2
<body bgcolor="#ffffff">
4
<img src="samba2_xs.gif" border="0" alt=" " height="100" width="76"
5
hspace="10" align="left" />
7
<h1 class="head0">Chapter 1. Learning the Samba</h1>
10
<p><a name="INDEX-1"/>Samba
11
is an extremely useful networking tool for anyone who has both
12
Windows and Unix systems on his network. Running on a Unix system, it
13
allows Windows to share files and printers on the Unix host, and it
14
also allows Unix users to access resources shared by Windows systems.</p>
16
<p>Although it might seem natural to use a Windows server to serve files
17
and printers to a network containing Windows clients, there are good
18
reasons for preferring a Samba server for this duty. Samba is
19
reliable software that runs on reliable Unix operating systems,
20
resulting in fewer problems and a low cost of maintenance. Samba also
21
offers better performance under heavy loads, outperforming Windows
22
2000 Server by a factor of 2 to 1 on identical PC hardware, according
23
to published third-party benchmarks. When common, inexpensive PC
24
hardware fails to meet the demands of a huge client load, the Samba
25
server can easily be moved to a proprietary "big
26
iron" Unix mainframe, which can outperform Windows
27
running on a PC many times. If all that weren't
28
enough, Samba has a very nice cost advantage: it's
29
free. Not only is the software itself freely available, but also no
30
client licenses are required, and it runs on high-quality, free
31
operating systems such as Linux and FreeBSD.</p>
33
<p>After reading the previous paragraph, you might come to the
34
conclusion that Samba is commonly used by large organizations with
35
thousands of users on their networks—and you'd
36
be right! But Samba's user base includes
37
organizations all over the planet, of all types and sizes: from
38
international corporations, to medium and small businesses, to
39
individuals who run Samba on their Linux laptops. In the last case, a
40
tool such as VMware is used to run Windows on the same computer, with
41
Samba enabling the two operating systems to share files.</p>
43
<p>The types of users vary even more—Samba is used by
44
corporations, banks and other financial institutions, government and
45
military organizations, schools, public libraries, art galleries,
46
families, and even authors! This book was developed on a Linux system
47
running VMware and Windows 2000, with Adobe FrameMaker running on
48
Windows and the document files served by Samba from the Linux
51
<p>Does all this whet your technological appetite? If so, we encourage
52
you to keep reading, learn about Samba, and follow our examples to
53
set up a Samba server of your own. In this and upcoming chapters, we
54
will tell you exactly how to get started.</p>
58
<div class="sect1"><a name="samba2-CHP-1-SECT-1"/>
60
<h2 class="head1">What Is Samba?</h2>
62
<p><a name="INDEX-2"/>Samba
63
is a suite of Unix applications that speak the
64
<a name="INDEX-3"/><a name="INDEX-4"/>Server
65
Message Block (SMB) protocol. Microsoft Windows operating systems and
66
the OS/2 operating system use SMB to perform client-server networking
67
for file and printer sharing and associated operations. By supporting
68
this protocol, Samba enables computers running Unix to get in on the
69
action, communicating with the same networking protocol as Microsoft
70
Windows and appearing as another Windows system on the network from
71
the perspective of a Windows client. A <a name="INDEX-5"/>Samba
72
server offers the following services:</p>
75
<p>Share one or more directory trees</p>
77
<p>Share one or more Distributed filesystem (Dfs) trees</p>
79
<p>Share printers installed on the server among Windows clients on the
82
<p>Assist clients with network browsing</p>
84
<p>Authenticate clients logging onto a Windows domain</p>
86
<p>Provide or assist with Windows Internet Name Service (WINS)
87
name-server resolution</p>
89
<p>The Samba suite also includes client tools that allow users on a Unix
90
system to access folders and printers that Windows systems and Samba
91
servers offer on the network.</p>
93
<p>Samba is the brainchild of Andrew <a name="INDEX-6"/>Tridgell, who currently heads the Samba
94
development team. Andrew started the project in 1991, while working
95
with a Digital Equipment Corporation (DEC) software suite called
96
Pathworks, created for connecting DEC VAX computers to computers made
97
by other companies. Without knowing the significance of what he was
98
doing, Andrew created a file-server program for an odd protocol that
99
was part of Pathworks. That protocol later turned out to be SMB. A
100
few years later, he expanded upon his custom-made SMB server and
101
began distributing it as a product on the Internet under the name
102
"SMB Server." However, Andrew
103
couldn't keep that name—it already belonged to
104
another company's product—so he tried the
105
following Unix renaming approach:</p>
107
<blockquote><pre class="code">$ <tt class="userinput"><b>grep -i '^s.*m.*b' /usr/dict/words</b></tt></pre></blockquote>
109
<p>And the response was:</p>
111
<blockquote><pre class="code">salmonberry
114
scramble</pre></blockquote>
116
<p>Thus, the name "Samba" was born.</p>
118
<p>Today, the Samba suite revolves around a pair of Unix daemons that
119
provide shared resources—called <em class="firstterm">shares
120
</em>or s<em class="firstterm">ervices</em>—to SMB clients
121
on the network. These are:</p>
124
<dt><b><a name="INDEX-7"/>smbd</b></dt>
126
<p>A daemon that handles file and printer sharing and provides
127
authentication and authorization for SMB clients.</p>
132
<dt><b><a name="INDEX-8"/>nmbd</b></dt>
134
<p>A daemon that supports NetBIOS Name Service and WINS, which is
135
Microsoft's implementation of a NetBIOS Name Server
136
(NBNS). It also assists with network browsing.</p>
141
<p>Samba is currently maintained and extended by a group of volunteers
142
under the active supervision of Andrew Tridgell. Like the Linux
143
operating system, Samba is distributed as open source software
144
(<a href="http://opensource.org">http://opensource.org</a>) by its
145
authors and is distributed under the GNU General Public License
146
(GPL). Since its inception, development of Samba has been sponsored
147
in part by the Australian National University, where Andrew Tridgell
148
earned his Ph.D. Since then, many other organizations have sponsored
149
Samba developers, including LinuxCare, VA Linux Systems,
150
Hewlett-Packard, and IBM. It is a true testament to Samba that both
151
commercial and noncommercial entities are prepared to spend money to
152
support an open source effort.</p>
154
<p>Microsoft has also contributed by offering its definition of the SMB
155
protocol to the Internet Engineering Task Force (IETF) in 1996 as the
156
<a name="INDEX-9"/><a name="INDEX-10"/>Common
157
Internet File System (CIFS). Although we prefer to use the term
158
"SMB" in this book, you will also
159
often find the protocol being referred to as
160
"CIFS." This is especially true on
161
Microsoft's web site.</p>
168
<div class="sect1"><a name="samba2-CHP-1-SECT-2"/>
170
<h2 class="head1">What Can Samba Do for Me?</h2>
172
<p><a name="INDEX-11"/>As explained earlier, Samba can help
173
Windows and Unix computers coexist in the same network. However,
174
there are some specific reasons why you might want to set up a Samba
175
server on your network:</p>
178
