients. Finally, copy the .pol file to the directory used for the [netlogon] share on the Samba PDC. The config.pol and ntconfig.pol files must go in this directory—unlike roaming profiles and logon scripts, there is no way to specify the location of the system policy files in smb.conf. If you want to have different system policies for different users or computers, you must perform that part of the configuration within the System Policy Editor.

TIP

If you have, or will have, any Windows Me clients on your network, be careful. Microsoft has stated that Windows Me does not support system policies. The odd thing about this is that it will download the policy from a config.pol file on the PDC, but there is no guarantee that the results will be what was intended. Check the effect of your system policy carefully on your Windows Me clients to make sure it is working how you want.

When a user logs on to the domain, her Windows client will download the .pol file from the server, and the settings in it (that is, the items either checked or cleared in the System Policy Editor) will override the client's settings.

If things "should work" but don't, try shutting down the Windows client and restarting, rather than just logging off and on again. Windows sometimes will hold the [netlogon] share open across logon sessions, and this can prevent the client from getting the updated .pol file from the server.

Samba as a Domain Member Server

Up to now, we've focused on configuring and using Samba as the primary domain controller. If you already have a domain controller on your network, either a Windows NT/2000 Server system or a Samba PDC, you can add a Samba server to the domain as a domain member server. This involves setting up the Samba server to have a computer account with the primary domain controller, in a similar way that Windows NT/2000/XP clients can have computer accounts on a Samba PDC. When a client accesses shares on the Samba domain member server, Samba will pass off the authentication to the domain controller rather than performing the task on the local system. If the PDC is a Windows server, any number of Windows BDCs might exist that can handle the authentication instead of the PDC.

The first step is to add the Samba server to the domain by creating a computer account for it on the primary domain controller. You can do this using the smbpasswd command, as follows:

# smbpasswd -j DOMAIN -r PDCNAME -Uadmin_acct%password

In this command, DOMAIN is replaced by the name of the domain the Samba host is joining, PDCNAME is replaced by the computer name of the primary domain controller, admin_acct is replaced by the username of an administrative account on the domain controller (either Administrator—or another user in the Administrators group—on Windows NT/2000, and root on Samba), and password is replaced with the password of that user. To give a more concrete example, on our domain that has a Windows NT 4 Server primary domain controller or a Windows 2000 Active Directory domain controller named SINAGUA, the command would be:

# smbpasswd -j METRAN -r SINAGUA -UAdministrator%hup8ter

and if the PDC is a Samba system, we would use the command:

# smbpasswd -j METRAN -r toltec -Uroot%jwun83jb

where jwun83jb is the password for the root user that is contained in the smbpasswd file, as we explained earlier in this chapter.

If you did it right, smbpasswd will respond with a message saying the domain has been joined. The security identifier [5] returned to Samba from the PDC is kept in the file /usr/local/samba/private/secrets.tdb. The information in secrets.tdb is security-sensitive, so make sure to protect secrets.tdb in the same way you would treat Samba's password file.

The next step is to modify the smb.conf file. Assuming you are starting with a valid smb.conf file that correctly configures Samba to function in a workgroup, such as the one we used in Chapter 2, it is simply a matter of adding the following three lines to the [global] section:

workgroup = METRAN
security = domain
password server = *

The first line establishes the name of the domain (even though it says "workgroup"). Instead of METRAN, use the name of the domain you are joining. Setting security to "domain" causes Samba to hand off authentication to a domain controller, and the password server = * line tells Samba to find the domain controller for authentication (which could be the primary domain controller or a backup domain controller) by querying the WINS server or using broadcast packets if a WINS server is not available.

At this point, it would be prudent to run testparm to check that your smb.conf is free of errors. Then restart the Samba daemons.

If the PDC is a Windows NT system, you can use Server Manager to check that the Samba server has been added successfully. Open the Start menu, then select Programs, then Administrative Tools (Common), and then Server Manager. Server Manager starts up with a window that looks like Figure 4-16.

Figure 4-16. The Windows NT Server Manager window

As you can see, we've added both toltec and mixtec to a domain for which the Windows NT 4.0 Server system, sinagua, is the primary domain controller.

You can check your setup on Windows 2000 Advanced Server by opening the Start menu and selecting Programs, then Administrative Tools, then Active Directory Users and Computers. The window that opens up will look like Figure 4-17.

Figure 4-17. The Windows 2000 Active Directory Users and Computers window

Click Computers in the left side of the window with the Tree tab. You should see your Samba system listed in the right pane of the window.

Windows NT Domain Options

Table 4-2 shows the options that are commonly used in association with Samba on a Windows NT domain.

