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<h1 class="head0">Chapter 1. Learning the Samba</h1>


<p><a name="INDEX-1"/>Samba
is an extremely useful networking tool for anyone who has both
Windows and Unix systems on his network. Running on a Unix system, it
allows Windows to share files and printers on the Unix host, and it
also allows Unix users to access resources shared by Windows systems.</p>

<p>Although it might seem natural to use a Windows server to serve files
and printers to a network containing Windows clients, there are good
reasons for preferring a Samba server for this duty. Samba is
reliable software that runs on reliable Unix operating systems,
resulting in fewer problems and a low cost of maintenance. Samba also
offers better performance under heavy loads, outperforming Windows
2000 Server by a factor of 2 to 1 on identical PC hardware, according
to published third-party benchmarks. When common, inexpensive PC
hardware fails to meet the demands of a huge client load, the Samba
server can easily be moved to a proprietary &quot;big
iron&quot; Unix mainframe, which can outperform Windows
running on a PC many times. If all that weren't
enough, Samba has a very nice cost advantage: it's
free. Not only is the software itself freely available, but also no
client licenses are required, and it runs on high-quality, free
operating systems such as Linux and FreeBSD.</p>

<p>After reading the previous paragraph, you might come to the
conclusion that Samba is commonly used by large organizations with
thousands of users on their networks&mdash;and you'd
be right! But Samba's user base includes
organizations all over the planet, of all types and sizes: from
international corporations, to medium and small businesses, to
individuals who run Samba on their Linux laptops. In the last case, a
tool such as VMware is used to run Windows on the same computer, with
Samba enabling the two operating systems to share files.</p>

<p>The types of users vary even more&mdash;Samba is used by
corporations, banks and other financial institutions, government and
military organizations, schools, public libraries, art galleries,
families, and even authors! This book was developed on a Linux system
running VMware and Windows 2000, with Adobe FrameMaker running on
Windows and the document files served by Samba from the Linux
filesystem.</p>

<p>Does all this whet your technological appetite? If so, we encourage
you to keep reading, learn about Samba, and follow our examples to
set up a Samba server of your own. In this and upcoming chapters, we
will tell you exactly how to get started.</p>



<div class="sect1"><a name="samba2-CHP-1-SECT-1"/>

<h2 class="head1">What Is Samba?</h2>

<p><a name="INDEX-2"/>Samba
is a suite of Unix applications that speak the
<a name="INDEX-3"/><a name="INDEX-4"/>Server
Message Block (SMB) protocol. Microsoft Windows operating systems and
the OS/2 operating system use SMB to perform client-server networking
for file and printer sharing and associated operations. By supporting
this protocol, Samba enables computers running Unix to get in on the
action, communicating with the same networking protocol as Microsoft
Windows and appearing as another Windows system on the network from
the perspective of a Windows client. A <a name="INDEX-5"/>Samba
server offers the following services:</p>

<ul><li>
<p>Share one or more directory trees</p>
</li><li>
<p>Share one or more Distributed filesystem (Dfs) trees</p>
</li><li>
<p>Share printers installed on the server among Windows clients on the
network</p>
</li><li>
<p>Assist clients with network browsing</p>
</li><li>
<p>Authenticate clients logging onto a Windows domain</p>
</li><li>
<p>Provide or assist with Windows Internet Name Service (WINS)
name-server resolution</p>
</li></ul>
<p>The Samba suite also includes client tools that allow users on a Unix
system to access folders and printers that Windows systems and Samba
servers offer on the network.</p>

<p>Samba is the brainchild of Andrew <a name="INDEX-6"/>Tridgell, who currently heads the Samba
development team. Andrew started the project in 1991, while working
with a Digital Equipment Corporation (DEC) software suite called
Pathworks, created for connecting DEC VAX computers to computers made
by other companies. Without knowing the significance of what he was
doing, Andrew created a file-server program for an odd protocol that
was part of Pathworks. That protocol later turned out to be SMB. A
few years later, he expanded upon his custom-made SMB server and
began distributing it as a product on the Internet under the name
&quot;SMB Server.&quot; However, Andrew
couldn't keep that name&mdash;it already belonged to
another company's product&mdash;so he tried the
following Unix renaming approach:</p>

<blockquote><pre class="code">$ <tt class="userinput"><b>grep -i '^s.*m.*b' /usr/dict/words</b></tt></pre></blockquote>

<p>And the response was:</p>

<blockquote><pre class="code">salmonberry
samba
sawtimber
scramble</pre></blockquote>

<p>Thus, the name &quot;Samba&quot; was born.</p>

<p>Today, the Samba suite revolves around a pair of Unix daemons that
provide shared resources&mdash;called <em class="firstterm">shares
</em>or s<em class="firstterm">ervices</em>&mdash;to SMB clients
on the network. These are:</p>

<dl>
<dt><b><a name="INDEX-7"/>smbd</b></dt>
<dd>
<p>A daemon that handles file and printer sharing and provides
authentication and authorization for SMB clients.</p>
</dd>



<dt><b><a name="INDEX-8"/>nmbd</b></dt>
<dd>
<p>A daemon that supports NetBIOS Name Service and WINS, which is
Microsoft's implementation of a NetBIOS Name Server
(NBNS). It also assists with network browsing.</p>
</dd>

</dl>

<p>Samba is currently maintained and extended by a group of volunteers
under the active supervision of Andrew Tridgell. Like the Linux
operating system, Samba is distributed as open source software
(<a href="http://opensource.org">http://opensource.org</a>) by its
authors and is distributed under the GNU General Public License
(GPL). Since its inception, development of Samba has been sponsored
in part by the Australian National University, where Andrew Tridgell
earned his Ph.D. Since then, many other organizations have sponsored
Samba developers, including LinuxCare, VA Linux Systems,
Hewlett-Packard, and IBM. It is a true testament to Samba that both
commercial and noncommercial entities are prepared to spend money to
support an open source effort.</p>

<p>Microsoft has also contributed by offering its definition of the SMB
protocol to the Internet Engineering Task Force (IETF) in 1996 as the
<a name="INDEX-9"/><a name="INDEX-10"/>Common
Internet File System (CIFS). Although we prefer to use the term
&quot;SMB&quot; in this book, you will also
often find the protocol being referred to as
&quot;CIFS.&quot; This is especially true on
Microsoft's web site.</p>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-2"/>

<h2 class="head1">What Can Samba Do for Me?</h2>

<p><a name="INDEX-11"/>As explained earlier, Samba can help
Windows and Unix computers coexist in the same network. However,
there are some specific reasons why you might want to set up a Samba
server on your network:</p>

<ul><li>
<p>You don't want to pay for&mdash;or
can't afford&mdash;a full-fledged Windows server,
yet you still need the functionality that one provides.</p>
</li><li>
<p>The Client Access Licenses (CALs) that Microsoft requires for each
Windows client to access a Windows server are unaffordable.</p>
</li><li>
<p>You want to provide a common area for data or user directories to
transition from a Windows server to a Unix one, or vice versa.</p>
</li><li>
<p>You want to share printers among Windows and Unix workstations.</p>
</li><li>
<p>You are supporting a group of computer users who have a mixture of
Windows and Unix computers.</p>
</li><li>
<p>You want to integrate Unix and Windows authentication, maintaining a
single database of user accounts that works with both systems.</p>
</li><li>
<p>You want to network Unix, Windows, Macintosh (OS X), and other
systems using a single protocol.</p>
</li></ul>
<p>Let's take a quick tour of
<a name="INDEX-12"/>Samba in action. Assume that we have
the following basic network configuration: a Samba-enabled Unix
system, to which we will assign the name <tt class="literal">toltec</tt>,
and a pair of Windows clients, to which we will assign the names
<tt class="literal">maya</tt> and <tt class="literal">aztec</tt>, all connected
via a local area network (LAN). Let's also assume
that <tt class="literal">toltec</tt> also has a local inkjet printer
connected to it, <tt class="literal">lp</tt>, and a disk share named
<tt class="literal">spirit</tt>&mdash;both of which it can offer to the
other two computers. A graphic of this network is shown in <a href="ch01.html#samba2-CHP-1-FIG-1">Figure 1-1</a>.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-1"/><img src="figs/sam2_0101.gif"/></div><h4 class="head4">Figure 1-1. A simple network set up with a Samba server</h4>

<p>In this network, each computer listed shares the same
<em class="firstterm">workgroup</em>. A workgroup is a group name tag
that identifies an arbitrary collection of computers and their
resources on an SMB network. Several workgroups can be on the network
at any time, but for our basic network example,
we'll have only one: the METRAN workgroup.</p>


<div class="sect2"><a name="samba2-CHP-1-SECT-2.1"/>

<h3 class="head2">Sharing a Disk Service</h3>

<p><a name="INDEX-13"/><a name="INDEX-14"/><a name="INDEX-15"/>If everything is properly
configured, we should be able to see the Samba server,
<tt class="literal">toltec</tt>, through the Network Neighborhood of the
<tt class="literal">maya</tt> Windows desktop. In fact, <a href="ch01.html#samba2-CHP-1-FIG-2">Figure 1-2</a> shows the Network Neighborhood of the
<tt class="literal">maya</tt> computer, including <tt class="literal">toltec</tt>
and each computer that resides in the METRAN workgroup. Note the
Entire Network icon at the top of the list. As we just mentioned,
more than one workgroup can be on an SMB network at any given time.
If a user clicks the Entire Network icon, she will see a list of all
the workgroups that currently exist on the network.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-2"/><img src="figs/sam2_0102.gif"/></div><h4 class="head4">Figure 1-2. The Network Neighborhood directory</h4>

<p>We can take a closer look at the <tt class="literal">toltec</tt> server by
double-clicking its icon. This contacts <tt class="literal">toltec</tt>
itself and requests a list of its
<em class="firstterm">shares</em>&mdash;the file and printer
resources&mdash;that the computer provides. In this case, a printer
named <tt class="literal">lp</tt>, a home directory named
<tt class="literal">jay</tt>, and a disk share named
<tt class="literal">spirit</tt> are on the server, as shown in <a href="ch01.html#samba2-CHP-1-FIG-3">Figure 1-3</a>. Note that the Windows display shows hostnames
in mixed case (Toltec). Case is irrelevant in hostnames, so you might
see toltec, Toltec, and TOLTEC in various displays or command output,
but they all refer to a single system. Thanks to Samba, Windows 98
sees the Unix server as a valid SMB server and can access the
<tt class="literal">spirit</tt> folder as if it were just another system
folder.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-3"/><img src="figs/sam2_0103.gif"/></div><h4 class="head4">Figure 1-3. Shares available on the Toltec server as viewed from maya</h4>

<p>One popular Windows feature is the ability to map a drive letter
(such as E:, F:, or Z:) to a shared directory on the network using
the Map Network Drive option in Windows Explorer.<a name="FNPTR-1"/><a href="#FOOTNOTE-1">[1]</a>
Once you do so, your applications can access the folder across the
network using the drive letter. You can store data on it, install and
run programs from it, and even password-protect it against unwanted
visitors. See <a href="ch01.html#samba2-CHP-1-FIG-4">Figure 1-4</a> for an example of mapping
a <a name="INDEX-16"/><a name="INDEX-17"/>drive letter to a network
directory.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-4"/><img src="figs/sam2_0104.gif"/></div><h4 class="head4">Figure 1-4. Mapping a network drive to a Windows drive letter</h4>

<p>Take a look at the Path: entry in the dialog box of <a href="ch01.html#samba2-CHP-1-FIG-4">Figure 1-4</a>. An equivalent way to represent a directory on
a network computer is by using two backslashes, followed by the name
of the networked computer, another backslash, and the networked
directory of the computer, as shown here:</p>

<blockquote><pre class="code">\\<em class="replaceable">network-computer</em>\<em class="replaceable">directory</em></pre></blockquote>

<p>This is known as the <em class="firstterm"/><a name="INDEX-18"/>Universal
Naming Convention (UNC)</em>  in the Windows world. For example, the dialog
box in <a href="ch01.html#samba2-CHP-1-FIG-4">Figure 1-4</a> represents the network directory
on the <tt class="literal">toltec</tt> server as:</p>

<blockquote><pre class="code">\\toltec\spirit</pre></blockquote>

<p>If this looks somewhat familiar to you, you're
probably thinking of <em class="firstterm">uniform resource
locators</em><a name="INDEX-19"/><a name="INDEX-20"/> (URLs), which are addresses that web
browsers such as Netscape Navigator and Internet Explorer use to
resolve systems across the Internet. Be sure not to confuse the two:
URLs such as <a href="http://www.oreilly.com">http://www.oreilly.com</a> use forward slashes
instead of backslashes, and they precede the initial slashes with the
data transfer protocol (i.e., ftp, http) and a colon (:). In reality,
URLs and UNCs are two completely separate things, although sometimes
you can specify an SMB share using a URL rather than a UNC. As a URL,
the <em class="filename">\\toltec\spirit</em> share would be specified as
<em class="filename">smb://toltec/spirit</em>.</p>

