path: root/docs/docbook/projdoc/winbind.sgml

<chapter id="winbind">


<chapterinfo>
	<author>
		<firstname>Tim</firstname><surname>Potter</surname>
		<affiliation>
			<orgname>Samba Team</orgname>
			<address><email>tpot@linuxcare.com.au</email></address>
		</affiliation>
	</author>
	<author>
		<firstname>Andrew</firstname><surname>Trigdell</surname>
		<affiliation>
			<orgname>Samba Team</orgname>
			<address><email>tridge@linuxcare.com.au</email></address>
		</affiliation>
	</author>
	
		
	<pubdate>16 Oct 2000</pubdate>
</chapterinfo>

<title>Unified Logons between Windows NT and UNIX using Winbind</title>

<sect1>
	<title>Abstract</title>

	<para>Integration of UNIX and Microsoft Windows NT through 
	a unified logon has been considered a "holy grail" in heterogeneous 
	computing environments for a long time. We present 
	<emphasis>winbind</emphasis>, a component of the Samba suite 
	of programs as a solution to the unified logon problem. Winbind 
	uses a UNIX implementation 
	of Microsoft RPC calls, Pluggable Authentication Modules, and the Name 
	Service Switch to allow Windows NT domain users to appear and operate 
	as UNIX users on a UNIX machine. This paper describes the winbind 
	system, explaining the functionality it provides, how it is configured, 
	and how it works internally.</para>
</sect1>


<sect1>
	<title>Introduction</title>
	
	<para>It is well known that UNIX and Microsoft Windows NT have 
	different models for representing user and group information and 
	use different technologies for implementing them. This fact has 
	made it difficult to integrate the two systems in a satisfactory 
	manner.</para>
	
	<para>One common solution in use today has been to create 
	identically named user accounts on both the UNIX and Windows systems 
	and use the Samba suite of programs to provide file and print services 
	between the two. This solution is far from perfect however, as 
	adding and deleting users on both sets of machines becomes a chore 
	and two sets of passwords are required both of which
	can lead to synchronization problems between the UNIX and Windows 
	systems and confusion for users.</para>
	
	<para>We divide the unified logon problem for UNIX machines into 
	three smaller problems:</para>
	
	<itemizedlist>
		<listitem><para>Obtaining Windows NT user and group information
		</para></listitem>
		
		<listitem><para>Authenticating Windows NT users
		</para></listitem>
		
		<listitem><para>Password changing for Windows NT users
		</para></listitem>
	</itemizedlist>


	<para>Ideally, a prospective solution to the unified logon problem 
	would satisfy all the above components without duplication of 
	information on the UNIX machines and without creating additional 
	tasks for the system administrator when maintaining users and 
	groups on either system. The winbind system provides a simple 
	and elegant solution to all three components of the unified logon 
	problem.</para>
</sect1>


<sect1>
	<title>What Winbind Provides</title>

	<para>Winbind unifies UNIX and Windows NT account management by 
	allowing a UNIX box to become a full member of a NT domain. Once 
	this is done the UNIX box will see NT users and groups as if 
	they were native UNIX users and groups, allowing the NT domain 
	to be used in much the same manner that NIS+ is used within 
	UNIX-only environments.</para>
	
	<para>The end result is that whenever any 
	program on the UNIX machine asks the operating system to lookup 
	a user or group name, the query will be resolved by asking the 
	NT domain controller for the specified domain to do the lookup.
	Because Winbind hooks into the operating system at a low level 
	(via the NSS name resolution modules in the C library) this 
	redirection to the NT domain controller is completely 
	transparent.</para>
	
	<para>Users on the UNIX machine can then use NT user and group 
	names as they would use "native" UNIX names. They can chown files 
	so that they are owned by NT domain users or even login to the 
	UNIX machine and run a UNIX X-Window session as a domain user.</para>
	
	<para>The only obvious indication that Winbind is being used is 
	that user and group names take the form DOMAIN\user and 
	DOMAIN\group. This is necessary as it allows Winbind to determine 
	that redirection to a domain controller is wanted for a particular 
	lookup and which trusted domain is being referenced.</para>
	