<p>You don't want to pay for—or
179
can't afford—a full-fledged Windows server,
180
yet you still need the functionality that one provides.</p>
182
<p>The Client Access Licenses (CALs) that Microsoft requires for each
183
Windows client to access a Windows server are unaffordable.</p>
185
<p>You want to provide a common area for data or user directories to
186
transition from a Windows server to a Unix one, or vice versa.</p>
188
<p>You want to share printers among Windows and Unix workstations.</p>
190
<p>You are supporting a group of computer users who have a mixture of
191
Windows and Unix computers.</p>
193
<p>You want to integrate Unix and Windows authentication, maintaining a
194
single database of user accounts that works with both systems.</p>
196
<p>You want to network Unix, Windows, Macintosh (OS X), and other
197
systems using a single protocol.</p>
199
<p>Let's take a quick tour of
200
<a name="INDEX-12"/>Samba in action. Assume that we have
201
the following basic network configuration: a Samba-enabled Unix
202
system, to which we will assign the name <tt class="literal">toltec</tt>,
203
and a pair of Windows clients, to which we will assign the names
204
<tt class="literal">maya</tt> and <tt class="literal">aztec</tt>, all connected
205
via a local area network (LAN). Let's also assume
206
that <tt class="literal">toltec</tt> also has a local inkjet printer
207
connected to it, <tt class="literal">lp</tt>, and a disk share named
208
<tt class="literal">spirit</tt>—both of which it can offer to the
209
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>
211
<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>
213
<p>In this network, each computer listed shares the same
214
<em class="firstterm">workgroup</em>. A workgroup is a group name tag
215
that identifies an arbitrary collection of computers and their
216
resources on an SMB network. Several workgroups can be on the network
217
at any time, but for our basic network example,
218
we'll have only one: the METRAN workgroup.</p>
221
<div class="sect2"><a name="samba2-CHP-1-SECT-2.1"/>
223
<h3 class="head2">Sharing a Disk Service</h3>
225
<p><a name="INDEX-13"/><a name="INDEX-14"/><a name="INDEX-15"/>If everything is properly
226
configured, we should be able to see the Samba server,
227
<tt class="literal">toltec</tt>, through the Network Neighborhood of the
228
<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
229
<tt class="literal">maya</tt> computer, including <tt class="literal">toltec</tt>
230
and each computer that resides in the METRAN workgroup. Note the
231
Entire Network icon at the top of the list. As we just mentioned,
232
more than one workgroup can be on an SMB network at any given time.
233
If a user clicks the Entire Network icon, she will see a list of all
234
the workgroups that currently exist on the network.</p>
236
<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>
238
<p>We can take a closer look at the <tt class="literal">toltec</tt> server by
239
double-clicking its icon. This contacts <tt class="literal">toltec</tt>
240
itself and requests a list of its
241
<em class="firstterm">shares</em>—the file and printer
242
resources—that the computer provides. In this case, a printer
243
named <tt class="literal">lp</tt>, a home directory named
244
<tt class="literal">jay</tt>, and a disk share named
245
<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
246
in mixed case (Toltec). Case is irrelevant in hostnames, so you might
247
see toltec, Toltec, and TOLTEC in various displays or command output,
248
but they all refer to a single system. Thanks to Samba, Windows 98
249
sees the Unix server as a valid SMB server and can access the
250
<tt class="literal">spirit</tt> folder as if it were just another system
253
<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>
255
<p>One popular Windows feature is the ability to map a drive letter
256
(such as E:, F:, or Z:) to a shared directory on the network using
257
the Map Network Drive option in Windows Explorer.<a name="FNPTR-1"/><a href="#FOOTNOTE-1">[1]</a>
258
Once you do so, your applications can access the folder across the
259
network using the drive letter. You can store data on it, install and
260
run programs from it, and even password-protect it against unwanted
261
visitors. See <a href="ch01.html#samba2-CHP-1-FIG-4">Figure 1-4</a> for an example of mapping
262
a <a name="INDEX-16"/><a name="INDEX-17"/>drive letter to a network
265
<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>
267
<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
268
a network computer is by using two backslashes, followed by the name
269
of the networked computer, another backslash, and the networked
270
directory of the computer, as shown here:</p>
272
<blockquote><pre class="code">\\<em class="replaceable">network-computer</em>\<em class="replaceable">directory</em></pre></blockquote>
274
<p>This is known as the <em class="firstterm"/><a name="INDEX-18"/>Universal
275
Naming Convention (UNC)</em> in the Windows world. For example, the dialog
276
box in <a href="ch01.html#samba2-CHP-1-FIG-4">Figure 1-4</a> represents the network directory
277
on the <tt class="literal">toltec</tt> server as:</p>
279
<blockquote><pre class="code">\\toltec\spirit</pre></blockquote>
281
<p>If this looks somewhat familiar to you, you're
282
probably thinking of <em class="firstterm">uniform resource
283
locators</em><a name="INDEX-19"/><a name="INDEX-20"/> (URLs), which are addresses that web
284
browsers such as Netscape Navigator and Internet Explorer use to
285
resolve systems across the Internet. Be sure not to confuse the two:
286
URLs such as <a href="http://www.oreilly.com">http://www.oreilly.com</a> use forward slashes
287
instead of backslashes, and they precede the initial slashes with the
288
data transfer protocol (i.e., ftp, http) and a colon (:). In reality,
289
URLs and UNCs are two completely separate things, although sometimes
290
you can specify an SMB share using a URL rather than a UNC. As a URL,
291
the <em class="filename">\\toltec\spirit</em> share would be specified as
292
<em class="filename">smb://toltec/spirit</em>.</p>
294
<p>Once the network drive is set up, Windows and its programs behave as
295
if the networked directory were a local disk. If you have any
296
applications that support multiuser functionality on a network, you
297
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
298
resulting network drive as it would appear with other storage devices
299
in the Windows 98 client. Note the pipeline attachment in the icon
300
for the J: drive; this indicates that it is a network drive rather
301
than a fixed drive.</p>
303
<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>
305
<p>My Network Places, found in Windows Me, 2000, and XP, works
306
differently from Network Neighborhood. It is necessary to click a few
307
more icons, but eventually we can get to the view of the
308
<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
309
up the network drive using the Map Network Drive option in Windows
310
2000 works similarly to other Windows versions. <a name="INDEX-21"/><a name="INDEX-22"/><a name="INDEX-23"/></p>
312
<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>
318
<div class="sect2"><a name="samba2-CHP-1-SECT-2.2"/>
320
<h3 class="head2">Sharing a Printer</h3>
322
<p><a name="INDEX-24"/><a name="INDEX-25"/><a name="INDEX-26"/>You probably noticed that the printer