<p>Once the network drive is set up, Windows and its programs behave as
if the networked directory were a local disk. If you have any
applications that support multiuser functionality on a network, you
can install those programs on the network drive.<a name="FNPTR-2"/><a href="#FOOTNOTE-2">[2]</a> <a href="ch01.html#samba2-CHP-1-FIG-5">Figure 1-5</a> shows the
resulting network drive as it would appear with other storage devices
in the Windows 98 client. Note the pipeline attachment in the icon
for the J: drive; this indicates that it is a network drive rather
than a fixed drive.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-5"/><img src="figs/sam2_0105.gif"/></div><h4 class="head4">Figure 1-5. The Network directory mapped to the client drive letter J</h4>

<p>My Network Places, found in Windows Me, 2000, and XP, works
differently from Network Neighborhood. It is necessary to click a few
more icons, but eventually we can get to the view of the
<tt class="literal">toltec</tt> server as shown in <a href="ch01.html#samba2-CHP-1-FIG-6">Figure 1-6</a>. This is from a Windows 2000 system. Setting
up the network drive using the Map Network Drive option in Windows
2000 works similarly to other Windows versions. <a name="INDEX-21"/><a name="INDEX-22"/><a name="INDEX-23"/></p>

<div class="figure"><a name="samba2-CHP-1-FIG-6"/><img src="figs/sam2_0106.gif"/></div><h4 class="head4">Figure 1-6. Shares available on Toltec (viewed from dine)</h4>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-2.2"/>

<h3 class="head2">Sharing a Printer</h3>

<p><a name="INDEX-24"/><a name="INDEX-25"/><a name="INDEX-26"/>You probably noticed that the printer
<tt class="literal">lp</tt> appeared under the available shares for
<tt class="literal">toltec</tt> in <a href="ch01.html#samba2-CHP-1-FIG-3">Figure 1-3</a>. This
indicates that the Unix server has a printer that can be shared by
the various SMB clients in the workgroup. Data sent to the printer
from any of the clients will be spooled on the Unix server and
printed in the order in which it is received.</p>

<p><a name="INDEX-27"/><a name="INDEX-28"/>Setting up a Samba-enabled
printer on the Windows side is even easier than setting up a disk
share. By double-clicking the printer and identifying the
manufacturer and model, you can install a driver for this printer on
the Windows client. Windows can then properly format any information
sent to the network printer and access it as if it were a local
printer. On Windows 98, double-clicking the Printers icon in the
Control Panel opens the Printers window shown in <a href="ch01.html#samba2-CHP-1-FIG-7">Figure 1-7</a>. Again, note the pipeline attachment below the
printer, which identifies it as being on a network.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-7"/><img src="figs/sam2_0107.gif"/></div><h4 class="head4">Figure 1-7. A network printer available on Toltec</h4>


<div class="sect3"><a name="samba2-CHP-1-SECT-2.2.1"/>

<h3 class="head3">Seeing things from the Unix side</h3>

<p><a name="INDEX-29"/><a name="INDEX-30"/>As mentioned earlier, Samba
appears in Unix as a set of daemon programs. You can view them with
the Unix <a name="INDEX-31"/><em class="emphasis">ps</em> command; you can
read any messages they generate through custom debug files or the
Unix <em class="emphasis">syslog</em> (depending on how Samba is set up);
and you can configure them from a single Samba configuration file:
<em class="emphasis">smb.conf</em>. In addition, if you want to get an idea of
what the daemons are doing, Samba has a program called
<em class="emphasis">smbstatus</em><a name="INDEX-32"/> that will lay it all on the line. Here
is how it works:</p>

<blockquote><pre class="code"># <tt class="userinput"><b>smbstatus</b></tt>
Processing section &quot;[homes]&quot;
Processing section &quot;[printers]&quot;
Processing section &quot;[spirit]&quot;

Samba version 2.2.6
Service     uid    gid    pid     machine
-----------------------------------------
spirit      jay    jay    7735    maya     (172.16.1.6) Sun Aug 12 12:17:14 2002
spirit      jay    jay    7779    aztec    (172.16.1.2) Sun Aug 12 12:49:11 2002
jay         jay    jay    7735    maya     (172.16.1.6) Sun Aug 12 12:56:19 2002

Locked files:
Pid    DenyMode   R/W        Oplock     Name
--------------------------------------------------
7735   DENY_WRITE RDONLY     NONE       /u/RegClean.exe   Sun Aug 12 13:01:22 2002

Share mode memory usage (bytes):
   1048368(99%) free + 136(0%) used + 72(0%) overhead = 1048576(100%) total</pre></blockquote>

<p>The Samba status from this output provides three sets of data, each
divided into separate sections. The first section tells which systems
have connected to the Samba server, identifying each client by its
machine name (<tt class="literal">maya</tt> and <tt class="literal">aztec</tt>)
and IP (Internet Protocol) address. The second section reports the
name and status of the files that are currently in use on a share on
the server, including the read/write status and any locks on the
files. Finally, Samba reports the amount of memory it has currently
allocated to the shares that it administers, including the amount
actively used by the shares plus additional overhead. (Note that this
is not the same as the total amount of memory that the
<em class="emphasis">smbd</em> or <em class="emphasis">nmbd</em> processes are
using.)</p>

<p>Don't worry if you don't understand
these statistics; they will become easier to understand as you move
through the book.</p>


</div>


</div>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-3"/>

<h2 class="head1">Getting Familiar with an SMB Network</h2>

<p><a name="INDEX-33"/>Now that you have had a brief tour of
Samba, let's take some time to get familiar with
Samba's adopted environment: an SMB network.
Networking with SMB is significantly different from working with
common TCP/IP protocols such as FTP and Telnet because there are
several new concepts to learn and a lot of information to cover.
First, we will discuss the basic concepts behind an SMB network,
followed by some Microsoft implementations of it, and finally we will
show you where a Samba server can and cannot fit into the picture.</p>


<div class="sect2"><a name="samba2-CHP-1-SECT-3.1"/>

<h3 class="head2">Understanding NetBIOS</h3>

<p>To begin, let's step back in time. In 1984, IBM
authored a simple application programming interface (API) for
networking its computers, called the <em class="firstterm">Network Basic
Input/Output System
</em>(<a name="INDEX-34"/>NetBIOS).
The NetBIOS API provided a rudimentary design for an application to
connect and share data with other computers.</p>

<p>It's helpful to think of the NetBIOS API as
networking extensions to the standard BIOS API calls. The BIOS
contains low-level code for performing filesystem operations on the
local computer. NetBIOS originally had to exchange instructions with
computers across IBM PC or Token Ring networks. It therefore required
a low-level transport protocol to carry its requests from one
computer to the next.</p>

<p>In late 1985, IBM released one such protocol, which it merged with
the NetBIOS API to become the <em class="firstterm">NetBIOS Extended User
Interface</em> (<em class="emphasis">NetBEUI</em> ).
<a name="INDEX-35"/>NetBEUI was
designed for small LANs, and it let each computer claim a name (up to
15 characters) that wasn't already in use on the
network. By a &quot;small LAN,&quot; we mean
fewer than 255 nodes on the network&mdash;which was considered a
generous number in 1985!</p>

<p>The NetBEUI protocol was very popular with networking applications,
including those running under Windows for Workgroups. Later,
implementations of NetBIOS over Novell's IPX
networking protocols also emerged, which competed with NetBEUI.
However, the networking protocols of choice for the burgeoning
Internet community were TCP/IP and UDP/IP, and implementing the
NetBIOS APIs over those protocols soon became a necessity.</p>

<p>Recall that TCP/IP uses numbers to represent computer addresses
(192.168.220.100, for instance) while NetBIOS uses only names. This
was a major issue when trying to mesh the two protocols together. In
1987, the IETF published standardization documents, titled RFC 1001
and 1002, that outlined how NetBIOS would work over a TCP/UDP
network. This set of documents still governs each implementation that
exists today, including those provided by Microsoft with its Windows
operating systems, as well as the Samba suite.</p>

<p>Since then, the standard that this document governs has become known
as <em class="firstterm">NetBIOS over
TCP/IP</em><a name="INDEX-36"/><a name="INDEX-37"/><a name="INDEX-38"/>, or NBT for short.<a name="FNPTR-3"/><a href="#FOOTNOTE-3">[3]</a> </p>

<p>The NBT standard (RFC 1001/1002)
currently outlines a trio of services on a network:</p>

<ul><li>
<p>A name service</p>
</li><li>
<p>Two communication services:</p>
<ul><li>
<p>Datagrams</p>
</li>

<li>
<p>Sessions</p>
</li></ul>
</li>
</ul>

<p>The <a name="INDEX-39"/>name
service solves the name-to-address problem mentioned earlier; it
allows each computer to declare a specific name on the network that
can be translated to a machine-readable IP address, much like
today's Domain Name System (DNS) on the Internet.
The <a name="INDEX-40"/>datagram and <a name="INDEX-41"/>session services are both
secondary communication protocols used to transmit data back and
forth from NetBIOS computers across the network.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-3.2"/>

<h3 class="head2">Getting a Name</h3>

<p><a name="INDEX-42"/><a name="INDEX-43"/>In the NetBIOS world, when each
computer comes online, it wants to claim a name for itself; this is
called <em class="firstterm">name registration</em>. However, no two
computers in the same workgroup should be able to claim the same
name; this would cause endless confusion for any computer that wanted
to communicate with either of them. There are two different
approaches to ensuring that this doesn't happen:</p>

<ul><li>
<p>Use an <em class="firstterm"/>NBNS</em> to keep track of which hosts have
registered a NetBIOS name.</p>
</li><li>
<p>Allow each computer on the network to defend its name in the event
that another computer attempts to use it.</p>
</li></ul>
<p><a href="ch01.html#samba2-CHP-1-FIG-8">Figure 1-8</a> illustrates a (failed) name
registration, with and without an NBNS.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-8"/><img src="figs/sam2_0108.gif"/></div><h4 class="head4">Figure 1-8. Broadcast versus NBNS name registration</h4>

<p><a name="INDEX-44"/><a name="INDEX-45"/>As mentioned earlier,
there must be a way to resolve a NetBIOS name to a specific IP
address; this is known as <em class="firstterm">name resolution</em>.
There are two different approaches with NBT here as well:</p>

<ul><li>
<p>Have each computer report back its IP address when it
&quot;hears&quot; a broadcast request for its
NetBIOS name.</p>
</li><li>
<p>Use an NBNS to help resolve NetBIOS names to IP addresses.</p>
</li></ul>
<p><a href="ch01.html#samba2-CHP-1-FIG-9">Figure 1-9</a> illustrates the two types of name
resolution.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-9"/><img src="figs/sam2_0109.gif"/></div><h4 class="head4">Figure 1-9. Broadcast versus NBNS name resolution</h4>

<p>As you might expect, having an NBNS on your network can help out
tremendously. To see exactly why, let's look at the
broadcast method.</p>

<p>Here, when a client computer boots, it will
<a name="INDEX-46"/>broadcast a
message declaring that it wishes to register a specified NetBIOS name
as its own. If nobody objects to the use of the name, it keeps the
name. On the other hand, if another computer on the local subnet is
currently using the requested name, it will send a message back to
the requesting client that the name is already taken. This is known
as <em class="firstterm">defending</em><a name="INDEX-47"/><a name="INDEX-48"/> the hostname. This type of system
comes in handy when one client has unexpectedly dropped off the
network&mdash;another can take its name unchallenged&mdash;but it
does incur an inordinate amount of traffic on the network for
something as simple as name registration.</p>

<p>With an NBNS, the same thing occurs, except the communication is
confined to the requesting computer and the NBNS. No broadcasting
occurs when the computer wishes to register the name; the
registration message is simply sent directly from the client to the
NBNS, and the NBNS replies regardless of whether the name is already
taken. This is known as <em class="firstterm">point-to-point
communication</em><a name="INDEX-49"/>, and it is often beneficial on
networks with more than one subnet. This is because routers are
generally configured to block incoming packets that are broadcast to
all computers in the subnet.</p>

<p>The same principles apply to name resolution. Without an NBNS,
NetBIOS name resolution would also be done with a broadcast
mechanism. All request packets would be sent to each computer in the
network, with the hope that one computer that might be affected will
respond directly back to the computer that asked. Using an NBNS and
point-to-point communication for this purpose is far less taxing on
the network than flooding the network with broadcasts for every
name-resolution request.</p>

<p>It can be argued that broadcast packets do not cause significant
problems in modern, high-bandwidth networks of hosts with fast CPUs,
if only a small number of hosts are on the network, or the demand for
bandwidth is low. There are certainly cases where this is true;
however, our advice throughout this book is to avoid relying on
broadcasts as much as possible. This is a good rule to follow for
large, busy networks, and if you follow our advice when configuring a
small network, your network will be able to grow without encountering
problems later on that might be difficult to diagnose. <a name="INDEX-50"/><a name="INDEX-51"/></p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-3.3"/>

<h3 class="head2">Node Types</h3>

<p><a name="INDEX-52"/><a name="INDEX-53"/>How can you tell what strategy each
client on your network will use when performing name registration and
resolution? Each computer on an NBT network earns one of the
following designations, depending on how it handles name registration
and resolution: <a name="INDEX-54"/><a name="INDEX-55"/><a name="INDEX-56"/><a name="INDEX-57"/>b-node, p-node, m-node, and h-node. The
behaviors of each type of node are summarized in <a href="ch01.html#samba2-CHP-1-TABLE-1">Table 1-1</a>.</p>