	<para>Additionally, Winbind provides an authentication service 
	that hooks into the Pluggable Authentication Modules (PAM) system 
	to provide authentication via a NT domain to any PAM enabled 
	applications. This capability solves the problem of synchronizing 
	passwords between systems since all passwords are stored in a single 
	location (on the domain controller).</para>
	
	<sect2>
		<title>Target Uses</title>
		
		<para>Winbind is targeted at organizations that have an 
		existing NT based domain infrastructure into which they wish 
		to put UNIX workstations or servers. Winbind will allow these 
		organizations to deploy UNIX workstations without having to 
		maintain a separate account infrastructure. This greatly 
		simplifies the administrative overhead of deploying UNIX 
		workstations into a NT based organization.</para>
		
		<para>Another interesting way in which we expect Winbind to 
		be used is as a central part of UNIX based appliances. Appliances 
		that provide file and print services to Microsoft based networks 
		will be able to use Winbind to provide seamless integration of 
		the appliance into the domain.</para>
	</sect2>
</sect1>



<sect1>
	<title>How Winbind Works</title>
	
	<para>The winbind system is designed around a client/server 
	architecture. A long running <command>winbindd</command> daemon 
	listens on a UNIX domain socket waiting for requests
	to arrive. These requests are generated by the NSS and PAM 
	clients and processed sequentially.</para>
	
	<para>The technologies used to implement winbind are described 
	in detail below.</para>
	
	<sect2>
		<title>Microsoft Remote Procedure Calls</title>
		
		<para>Over the last two years, efforts have been underway 
		by various Samba Team members to decode various aspects of 
		the Microsoft Remote Procedure Call (MSRPC) system. This 
		system is used for most network related operations between 
		Windows NT machines including remote management, user authentication
		and print spooling. Although initially this work was done 
		to aid the implementation of Primary Domain Controller (PDC) 
		functionality in Samba, it has also yielded a body of code which 
		can be used for other purposes.</para>
		
		<para>Winbind uses various MSRPC calls to enumerate domain users 
		and groups and to obtain detailed information about individual 
		users or groups. Other MSRPC calls can be used to authenticate 
		NT domain users and to change user passwords. By directly querying 
		a Windows PDC for user and group information, winbind maps the 
		NT account information onto UNIX user and group names.</para>
	</sect2>
	
	<sect2>
		<title>Name Service Switch</title>
		
		<para>The Name Service Switch, or NSS, is a feature that is 
		present in many UNIX operating systems. It allows system 
		information such as hostnames, mail aliases and user information 
		to be resolved from different sources. For example, a standalone 
		UNIX workstation may resolve system information from a series of 
		flat files stored on the local filesystem. A networked workstation 
		may first attempt to resolve system information from local files, 
		and then consult a NIS database for user information or a DNS server 
		for hostname information.</para>
		
		<para>The NSS application programming interface allows winbind 
		to present itself as a source of system information when 
		resolving UNIX usernames and groups.  Winbind uses this interface, 
		and information obtained from a Windows NT server using MSRPC 
		calls to provide a new source of account enumeration.  Using standard 
		UNIX library calls, one can enumerate the users and groups on
		a UNIX machine running winbind and see all users and groups in 
		a NT domain plus any trusted domain as though they were local 
		users and groups.</para>
		
		<para>The primary control file for NSS is 
		<filename>/etc/nsswitch.conf</filename>. 
		When a UNIX application makes a request to do a lookup 
		the C library looks in <filename>/etc/nsswitch.conf</filename> 
		for a line which matches the service type being requested, for 
		example the "passwd" service type is used when user or group names 
		are looked up. This	config line species which implementations 
		of that service should be tried and in what order. If the passwd 
		config line is:</para>

		<para><command>passwd: files example</command></para>

		<para>then the C library will first load a module called 
		<filename>/lib/libnss_files.so</filename> followed by
		the module <filename>/lib/libnss_example.so</filename>. The 
		C library will dynamically load each of these modules in turn 
		and call resolver functions within the modules to try to resolve 
		the request. Once the request is resolved the C library returns the
		result to the application.</para>
		