323
<tt class="literal">lp</tt> appeared under the available shares for
324
<tt class="literal">toltec</tt> in <a href="ch01.html#samba2-CHP-1-FIG-3">Figure 1-3</a>. This
325
indicates that the Unix server has a printer that can be shared by
326
the various SMB clients in the workgroup. Data sent to the printer
327
from any of the clients will be spooled on the Unix server and
328
printed in the order in which it is received.</p>
330
<p><a name="INDEX-27"/><a name="INDEX-28"/>Setting up a Samba-enabled
331
printer on the Windows side is even easier than setting up a disk
332
share. By double-clicking the printer and identifying the
333
manufacturer and model, you can install a driver for this printer on
334
the Windows client. Windows can then properly format any information
335
sent to the network printer and access it as if it were a local
336
printer. On Windows 98, double-clicking the Printers icon in the
337
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
338
printer, which identifies it as being on a network.</p>
340
<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>
343
<div class="sect3"><a name="samba2-CHP-1-SECT-2.2.1"/>
345
<h3 class="head3">Seeing things from the Unix side</h3>
347
<p><a name="INDEX-29"/><a name="INDEX-30"/>As mentioned earlier, Samba
348
appears in Unix as a set of daemon programs. You can view them with
349
the Unix <a name="INDEX-31"/><em class="emphasis">ps</em> command; you can
350
read any messages they generate through custom debug files or the
351
Unix <em class="emphasis">syslog</em> (depending on how Samba is set up);
352
and you can configure them from a single Samba configuration file:
353
<em class="emphasis">smb.conf</em>. In addition, if you want to get an idea of
354
what the daemons are doing, Samba has a program called
355
<em class="emphasis">smbstatus</em><a name="INDEX-32"/> that will lay it all on the line. Here
358
<blockquote><pre class="code"># <tt class="userinput"><b>smbstatus</b></tt>
359
Processing section "[homes]"
360
Processing section "[printers]"
361
Processing section "[spirit]"
364
Service uid gid pid machine
365
-----------------------------------------
366
spirit jay jay 7735 maya (172.16.1.6) Sun Aug 12 12:17:14 2002
367
spirit jay jay 7779 aztec (172.16.1.2) Sun Aug 12 12:49:11 2002
368
jay jay jay 7735 maya (172.16.1.6) Sun Aug 12 12:56:19 2002
371
Pid DenyMode R/W Oplock Name
372
--------------------------------------------------
373
7735 DENY_WRITE RDONLY NONE /u/RegClean.exe Sun Aug 12 13:01:22 2002
375
Share mode memory usage (bytes):
376
1048368(99%) free + 136(0%) used + 72(0%) overhead = 1048576(100%) total</pre></blockquote>
378
<p>The Samba status from this output provides three sets of data, each
379
divided into separate sections. The first section tells which systems
380
have connected to the Samba server, identifying each client by its
381
machine name (<tt class="literal">maya</tt> and <tt class="literal">aztec</tt>)
382
and IP (Internet Protocol) address. The second section reports the
383
name and status of the files that are currently in use on a share on
384
the server, including the read/write status and any locks on the
385
files. Finally, Samba reports the amount of memory it has currently
386
allocated to the shares that it administers, including the amount
387
actively used by the shares plus additional overhead. (Note that this
388
is not the same as the total amount of memory that the
389
<em class="emphasis">smbd</em> or <em class="emphasis">nmbd</em> processes are
392
<p>Don't worry if you don't understand
393
these statistics; they will become easier to understand as you move
394
through the book.</p>
407
<div class="sect1"><a name="samba2-CHP-1-SECT-3"/>
409
<h2 class="head1">Getting Familiar with an SMB Network</h2>
411
<p><a name="INDEX-33"/>Now that you have had a brief tour of
412
Samba, let's take some time to get familiar with
413
Samba's adopted environment: an SMB network.
414
Networking with SMB is significantly different from working with
415
common TCP/IP protocols such as FTP and Telnet because there are
416
several new concepts to learn and a lot of information to cover.
417
First, we will discuss the basic concepts behind an SMB network,
418
followed by some Microsoft implementations of it, and finally we will
419
show you where a Samba server can and cannot fit into the picture.</p>
422
<div class="sect2"><a name="samba2-CHP-1-SECT-3.1"/>
424
<h3 class="head2">Understanding NetBIOS</h3>
426
<p>To begin, let's step back in time. In 1984, IBM
427
authored a simple application programming interface (API) for
428
networking its computers, called the <em class="firstterm">Network Basic
430
</em>(<a name="INDEX-34"/>NetBIOS).
431
The NetBIOS API provided a rudimentary design for an application to
432
connect and share data with other computers.</p>
434
<p>It's helpful to think of the NetBIOS API as
435
networking extensions to the standard BIOS API calls. The BIOS
436
contains low-level code for performing filesystem operations on the
437
local computer. NetBIOS originally had to exchange instructions with
438
computers across IBM PC or Token Ring networks. It therefore required
439
a low-level transport protocol to carry its requests from one
440
computer to the next.</p>
442
<p>In late 1985, IBM released one such protocol, which it merged with
443
the NetBIOS API to become the <em class="firstterm">NetBIOS Extended User
444
Interface</em> (<em class="emphasis">NetBEUI</em> ).
445
<a name="INDEX-35"/>NetBEUI was
446
designed for small LANs, and it let each computer claim a name (up to
447
15 characters) that wasn't already in use on the
448
network. By a "small LAN," we mean
449
fewer than 255 nodes on the network—which was considered a
450
generous number in 1985!</p>
452
<p>The NetBEUI protocol was very popular with networking applications,
453
including those running under Windows for Workgroups. Later,
454
implementations of NetBIOS over Novell's IPX
455
networking protocols also emerged, which competed with NetBEUI.
456
However, the networking protocols of choice for the burgeoning
457
Internet community were TCP/IP and UDP/IP, and implementing the
458
NetBIOS APIs over those protocols soon became a necessity.</p>
460
<p>Recall that TCP/IP uses numbers to represent computer addresses
461
(192.168.220.100, for instance) while NetBIOS uses only names. This
462
was a major issue when trying to mesh the two protocols together. In
463
1987, the IETF published standardization documents, titled RFC 1001
464
and 1002, that outlined how NetBIOS would work over a TCP/UDP
465
network. This set of documents still governs each implementation that
466
exists today, including those provided by Microsoft with its Windows
467
operating systems, as well as the Samba suite.</p>
469
<p>Since then, the standard that this document governs has become known
470
as <em class="firstterm">NetBIOS over
471
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>
473
<p>The NBT standard (RFC 1001/1002)
474
currently outlines a trio of services on a network:</p>
477
<p>A name service</p>
479
<p>Two communication services:</p>
490
<p>The <a name="INDEX-39"/>name
491
service solves the name-to-address problem mentioned earlier; it
492
allows each computer to declare a specific name on the network that
493
can be translated to a machine-readable IP address, much like
494
today's Domain Name System (DNS) on the Internet.