<a name="samba2-CHP-1-TABLE-1"/><h4 class="head4">Table 1-1. NetBIOS node types</h4><table border="1">



<tr>
<th>
<p>Role</p>
</th>
<th>
<p>Value</p>
</th>
</tr>


<tr>
<td>
<p>b-node</p>
</td>
<td>
<p>Uses broadcast registration and resolution only.</p>
</td>
</tr>
<tr>
<td>
<p>p-node</p>
</td>
<td>
<p>Uses point-to-point registration and resolution only.</p>
</td>
</tr>
<tr>
<td>
<p>m-node (mixed)</p>
</td>
<td>
<p>Uses broadcast for registration. If successful, it notifies the NBNS
of the result. Uses broadcast for resolution; uses the NBNS if
broadcast is unsuccessful.</p>
</td>
</tr>
<tr>
<td>
<p>h-node (hybrid)</p>
</td>
<td>
<p>Uses the NBNS for registration and resolution; uses broadcast if the
NBNS is unresponsive or inoperative.</p>
</td>
</tr>

</table>

<p>In the case of Windows clients, you will usually find them listed as
h-nodes or hybrid nodes. The first three node types appear in RFC
1001/1002, and h-nodes were invented later by Microsoft, as a more
fault-tolerant method.</p>

<p>You can find the node type of a Windows 95/98/Me computer by running
the <em class="emphasis">winipcfg</em><a name="INDEX-58"/><a name="INDEX-59"/> command from the Start
&rarr; Run dialog (or from an MS-DOS prompt) and clicking
the More Info&gt;&gt; button. On Windows NT/2000/XP, you can use the
<tt class="literal">ipconfig</tt><a name="INDEX-60"/><a name="INDEX-61"/><a name="INDEX-62"/><a name="INDEX-63"/>
<tt class="literal">/all</tt> command in a command-prompt window. In either
case, search for the line that says <tt class="literal">Node Type</tt>.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-3.4"/>

<h3 class="head2">What's in a Name?</h3>

<p>The names <a name="INDEX-64"/><a name="INDEX-65"/>NetBIOS uses are quite different
from the DNS hostnames you might be familiar with. First, NetBIOS
names exist in a flat namespace. In other words, there are no
hierarchical levels, such as in <tt class="literal">oreilly.com</tt> (two
levels) or <em class="emphasis">ftp</em><em class="emphasis">.samba.org</em> (three
levels). NetBIOS names consist of a single unique string such as
<tt class="literal">navaho</tt> or <tt class="literal">hopi</tt> within each
workgroup or domain. Second, NetBIOS names are allowed to be only 15
characters and can consist only of standard alphanumeric characters
(a-z, A-Z, 0-9) and the following:</p>

<blockquote><pre class="code">! @ # $ % ^ &amp; ( ) - ' { } . ~</pre></blockquote>

<p>Although you are allowed to use a <a name="INDEX-66"/><a name="INDEX-67"/><a name="INDEX-68"/>period (.) in a NetBIOS name, we recommend
against it because those names are not guaranteed to work in future
versions of NBT.</p>

<p>It's not a coincidence that all valid DNS names are
also valid NetBIOS names. In fact, the unqualified DNS name for a
Samba server is often reused as its NetBIOS name. For example, if you
had a system with a hostname of <tt class="literal">mixtec.ora.com</tt> ,
its NetBIOS name would likely be MIXTEC (followed by 9 spaces).</p>


<div class="sect3"><a name="samba2-CHP-1-SECT-3.4.1"/>

<h3 class="head3">Resource names and types</h3>

<p><a name="INDEX-69"/><a name="INDEX-70"/>With NetBIOS, a computer not
only advertises its presence, but also tells others what types of
services it offers. For example, <tt class="literal">mixtec</tt> can
indicate that it's not just a workstation, but that
it's also a file server and can receive Windows
Messenger messages. This is done by adding a 16th byte to the end of
the machine (resource) name, called the <em class="firstterm">resource
type</em>, and registering the name multiple times, once for
each service that it offers. See <a href="ch01.html#samba2-CHP-1-FIG-10">Figure 1-10</a>.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-10"/><img src="figs/sam2_0110.gif"/></div><h4 class="head4">Figure 1-10. The structure of NetBIOS names</h4>

<p>The 1-byte resource type indicates a unique service that the named
computer provides. In this book, you will often see the resource type
shown in angled brackets (&lt;&gt;) after the NetBIOS name, such as:</p>

<blockquote><pre class="code">MIXTEC&lt;00&gt;</pre></blockquote>

<p>You can see which names are registered for a particular NBT computer
using the Windows command-line
<em class="emphasis">nbtstat</em><a name="INDEX-71"/> utility.
Because these services are unique (i.e., there cannot be more than
one registered), you will see them listed as type UNIQUE in the
output. For example, the following partial output describes the
<tt class="literal">toltec</tt> server:</p>

<blockquote><pre class="code">C:\&gt;<tt class="userinput"><b>nbtstat -a toltec</b></tt>

       NetBIOS Remote Machine Name Table
   Name               Type         Status
---------------------------------------------
TOLTEC          &lt;00&gt;  UNIQUE      Registered
TOLTEC          &lt;03&gt;  UNIQUE      Registered
TOLTEC          &lt;20&gt;  UNIQUE      Registered
...</pre></blockquote>

<p>This says the server has registered the NetBIOS name
<tt class="literal">toltec</tt> as a machine (computer) name, as a
recipient of messages from the Windows Messenger service, and as a
file server. Some possible attributes a name can have are listed in
<a href="ch01.html#samba2-CHP-1-TABLE-2">Table 1-2</a>.</p>

<a name="samba2-CHP-1-TABLE-2"/><h4 class="head4">Table 1-2. NetBIOS unique resource types</h4><table border="1">



<tr>
<th>
<p>Named resource</p>
</th>
<th>
<p>Hexadecimal byte value</p>
</th>
</tr>


<tr>
<td>
<p>Standard Workstation Service</p>
</td>
<td>
<p>00</p>
</td>
</tr>
<tr>
<td>
<p>Messenger Service</p>
</td>
<td>
<p>03</p>
</td>
</tr>
<tr>
<td>
<p>RAS Server Service</p>
</td>
<td>
<p>06</p>
</td>
</tr>
<tr>
<td>
<p>Domain Master Browser Service (associated with primary domain controller)</p>
</td>
<td>
<p>1B</p>
</td>
</tr>
<tr>
<td>
<p>Master Browser name</p>
</td>
<td>
<p>1D</p>
</td>
</tr>
<tr>
<td>
<p>NetDDE Service</p>
</td>
<td>
<p>1F</p>
</td>
</tr>
<tr>
<td>
<p>Fileserver (including printer server)</p>
</td>
<td>
<p>20</p>
</td>
</tr>
<tr>
<td>
<p>RAS Client Service</p>
</td>
<td>
<p>21</p>
</td>
</tr>
<tr>
<td>
<p>Network Monitor Agent</p>
</td>
<td>
<p>BE</p>
</td>
</tr>
<tr>
<td>
<p>Network Monitor Utility</p>
</td>
<td>
<p>BF</p>
</td>
</tr>

</table>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-3.4.2"/>

<h3 class="head3">Group names and types</h3>

<p>SMB also uses the concept of groups, with which computers can
register themselves. Earlier we mentioned that the computers in our
example belonged to a
<em class="firstterm">workgroup</em><a name="INDEX-73"/>,
which is a partition of computers on the same network. For example, a
business might very easily have an ACCOUNTING and a SALES workgroup,
each with different servers and printers. In the Windows world, a
workgroup and an
<a name="INDEX-74"/>SMB
group are the same thing.</p>

<p>Continuing our
<em class="emphasis">nbtstat</em><a name="INDEX-75"/> example,
the <tt class="literal">toltec</tt> Samba server is also a member of the
METRAN workgroup (the GROUP attribute hex 00) and will participate in
elections for the browse master (GROUP attribute 1E). Here is the
remainder of the <em class="emphasis">nbtstat</em> output:</p>

<blockquote><pre class="code">       NetBIOS Remote Machine Name Table
   Name               Type         Status
---------------------------------------------
METRAN         &lt;00&gt;   GROUP       Registered
METRAN         &lt;1E&gt;   GROUP       Registered
..__MSBROWSE__.&lt;01&gt;   GROUP       Registered</pre></blockquote>

<p>The possible group attributes a computer can have are illustrated in
<a href="ch01.html#samba2-CHP-1-TABLE-3">Table 1-3</a>. More
<a name="INDEX-76"/><a name="INDEX-77"/>information
is available in <em class="emphasis">Windows NT in a Nutshell</em> by Eric
<a name="INDEX-78"/>Pearce, also
published by O'Reilly.</p>

<a name="samba2-CHP-1-TABLE-3"/><h4 class="head4">Table 1-3. NetBIOS group resource types</h4><table border="1">



<tr>
<th>
<p>Named resource</p>
</th>
<th>
<p>Hexadecimal byte value</p>
</th>
</tr>


<tr>
<td>
<p>Standard Workstation group</p>
</td>
<td>
<p>00</p>
</td>
</tr>
<tr>
<td>
<p>Logon server</p>
</td>
<td>
<p>1C</p>
</td>
</tr>
<tr>
<td>
<p>Master Browser name</p>
</td>
<td>
<p>1D</p>
</td>
</tr>
<tr>
<td>
<p>Normal Group name (used in browser elections)</p>
</td>
<td>
<p>1E</p>
</td>
</tr>
<tr>
<td>
<p>Internet Group name (administrative)</p>
</td>
<td>
<p>20</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">&lt;01&gt;&lt;02&gt;_ _MSBROWSE_ _&lt;02&gt;</tt></p>
</td>
<td>
<p>01</p>
</td>
</tr>

</table>

<p>The final entry, <tt class="literal">_ _ MSBROWSE _ _</tt>
<a name="INDEX-80"/>, is used to announce a group to other
master browsers. The nonprinting characters in the name show up as
dots in an <em class="emphasis">nbtstat</em> printout.
Don't worry if you don't understand
all of the resource or group types. Some of them you will not need
with Samba, and others you will pick up as you move through the rest
of the chapter. The important thing to remember here is the logistics
of the naming mechanism.</p>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-3.4.3"/>

<h3 class="head3">Scope ID</h3>

<p>In the dark ages of SMB networking before NetBIOS groups were
introduced, you could use a very primitive method to isolate groups
of computers from the rest of the network. Each SMB packet contains a
field called the <em class="firstterm">scope
ID</em><a name="INDEX-81"/><a name="INDEX-82"/>, with the idea being that
systems on the network could be configured to accept only packets
with a scope ID matching that of their configuration. This feature
was hardly ever used and unfortunately lingers in modern
implementations. Some of the utilities included in the Samba
distribution allow the scope ID to be set. Setting the scope ID in a
network is likely to cause problems, and we are mentioning scope ID
only so that you will not be confused by it when you later encounter
it in various places.</p>


</div>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-3.5"/>

<h3 class="head2">Datagrams and Sessions</h3>

<p>At this point, let's digress to discuss the
responsibility of NBT: to provide connection services between two
NetBIOS computers.
<a name="INDEX-83"/>NBT
offers two services: the <em class="firstterm">session
service</em><a name="INDEX-84"/> and the
<em class="firstterm">datagram service</em><a name="INDEX-85"/>.
Understanding how these two services work is not essential to using
Samba, but it does give you an idea of how NBT works and how to
troubleshoot Samba when it doesn't work.</p>

<p>The datagram service has no stable connection between computers.
Packets of data are simply sent or broadcast from one computer to
another, without regard to the order in which they arrive at the
destination, or even if they arrive at all. The use of datagrams
requires less processing overhead than sessions, although the
reliability of the connection can suffer. Datagrams, therefore, are
used for quickly sending nonvital blocks of data to one or more
computers. The datagram service communicates using the simple
primitives shown in <a href="ch01.html#samba2-CHP-1-TABLE-4">Table 1-4</a>.</p>

<a name="samba2-CHP-1-TABLE-4"/><h4 class="head4">Table 1-4. Datagram primitives</h4><table border="1">



<tr>
<th>
<p>Primitive</p>
</th>
<th>
<p>Description</p>
</th>
</tr>


<tr>
<td>
<p>Send Datagram</p>
</td>
<td>
<p>Send datagram packet to computer or groups of computers.</p>
</td>
</tr>
<tr>
<td>
<p>Send Broadcast Datagram</p>
</td>
<td>
<p>Broadcast datagram to any computer waiting with a Receive Broadcast
datagram.</p>
</td>
</tr>
<tr>
<td>
<p>Receive Datagram</p>
</td>
<td>
<p>Receive a datagram from a computer.</p>
</td>
</tr>
<tr>
<td>
<p>Receive Broadcast Datagram</p>
</td>
<td>
<p>Wait for a Broadcast datagram.</p>
</td>
</tr>