		<para>This NSS interface provides a very easy way for Winbind 
		to hook into the operating system. All that needs to be done 
		is to put <filename>libnss_winbind.so</filename> in <filename>/lib/</filename> 
		then add "winbind" into <filename>/etc/nsswitch.conf</filename> at 
		the appropriate place. The C library will then call Winbind to 
		resolve user and group names.</para>
	</sect2>
	
	<sect2>
		<title>Pluggable Authentication Modules</title>
		
		<para>Pluggable Authentication Modules, also known as PAM, 
		is a system for abstracting authentication and authorization 
		technologies. With a PAM module it is possible to specify different 
		authentication methods for different system applications without 
		having to recompile these applications. PAM is also useful
		for implementing a particular policy for authorization. For example, 
		a system administrator may only allow console logins from users 
		stored in the local password file but only allow users resolved from 
		a NIS database to log in over the network.</para>
		
		<para>Winbind uses the authentication management and password 
		management PAM interface to integrate Windows NT users into a 
		UNIX system. This allows Windows NT users to log in to a UNIX 
		machine and be authenticated against a suitable Primary Domain 
		Controller. These users can also change their passwords and have 
		this change take effect directly on the Primary Domain Controller.
		</para>
		
		<para>PAM is configured by providing control files in the directory 
		<filename>/etc/pam.d/</filename> for each of the services that 
		require authentication. When an authentication request is made 
		by an application the PAM code in the C library looks up this
		control file to determine what modules to load to do the 
		authentication check and in what order. This interface makes adding 
		a new authentication service for Winbind very easy, all that needs 
		to be done is that the <filename>pam_winbind.so</filename> module 
		is copied to <filename>/lib/security/</filename> and the PAM 
		control files for relevant services are updated to allow 
		authentication via winbind. See the PAM documentation
		for more details.</para>
	</sect2>
	
	
	<sect2>
		<title>User and Group ID Allocation</title>
		
		<para>When a user or group is created under Windows NT 
		is it allocated a numerical relative identifier (RID). This is 
		slightly different to UNIX which has a range of numbers that are 
		used to identify users, and the same range in which to identify 
		groups. It is winbind's job to convert RIDs to UNIX id numbers and
		vice versa.  When winbind is configured it is given part of the UNIX 
		user id space and a part of the UNIX group id space in which to 
		store Windows NT users and groups. If a Windows NT user is 
		resolved for the first time, it is allocated the next UNIX id from 
		the range. The same process applies for Windows NT groups. Over 
		time, winbind will have mapped all Windows NT users and groups
		to UNIX user ids and group ids.</para>

		<para>The results of this mapping are stored persistently in 
		an ID mapping database held in a tdb database). This ensures that 
		RIDs are mapped to UNIX IDs in a consistent way.</para>
	</sect2>
	
	
	<sect2>
		<title>Result Caching</title>

		<para>An active system can generate a lot of user and group 
		name lookups. To reduce the network cost of these lookups winbind 
		uses a caching scheme based on the SAM sequence number supplied 
		by NT domain controllers.  User or group information returned 
		by a PDC is cached by winbind along with a sequence number also 
		returned by the PDC. This sequence number is incremented by 
		Windows NT whenever any user or group information is modified. If 
		a cached entry has expired, the sequence number is requested from 
		the PDC and compared against the sequence number of the cached entry. 
		If the sequence numbers do not match, then the cached information 
		is discarded and up to date information is requested directly 
		from the PDC.</para>
	</sect2>
</sect1>


<sect1>
	<title>Installation and Configuration</title>
	
<para>
Many thanks to John Trostel <ulink 
url="mailto:jtrostel@snapserver.com">jtrostel@snapserver.com</ulink>
for providing the HOWTO for this section.
</para>

<para>
This HOWTO describes how to get winbind services up and running 
to control access and authenticate users on your Linux box using 
the winbind services which come with SAMBA 2.2.2.
</para>


<sect2>
<title>Introduction</title>

<para>
This HOWTO describes the procedures used to get winbind up and 
running on my RedHat 7.1 system.  Winbind is capable of providing access 
and authentication control for Windows Domain users through an NT 
or Win2K PDC for 'regular' services, such as telnet a nd ftp, as
well for SAMBA services.
</para>

<para>
This HOWTO has been written from a 'RedHat-centric' perspective, so if 
you are using another distribution, you may have to modify the instructions 
somewhat to fit the way your distribution works.
</para>