495
The <a name="INDEX-40"/>datagram and <a name="INDEX-41"/>session services are both
496
secondary communication protocols used to transmit data back and
497
forth from NetBIOS computers across the network.</p>
503
<div class="sect2"><a name="samba2-CHP-1-SECT-3.2"/>
505
<h3 class="head2">Getting a Name</h3>
507
<p><a name="INDEX-42"/><a name="INDEX-43"/>In the NetBIOS world, when each
508
computer comes online, it wants to claim a name for itself; this is
509
called <em class="firstterm">name registration</em>. However, no two
510
computers in the same workgroup should be able to claim the same
511
name; this would cause endless confusion for any computer that wanted
512
to communicate with either of them. There are two different
513
approaches to ensuring that this doesn't happen:</p>
516
<p>Use an <em class="firstterm"/>NBNS</em> to keep track of which hosts have
517
registered a NetBIOS name.</p>
519
<p>Allow each computer on the network to defend its name in the event
520
that another computer attempts to use it.</p>
522
<p><a href="ch01.html#samba2-CHP-1-FIG-8">Figure 1-8</a> illustrates a (failed) name
523
registration, with and without an NBNS.</p>
525
<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>
527
<p><a name="INDEX-44"/><a name="INDEX-45"/>As mentioned earlier,
528
there must be a way to resolve a NetBIOS name to a specific IP
529
address; this is known as <em class="firstterm">name resolution</em>.
530
There are two different approaches with NBT here as well:</p>
533
<p>Have each computer report back its IP address when it
534
"hears" a broadcast request for its
537
<p>Use an NBNS to help resolve NetBIOS names to IP addresses.</p>
539
<p><a href="ch01.html#samba2-CHP-1-FIG-9">Figure 1-9</a> illustrates the two types of name
542
<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>
544
<p>As you might expect, having an NBNS on your network can help out
545
tremendously. To see exactly why, let's look at the
546
broadcast method.</p>
548
<p>Here, when a client computer boots, it will
549
<a name="INDEX-46"/>broadcast a
550
message declaring that it wishes to register a specified NetBIOS name
551
as its own. If nobody objects to the use of the name, it keeps the
552
name. On the other hand, if another computer on the local subnet is
553
currently using the requested name, it will send a message back to
554
the requesting client that the name is already taken. This is known
555
as <em class="firstterm">defending</em><a name="INDEX-47"/><a name="INDEX-48"/> the hostname. This type of system
556
comes in handy when one client has unexpectedly dropped off the
557
network—another can take its name unchallenged—but it
558
does incur an inordinate amount of traffic on the network for
559
something as simple as name registration.</p>
561
<p>With an NBNS, the same thing occurs, except the communication is
562
confined to the requesting computer and the NBNS. No broadcasting
563
occurs when the computer wishes to register the name; the
564
registration message is simply sent directly from the client to the
565
NBNS, and the NBNS replies regardless of whether the name is already
566
taken. This is known as <em class="firstterm">point-to-point
567
communication</em><a name="INDEX-49"/>, and it is often beneficial on
568
networks with more than one subnet. This is because routers are
569
generally configured to block incoming packets that are broadcast to
570
all computers in the subnet.</p>
572
<p>The same principles apply to name resolution. Without an NBNS,
573
NetBIOS name resolution would also be done with a broadcast
574
mechanism. All request packets would be sent to each computer in the
575
network, with the hope that one computer that might be affected will
576
respond directly back to the computer that asked. Using an NBNS and
577
point-to-point communication for this purpose is far less taxing on
578
the network than flooding the network with broadcasts for every
579
name-resolution request.</p>
581
<p>It can be argued that broadcast packets do not cause significant
582
problems in modern, high-bandwidth networks of hosts with fast CPUs,
583
if only a small number of hosts are on the network, or the demand for
584
bandwidth is low. There are certainly cases where this is true;
585
however, our advice throughout this book is to avoid relying on
586
broadcasts as much as possible. This is a good rule to follow for
587
large, busy networks, and if you follow our advice when configuring a
588
small network, your network will be able to grow without encountering
589
problems later on that might be difficult to diagnose. <a name="INDEX-50"/><a name="INDEX-51"/></p>
595
<div class="sect2"><a name="samba2-CHP-1-SECT-3.3"/>
597
<h3 class="head2">Node Types</h3>
599
<p><a name="INDEX-52"/><a name="INDEX-53"/>How can you tell what strategy each
600
client on your network will use when performing name registration and
601
resolution? Each computer on an NBT network earns one of the
602
following designations, depending on how it handles name registration
603
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
604
behaviors of each type of node are summarized in <a href="ch01.html#samba2-CHP-1-TABLE-1">Table 1-1</a>.</p>
606
<a name="samba2-CHP-1-TABLE-1"/><h4 class="head4">Table 1-1. NetBIOS node types</h4><table border="1">
625
<p>Uses broadcast registration and resolution only.</p>
633
<p>Uses point-to-point registration and resolution only.</p>
638
<p>m-node (mixed)</p>
641
<p>Uses broadcast for registration. If successful, it notifies the NBNS
642
of the result. Uses broadcast for resolution; uses the NBNS if
643
broadcast is unsuccessful.</p>
648
<p>h-node (hybrid)</p>
651
<p>Uses the NBNS for registration and resolution; uses broadcast if the
652
NBNS is unresponsive or inoperative.</p>
658
<p>In the case of Windows clients, you will usually find them listed as
659
h-nodes or hybrid nodes. The first three node types appear in RFC
660
1001/1002, and h-nodes were invented later by Microsoft, as a more
661
fault-tolerant method.</p>
663
<p>You can find the node type of a Windows 95/98/Me computer by running
664
the <em class="emphasis">winipcfg</em><a name="INDEX-58"/><a name="INDEX-59"/> command from the Start
665
→ Run dialog (or from an MS-DOS prompt) and clicking
666
the More Info>> button. On Windows NT/2000/XP, you can use the
667
<tt class="literal">ipconfig</tt><a name="INDEX-60"/><a name="INDEX-61"/><a name="INDEX-62"/><a name="INDEX-63"/>
668
<tt class="literal">/all</tt> command in a command-prompt window. In either
669
case, search for the line that says <tt class="literal">Node Type</tt>.</p>
675
<div class="sect2"><a name="samba2-CHP-1-SECT-3.4"/>
677
<h3 class="head2">What's in a Name?</h3>
679
<p>The names <a name="INDEX-64"/><a name="INDEX-65"/>NetBIOS uses are quite different
680
from the DNS hostnames you might be familiar with. First, NetBIOS
681
names exist in a flat namespace. In other words, there are no
682
hierarchical levels, such as in <tt class="literal">oreilly.com</tt> (two
683
levels) or <em class="emphasis">ftp</em><em class="emphasis">.samba.org</em> (three
684
levels). NetBIOS names consist of a single unique string such as
685
<tt class="literal">navaho</tt> or <tt class="literal">hopi</tt> within each
686
workgroup or domain. Second, NetBIOS names are allowed to be only 15
687
characters and can consist only of standard alphanumeric characters
688
(a-z, A-Z, 0-9) and the following:</p>
690
<blockquote><pre class="code">! @ # $ % ^ & ( ) - ' { } . ~</pre></blockquote>
692
<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
693
against it because those names are not guaranteed to work in future
696
<p>It's not a coincidence that all valid DNS names are
697
also valid NetBIOS names. In fact, the unqualified DNS name for a
698
Samba server is often reused as its NetBIOS name. For example, if you
699
had a system with a hostname of <tt class="literal">mixtec.ora.com</tt> ,
700
its NetBIOS name would likely be MIXTEC (followed by 9 spaces).</p>
703
<div class="sect3"><a name="samba2-CHP-1-SECT-3.4.1"/>
705
<h3 class="head3">Resource names and types</h3>
707
<p><a name="INDEX-69"/><a name="INDEX-70"/>With NetBIOS, a computer not
708
only advertises its presence, but also tells others what types of
709
services it offers. For example, <tt class="literal">mixtec</tt> can
710
indicate that it's not just a workstation, but that
711
it's also a file server and can receive Windows
712
Messenger messages. This is done by adding a 16th byte to the end of
713
the machine (resource) name, called the <em class="firstterm">resource
714
type</em>, and registering the name multiple times, once for
715
each service that it offers. See <a href="ch01.html#samba2-CHP-1-FIG-10">Figure 1-10</a>.</p>
717
<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>
719
<p>The 1-byte resource type indicates a unique service that the named
720
computer provides. In this book, you will often see the resource type
721
shown in angled brackets (<>) after the NetBIOS name, such as:</p>
723
<blockquote><pre class="code">MIXTEC<00></pre></blockquote>
725
<p>You can see which names are registered for a particular NBT computer
726
using the Windows command-line
727
<em class="emphasis">nbtstat</em><a name="INDEX-71"/> utility.