</table>

<p>The session service is more complex. Sessions are a communication
method that, in theory, offers the ability to detect problematic or
inoperable connections between two NetBIOS applications. It helps to
think of an NBT session as being similar to a telephone call, an
analogy that obviously influenced the design of the CIFS standard.</p>

<p>Once the connection is made, it remains open throughout the duration
of the conversation, each side knows who the caller and the called
computer are, and each can communicate with the simple primitives
shown in <a href="ch01.html#samba2-CHP-1-TABLE-5">Table 1-5</a>.</p>

<a name="samba2-CHP-1-TABLE-5"/><h4 class="head4">Table 1-5. Session primitives</h4><table border="1">



<tr>
<th>
<p>Primitive</p>
</th>
<th>
<p>Description</p>
</th>
</tr>


<tr>
<td>
<p>Call</p>
</td>
<td>
<p>Initiate a session with a computer listening under a specified name.</p>
</td>
</tr>
<tr>
<td>
<p>Listen</p>
</td>
<td>
<p>Wait for a call from a known caller or any caller.</p>
</td>
</tr>
<tr>
<td>
<p>Hang-up</p>
</td>
<td>
<p>Exit a call.</p>
</td>
</tr>
<tr>
<td>
<p>Send</p>
</td>
<td>
<p>Send data to the other computer.</p>
</td>
</tr>
<tr>
<td>
<p>Receive</p>
</td>
<td>
<p>Receive data from the other computer.</p>
</td>
</tr>
<tr>
<td>
<p>Session Status</p>
</td>
<td>
<p>Get information on requested sessions.</p>
</td>
</tr>

</table>

<p>Sessions are the backbone of resource sharing on an NBT network. They
are typically used for establishing stable connections from client
computers to disk or printer shares on a server. The client
&quot;calls&quot; the server and starts
trading information such as which files it wishes to open, which data
it wishes to exchange, etc. These calls can last a long
time&mdash;hours, even days&mdash;and all of this occurs within the
context of a single connection. If there is an error, the session
software (TCP) will retransmit until the data is received properly,
unlike the &quot;punt-and-pray&quot; approach
of the datagram service (UDP).</p>

<p>In truth, while sessions are supposed to handle problematic
communications, they sometimes don't. If the
connection is interrupted, session information that is open between
the two computers might become invalid. If that happens, the only way
to regain the session information is for the same two computers to
call each other again and start over.</p>

<p>If you want more information on each service, we recommend you look
at RFC 1001. However, there are two important things to remember
here:</p>

<ul><li>
<p><a name="INDEX-88"/>Sessions always
occur between two NetBIOS computers. If a session service is
interrupted, the client is supposed to store sufficient state
information for it to reestablish the connection. However, in
practice, this often does not happen.</p>
</li><li>
<p><a name="INDEX-89"/>Datagrams can
be broadcast to multiple computers, but they are unreliable. In other
words, there is no way for the source to know that the datagrams it
sent have indeed arrived at their destinations. <a name="INDEX-90"/></p>
</li></ul>

</div>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-4"/>

<h2 class="head1">An Introduction to the SMB Protocol</h2>

<p><a name="INDEX-91"/>Now
we're going to cover some low-level technical
details and explore the elementals of the SMB protocol. You probably
don't need to know much about this to implement a
simple Samba network, and therefore you might want to skip or skim
over this section and go on to the next one
(&quot;Windows Workgroups and Domains&quot;)
on your first reading. However, assuming you are going to be
responsible for long-term maintenance of a Samba network, it will
help if you understand how it actually works. You will more easily be
able to diagnose and correct any odd problems that pop up.</p>

<p>At a high level, the SMB protocol suite is relatively simple. It
includes commands for all the file and print operations that you
might perform on a local disk or printer, such as:</p>

<ul><li>
<p>Opening and closing files</p>
</li><li>
<p>Creating and deleting files and directories</p>
</li><li>
<p>Reading and writing files</p>
</li><li>
<p>Searching for files</p>
</li><li>
<p>Queueing and dequeueing files in a print spool</p>
</li></ul>
<p>Each operation can be encoded into an SMB message and transmitted to
and from a server. The original name
&quot;SMB&quot; comes from the way in which
the commands are formatted: they are versions of the standard DOS
system-call data structures, or <em class="firstterm">Server Message
Blocks</em>, redesigned for transmitting to another computer
across a network.</p>


<div class="sect2"><a name="samba2-CHP-1-SECT-4.1"/>

<h3 class="head2">SMB Format</h3>

<p>Richard <a name="INDEX-92"/>Sharpe of the Samba team defines SMB as
a <em class="firstterm">request-response</em> protocol.<a name="FNPTR-4"/><a href="#FOOTNOTE-4">[4]</a> In effect,
this means that a client sends an SMB request to a server and the
server sends an SMB response back to the client. In only one rare
circumstance does a server send a message that is not in response to
a client.</p>

<p>An <a name="INDEX-94"/>SMB message is not as complex as you
might think. Let's take a closer look at the
internal structure of such a message. It can be broken down into two
parts: the <em class="firstterm">header</em>, which is a fixed size, and
the <em class="firstterm">command string</em>, whose size can vary
dramatically based on the contents of the message.</p>


<div class="sect3"><a name="samba2-CHP-1-SECT-4.1.1"/>

<h3 class="head3">SMB header format</h3>

<p><a href="ch01.html#samba2-CHP-1-TABLE-6">Table 1-6</a> shows the format of an
<a name="INDEX-95"/>SMB header. The COM field identifies
the command being performed. SMB commands are not required to use all
the fields in the SMB header. For example, when a client first
attempts to connect to a server, it does not yet have a tree
identifier (TID) value&mdash;one is assigned after it successfully
connects&mdash;so a null TID is placed in its header field. Other
fields can be padded with zeros when not used.</p>

<p>The <a name="INDEX-96"/>SMB header fields are listed in <a href="ch01.html#samba2-CHP-1-TABLE-6">Table 1-6</a>.</p>

<a name="samba2-CHP-1-TABLE-6"/><h4 class="head4">Table 1-6. SMB header fields</h4><table border="1">




<tr>
<th>
<p>Field</p>
</th>
<th>
<p>Size (bytes)</p>
</th>
<th>
<p>Description</p>
</th>
</tr>


<tr>
<td>
<p><tt class="literal">0xFF 'SMB</tt>'</p>
</td>
<td>
<p><tt class="literal">1</tt></p>
</td>
<td>
<p>Protocol identifier</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">COM</tt></p>
</td>
<td>
<p><tt class="literal">1</tt></p>
</td>
<td>
<p>Command code, from 0x00 to 0xFF</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">RCLS</tt></p>
</td>
<td>
<p><tt class="literal">1</tt></p>
</td>
<td>
<p>Error class</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">REH</tt></p>
</td>
<td>
<p><tt class="literal">1</tt></p>
</td>
<td>
<p>Reserved</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">ERR</tt></p>
</td>
<td>
<p><tt class="literal">2</tt></p>
</td>
<td>
<p>Error code</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">REB</tt></p>
</td>
<td>
<p><tt class="literal">1</tt></p>
</td>
<td>
<p>Reserved</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">RES</tt></p>
</td>
<td>
<p><tt class="literal">14</tt></p>
</td>
<td>
<p>Reserved</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">TID</tt></p>
</td>
<td>
<p><tt class="literal">2</tt></p>
</td>
<td>
<p>TID; a unique ID for a resource in use by the client</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">PID</tt></p>
</td>
<td>
<p><tt class="literal">2</tt></p>
</td>
<td>
<p>Caller process ID</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">UID</tt></p>
</td>
<td>
<p><tt class="literal">2</tt></p>
</td>
<td>
<p>User identifier</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">MID</tt></p>
</td>
<td>
<p><tt class="literal">2</tt></p>
</td>
<td>
<p>Multiplex identifier; used to route requests inside a process</p>
</td>
</tr>

</table>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-4.1.2"/>

<h3 class="head3">SMB command format</h3>

<p>Immediately after the header is a variable number of bytes that
constitute an <a name="INDEX-97"/>SMB command or reply. Each command,
such as Open File (COM field identifier: <tt class="literal">SMBopen</tt>)
or Get Print Queue (<tt class="literal">SMBsplretq</tt> ), has its own set
of parameters and data. Like the SMB header fields, not all of the
command fields need to be filled, depending on the specific command.
For example, the Get Server Attributes
(<tt class="literal">SMBdskattr</tt>) command sets the WCT and BCC fields
to zero. The fields of the command segment are shown in <a href="ch01.html#samba2-CHP-1-TABLE-7">Table 1-7</a>.</p>

<a name="samba2-CHP-1-TABLE-7"/><h4 class="head4">Table 1-7. SMB command contents</h4><table border="1">




<tr>
<th>
<p>Field</p>
</th>
<th>
<p>Size (bytes)</p>
</th>
<th>
<p>Description</p>
</th>
</tr>


<tr>
<td>
<p><tt class="literal">WCT</tt></p>
</td>
<td>
<p><tt class="literal">1</tt></p>
</td>
<td>
<p>Word count</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">VWV</tt></p>
</td>
<td>
<p>Variable</p>
</td>
<td>
<p>Parameter words (size given by WCT)</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">BCC</tt></p>
</td>
<td>
<p><tt class="literal">2</tt></p>
</td>
<td>
<p>Parameter byte count</p>
</td>
</tr>
<tr>
<td>
<p><tt class="literal">DATA</tt></p>
</td>
<td>
<p>Variable</p>
</td>
<td>
<p>Data (size given by BCC)</p>
</td>
</tr>

</table>

<p>Don't worry if you don't understand
each field; they are not necessary for using Samba at an
administrator level. However, they do come in handy when debugging
system messages. We will show you some of the more common SMB
messages that clients and servers send using a modified version of
<em class="filename">tcpdump</em> later in this section. (If you prefer an
<a name="INDEX-98"/><a name="INDEX-99"/>SMB sniffer with a graphical
interface, try Ethereal, which uses the GTK libraries; see
<a href="http://www.ethereal.com">http://www.ethereal.com</a> for more
information on this tool.)</p>

<a name="samba2-CHP-1-NOTE-84"/><blockquote class="note"><h4 class="objtitle">TIP</h4>
<p>For more information on each command in the
<a name="INDEX-100"/>SMB protocol, see the
<em class="citetitle">CIFS Technical
Reference</em><a name="INDEX-101"/> at <a href="http://www.snia.org/tech_activities/CIFS">http://www.snia.org/tech_activities/CIFS</a>.</p>
</blockquote>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-4.1.3"/>

<h3 class="head3">SMB variations</h3>

<p>The SMB protocol has been extended with new commands several times
since its inception. Each new version is backward-compatible with the
previous versions, so it is possible for a LAN to have clients and
servers concurrently running different versions of the SMB protocol.</p>

<p><a href="ch01.html#samba2-CHP-1-TABLE-8">Table 1-8</a> outlines the major versions of the
<a name="INDEX-102"/>SMB
protocol. Within each &quot;dialect&quot; of
SMB are many sub-versions that include commands supporting particular
releases of major operating systems. The ID string in column 2 is
used by clients and servers to determine in which level of the
protocol they will speak to each other.</p>

<a name="samba2-CHP-1-TABLE-8"/><h4 class="head4">Table 1-8. SMB protocol dialects</h4><table border="1">




<tr>
<th>
<p>Protocol name</p>
</th>
<th>
<p>ID string</p>
</th>
<th>
<p>Used by</p>
</th>
</tr>


<tr>
<td>
<p>Core</p>
</td>
<td>
<p><tt class="literal">PC NETWORK PROGRAM 1.0</tt></p>
</td>
<td>
</td>
</tr>
<tr>
<td>
<p><a name="INDEX-103"/>Core Plus</p>
</td>
<td>
<p><tt class="literal">MICROSOFT NETWORKS 1.03</tt></p>
</td>
<td>
</td>
</tr>
<tr>
<td>
<p><a name="INDEX-104"/>LAN Manager 1.0</p>
</td>
<td>
<p><tt class="literal">LANMAN1.0</tt></p>
</td>
<td>
</td>
</tr>
<tr>
<td>
<p>LAN Manager 2.0</p>
</td>
<td>
<p><tt class="literal">LM1.2X002</tt></p>
</td>
<td>
</td>
</tr>
<tr>
<td>
<p>LAN Manager 2.1</p>
</td>
<td>
<p><tt class="literal">LANMAN2.1</tt></p>
</td>
<td>
</td>
</tr>
<tr>
<td>
<p><a name="INDEX-105"/>NT LAN
Manager 1.0</p>
</td>
<td>
<p><tt class="literal">NT LM 0.12</tt></p>
</td>
<td>
<p>Windows NT 4.0</p>
</td>
</tr>
<tr>
<td>
<p><a name="INDEX-106"/>Samba's NT LM 0.12</p>
</td>
<td>
<p><tt class="literal">Samba</tt></p>
</td>
<td>
<p>Samba</p>
</td>
</tr>
<tr>
<td>
<p><a name="INDEX-107"/><a name="INDEX-108"/>Common
Internet File System</p>
</td>
<td>
<p><tt class="literal">CIFS 1.0</tt></p>
</td>
<td>
<p>Windows 2000/XP</p>
</td>
</tr>