<itemizedlist>
<listitem>
	<para>
	<emphasis>Why should I to this?</emphasis>
	</para>
	
	<para>This allows the SAMBA administrator to rely on the 
	authentication mechanisms on the NT/Win2K PDC for the authentication 
	of domain members.  NT/Win2K users no longer need to have separate 
	accounts on the SAMBA server.
	</para>
</listitem>

<listitem>
	<para>
	<emphasis>Who should be reading this document?</emphasis>
	</para>
	
	<para>
	This HOWTO is designed for system administrators.  If you are 
	implementing SAMBA on a file server and wish to (fairly easily) 
	integrate existing NT/Win2K users from your PDC onto the
	SAMBA server, this HOWTO is for you.  That said, I am no NT or PAM 
	expert, so you may find a better or easier way to accomplish 
	these tasks.
	</para>
</listitem>
</itemizedlist>
</sect2>


<sect2>
<title>Requirements</title>

<para>
If you have a samba configuration file that you are currently 
using... BACK IT UP!  If your system already uses PAM, BACK UP 
THE <filename>/etc/pam.d</filename> directory contents! If you 
haven't already made a boot disk, MAKE ON NOW!
</para>

<para>
Messing with the pam configuration files can make it nearly impossible 
to log in to yourmachine. That's why you want to be able to boot back 
into your machine in single user mode and restore your 
<filename>/etc/pam.d</filename> back to the original state they were in if 
you get frustrated with the way things are going.  ;-)
</para>

<para>
The newest version of SAMBA (version 2.2.2), available from 
cvs.samba.org, now include a functioning winbindd daemon.  Please refer 
to the main SAMBA web page or, better yet, your closest SAMBA mirror 
site for instructions on downloading the source code.
</para>

<para>
To allow Domain users the ability to access SAMBA shares and 
files, as well as potentially other services provided by your 
SAMBA machine, PAM (pluggable authentication modules) must
be setup properly on your machine.  In order to compile the 
winbind modules, you should have at least the pam libraries resident 
on your system.  For recent RedHat systems (7.1, for instance), that 
means 'pam-0.74-22'.  For best results, it is helpful to also
install the development packages in 'pam-devel-0.74-22'.
</para>

</sect2>


<sect2>
<title>Testing Things Out</title>

<para>
Before starting, it is probably best to kill off all the SAMBA 
related daemons running on your server.  Kill off all <command>smbd</command>, 
<command>nmbd</command>, and <command>winbindd</command> processes that may 
be running.  To use PAM, you will want to make sure that you have the 
standard PAM package (for RedHat) which supplies the <filename>/etc/pam.d</filename> 
directory structure, including the pam modules are used by pam-aware 
services, several pam libraries, and the <filename>/usr/doc</filename> 
and <filename>/usr/man</filename> entries for pam.  Winbind built better 
in SAMBA if the pam-devel package was also installed.  This package includes 
the header files needed to compile pam-aware applications. For instance, my RedHat 
system has both 'pam-0.74-22' and 'pam-devel-0.74-22' RPMs installed.
</para>

<sect3>
<title>Configure and compile SAMBA</title>

<para>
The configuration and compilation of SAMBA is pretty straightforward.
The first three steps maynot be necessary depending upon
whether or not you have previously built the Samba binaries.
</para>

<para><programlisting>
<prompt>root# </prompt> autoconf
<prompt>root# </prompt> make clean
<prompt>root# </prompt> rm config.cache
<prompt>root# </prompt> ./configure --with-winbind
<prompt>root# </prompt> make
<prompt>root# </prompt> make install
</programlisting></para>


<para>
This will, by default, install SAMBA in /usr/local/samba.  See the 
main SAMBA documentation if you want to install SAMBA somewhere else.  
It will also build the winbindd executable and libraries. 
</para>

</sect3>

<sect3>
<title>Configure nsswitch.conf and the winbind libraries</title>

<para>
The libraries needed to run the winbind daemon through nsswitch 
need to be copied to their proper locations, so
</para>

<para>
<prompt>root# </prompt> cp ../samba/source/nsswitch/libnss_winbind.so /lib
</para>