728
Because these services are unique (i.e., there cannot be more than
729
one registered), you will see them listed as type UNIQUE in the
730
output. For example, the following partial output describes the
731
<tt class="literal">toltec</tt> server:</p>
733
<blockquote><pre class="code">C:\><tt class="userinput"><b>nbtstat -a toltec</b></tt>
735
NetBIOS Remote Machine Name Table
737
---------------------------------------------
738
TOLTEC <00> UNIQUE Registered
739
TOLTEC <03> UNIQUE Registered
740
TOLTEC <20> UNIQUE Registered
741
...</pre></blockquote>
743
<p>This says the server has registered the NetBIOS name
744
<tt class="literal">toltec</tt> as a machine (computer) name, as a
745
recipient of messages from the Windows Messenger service, and as a
746
file server. Some possible attributes a name can have are listed in
747
<a href="ch01.html#samba2-CHP-1-TABLE-2">Table 1-2</a>.</p>
749
<a name="samba2-CHP-1-TABLE-2"/><h4 class="head4">Table 1-2. NetBIOS unique resource types</h4><table border="1">
755
<p>Named resource</p>
758
<p>Hexadecimal byte value</p>
765
<p>Standard Workstation Service</p>
773
<p>Messenger Service</p>
781
<p>RAS Server Service</p>
789
<p>Domain Master Browser Service (associated with primary domain controller)</p>
797
<p>Master Browser name</p>
805
<p>NetDDE Service</p>
813
<p>Fileserver (including printer server)</p>
821
<p>RAS Client Service</p>
829
<p>Network Monitor Agent</p>
837
<p>Network Monitor Utility</p>
851
<div class="sect3"><a name="samba2-CHP-1-SECT-3.4.2"/>
853
<h3 class="head3">Group names and types</h3>
855
<p>SMB also uses the concept of groups, with which computers can
856
register themselves. Earlier we mentioned that the computers in our
857
example belonged to a
858
<em class="firstterm">workgroup</em><a name="INDEX-73"/>,
859
which is a partition of computers on the same network. For example, a
860
business might very easily have an ACCOUNTING and a SALES workgroup,
861
each with different servers and printers. In the Windows world, a
863
<a name="INDEX-74"/>SMB
864
group are the same thing.</p>
867
<em class="emphasis">nbtstat</em><a name="INDEX-75"/> example,
868
the <tt class="literal">toltec</tt> Samba server is also a member of the
869
METRAN workgroup (the GROUP attribute hex 00) and will participate in
870
elections for the browse master (GROUP attribute 1E). Here is the
871
remainder of the <em class="emphasis">nbtstat</em> output:</p>
873
<blockquote><pre class="code"> NetBIOS Remote Machine Name Table
875
---------------------------------------------
876
METRAN <00> GROUP Registered
877
METRAN <1E> GROUP Registered
878
..__MSBROWSE__.<01> GROUP Registered</pre></blockquote>
880
<p>The possible group attributes a computer can have are illustrated in
881
<a href="ch01.html#samba2-CHP-1-TABLE-3">Table 1-3</a>. More
882
<a name="INDEX-76"/><a name="INDEX-77"/>information
883
is available in <em class="emphasis">Windows NT in a Nutshell</em> by Eric
884
<a name="INDEX-78"/>Pearce, also
885
published by O'Reilly.</p>
887
<a name="samba2-CHP-1-TABLE-3"/><h4 class="head4">Table 1-3. NetBIOS group resource types</h4><table border="1">
893
<p>Named resource</p>
896
<p>Hexadecimal byte value</p>
903
<p>Standard Workstation group</p>
919
<p>Master Browser name</p>
927
<p>Normal Group name (used in browser elections)</p>
935
<p>Internet Group name (administrative)</p>
943
<p><tt class="literal"><01><02>_ _MSBROWSE_ _<02></tt></p>
952
<p>The final entry, <tt class="literal">_ _ MSBROWSE _ _</tt>
953
<a name="INDEX-80"/>, is used to announce a group to other
954
master browsers. The nonprinting characters in the name show up as
955
dots in an <em class="emphasis">nbtstat</em> printout.
956
Don't worry if you don't understand
957
all of the resource or group types. Some of them you will not need
958
with Samba, and others you will pick up as you move through the rest
959
of the chapter. The important thing to remember here is the logistics
960
of the naming mechanism.</p>
967
<div class="sect3"><a name="samba2-CHP-1-SECT-3.4.3"/>
969
<h3 class="head3">Scope ID</h3>
971
<p>In the dark ages of SMB networking before NetBIOS groups were
972
introduced, you could use a very primitive method to isolate groups
973
of computers from the rest of the network. Each SMB packet contains a
974
field called the <em class="firstterm">scope
975
ID</em><a name="INDEX-81"/><a name="INDEX-82"/>, with the idea being that
976
systems on the network could be configured to accept only packets
977
with a scope ID matching that of their configuration. This feature
978
was hardly ever used and unfortunately lingers in modern
979
implementations. Some of the utilities included in the Samba
980
distribution allow the scope ID to be set. Setting the scope ID in a
981
network is likely to cause problems, and we are mentioning scope ID
982
only so that you will not be confused by it when you later encounter
983
it in various places.</p>
992
<div class="sect2"><a name="samba2-CHP-1-SECT-3.5"/>
994
<h3 class="head2">Datagrams and Sessions</h3>
996
<p>At this point, let's digress to discuss the
997
responsibility of NBT: to provide connection services between two
999
<a name="INDEX-83"/>NBT
1000
offers two services: the <em class="firstterm">session
1001
service</em><a name="INDEX-84"/> and the
1002
<em class="firstterm">datagram service</em><a name="INDEX-85"/>.