</table>

<p>Samba implements the NT LM 0.12 specification for NT LAN Manager 1.0.
It is backward-compatible with all the other SMB variants. The CIFS
specification is, in reality, LAN Manager 0.12 with a few specific
additions.</p>


</div>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-4.2"/>

<h3 class="head2">SMB Clients and Servers</h3>

<p><a name="INDEX-109"/><a name="INDEX-110"/>As
mentioned earlier, SMB is a client/server protocol. In the purest
sense, this means that a client sends a request to a server, which
acts on the request and returns a reply. However, the client/server
roles can often be reversed, sometimes within the context of a single
SMB session. For example, consider the two Windows 95/98/Me computers
in <a href="ch01.html#samba2-CHP-1-FIG-11">Figure 1-11</a>. The computer named
<tt class="literal">maya</tt> shares a printer to the network, and the
computer named <tt class="literal">toltec</tt> shares a disk directory.
<tt class="literal">maya</tt> is in the client role when accessing
<tt class="literal">toltec</tt>'s network drive and in the
server role when printing a job for <tt class="literal">toltec</tt>.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-11"/><img src="figs/sam2_0111.gif"/></div><h4 class="head4">Figure 1-11. Two computers that both have resources to share</h4>

<p>This brings out an important point in Samba terminology:</p>

<ul><li>
<p>A <em class="firstterm">server</em> is a computer with a resource to
share.</p>
</li><li>
<p>A <em class="firstterm">client</em> is a computer that wishes to use that
resource.</p>
</li><li>
<p>A computer can be a client, a server, or both, or it can be neither
at any given time.</p>
</li></ul>
<p>Microsoft Windows products have both the SMB client and server built
into the operating system, and it is common to find Windows acting as
a server, client, both, or neither at any given time in a production
network. Although Samba has been developed primarily to function as a
server, there are also ways that it and associated software can act
as an SMB client. As with Windows, it is even possible to set up a
Unix system to act as an SMB client and not as a server. See <a href="ch05.html">Chapter 5</a> for more details on this topic.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-4.3"/>

<h3 class="head2">A Simple SMB Connection</h3>

<p><a name="INDEX-111"/>The client and server must complete
three steps to establish a connection to a resource:</p>

<ol><li>
<p>Establish a NetBIOS session.</p>
</li><li>
<p>Negotiate the protocol variant.</p>
</li><li>
<p>Set session parameters, and make a tree connection to a resource.</p>
</li></ol>
<p>We will examine each step through the eyes of a useful tool that we
mentioned earlier: the modified
<em class="filename">tcpdump</em><a name="INDEX-112"/> that is
available from the Samba web site.</p>

<a name="samba2-CHP-1-NOTE-85"/><blockquote class="note"><h4 class="objtitle">TIP</h4>
<p>You can download the tcpdump program at <a href="http://www.samba.org">http://www.samba.org</a> in the
<em class="filename">samba/ftp/tcpdump-smb</em> directory; the latest
version as of this writing is 3.4-10. Use this program as you would
use the standard <em class="filename">tcpdump</em> application, but add
the <tt class="literal">-s 1500</tt> switch to ensure that you get the
whole packet and not just the first few bytes.</p>
</blockquote>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-4.4"/>

<h3 class="head2">Establishing a NetBIOS Session</h3>

<p><a name="INDEX-113"/>When a user first makes a request
to access a network disk or send a print job to a remote printer,
NetBIOS takes care of making a connection at the session layer. The
result is a bidirectional channel between the client and server. The
client and server need only two messages to establish this
connection. This is shown in the following example session request
and response, as captured by <em class="filename">tcpdump</em> .</p>

<p>First, the client sends a request to open a session, and
<em class="filename">tcpdump </em><a name="INDEX-114"/>reports:</p>

<blockquote><pre class="code">&gt;&gt;&gt; NBT Packet
NBT Session Request
Flags=0x81000044
Destination=TOLTEC      NameType=0x20 (Server)
Source=MAYA             NameType=0x00 (Workstation)</pre></blockquote>

<p>Then the server responds, granting a session to the client:</p>

<blockquote><pre class="code">&gt;&gt;&gt; NBT Packet
NBT Session Granted
Flags=0x82000000</pre></blockquote>

<p>At this point, there is an open channel between the client and server.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-4.5"/>

<h3 class="head2">Negotiating the Protocol Variant</h3>

<p>Next, the client sends a message to the server to negotiate an
<a name="INDEX-115"/>SMB protocol. As mentioned
earlier, the client sets its <a name="INDEX-116"/>tree identifier (TID) field to
zero, because it does not yet know what TID to use. A <em class="emphasis">tree
identifier</em> is a number that represents a connection to a
share on a server.</p>

<p>The command in the message is <tt class="literal">SMBnegprot</tt>, a
request to negotiate a protocol variant that will be used for the
entire session. Note that the client sends to the server a list of
all the variants that it can speak, not vice versa:</p>

<blockquote><pre class="code">&gt;&gt;&gt; NBT Packet
NBT Session Packet
Flags=0x0
Length=154

SMB PACKET: SMBnegprot (REQUEST)
SMB Command   =  0x72
Error class   =  0x0
Error code    =  0
Flags1        =  0x0
Flags2        =  0x0
Tree ID       =  0
Proc ID       =  5315
UID           =  0
MID           =  257
Word Count    =  0
Dialect=PC NETWORK PROGRAM 1.0
Dialect=MICROSOFT NETWORKS 3.0
Dialect=DOS LM1.2X002
Dialect=DOS LANMAN2.1
Dialect=Windows for Workgroups 3.1a
Dialect=NT LM 0.12</pre></blockquote>

<p>The server responds to the
<tt class="literal">SMBnegprot</tt><a name="INDEX-117"/> request with an index (with counting
starting at 0) into the list of variants that the client offered, or
with the value 0xFF if none of the protocol variants is acceptable:</p>

<blockquote><pre class="code">&gt;&gt;&gt; NBT Packet
NBT Session Packet
Flags=0x0
Length=84

SMB PACKET: SMBnegprot (REPLY)
SMB Command   =  0x72
Error class   =  0x0
Error code    =  0
Flags1        =  0x80
Flags2        =  0x1
Tree ID       =  0
Proc ID       =  5315
UID           =  0
MID           =  257
Word Count    =  17
NT1 Protocol
DialectIndex=5
[...]</pre></blockquote>

<p>In this example, the server responds with the value 5, which
indicates that the <tt class="literal">NT</tt> <tt class="literal">LM</tt>
<tt class="literal">0.12</tt> dialect will be used for the remainder of the
session.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-4.6"/>

<h3 class="head2">Set Session and Login Parameters</h3>

<p><a name="INDEX-118"/><a name="INDEX-119"/>The next step is to transmit session and
login parameters for the session, which you do using the
<a name="INDEX-120"/><tt class="literal">SMBSesssetupX</tt>
command. The parameters include the following:</p>

<ul><li>
<p>The account name and password (if there is one)</p>
</li><li>
<p>The workgroup name</p>
</li><li>
<p>The maximum size of data that can be transferred</p>
</li><li>
<p>The number of pending requests that can be in the queue at a time</p>
</li></ul>
<p>The resulting output from <em class="filename">tcpdump </em>is:</p>

<blockquote><pre class="code">&gt;&gt;&gt; NBT Packet
NBT Session Packet
Flags=0x0
Length=150

SMB PACKET: SMBsesssetupX (REQUEST)
SMB Command   =  0x73
Error class   =  0x0
Error code    =  0
Flags1        =  0x10
Flags2        =  0x0
Tree ID       =  0
Proc ID       =  5315
UID           =  1
MID           =  257
Word Count    =  13
Com2=0x75
Res1=0x0
Off2=120
MaxBuffer=2920
MaxMpx=50
VcNumber=0
SessionKey=0x1380
CaseInsensitivePasswordLength=24
CaseSensitivePasswordLength=0
Res=0x0
Capabilities=0x1
Pass1&amp;Pass2&amp;Account&amp;Domain&amp;OS&amp;LanMan=  
  JAY METRAN Windows 4.0 Windows 4.0

SMB PACKET: SMBtconX (REQUEST) (CHAINED)
smbvwv[]=
Com2=0xFF
Off2=0
Flags=0x2
PassLen=1
Passwd&amp;Path&amp;Device=
smb_bcc=23
smb_buf[]=\\TOLTEC\SPIRIT</pre></blockquote>

<p>In this example, the <tt class="literal">SMBsesssetupX</tt> Session Setup
command allows for an additional SMB command to be piggybacked onto
it (indicated by the letter X at the end of the command name). The
hexadecimal code of the second command is given in the
<tt class="literal">Com2</tt> field. In this case the command is
<tt class="literal">0x75</tt>, which is the <tt class="literal">SMBtconX</tt>
<tt class="literal">(</tt>Tree Connect and X) command. The
<tt class="literal">SMBtconX</tt><a name="INDEX-121"/> message looks for the name of the
resource in the <em class="emphasis">smb_buf</em> buffer. In this example,
<em class="emphasis">smb_buf</em> contains the string
<tt class="literal">\\TOLTEC\SPIRIT</tt>, which is the full pathname to a
shared directory on <tt class="literal">toltec</tt>. Using the
&quot;and X&quot; commands like this speeds
up each transaction because the server doesn't have
to wait on the client to make a second request.</p>

<p>Note that the TID is still zero. Finally, the server returns a TID to
the client, indicating that the user has been authorized access and
that the resource is ready to be used:</p>

<blockquote><pre class="code">&gt;&gt;&gt; NBT Packet
NBT Session Packet
Flags=0x0
Length=85

SMB PACKET: SMBsesssetupX (REPLY)
SMB Command   =  0x73
Error class   =  0x0
Error code    =  0
Flags1        =  0x80
Flags2        =  0x1
Tree ID       =  1
Proc ID       =  5315
UID           =  100
MID           =  257
Word Count    =  3
Com2=0x75
Off2=68
Action=0x1
[000] Unix Samba 2.2.6
[010] METRAN

SMB PACKET: SMBtconX (REPLY) (CHAINED)
smbvwv[]=
Com2=0xFF
Off2=0
smbbuf[]=
ServiceType=A:</pre></blockquote>

<p>The <em class="emphasis">ServiceType</em> field is set to
&quot;A&quot; to indicate that this is a file
service. Available service types are:</p>

<ul><li>
<p>&quot;A&quot; for a disk or file</p>
</li><li>
<p>&quot;LPT1&quot; for a spooled output</p>
</li><li>
<p>&quot;COMM&quot; for a direct-connect printer
or modem</p>
</li><li>
<p>&quot;IPC&quot; for a named pipe</p>
</li></ul>
<p>Now that a TID has been assigned, the client can use it as a handle
to perform any operation that it would use on a local disk drive. It
can open files, read and write to them, delete them, create new
files, search for filenames, and so on. <a name="INDEX-122"/></p>


</div>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-5"/>

<h2 class="head1">Windows Workgroups and Domains</h2>

<p>Up to now, we've covered basic SMB technology, which
is all you would need if you had nothing more advanced than MS-DOS
clients on your network. We do assume you want to support Windows
clients, especially the more recent versions, so next
we'll describe the enhancements Microsoft has added
to SMB networking&mdash;namely, Windows for Workgroups and Windows
domains.</p>


<div class="sect2"><a name="samba2-CHP-1-SECT-5.1"/>

<h3 class="head2">Windows Workgroups</h3>

<p><a name="INDEX-123"/><a name="INDEX-124"/>Windows
Workgroups are very similar to the SMB groups already described. You
need to know just a few additional things.</p>


<div class="sect3"><a name="samba2-CHP-1-SECT-5.1.1"/>

<h3 class="head3">Browsing</h3>

<p><a name="INDEX-125"/>Browsing
is the process of finding the other computers and shared resources in
the Windows network. Note that there is no connection with a World
Wide Web browser, apart from the general idea of
&quot;discovering what's
there.&quot; On the other hand, browsing the Windows
network is like the Web in that what's out there can
change without warning.</p>

<p>Before browsing existed, users had to know the name of the computer
they wanted to connect to on the network and then manually enter a
UNC such as the following into an application or file manager to
access resources:</p>

<blockquote><pre class="code">\\toltec\spirit\</pre></blockquote>

<p>Browsing is much more convenient, making it possible to examine the
contents of a network by using the point-and-click GUI interface of
the Network Neighborhood (or My Network Places<a name="FNPTR-5"/><a href="#FOOTNOTE-5">[5]</a>) on a Windows client.</p>

<p>You will encounter two types of browsing in an SMB network:</p>

<ul><li>
<p><a name="INDEX-129"/>Browsing a list
of computers and shared resources</p>
</li><li>
<p><a name="INDEX-130"/>Browsing the shared resource
of a specific computer</p>
</li></ul>
<p>Let's look at the first one. On each LAN (or subnet)
with a Windows workgroup or domain, one computer has the
responsibility of maintaining a list of the computers that are
currently accessible through the network. This computer is called the
<em class="firstterm">local master
browser</em><a name="INDEX-131"/><a name="INDEX-132"/>, and the list that it maintains is
called the <em class="firstterm">browse
list</em><a name="INDEX-133"/>. Computers on a subnet use the browse
list to cut down on the amount of network traffic generated while
browsing. Instead of each computer dynamically polling to determine a
list of the currently available computers, the computer can simply
query the local master browser to obtain a complete, up-to-date list.</p>