Table 4-2. Windows NT domain options

Option	Parameters	Function	Default	Scope
`domain logons`	boolean	Indicates whether Windows domain logons are to be used	`No`	Global
`domain master`	boolean	For telling Samba to take the role of domain master browser	Auto	Global
`add user script`	string (command)	Script to run to add a user or computer account	None	Global
`delete user` `script`	string (command)	Script to run to delete a user or computer account	None	Global
`domain admin group`	string (list of users)	Users that are in the Domain Admins group	None	Global
`domain guest group`	string (list of users)	Users that are in the Domain Guests group	None	Global
`password server`	string (list of computers)	List of domain controllers used for authentication when Samba is running as a domain member server	None	Global
`machine password timeout`	numeric (seconds)	Sets the renewal interval for NT domain machine passwords	`604,800` (1 week )	Global

Here are detailed explanations of each Windows NT domain option listed in Table 4-2.

domain logons

This option configures Samba to accept domain logons as a primary domain controller. When a client successfully logs on to the domain, Samba will return a special token to the client that allows the client to access domain shares without consulting the PDC again for authentication. Note that the Samba machine must employ user-level security (security = user) and must be the PDC for this option to function. In addition, Windows machines will expect a [netlogon] share to exist on the Samba server.

domain master

In a Windows network, a local master browser handles browsing within a subnet. A Windows domain can be made up of a number of subnets, each of which has its own local master browser. The primary domain controller serves the function of domain master browser, collecting the browse lists from the local master browser of each subnet. Each local master browser queries the domain master browser and adds the information about other subnets to their own browse lists. When Samba is configured as a primary domain controller, it automatically sets domain master = yes, making itself the domain master browser.

Because Windows NT PDCs always claim the role of domain master browser, Samba should never be allowed to be domain master if there is a Windows PDC in the domain.

add user script

There are two ways in which add user script can be used. When the Samba server is set up as a primary domain controller, it can be assigned to a command that will run on the Samba server to add a Windows NT/2000/XP computer account to Samba's password database. When the user on the Windows system changes the computer's settings to join a domain, he is asked for the username and password of a user who has administrative rights on the domain controller. Samba authenticates this user and then runs the add user script with root permissions.

When Samba is configured as a domain member server, the add user script can be assigned to a command to add a user to the system. This allows Windows clients to add users that can access shares on the Samba system without requiring an administrator to create the account manually on the Samba host.

delete user script

There are times when users are automatically deleted from the domain, and the delete user script can be assigned to a command that removes a user from the Samba host as a Windows server would do. However, you might not want this to happen, because the Unix user might need the account for reasons other than use with Samba. Therefore, we recommend that you be very careful about using this option.

domain admin group

In a domain of Windows systems, it is possible for a server to get a list of the members of the Domain Admins group from a domain controller. Samba 2.2 does not have the ability to handle this, and the domain admin group parameter exists as a manual means of informing Samba who is in the group. The list should contain root (necessary for adding computer accounts) and any users on Windows NT/2000/XP clients in the domain who are in the Domain Admins group. These users must be recognized by the primary controller in order for them to perform some administrative duties such as adding users to the domain.

password server

In a Windows domain in which the domain controllers are a Windows primary domain controller, along with any number of Windows backup domain controllers, clients and domain member servers authenticate users by querying either the PDC or any of the BDCs. When Samba is configured as a domain member server, the password server parameter allows some control over how Samba finds a domain controller. Earlier versions of Samba could not use the same method that Windows systems use, and it was necessary to specify a list of systems to try. When you set password server = *, Samba 2.2 is able to find the domain controller in the same manner that Windows does, which helps to spread the requests over several backup domain controllers, minimizing the possibility of them becoming overloaded with authentication requests. We recommend that you use this method.

machine password timeout

The machine password timeout global option sets a retention period for Windows NT domain machine passwords. The default is currently set to the same time period that Windows NT 4.0 uses: 604,800 seconds (one week). Samba will periodically attempt to change the machine account password, which is a password used specifically by another server to report changes to it. This option specifies the number of seconds that Samba should wait before attempting to change that password. The timeout period can be changed to a single day by specifying the following:

[global]
    machine password timeout = 86400

TIP

If you would like more information on how Windows NT uses domain usernames and groups, we recommend Eric Pearce's Windows NT in a Nutshell, published by O'Reilly.

Footnotes

[1] 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.

[2] The entry in /etc/passwd might not be required in future Samba versions.

[3] If you want to follow our example in this section, and your network doesn't have any Windows systems offering shares, see Chapter 5 for directions on how to create one. Make sure you understand how to set up shares before continuing with the directions presented here!

[4] The version of the System Policy Editor distributed with Windows 98 is an update of the version shipped with Windows 95. Use the version from the Windows 98 distribution if you can.

[5] This security identifier (SID) is part of an access token that allows the PDC to identify and authenticate the client.