1003
Understanding how these two services work is not essential to using
1004
Samba, but it does give you an idea of how NBT works and how to
1005
troubleshoot Samba when it doesn't work.</p>
1007
<p>The datagram service has no stable connection between computers.
1008
Packets of data are simply sent or broadcast from one computer to
1009
another, without regard to the order in which they arrive at the
1010
destination, or even if they arrive at all. The use of datagrams
1011
requires less processing overhead than sessions, although the
1012
reliability of the connection can suffer. Datagrams, therefore, are
1013
used for quickly sending nonvital blocks of data to one or more
1014
computers. The datagram service communicates using the simple
1015
primitives shown in <a href="ch01.html#samba2-CHP-1-TABLE-4">Table 1-4</a>.</p>
1017
<a name="samba2-CHP-1-TABLE-4"/><h4 class="head4">Table 1-4. Datagram primitives</h4><table border="1">
1033
<p>Send Datagram</p>
1036
<p>Send datagram packet to computer or groups of computers.</p>
1041
<p>Send Broadcast Datagram</p>
1044
<p>Broadcast datagram to any computer waiting with a Receive Broadcast
1050
<p>Receive Datagram</p>
1053
<p>Receive a datagram from a computer.</p>
1058
<p>Receive Broadcast Datagram</p>
1061
<p>Wait for a Broadcast datagram.</p>
1067
<p>The session service is more complex. Sessions are a communication
1068
method that, in theory, offers the ability to detect problematic or
1069
inoperable connections between two NetBIOS applications. It helps to
1070
think of an NBT session as being similar to a telephone call, an
1071
analogy that obviously influenced the design of the CIFS standard.</p>
1073
<p>Once the connection is made, it remains open throughout the duration
1074
of the conversation, each side knows who the caller and the called
1075
computer are, and each can communicate with the simple primitives
1076
shown in <a href="ch01.html#samba2-CHP-1-TABLE-5">Table 1-5</a>.</p>
1078
<a name="samba2-CHP-1-TABLE-5"/><h4 class="head4">Table 1-5. Session primitives</h4><table border="1">
1097
<p>Initiate a session with a computer listening under a specified name.</p>
1105
<p>Wait for a call from a known caller or any caller.</p>
1121
<p>Send data to the other computer.</p>
1129
<p>Receive data from the other computer.</p>
1134
<p>Session Status</p>
1137
<p>Get information on requested sessions.</p>
1143
<p>Sessions are the backbone of resource sharing on an NBT network. They
1144
are typically used for establishing stable connections from client
1145
computers to disk or printer shares on a server. The client
1146
"calls" the server and starts
1147
trading information such as which files it wishes to open, which data
1148
it wishes to exchange, etc. These calls can last a long
1149
time—hours, even days—and all of this occurs within the
1150
context of a single connection. If there is an error, the session
1151
software (TCP) will retransmit until the data is received properly,
1152
unlike the "punt-and-pray" approach
1153
of the datagram service (UDP).</p>
1155
<p>In truth, while sessions are supposed to handle problematic
1156
communications, they sometimes don't. If the
1157
connection is interrupted, session information that is open between
1158
the two computers might become invalid. If that happens, the only way
1159
to regain the session information is for the same two computers to
1160
call each other again and start over.</p>
1162
<p>If you want more information on each service, we recommend you look
1163
at RFC 1001. However, there are two important things to remember
1167
<p><a name="INDEX-88"/>Sessions always
1168
occur between two NetBIOS computers. If a session service is
1169
interrupted, the client is supposed to store sufficient state
1170
information for it to reestablish the connection. However, in
1171
practice, this often does not happen.</p>
1173
<p><a name="INDEX-89"/>Datagrams can
1174
be broadcast to multiple computers, but they are unreliable. In other
1175
words, there is no way for the source to know that the datagrams it
1176
sent have indeed arrived at their destinations. <a name="INDEX-90"/></p>
1186
<div class="sect1"><a name="samba2-CHP-1-SECT-4"/>
1188
<h2 class="head1">An Introduction to the SMB Protocol</h2>
1190
<p><a name="INDEX-91"/>Now
1191
we're going to cover some low-level technical
1192
details and explore the elementals of the SMB protocol. You probably
1193
don't need to know much about this to implement a
1194
simple Samba network, and therefore you might want to skip or skim
1195
over this section and go on to the next one
1196
("Windows Workgroups and Domains")
1197
on your first reading. However, assuming you are going to be
1198
responsible for long-term maintenance of a Samba network, it will
1199
help if you understand how it actually works. You will more easily be
1200
able to diagnose and correct any odd problems that pop up.</p>
1202
<p>At a high level, the SMB protocol suite is relatively simple. It
1203
includes commands for all the file and print operations that you
1204
might perform on a local disk or printer, such as:</p>
1207
<p>Opening and closing files</p>
1209
<p>Creating and deleting files and directories</p>
1211
<p>Reading and writing files</p>
1213
<p>Searching for files</p>
1215
<p>Queueing and dequeueing files in a print spool</p>
1217
<p>Each operation can be encoded into an SMB message and transmitted to
1218
and from a server. The original name
1219
"SMB" comes from the way in which
1220
the commands are formatted: they are versions of the standard DOS
1221
system-call data structures, or <em class="firstterm">Server Message
1222
Blocks</em>, redesigned for transmitting to another computer
1223
across a network.</p>
1226
<div class="sect2"><a name="samba2-CHP-1-SECT-4.1"/>
1228
<h3 class="head2">SMB Format</h3>
1230
<p>Richard <a name="INDEX-92"/>Sharpe of the Samba team defines SMB as
1231
a <em class="firstterm">request-response</em> protocol.<a name="FNPTR-4"/><a href="#FOOTNOTE-4">[4]</a> In effect,
1232
this means that a client sends an SMB request to a server and the
1233
server sends an SMB response back to the client. In only one rare
1234
circumstance does a server send a message that is not in response to
1237
<p>An <a name="INDEX-94"/>SMB message is not as complex as you
1238
might think. Let's take a closer look at the
1239
internal structure of such a message. It can be broken down into two
1240
parts: the <em class="firstterm">header</em>, which is a fixed size, and
1241
the <em class="firstterm">command string</em>, whose size can vary
1242
dramatically based on the contents of the message.</p>
1245
<div class="sect3"><a name="samba2-CHP-1-SECT-4.1.1"/>
1247
<h3 class="head3">SMB header format</h3>