<para>
I also found it necessary to make the following symbolic link:
</para>

<para>
<prompt>root# </prompt> ln -s /lib/libnss_winbind.so /lib/libnss_winbind.so.2
</para>

<para>
Now, as root you need to edit <filename>/etc/nsswitch.conf</filename> to 
allow user and group entries to be visible from the <command>winbindd</command> 
daemon, as well as from your /etc/hosts files and NIS servers.  My 
<filename>/etc/nsswitch.conf</filename> file look like this after editing:
</para>

<para><programlisting>
	passwd:     files winbind
	shadow:     files winbind
	group:      files winbind
</programlisting></para>

<para>	
The libraries needed by the winbind daemon will be automatically 
entered into the ldconfig cache the next time your system reboots, but it 
is faster (and you don't need to reboot) if you do it manually:
</para>

<para>
<prompt>root# </prompt> /sbin/ldconfig -v | grep winbind
</para>

<para>
This makes <filename>libnss_winbind</filename> available to winbindd 
and echos back a check to you.
</para>

</sect3>


<sect3>
<title>Configure smb.conf</title>

<para>
Several parameters are needed in the smb.conf file to control 
the behavior of <command>winbindd</command>. Configure 
<filename>smb.conf</filename> These are described in more detail in 
the <ulink url="winbindd.8.html">winbindd(8)</ulink> man page.  My 
<filename>smb.conf</filename> file was modified to
include the following entries in the [global] section:
</para>

<para><programlisting>
[global]
     <...>
     # separate domain and username with '+', like DOMAIN+username
     winbind separator = +
     # use uids from 10000 to 20000 for domain users
     winbind uid = 10000-20000
     # use gids from 10000 to 20000 for domain groups
     winbind gid = 10000-20000
     # allow enumeration of winbind users and groups
     winbind enum users = yes
     winbind enum groups = yes
     # give winbind users a real shell (only needed if they have telnet access)
     template shell = /bin/bash
</programlisting></para>

</sect3>


<sect3>
<title>Join the SAMBA server to the PDC domain</title>

<para>
Enter the following command to make the SAMBA server join the 
PDC domain, where <replaceable>DOMAIN</replaceable> is the name of 
your Windows domain and <replaceable>Administrator</replaceable> is 
a domain user who has administrative privileges in the domain.
</para>
	

<para>
<prompt>root# </prompt>/usr/local/samba/bin/smbpasswd -j DOMAIN -r PDC -U Administrator
</para>


<para>
The proper response to the command should be: "Joined the domain 
<replaceable>DOMAIN</replaceable>" where <replaceable>DOMAIN</replaceable> 
is your DOMAIN name.
</para>

</sect3>


<sect3>
<title>Start up the winbindd daemon and test it!</title>

<para>
Eventually, you will want to modify your smb startup script to 
automatically invoke the winbindd daemon when the other parts of 
SAMBA start, but it is possible to test out just the winbind
portion first.  To start up winbind services, enter the following 
command as root:
</para>
	
<para>
<prompt>root# </prompt>/usr/local/samba/bin/winbindd
</para>

<para>
I'm always paranoid and like to make sure the daemon 
is really running...
</para>

<para>
<prompt>root# </prompt> ps -ae | grep winbindd 
3025 ?        00:00:00 winbindd
</para>

<para>
Now... for the real test, try to get some information about the 
users on your PDC
</para>

<para>
<prompt>root# </prompt> # /usr/local/samba/bin/wbinfo -u
</para>

<para>	
This should echo back a list of users on your Windows users on 
your PDC.  For example, I get the following response:
</para>

<para><programlisting>
CEO+Administrator
CEO+burdell
CEO+Guest
CEO+jt-ad
CEO+krbtgt
CEO+TsInternetUser
</programlisting></para>

<para>
Obviously, I have named my domain 'CEO' and my winbindd separator is '+'.
</para>

<para>
You can do the same sort of thing to get group information from 
the PDC:
</para>

<para><programlisting>
<prompt>root# </prompt>/usr/local/samba/bin/wbinfo -g
CEO+Domain Admins
CEO+Domain Users
CEO+Domain Guests
CEO+Domain Computers
CEO+Domain Controllers
CEO+Cert Publishers
CEO+Schema Admins
CEO+Enterprise Admins
CEO+Group Policy Creator Owners
</programlisting></para>