<p>To browse the resources on a computer, a user must connect to the
specific computer; this information cannot be obtained from the
browse list. Browsing the list of resources on a computer can be done
by double-clicking the computer's icon when it is
presented in the Network Neighborhood. As you saw at the opening of
the chapter, the computer will respond with a list of shared
resources that can be accessed after the user is successfully
authenticated.</p>

<p>Each server on a Windows workgroup is required to announce its
presence to the local master browser after it has registered a
NetBIOS name, and (theoretically) announce that it is leaving the
workgroup when it is shut down. It is the local master
browser's responsibility to record what the servers
have announced.</p>
<a name="samba2-CHP-1-NOTE-86"/><blockquote class="note"><h4 class="objtitle">WARNING</h4>
<p>The Windows <a name="INDEX-134"/>Network Neighborhood can behave
oddly: until you select a particular computer to browse, the Network
Neighborhood window might contain data that is not up-to-date. That
means the Network Neighborhood window can be showing computers that
have crashed or can be missing computers that
haven't been noticed yet. Put succinctly, once
you've selected a server and connected to it, you
can be a lot more confident that the shares and printers really exist
on the network.</p>
</blockquote>

<p>Unlike the roles you've seen earlier, almost any
Windows system (including Windows for Workgroups and Windows 95/98/Me
or NT/2000/XP) can act as a local master browser. The local master
browser can have one or more
<em class="firstterm"/><a name="INDEX-135"/><a name="INDEX-136"/>backup 
browsers</em> on the local subnet
that will take over in the event that the local master browser fails
or becomes inaccessible. To ensure fluid operation, the local backup
browsers will frequently synchronize their browse list with the local
master browser.</p>

<p>Here is how to calculate the minimum number of backup browsers that
will be allocated on a workgroup:</p>

<ul><li>
<p>If up to 32 Windows NT/2000/XP workstations are on the network, or up
to 16 Windows 95/98/Me computers are on the network, the local master
browser allocates one backup browser in addition to the local master
browser.</p>
</li><li>
<p>If the number of Windows NT/2000/XP workstations falls between 33 and
64, or the number of Windows 95/98/Me workstations falls between 17
and 32, the local master browser allocates two backup browsers.</p>
</li><li>
<p>For each group of 32 NT/2000/XP workstations or 16 Windows 95/98/Me
computers beyond this, the local master browser allocates another
backup browser.</p>
</li></ul>
<p>There is currently no upper limit on the number of backup browsers
that can be allocated by the local master browser.</p>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-5.1.2"/>

<h3 class="head3">Browsing elections</h3>

<p><a name="INDEX-137"/>Browsing
is a critical aspect of any Windows workgroup. However, not
everything runs perfectly on any network. For example,
let's say that a computer running Windows on the
desk of a small company's CEO is the local master
browser&mdash;that is, until he switches it off while plugging in his
massage chair. At this point the Windows NT Workstation in the spare
parts department might agree to take over the job. However, that
computer is currently running a large, poorly written program that
has brought its processor to its knees. The moral: browsing has to be
very tolerant of servers coming and going. Because nearly every
Windows system can serve as a browser, there has to be a way of
deciding at any time who will take on the job. This decision-making
process is called an <em class="firstterm">election</em>.</p>

<p>An election algorithm is built into nearly all Windows operating
systems such that they can each agree who is going to be a local
master browser and who will be local backup browsers. An election can
be forced at any time. For example, let's assume
that the CEO has finished his massage and reboots his server. As the
server comes online, it will announce its presence, and an election
will take place to see if the PC in the spare parts department should
still be the master browser.</p>

<p>When an election is performed, each computer broadcasts information
about itself via datagrams. This information includes the following:</p>

<ul><li>
<p>The version of the election protocol used</p>
</li><li>
<p>The operating system on the computer</p>
</li><li>
<p>The amount of time the client has been on the network</p>
</li><li>
<p>The hostname of the client</p>
</li></ul>
<p>These values determine which operating system has seniority and will
fulfill the role of the local master browser. (<a href="ch07.html">Chapter 7</a> describes the election process in more
detail.) The architecture developed to achieve this is not elegant
and has built-in security problems. While a browsing domain can be
integrated with domain security, the election algorithm does not take
into consideration which computers become browsers. Thus it is
possible for any computer running a browser service to register
itself as participating in the browsing election and (after winning)
being able to change the browse list. Nevertheless, browsing is a key
feature of Windows networking, and backward-compatibility
requirements will ensure that it is in use for years to come.
<a name="INDEX-138"/></p>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-5.1.3"/>

<h3 class="head3">Windows 95/98/Me authentication</h3>

<p>Three types of passwords arise when
<a name="INDEX-139"/><a name="INDEX-140"/>Windows
95/98/Me is operating in a Windows workgroup:</p>

<ul><li>
<p>A Windows password</p>
</li><li>
<p>A Windows Networking password</p>
</li><li>
<p>A password for each shared resource that has been assigned password
protection</p>
</li></ul>
<p>The Windows <a name="INDEX-141"/>password functions in a manner
that might be a source of confusion for Unix system administrators.
It is not there to prevent unauthorized users from using the
computer. (If you don't believe that, try clicking
the Cancel button on the password dialog box and see what happens!)
Instead, the Windows password is used to gain access to a file that
contains the Windows Networking and network resource passwords. There
is one such file per registered user of the system, and they can be
found in the <em class="filename">C:\Windows</em> directory with a name
composed of the user's account name, followed by a
<em class="filename">.pwl</em><a name="INDEX-142"/><a name="INDEX-143"/><a name="INDEX-144"/> extension. For example, if the
user's account name is
&quot;sarah,&quot; the file will be
<em class="filename">C:\Windows\sarah.pwl</em>. This file is encrypted
using the Windows password as the encryption key.</p>

<a name="samba2-CHP-1-NOTE-87"/><blockquote class="note"><h4 class="objtitle">TIP</h4>
<p>As a security measure, you might want to check for junk
<em class="filename">.pwl</em> files on Windows 95/98/Me clients, which
might have been created by mistakes users made while attempting to
log on. A <em class="filename">.pwl</em> file is easily cracked and can
contain valid passwords for Samba accounts and network shares.</p>
</blockquote>

<p>The first time the network is accessed, Windows attempts to use the
Windows password as the Windows Networking password. If this is
successful, the user will not be prompted for two separate passwords,
and subsequent logins to the Windows system will automatically result
in logging on to the Windows network as well, making things much
simpler for the user.</p>

<p>Shared network resources in the workgroup can also have passwords
assigned to them to limit their accessibility. The first time a user
attempts to access the resource, she is asked for its password, and a
checkbox in the password dialog box gives the user the option to add
the password to her password list. This is the default; if it is
accepted, Windows will store the password in the
user's <em class="filename">.pwl</em> file, and all
further authentication to the resource will be handled automatically
by Windows.</p>

<p>Samba's approach to workgroup authentication is a
little different, which is a result of blending the Windows workgroup
model with that of the Unix host upon which Samba runs. This will be
discussed further in <a href="ch09.html">Chapter 9</a>. <a name="INDEX-145"/></p>


</div>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-5.2"/>

<h3 class="head2">Windows NT Domains</h3>

<p><a name="INDEX-146"/>The
peer-to-peer networking model of
<a name="INDEX-147"/>workgroups functions fairly well as long as
the number of computers on the network is small and there is a
close-knit community of users. However, in larger networks the
simplicity of workgroups becomes a limiting factor. Workgroups offer
only the most basic level of security, and because each resource can
have its own password, it is inconvenient (to say the least) for
users to remember the password for each resource in a large network.
Even if that were not a problem, many people find it frustrating to
have to interrupt their creative workflow to enter a shared password
into a dialog box every time another network resource is accessed.</p>

<p>To support the needs of larger networks, such as those found in
departmental computing environments, Microsoft introduced domains
with Windows NT 3.51. A <em class="firstterm">Windows NT domain</em> is
essentially a workgroup of SMB computers that has one addition: a
server acting as a <em class="firstterm">domain
controller</em><a name="INDEX-148"/> (see <a href="ch01.html#samba2-CHP-1-FIG-12">Figure 1-12</a>).</p>

<div class="figure"><a name="samba2-CHP-1-FIG-12"/><img src="figs/sam2_0112.gif"/></div><h4 class="head4">Figure 1-12. A simple Windows domain</h4>


<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.1"/>

<h3 class="head3">Domain controllers</h3>

<p>A domain controller in a Windows NT domain functions much like a
<a name="INDEX-149"/><a name="INDEX-150"/>Network
Information Service (NIS) server in a Unix network, maintaining a
domain-wide database of user and group information, as well as
performing related services. The responsibilities of a domain
controller are mainly centered around security, including
<em class="firstterm">authentication</em><a name="INDEX-151"/>,
the process of granting or denying a user access to the resources of
the domain. This is typically done through the use of a username and
password. The service that maintains the database on the domain
controllers is called the <a name="INDEX-152"/><a name="INDEX-153"/>Security Account Manager (SAM).</p>

<p>The <a name="INDEX-154"/>Windows NT security model revolves
around <em class="firstterm">security
identifiers</em><a name="INDEX-155"/><a name="INDEX-156"/> (SIDs) and <em class="firstterm">access
control lists</em><a name="INDEX-157"/><a name="INDEX-158"/>
(ACLs). Security identifiers are used to represent objects in the
domain, which include (but are not limited to) users, groups,
computers, and processes. SIDs are commonly written in ASCII form as
hyphen-separated fields, like this:</p>

<blockquote><pre class="code">S-1-5-21-1638239387-7675610646-9254035128-545</pre></blockquote>

<p>The part of the SID starting with the
&quot;S&quot; and leading up to the rightmost
hyphen identifies a domain. The number after the rightmost hyphen is
called a <a name="INDEX-159"/>relative identifier (RID) and is a unique
number within the domain that identifies the user, group, computer,
or other object. The RID is the analog of a <a name="INDEX-160"/>user ID (UID) or
<a name="INDEX-161"/>group ID
(GID) on a Unix system or within an NIS domain.</p>

<p>ACLs supply the same function as
&quot;rwx&quot;
<a name="INDEX-162"/><a name="INDEX-163"/><a name="INDEX-164"/><a name="INDEX-165"/><a name="INDEX-166"/>file permissions that are common in Unix
systems. However, ACLs are more versatile. Unix file permissions only
set permissions for the owner and group to which the file belongs,
and &quot;other,&quot; meaning everyone else.
Windows NT/2000/XP ACLs allow permissions to be set individually for
any number of arbitrary users and/or groups. ACLs are made up of one
or more <em class="firstterm">access control
entries</em><a name="INDEX-167"/> (ACEs), each of which contains an SID
and the access rights associated with it.</p>

<p>ACL support has been added as a standard feature for some Unix
variants and is available as an add-on for others. Samba supports
mappings between Windows and Unix ACLs, and this will be covered in
<a href="ch08.html">Chapter 8</a>.</p>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.2"/>

<h3 class="head3">Primary and backup domain controllers</h3>

<p>You've already read about master and backup
browsers. Domain controllers are similar in that a domain has a
<em class="firstterm">primary domain
controller</em><a name="INDEX-168"/><a name="INDEX-169"/><a name="INDEX-170"/> (PDC) and can have
one or more <em class="firstterm">backup domain
controllers</em><a name="INDEX-171"/> (BDCs) as well. If the PDC fails or
becomes inaccessible, its duties are automatically taken over by one
of the BDCs. BDCs frequently synchronize their SAM data with the PDC
so if the need arises, any one of them can immediately begin
performing domain-controller services without impacting the clients.
However, note that BDCs have read-only copies of the SAM database;
they can update their data only by synchronizing with a PDC. A server
in a Windows domain can use the SAM of any PDC or BDC to authenticate
a user who attempts to access its resources and log on to the domain.</p>

<p>All recent versions of Windows can log on to a domain as clients to
access the resources of the domain servers. The systems that are
considered members of the domain are a more exclusive class, composed
of the PDC and BDCs, as well as domain member servers, which are
systems that have joined a domain as members, and are known to the
domain controllers by having a computer account in the SAM database.</p>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.3"/>

<h3 class="head3">Authentication</h3>

<p><a name="INDEX-172"/>When
a user logs on to a Windows domain by typing in a username and
password, a secure challenge and response protocol is invoked between
the client computer and a domain controller to verify that the
username and password are valid. Then the domain controller sends a
SID back to the client, which uses it to create a
<a name="INDEX-173"/>Security Access Token (SAT) that is valid
only for that system, to be used for further authentication. This
access token has information about the user coded into it, including
the username, the group, and the rights the user has within the
domain. At this point, the user is logged on to the domain.</p>