1249
<p><a href="ch01.html#samba2-CHP-1-TABLE-6">Table 1-6</a> shows the format of an
1250
<a name="INDEX-95"/>SMB header. The COM field identifies
1251
the command being performed. SMB commands are not required to use all
1252
the fields in the SMB header. For example, when a client first
1253
attempts to connect to a server, it does not yet have a tree
1254
identifier (TID) value—one is assigned after it successfully
1255
connects—so a null TID is placed in its header field. Other
1256
fields can be padded with zeros when not used.</p>
1258
<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>
1260
<a name="samba2-CHP-1-TABLE-6"/><h4 class="head4">Table 1-6. SMB header fields</h4><table border="1">
1280
<p><tt class="literal">0xFF 'SMB</tt>'</p>
1283
<p><tt class="literal">1</tt></p>
1286
<p>Protocol identifier</p>
1291
<p><tt class="literal">COM</tt></p>
1294
<p><tt class="literal">1</tt></p>
1297
<p>Command code, from 0x00 to 0xFF</p>
1302
<p><tt class="literal">RCLS</tt></p>
1305
<p><tt class="literal">1</tt></p>
1313
<p><tt class="literal">REH</tt></p>
1316
<p><tt class="literal">1</tt></p>
1324
<p><tt class="literal">ERR</tt></p>
1327
<p><tt class="literal">2</tt></p>
1335
<p><tt class="literal">REB</tt></p>
1338
<p><tt class="literal">1</tt></p>
1346
<p><tt class="literal">RES</tt></p>
1349
<p><tt class="literal">14</tt></p>
1357
<p><tt class="literal">TID</tt></p>
1360
<p><tt class="literal">2</tt></p>
1363
<p>TID; a unique ID for a resource in use by the client</p>
1368
<p><tt class="literal">PID</tt></p>
1371
<p><tt class="literal">2</tt></p>
1374
<p>Caller process ID</p>
1379
<p><tt class="literal">UID</tt></p>
1382
<p><tt class="literal">2</tt></p>
1385
<p>User identifier</p>
1390
<p><tt class="literal">MID</tt></p>
1393
<p><tt class="literal">2</tt></p>
1396
<p>Multiplex identifier; used to route requests inside a process</p>
1407
<div class="sect3"><a name="samba2-CHP-1-SECT-4.1.2"/>
1409
<h3 class="head3">SMB command format</h3>
1411
<p>Immediately after the header is a variable number of bytes that
1412
constitute an <a name="INDEX-97"/>SMB command or reply. Each command,
1413
such as Open File (COM field identifier: <tt class="literal">SMBopen</tt>)
1414
or Get Print Queue (<tt class="literal">SMBsplretq</tt> ), has its own set
1415
of parameters and data. Like the SMB header fields, not all of the
1416
command fields need to be filled, depending on the specific command.
1417
For example, the Get Server Attributes
1418
(<tt class="literal">SMBdskattr</tt>) command sets the WCT and BCC fields
1419
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>
1421
<a name="samba2-CHP-1-TABLE-7"/><h4 class="head4">Table 1-7. SMB command contents</h4><table border="1">
1441
<p><tt class="literal">WCT</tt></p>
1444
<p><tt class="literal">1</tt></p>
1452
<p><tt class="literal">VWV</tt></p>
1458
<p>Parameter words (size given by WCT)</p>
1463
<p><tt class="literal">BCC</tt></p>
1466
<p><tt class="literal">2</tt></p>
1469
<p>Parameter byte count</p>
1474
<p><tt class="literal">DATA</tt></p>
1480
<p>Data (size given by BCC)</p>
1486
<p>Don't worry if you don't understand
1487
each field; they are not necessary for using Samba at an
1488
administrator level. However, they do come in handy when debugging
1489
system messages. We will show you some of the more common SMB
1490
messages that clients and servers send using a modified version of
1491
<em class="filename">tcpdump</em> later in this section. (If you prefer an
1492
<a name="INDEX-98"/><a name="INDEX-99"/>SMB sniffer with a graphical
1493
interface, try Ethereal, which uses the GTK libraries; see
1494
<a href="http://www.ethereal.com">http://www.ethereal.com</a> for more
1495
information on this tool.)</p>
1497
<a name="samba2-CHP-1-NOTE-84"/><blockquote class="note"><h4 class="objtitle">TIP</h4>
1498
<p>For more information on each command in the
1499
<a name="INDEX-100"/>SMB protocol, see the
1500
<em class="citetitle">CIFS Technical
1501
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>
1509
<div class="sect3"><a name="samba2-CHP-1-SECT-4.1.3"/>
1511
<h3 class="head3">SMB variations</h3>
1513
<p>The SMB protocol has been extended with new commands several times
1514
since its inception. Each new version is backward-compatible with the
1515
previous versions, so it is possible for a LAN to have clients and
1516
servers concurrently running different versions of the SMB protocol.</p>
1518
<p><a href="ch01.html#samba2-CHP-1-TABLE-8">Table 1-8</a> outlines the major versions of the
1519
<a name="INDEX-102"/>SMB
1520
protocol. Within each "dialect" of
1521
SMB are many sub-versions that include commands supporting particular
1522
releases of major operating systems. The ID string in column 2 is
1523
used by clients and servers to determine in which level of the
1524
protocol they will speak to each other.</p>
1526
<a name="samba2-CHP-1-TABLE-8"/><h4 class="head4">Table 1-8. SMB protocol dialects</h4><table border="1">
1533
<p>Protocol name</p>
1549
<p><tt class="literal">PC NETWORK PROGRAM 1.0</tt></p>
1556
<p><a name="INDEX-103"/>Core Plus</p>
1559
<p><tt class="literal">MICROSOFT NETWORKS 1.03</tt></p>
1566
<p><a name="INDEX-104"/>LAN Manager 1.0</p>
1569
<p><tt class="literal">LANMAN1.0</tt></p>
1576
<p>LAN Manager 2.0</p>
1579
<p><tt class="literal">LM1.2X002</tt></p>
1586
<p>LAN Manager 2.1</p>
1589
<p><tt class="literal">LANMAN2.1</tt></p>
1596
<p><a name="INDEX-105"/>NT LAN
1600
<p><tt class="literal">NT LM 0.12</tt></p>
1603
<p>Windows NT 4.0</p>
1608
<p><a name="INDEX-106"/>Samba's NT LM 0.12</p>
1611
<p><tt class="literal">Samba</tt></p>
1619
<p><a name="INDEX-107"/><a name="INDEX-108"/>Common
1620
Internet File System</p>
1623
<p><tt class="literal">CIFS 1.0</tt></p>
1626
<p>Windows 2000/XP</p>
1632
<p>Samba implements the NT LM 0.12 specification for NT LAN Manager 1.0.
1633
It is backward-compatible with all the other SMB variants. The CIFS
1634
specification is, in reality, LAN Manager 0.12 with a few specific
1644
<div class="sect2"><a name="samba2-CHP-1-SECT-4.2"/>
1646
<h3 class="head2">SMB Clients and Servers</h3>
1648
<p><a name="INDEX-109"/><a name="INDEX-110"/>As
1649
mentioned earlier, SMB is a client/server protocol. In the purest
1650
sense, this means that a client sends a request to a server, which
1651
acts on the request and returns a reply. However, the client/server
1652
roles can often be reversed, sometimes within the context of a single
1653
SMB session. For example, consider the two Windows 95/98/Me computers
1654
in <a href="ch01.html#samba2-CHP-1-FIG-11">Figure 1-11</a>. The computer named
1655
<tt class="literal">maya</tt> shares a printer to the network, and the
1656
computer named <tt class="literal">toltec</tt> shares a disk directory.