<para>
The function 'getent' can now be used to get unified 
lists of both local and PDC users and groups.
Try the following command:
</para>

<para>
<prompt>root# </prompt> getent passwd
</para>
	
<para>
You should get a list that looks like your <filename>/etc/passwd</filename> 
list followed by the domain users with their new uids, gids, home 
directories and default shells.
</para>

<para>
The same thing can be done for groups with the command
</para>

<para>
<prompt>root# </prompt> getent group
</para>

</sect3>


<sect3>
<title>Fix the /etc/rc.d/init.d/smb startup files</title>

<para>
The <command>winbindd</command> daemon needs to start up after the 
<command>smbd</command> and <command>nmbd</command> daemons are running.  
To accomplish this task, you need to modify the <filename>/etc/init.d/smb</filename>
script to add commands to invoke this daemon in the proper sequence.  My 
<filename>/etc/init.d/smb</filename> file starts up <command>smbd</command>, 
<command>nmbd</command>, and <command>winbindd</command> from the 
<filename>/usr/local/samba/bin</filename> directory directly.  The 'start' 
function in the script looks like this:
</para>

<para><programlisting>
start() {
        KIND="SMB"
        echo -n $"Starting $KIND services: "
        daemon /usr/local/samba/bin/smbd $SMBDOPTIONS
        RETVAL=$?
        echo
        KIND="NMB"
        echo -n $"Starting $KIND services: "
        daemon /usr/local/samba/bin/nmbd $NMBDOPTIONS
        RETVAL2=$?
        echo
        KIND="Winbind"
        echo -n $"Starting $KIND services: "
        daemon /usr/local/samba/bin/winbindd
        RETVAL3=$?
        echo
        [ $RETVAL -eq 0 -a $RETVAL2 -eq 0 -a $RETVAL3 -eq 0 ] && touch /var/lock/subsys/smb || \
           RETVAL=1
        return $RETVAL
}
</programlisting></para>

<para>
The 'stop' function has a corresponding entry to shut down the 
services and look s like this:
</para>

<para><programlisting>
stop() {
        KIND="SMB"
        echo -n $"Shutting down $KIND services: "
        killproc smbd
        RETVAL=$?
        echo
        KIND="NMB"
        echo -n $"Shutting down $KIND services: "
        killproc nmbd
        RETVAL2=$?
        echo
        KIND="Winbind"
        echo -n $"Shutting down $KIND services: "
        killproc winbindd
        RETVAL3=$?
        [ $RETVAL -eq 0 -a $RETVAL2 -eq 0 -a $RETVAL3 -eq 0 ] && rm -f /var/lock/subsys/smb
        echo ""
        return $RETVAL
}
</programlisting></para>

</sect3>



<sect3>
<title>Configure Winbind and PAM</title>

<para>
If you have made it this far, you know that winbindd is working.  
Now it is time to integrate it into the operation of samba and other 
services.  The pam configuration files need to be altered in
this step.  (Did you remember to make backups of your original 
<filename>/etc/pam.d</filename> files? If not, do it now.)
</para>

<para>
To get samba to allow domain users and groups, I modified the 
<filename>/etc/pam.d/samba</filename> file from
</para>


<para><programlisting>
auth    required        /lib/security/pam_stack.so service=system-auth
account required        /lib/security/pam_stack.so service=system-auth
</programlisting></para>

<para>
to
</para>

<para><programlisting>
auth    required        /lib/security/pam_winbind.so
auth    required        /lib/security/pam_stack.so service=system-auth
account required        /lib/security/pam_winbind.so
account required        /lib/security/pam_stack.so service=system-auth
</programlisting></para>

<para>
The other services that I modified to allow the use of winbind 
as an authentication service were the normal login on the console (or a terminal 
session), telnet logins, and ftp service.  In order to enable these 
services, you may first need to change the entries in 
<filename>/etc/xinetd.d</filename> (or <filename>/etc/inetd.conf</filename>).  
RedHat 7.1 uses the new xinetd.d structure, in this case you need 
to change the lines in <filename>/etc/xinetd.d/telnet</filename> 
and <filename>/etc/xinetd.d/wu-ftp</filename> from 
</para>