<p>Subsequently, when the client attempts to access a shared resource
within the domain, the client system enters into a secure challenge
and response exchange with the server of the resource. The server
then enters into another secure challenge and response conversation
with a domain controller to check that the client is valid. (What
actually happens is that the server uses information it gets from the
client to pretend to be the client and authenticate itself with the
domain controller. If the domain controller validates the
credentials, it sends an SID back to the server, which uses the SID
to create its own SAT for the client to enable access to its local
resources on the client's behalf.) At this point,
the client is authenticated for resources on the server and is
allowed to access them. The server then uses the SID in the access
token to determine what permissions the client has to use and modify
the requested resource by comparing them to entries in the ACL of the
resource.</p>

<p>Although this method of authentication might seem overly complicated,
it allows clients to authenticate without having plain-text passwords
travel through the network, and it is much more difficult to crack
than the relatively weak workgroup security we described earlier.</p>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.4"/>

<h3 class="head3">Name service with WINS and DNS</h3>

<p>The <a name="INDEX-174"/><a name="INDEX-175"/>Windows
Internet Name Service (WINS) is Microsoft's
implementation of a NetBIOS name server (NBNS). As such, WINS
inherits much of NetBIOS's characteristics. First,
WINS is flat; you can have only simple machine names such as
<tt class="literal">inca</tt>, <tt class="literal">mixtec</tt>, or
<tt class="literal">navaho</tt>, and workgroups such as PERU, MEXICO, or
USA. In addition, WINS is dynamic: when a client first comes online,
it is required to report its hostname, its address, and its workgroup
to the local WINS server. This WINS server will retain the
information so long as the client periodically refreshes its WINS
registration, which indicates that it's still
connected to the network. Note that WINS servers are not workgroup-
or domain-specific; they can contain information for multiple domains
and/or workgroups, which might exist on more than one subnet.</p>

<p>Multiple <a name="INDEX-176"/>WINS
servers can be set to synchronize with each other. This allows
entries for computers that come online and go offline in the network
to propagate from one WINS server to another. While in theory this
seems efficient, it can quickly become cumbersome if several WINS
servers are covering a network. Because WINS services can cross
multiple subnets (you'll either hardcode the address
of a WINS server in each of your clients or obtain it via DHCP), it
is often more efficient to have each Windows client, regardless of
the number of Windows domains, point themselves to the same WINS
server. That way, only one authoritative WINS server will have the
correct information, instead of several WINS servers continually
struggling to synchronize themselves with the most recent changes.</p>

<p>The currently active WINS server is known as the <em class="firstterm">primary
WINS server</em><a name="INDEX-177"/><a name="INDEX-178"/>. You can also install a secondary WINS
server, which will take over if the primary WINS server fails or
becomes inaccessible. Both the primary and any other WINS servers
will synchronize their address databases on a periodic basis.</p>

<p>In the Windows family of operating systems, only a server edition of
Windows NT/2000 can act as a WINS server. Samba 2.2 can function as a
primary WINS server, but cannot <a name="INDEX-179"/><a name="INDEX-180"/>synchronize
its database with other WINS servers. It therefore cannot act as a
secondary WINS server or as a primary WINS server for a Windows
secondary WINS server.</p>

<p>WINS handles name service by default, although Microsoft added DNS
starting with Windows NT 4 Server. It is compatible with DNS that is
standard on virtually every Unix system, and a Unix server (such as
the Samba host) can also be used for DNS.</p>


</div>



<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.5"/>

<h3 class="head3">Trust relationships</h3>

<p>One additional aspect of Windows NT domains not yet supported in
Samba 2.2 is that it is possible to set up a <em class="emphasis">trust
relationship</em><a name="INDEX-181"/><a name="INDEX-182"/><a name="INDEX-183"/> between domains, allowing clients
within one domain to access the resources within another without the
user having to go through additional authentication. The protocol
that is followed is called <em class="emphasis">pass-through authentication</em>,
<a name="INDEX-184"/><a name="INDEX-185"/>in which the
user's credentials are passed from the client system
in the first domain to the server in the second domain, which
consults a domain controller in the first (trusted) domain to check
that the user is valid before granting access to the resource.</p>

<p>Note that in many aspects, the behaviors of a Windows workgroup and a
Windows NT domain overlap. For example, the master and backup
browsers in a domain are always the PDC and BDC, respectively.
Let's update our Windows domain diagram to include
both a local master and local backup browser. The result is shown in
<a href="ch01.html#samba2-CHP-1-FIG-13">Figure 1-13</a>.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-13"/><a name="INDEX-186"/><img src="figs/sam2_0113.gif"/></div><h4 class="head4">Figure 1-13. A Windows domain with a local master and local backup browser</h4>

<p>The similarity between workgroups and NT domains is not accidental
because the concept of Windows domains did not evolve until Windows
NT 3.5 was introduced, and Windows domains were forced to remain
backward-compatible with the workgroups present in Windows for
Workgroups.</p>

<p>Samba can function as a primary domain controller for Windows
95/98/Me and Windows NT/2000/XP clients with the limitation that it
can act as a PDC only, and not as a BDC.</p>

<p>Samba can also function as a <em class="firstterm">domain member
server</em><a name="INDEX-187"/><a name="INDEX-188"/>, meaning that it has a computer account
in the PDC's account database and is therefore
recognized as being part of the domain. A domain member server does
not authenticate users logging on to the domain, but still handles
security functions (such as file permissions) for domain users
accessing its resources.</p>


</div>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-5.3"/>

<h3 class="head2">Active Directory Domains</h3>

<p>Starting with Windows 2000, Microsoft has introduced
<a name="INDEX-189"/><a name="INDEX-190"/>Active
Directory, the next step beyond Windows NT domains. We
won't go into much detail concerning Active
Directory because it is a huge topic. <a name="INDEX-191"/>Samba 2.2 doesn't
support Active Directory at all, and support in Samba 3.0 is limited
to acting as a client. For now, be aware that with Active Directory,
the authentication model is centered around
<a name="INDEX-192"/>Lightweight Directory
Access Protocol (LDAP), and name service is provided by DNS instead
of WINS. Domains in Active Directory can be organized in a
hierarchical tree structure, in which each domain controller operates
as a peer, with no distinction between primary and backup controllers
as in Windows NT domains.</p>

<p>Windows 2000/XP systems can be set up as simple workgroup or Windows
NT domain clients (which will function with Samba). The server
editions of Windows 2000 can be set up to run Active Directory and
support Windows NT domains for backward compatibility
(<em class="firstterm">mixed mode</em>). In this case, Samba 2.2 works
with Windows 2000 servers in the same way it works with Windows NT
4.0 servers. When set up to operate in <em class="firstterm">native mode,
</em><a name="INDEX-193"/>Windows 2000 servers support only
Active Directory. Even so, <a name="INDEX-194"/>Samba 2.2 can operate as a server
in a domain hosted by a native-mode Windows 2000 server, using the
<a name="INDEX-195"/>Windows 2000 server's
<em class="firstterm">PDC emulation mode</em>. However, it is not
possible for Samba 2.2 or 3.0 to operate as a domain controller in a
Windows 2000 Active Directory domain.</p>

<p>If you want to know more about Active Directory, we encourage you to
obtain a copy of the O'Reilly book,
<em class="emphasis">Windows 2000 Active Directory</em>. <a name="INDEX-196"/></p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-5.4"/>

<h3 class="head2">Can a Windows Workgroup Span Multiple Subnets?</h3>

<p><a name="INDEX-197"/><a name="INDEX-198"/>Yes, but most people who have
done it have had their share of headaches. Spanning multiple subnets
was not part of the initial design of Windows NT 3.5 or Windows for
Workgroups. As a result, a Windows domain that spans two or more
subnets is, in reality, the
&quot;gluing&quot; together of two or more
workgroups that share an identical name. The good news is that you
can still use a PDC to control authentication across each subnet. The
bad news is that things are not as simple with browsing.</p>

<p>As mentioned previously, each subnet must have its own local master
browser. When a Windows domain spans multiple subnets, a system
administrator will have to assign one of the computers as the
<em class="firstterm">domain master
browser</em><a name="INDEX-199"/><a name="INDEX-200"/>. The domain master browser will keep a
browse list for the entire Windows domain. This browse list is
created by periodically synchronizing the browse lists of each local
master browser with the browse list of the domain master browser.
After the synchronization, the local master browser and the domain
master browser should contain identical entries. See <a href="ch01.html#samba2-CHP-1-FIG-14">Figure 1-14</a> for an illustration.</p>

<div class="figure"><a name="samba2-CHP-1-FIG-14"/><img src="figs/sam2_0114.gif"/></div><h4 class="head4">Figure 1-14. A workgroup that spans more than one subnet</h4>

<p>Sound good? <a name="INDEX-201"/>Well, it's not quite
nirvana for the following reasons:</p>

<ul><li>
<p>If it exists, a PDC always plays the role of the domain master
browser. By Microsoft design, the two always share the NetBIOS
resource type <tt class="literal">&lt;1B&gt;</tt> and (unfortunately)
cannot be separated.</p>
</li><li>
<p>Windows 95/98/Me computers cannot become <em class="emphasis">or</em>
<em class="emphasis">even contact</em> a domain master browser. This means
that it is necessary to have at least one Windows NT/2000/XP system
(or Samba server) on each subnet of a multisubnet workgroup.</p>
</li></ul>
<p>Each subnet's local master browser continues to
maintain the browse list for its subnet, for which it becomes
authoritative. So if a computer wants to see a list of servers within
its own subnet, the local master browser of that subnet will be
queried. If a computer wants to see a list of servers outside the
subnet, it can still go only as far as the local master browser. This
works because at appointed intervals, the authoritative browse list
of a subnet's local master browser is synchronized
with the domain master browser, which is synchronized with the local
master browser of the other subnets in the domain. This is called
<em class="firstterm">browse list propagation</em>.</p>

<p>Samba can act as a domain master browser in a Windows NT domain, or
it can act as a local master browser for a subnet, synchronizing its
browse list with the domain master browser.</p>


</div>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-6"/>

<h2 class="head1">What's New in Samba 2.2?</h2>

<p><a name="INDEX-202"/><a name="INDEX-203"/>In
Version 2.2, Samba has more advanced support for Windows networking,
including the ability to perform the more important tasks necessary
for acting in a Windows NT domain. In addition, Samba 2.2 has some
support for technologies that Microsoft introduced in Windows 2000,
although the Samba team has saved Active Directory support for
Version 3.0.</p>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.1"/>

<h3 class="head2">PDC Support for Windows 2000/XP Clients</h3>

<p>Samba previously could act as a PDC to authenticate Windows 95/98/Me
and Windows NT 4 systems. This functionality has been extended in
Release 2.2 to include Windows 2000 and Windows XP. Thus, it is
possible to have a Samba server supporting domain logons for a
network of Windows clients, including the most recent releases from
Microsoft. This can result in a very stable, high-performance, and
more secure network, and gives you the added benefit of not having to
purchase per-seat Windows CALs from Microsoft.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.2"/>

<h3 class="head2">Microsoft Dfs Support</h3>

<p><a name="INDEX-204"/>Microsoft Dfs allows shared resources that
are dispersed among a number of servers in the network to be gathered
together and appear to users as if they all exist in a single
directory tree on one server. This method of organization makes life
much simpler for users. Instead of having to browse around the
network on a treasure hunt to locate the resource they want to use,
they can go directly to the Dfs server and grab what they want. Samba
2.2 offers support for serving Dfs, so a Windows server is no longer
needed for this purpose.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.3"/>

<h3 class="head2">Windows NT/2000/XP Printing Support</h3>

<p>Windows NT/2000/XP has a different Remote Procedure Call (RPC)-based
printer interface than Windows 95/98/Me does. In Samba 2.2, the
Windows NT/2000/XP interface is supported. Along with this, the Samba
team has been adding support for automatically downloading the
printer driver from the Samba server while adding a new printer to a
Windows client.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.4"/>

<h3 class="head2">ACLs</h3>

<p>Samba now supports
<a name="INDEX-205"/>ACLs on its Unix host for Unix variants
that support them. The list includes Solaris 2.6, 7, and 8, Irix,
AIX, Linux (with either the ACL patch for the
<a name="INDEX-206"/>ext2/ext3 filesystem from <a href="http://acl.bestbits.at">http://acl.bestbits.at</a> or when using the
<a name="INDEX-207"/>XFS
filesystem), and FreeBSD (Version 5.0 and later). When using ACL
support, Samba translates between Unix ACLs and Windows NT/2000/XP
ACLs, making the Samba host look and act more like a Windows
NT/2000/XP server from the point of view of Windows clients.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.5"/>

<h3 class="head2">Support for Windows Client Administration Tools</h3>

<p>Windows comes with tools that can be used from a client to manage
shared resources remotely on a Windows server. Samba 2.2 allows these
tools to operate on shares on the Samba server as well.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.6"/>

<h3 class="head2">Integration with Winbind</h3>

<p><a name="INDEX-208"/>Winbind is a
facility that allows users whose account information is stored in a
Windows domain database to authenticate on a Unix system. The result
is a unified logon environment, in which a user account can be kept
on either the Unix system or a Windows NT/2000 domain controller.
This greatly facilitates account management because administrators no
longer need to keep the two systems synchronized, and it is possible
for users whose accounts are held in a Windows domain to authenticate
when accessing Samba shares.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.7"/>

<h3 class="head2">Unix CIFS Extensions</h3>

<p>The <a name="INDEX-209"/><a name="INDEX-210"/>Unix CIFS extensions were developed
at Hewlett-Packard and introduced in Samba 2.2.4. They allow Samba
servers to support Unix filesystem attributes, such as links and
permissions, when sharing files with other Unix systems. This allows
Samba to be used as an alternative to network file sharing (NFS) for
Unix-to-Unix file sharing. An advantage of using Samba is that it
authenticates individual users, whereas NFS authenticates only
clients (based on their IP addresses, which is a poor security
model). This gives Samba an edge in the area of security, along with
its much greater configurability. See <a href="ch05.html">Chapter 5</a>
for information on how to operate Unix systems as Samba clients.</p>


</div>


<div class="sect2"><a name="samba2-CHP-1-SECT-6.8"/>

<h3 class="head2">And More...</h3>

<p>As usual, the code has numerous improvements that do not show up at
the administrative level in an immediate or obvious way. Samba now
functions better on systems that employ <a name="INDEX-211"/>PAM
(Pluggable Authentication Modules), and there is new support for
profiling. Samba's support for oplocks has been
strengthened, offering better integration with NFS server-terminated
leases (currently on Irix and Linux only) and in the local filesystem
with SMB locks mapped to POSIX locks (which is dependent on each Unix
variant's implementation of POSIX locks). And of
course there have been the usual bug fixes.</p>


</div>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-7"/>

<h2 class="head1">What's New in Samba 3.0?</h2>

<p>The main distinguishing feature of <a name="INDEX-212"/><a name="INDEX-213"/>Samba 3.0
is that it includes support for <a name="INDEX-214"/>Kerberos 5 authentication and
<a name="INDEX-215"/>LDAP, which are
required to act as clients in an Active Directory domain. Another
feature that appeared in Samba 3.0 is support for Unicode, which
greatly simplifies supporting international languages.</p>

<p>In later Version 3 releases, the Samba team plans to develop support
for
<a name="INDEX-216"/>WINS
replication, allowing Samba to act as a secondary WINS server or as a
primary WINS server with Windows or Samba secondary WINS servers.
Also planned are support for acting as a Windows NT BDC and support
for Windows NT domain trust relationships.</p>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-8"/>

<h2 class="head1">What Can Samba Do?</h2>

<p>Now let's wrap up by showing where Samba can help
out and where it is limited. <a href="ch01.html#samba2-CHP-1-TABLE-9">Table 1-9</a> summarizes
which roles Samba can and cannot play in a Windows NT or Active
Directory domain or a Windows workgroup. Many of the Windows domain
protocols are proprietary and have not been documented by Microsoft
and therefore must be reverse-engineered by the Samba team before
Samba can support them. As of Version 3.0, Samba cannot act as a
backup in most roles and does not yet fully support Active Directory.</p>

<a name="samba2-CHP-1-TABLE-9"/><h4 class="head4">Table 1-9. Samba roles (as of Version 3.0)</h4><table border="1">



<tr>
<th>
<p>Role</p>
</th>
<th>
<p>Can perform?</p>
</th>
</tr>


<tr>
<td>
<p><a name="INDEX-217"/>File server</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Printer server</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Microsoft Dfs server</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Primary domain controller</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Backup domain controller</p>
</td>
<td>
<p>No</p>
</td>
</tr>
<tr>
<td>
<p>Active Directory domain controller</p>
</td>
<td>
<p>No</p>
</td>
</tr>
<tr>
<td>
<p>Windows 95/98/Me authentication</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Windows NT/2000/XP authentication</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Local master browser</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Local backup browser</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Domain master browser</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Primary WINS server</p>
</td>
<td>
<p>Yes</p>
</td>
</tr>
<tr>
<td>
<p>Secondary WINS server</p>
</td>
<td>
<p>No</p>
</td>
</tr>

</table>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-9"/>

<h2 class="head1">An Overview of the Samba Distribution</h2>

<p><a name="INDEX-218"/>As mentioned earlier, Samba actually
contains several programs that serve different but related purposes.
These programs are documented more fully in <a href="appc.html">Appendix C</a>. For now, we will introduce each of them
briefly and describe how they work together.</p>

<p>The majority of the programs that come with Samba center on its two
daemons. Let's take a refined look at the
responsibilities of each daemon:</p>

<dl>
<dt><b><em class="emphasis">nmbd</em></b></dt>
<dd>
<p>The <em class="emphasis">nmbd</em><a name="INDEX-219"/> daemon is a simple name server that
supplies WINS functionality. This daemon listens for name-server
requests and provides the appropriate IP addresses when called upon.
It also provides browse lists for the Network Neighborhood and
participates in browsing elections.</p>
</dd>



<dt><b><em class="emphasis">smbd</em></b></dt>
<dd>
<p>The <em class="emphasis">smbd</em><a name="INDEX-220"/> daemon manages the shared resources
between the Samba server and its clients. It provides file, print,
and browse services to <span class="acronym">SMB</span> clients across one or
more networks and handles all notifications between the Samba server
and the network clients. In addition, it is responsible for user
authentication, resource locking, and data sharing through the
<span class="acronym">SMB</span> protocol.</p>
</dd>

</dl>

<p>New with Version 2.2, there is an additional daemon:</p>

<dl>
<dt><b><a name="INDEX-221"/><em class="emphasis">winbindd</em></b></dt>
<dd>
<p>This daemon is used along with the name service switch to get
information on users and groups from a Windows NT server and allows
Samba to authorize users through a Windows NT/2000 server.</p>
</dd>

</dl>

<p>The Samba distribution also comes with a small set of Unix
command-line tools:</p>

<dl>
<dt><b><em class="emphasis">findsmb</em><a name="INDEX-222"/></b></dt>
<dd>
<p>A program that searches the local network for computers that respond
to SMB protocol and prints information on them.</p>
</dd>



<dt><b><em class="emphasis">make_smbcodepage</em><a name="INDEX-223"/></b></dt>
<dd>
<p>A program used when working with Samba's
internationalization features for telling Samba how to convert
between upper- and lowercase in different character sets.</p>
</dd>



<dt><b><em class="emphasis">make_unicodemap</em><a name="INDEX-224"/></b></dt>
<dd>
<p>Another internationalization program used with Samba for compiling
Unicode map files that Samba uses to translate DOS codepages or Unix
character sets into 16-bit unicode.</p>
</dd>



<dt><b><a name="INDEX-225"/><em class="emphasis">net</em></b></dt>
<dd>
<p>A new program distributed with Samba 3.0 that can be used to perform
remote administration of servers.</p>
</dd>



<dt><b><em class="emphasis">nmblookup</em><a name="INDEX-226"/></b></dt>
<dd>
<p>A program that provides NBT name lookups to find a
computer's IP address when given its machine name.</p>
</dd>



<dt><b><a name="INDEX-227"/><em class="emphasis">pdbedit</em></b></dt>
<dd>
<p>A new program distributed with Samba 3.0 that is helpful for managing
user accounts held in SAM databases.</p>
</dd>



<dt><b><em class="emphasis">rpcclient</em><a name="INDEX-228"/></b></dt>
<dd>
<p>A program that can be used to run MS-RPC functions on Windows clients.</p>
</dd>



<dt><b><em class="emphasis">smbcacls</em><a name="INDEX-229"/></b></dt>
<dd>
<p>A program that is used to set or show ACLs on Windows NT filesystems.</p>
</dd>



<dt><b><em class="emphasis">smbclient</em><a name="INDEX-230"/></b></dt>
<dd>
<p>An <em class="emphasis">ftp</em>-like Unix client that can be used to connect to
SMB shares and operate on them. The <em class="emphasis">smbclient</em>
command is discussed in detail in <a href="ch05.html">Chapter 5</a>.</p>
</dd>



<dt><b><em class="emphasis">smbcontrol</em><a name="INDEX-231"/></b></dt>
<dd>
<p>A simple administrative utility that sends messages to <em class="emphasis">nmbd</em>
or <em class="emphasis">smbd</em>.</p>
</dd>



<dt><b><a name="INDEX-232"/><em class="emphasis">smbgroupedit</em></b></dt>
<dd>
<p>A command that can be used to define mappings between Windows NT
groups and Unix groups. It is new in Samba 3.0.</p>
</dd>



<dt><b><em class="emphasis">smbmnt</em><a name="INDEX-233"/></b></dt>
<dd>
<p>A helper utility used along with <em class="emphasis">smbmount.</em></p>
</dd>



<dt><b><em class="emphasis">smbmount</em><a name="INDEX-234"/></b></dt>
<dd>
<p>A program that mounts an smbfs filesystem, allowing remote SMB shares
to be mounted in the filesystem of the Samba host.</p>
</dd>



<dt><b><em class="emphasis">smbpasswd</em><a name="INDEX-235"/></b></dt>
<dd>
<p>A program that allows an administrator to change the passwords used
by Samba.</p>
</dd>



<dt><b><em class="emphasis">smbsh</em><a name="INDEX-236"/></b></dt>
<dd>
<p>A tool that functions like a command shell to allow access to a
remote SMB filesystem and allow Unix utilities to operate on it. This
command is covered in <a href="ch05.html">Chapter 5</a>.</p>
</dd>



<dt><b><em class="emphasis">smbspool</em><a name="INDEX-237"/></b></dt>
<dd>
<p>A print-spooling program used to send files to remote printers that
are shared on the SMB network.</p>
</dd>



<dt><b><em class="emphasis">smbstatus</em><a name="INDEX-238"/></b></dt>
<dd>
<p>A program that reports the current network connections to the shares
on a Samba server.</p>
</dd>



<dt><b><em class="emphasis">smbtar</em><a name="INDEX-239"/></b></dt>
<dd>
<p>A program similar to the Unix <em class="filename">tar</em> command, for
backing up data in SMB shares.</p>
</dd>



<dt><b><em class="emphasis">smbumount</em><a name="INDEX-240"/></b></dt>
<dd>
<p>A program that works along with <em class="emphasis">smbmount</em> to unmount
smbfs filesystems.</p>
</dd>



<dt><b><em class="emphasis">testparm</em><a name="INDEX-241"/></b></dt>
<dd>
<p>A simple program for checking the Samba configuration file.</p>
</dd>



<dt><b><em class="emphasis">testprns</em><a name="INDEX-242"/></b></dt>
<dd>
<p>A program that tests whether printers on the Samba host are
recognized by the <em class="filename">smbd</em> daemon.</p>
</dd>



<dt><b><em class="emphasis">wbinfo</em><a name="INDEX-243"/></b></dt>
<dd>
<p>A utility used to query the <em class="filename">winbindd
</em><a name="INDEX-244"/>daemon.</p>
</dd>

</dl>

<p>Each major release of Samba goes through an exposure test before
it's announced. In addition, it is quickly updated
afterward if problems or unwanted side effects are found. The latest
stable distribution as of this writing is Samba 2.2.6, and this book
focuses mainly on the functionality supported in Samba 2.2.6, as
opposed to older versions of Samba.</p>


</div>



<div class="sect1"><a name="samba2-CHP-1-SECT-10"/>

<h2 class="head1">How Can I Get Samba?</h2>

<p><a name="INDEX-245"/><a name="INDEX-246"/>Source
and binary distributions of Samba are available from mirror sites
across the Internet. The primary web site for Samba is located at
<a href="http://www.samba.org/">http://www.samba.org/</a>. From there, you
can select a mirror site that is geographically near you.</p>

<p>Most Linux and many Unix vendors provide binary packages. These can
be more convenient to install and maintain than the Samba
team's source or binary packages, due to the
vendor's efforts to supply a package that matches
its specific products. <a name="INDEX-247"/></p>


</div>

<hr/><h4 class="head4">Footnotes</h4><blockquote><a name="FOOTNOTE-1"/> <p><a href="#FNPTR-1">[1]</a> You
can also right-click the shared resource in the Network Neighborhood
and then select the Map Network Drive menu item.</p> <a name="FOOTNOTE-2"/> <p><a href="#FNPTR-2">[2]</a> Be
warned that many end-user license agreements forbid installing a
program on a network so that multiple clients can access it. Check
the legal agreements that accompany the product to be absolutely
sure.</p> <a name="FOOTNOTE-3"/> <p><a href="#FNPTR-3">[3]</a> You
might also see the abbreviation NetBT, which is common in Microsoft
literature.</p> <a name="FOOTNOTE-4"/>
<p><a href="#FNPTR-4">[4]</a> See
<a href="http://www.samba.org/cifs/docs/what-is-smb.html">http://www.samba.org/cifs/docs/what-is-smb.html</a>
for Richard's excellent summary of
<a name="INDEX-93"/>SMB.</p> <a name="FOOTNOTE-5"/> <p><a href="#FNPTR-5">[5]</a> This
was originally called <a name="INDEX-126"/><a name="INDEX-127"/><a name="INDEX-128"/>Network Neighborhood in Windows 95/98/NT,
but Microsoft has changed the name to My Network Places in the more
recent Windows Me/2000/XP. We will continue to call it Network
Neighborhood, and if you're using a new version of
Windows, be aware that My Network Places can act a little differently
in some ways.</p> </blockquote>


<hr/><h4 class="head4"><a href="toc.html">TOC</a></h4>
</body></html>