<para><programlisting>
enable = no
</programlisting></para>

<para>
to
</para>

<para><programlisting>
enable = yes
</programlisting></para>

<para>	
For ftp services to work properly, you will also need to either 
have individual directories for the domain users already present on 
the server, or change the home directory template to a general
directory for all domain users.  These can be easily set using 
the <filename>smb.conf</filename> global entry 
<command>template homedir</command>.
</para>

<para>
The <filename>/etc/pam.d/ftp</filename> file can be changed 
to allow winbind ftp access in a manner similar to the
samba file.  My <filename>/etc/pam.d/ftp</filename> file was 
changed to look like this:
</para>

<para><programlisting>
auth       sufficient   /lib/security/pam_winbind.so
auth       required     /lib/security/pam_listfile.so item=user sense=deny file=/etc/ftpusers onerr=succeed
auth       required     /lib/security/pam_stack.so service=system-auth
auth       required     /lib/security/pam_shells.so
account    required     /lib/security/pam_stack.so service=system-auth
session    required     /lib/security/pam_stack.so service=system-auth
</programlisting></para>

<para>
The <filename>/etc/pam.d/login</filename> file can be changed nearly the 
same way.  It now looks like this:
</para>

<para><programlisting>
auth       required     /lib/security/pam_securetty.so
auth       sufficient   /lib/security/pam_winbind.so
auth       sufficient   /lib/security/pam_unix.so use_first_pass
auth       required     /lib/security/pam_stack.so service=system-auth
auth       required     /lib/security/pam_nologin.so
account    sufficient   /lib/security/pam_winbind.so
account    required     /lib/security/pam_stack.so service=system-auth
password   required     /lib/security/pam_stack.so service=system-auth
session    required     /lib/security/pam_stack.so service=system-auth
session    optional     /lib/security/pam_console.so
</programlisting></para>

<para>
In this case, I added the <command>auth sufficient /lib/security/pam_winbind.so</command> 
lines as before, but also added the <command>required pam_securetty.so</command> 
above it, to disallow root logins over the network.  I also added a 
<command>sufficient /lib/security/pam_unix.so use_first_pass</command>
line after the <command>winbind.so</command> line to get rid of annoying 
double prompts for passwords.
</para>

<para>
Finally, don't forget to copy the winbind pam modules from 
the source directory in which you originally compiled the new 
SAMBA up to the /lib/security directory so that pam can use it:
</para>

<para>
<prompt>root# </prompt> cp ../samba/source/nsswitch/pam_winbind.so /lib/security
</para>

</sect3>

</sect2>

</sect1>

<sect1>
	<title>Limitations</title>
	
	<para>Winbind has a number of limitations in its current 
	released version that we hope to overcome in future 
	releases:</para>

	<itemizedlist>
		<listitem><para>Winbind is currently only available for 
		the Linux operating system, although ports to other operating 
		systems are certainly possible. For such ports to be feasible, 
		we require the C library of the target operating system to 
		support the Name Service Switch and Pluggable Authentication
		Modules systems. This is becoming more common as NSS and 
		PAM gain	support among UNIX vendors.</para></listitem>
		
		<listitem><para>The mappings of Windows NT RIDs to UNIX ids 
		is not made algorithmically and depends on the order in which 
		unmapped users or groups are seen by winbind. It may be difficult 
		to recover the mappings of rid to UNIX id mapping if the file 
		containing this information is corrupted or destroyed.</para>
		</listitem>
		
		<listitem><para>Currently the winbind PAM module does not take 
		into account possible workstation and logon time restrictions 
		that may be been set for Windows NT users.</para></listitem>
	</itemizedlist>
</sect1>


<sect1>
	<title>Conclusion</title>

	<para>The winbind system, through the use of the Name Service 
	Switch, Pluggable Authentication Modules, and appropriate 
	Microsoft RPC calls have allowed us to provide seamless 
	integration of Microsoft Windows NT domain users on a
	UNIX system. The result is a great reduction in the administrative 
	cost of running a mixed UNIX and NT network.</para>
	
</sect1>

</chapter>