1657
<tt class="literal">maya</tt> is in the client role when accessing
1658
<tt class="literal">toltec</tt>'s network drive and in the
1659
server role when printing a job for <tt class="literal">toltec</tt>.</p>
1661
<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>
1663
<p>This brings out an important point in Samba terminology:</p>
1666
<p>A <em class="firstterm">server</em> is a computer with a resource to
1669
<p>A <em class="firstterm">client</em> is a computer that wishes to use that
1672
<p>A computer can be a client, a server, or both, or it can be neither
1673
at any given time.</p>
1675
<p>Microsoft Windows products have both the SMB client and server built
1676
into the operating system, and it is common to find Windows acting as
1677
a server, client, both, or neither at any given time in a production
1678
network. Although Samba has been developed primarily to function as a
1679
server, there are also ways that it and associated software can act
1680
as an SMB client. As with Windows, it is even possible to set up a
1681
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>
1687
<div class="sect2"><a name="samba2-CHP-1-SECT-4.3"/>
1689
<h3 class="head2">A Simple SMB Connection</h3>
1691
<p><a name="INDEX-111"/>The client and server must complete
1692
three steps to establish a connection to a resource:</p>
1695
<p>Establish a NetBIOS session.</p>
1697
<p>Negotiate the protocol variant.</p>
1699
<p>Set session parameters, and make a tree connection to a resource.</p>
1701
<p>We will examine each step through the eyes of a useful tool that we
1702
mentioned earlier: the modified
1703
<em class="filename">tcpdump</em><a name="INDEX-112"/> that is
1704
available from the Samba web site.</p>
1706
<a name="samba2-CHP-1-NOTE-85"/><blockquote class="note"><h4 class="objtitle">TIP</h4>
1707
<p>You can download the tcpdump program at <a href="http://www.samba.org">http://www.samba.org</a> in the
1708
<em class="filename">samba/ftp/tcpdump-smb</em> directory; the latest
1709
version as of this writing is 3.4-10. Use this program as you would
1710
use the standard <em class="filename">tcpdump</em> application, but add
1711
the <tt class="literal">-s 1500</tt> switch to ensure that you get the
1712
whole packet and not just the first few bytes.</p>
1719
<div class="sect2"><a name="samba2-CHP-1-SECT-4.4"/>
1721
<h3 class="head2">Establishing a NetBIOS Session</h3>
1723
<p><a name="INDEX-113"/>When a user first makes a request
1724
to access a network disk or send a print job to a remote printer,
1725
NetBIOS takes care of making a connection at the session layer. The
1726
result is a bidirectional channel between the client and server. The
1727
client and server need only two messages to establish this
1728
connection. This is shown in the following example session request
1729
and response, as captured by <em class="filename">tcpdump</em> .</p>
1731
<p>First, the client sends a request to open a session, and
1732
<em class="filename">tcpdump </em><a name="INDEX-114"/>reports:</p>
1734
<blockquote><pre class="code">>>> NBT Packet
1737
Destination=TOLTEC NameType=0x20 (Server)
1738
Source=MAYA NameType=0x00 (Workstation)</pre></blockquote>
1740
<p>Then the server responds, granting a session to the client:</p>
1742
<blockquote><pre class="code">>>> NBT Packet
1744
Flags=0x82000000</pre></blockquote>
1746
<p>At this point, there is an open channel between the client and server.</p>
1752
<div class="sect2"><a name="samba2-CHP-1-SECT-4.5"/>
1754
<h3 class="head2">Negotiating the Protocol Variant</h3>
1756
<p>Next, the client sends a message to the server to negotiate an
1757
<a name="INDEX-115"/>SMB protocol. As mentioned
1758
earlier, the client sets its <a name="INDEX-116"/>tree identifier (TID) field to
1759
zero, because it does not yet know what TID to use. A <em class="emphasis">tree
1760
identifier</em> is a number that represents a connection to a
1761
share on a server.</p>
1763
<p>The command in the message is <tt class="literal">SMBnegprot</tt>, a
1764
request to negotiate a protocol variant that will be used for the
1765
entire session. Note that the client sends to the server a list of
1766
all the variants that it can speak, not vice versa:</p>
1768
<blockquote><pre class="code">>>> NBT Packet
1773
SMB PACKET: SMBnegprot (REQUEST)
1784
Dialect=PC NETWORK PROGRAM 1.0
1785
Dialect=MICROSOFT NETWORKS 3.0
1786
Dialect=DOS LM1.2X002
1787
Dialect=DOS LANMAN2.1
1788
Dialect=Windows for Workgroups 3.1a
1789
Dialect=NT LM 0.12</pre></blockquote>
1791
<p>The server responds to the
1792
<tt class="literal">SMBnegprot</tt><a name="INDEX-117"/> request with an index (with counting
1793
starting at 0) into the list of variants that the client offered, or
1794
with the value 0xFF if none of the protocol variants is acceptable:</p>
1796
<blockquote><pre class="code">>>> NBT Packet
1801
SMB PACKET: SMBnegprot (REPLY)
1814
[...]</pre></blockquote>
1816
<p>In this example, the server responds with the value 5, which
1817
indicates that the <tt class="literal">NT</tt> <tt class="literal">LM</tt>
1818
<tt class="literal">0.12</tt> dialect will be used for the remainder of the
1825
<div class="sect2"><a name="samba2-CHP-1-SECT-4.6"/>
1827
<h3 class="head2">Set Session and Login Parameters</h3>
1829
<p><a name="INDEX-118"/><a name="INDEX-119"/>The next step is to transmit session and
1830
login parameters for the session, which you do using the
1831
<a name="INDEX-120"/><tt class="literal">SMBSesssetupX</tt>
1832
command. The parameters include the following:</p>
1835
<p>The account name and password (if there is one)</p>
1837
<p>The workgroup name</p>
1839
<p>The maximum size of data that can be transferred</p>
1841
<p>The number of pending requests that can be in the queue at a time</p>
1843
<p>The resulting output from <em class="filename">tcpdump </em>is:</p>
1845
<blockquote><pre class="code">>>> NBT Packet
1850
SMB PACKET: SMBsesssetupX (REQUEST)
1868
CaseInsensitivePasswordLength=24
1869
CaseSensitivePasswordLength=0
1872
Pass1&Pass2&Account&Domain&OS&LanMan=
1873
JAY METRAN Windows 4.0 Windows 4.0
1875
SMB PACKET: SMBtconX (REQUEST) (CHAINED)
1881
Passwd&Path&Device=
1883
smb_buf[]=\\TOLTEC\SPIRIT</pre></blockquote>
1885
<p>In this example, the <tt class="literal">SMBsesssetupX</tt> Session Setup
1886
command allows for an additional SMB command to be piggybacked onto
1887
it (indicated by the letter X at the end of the command name). The
1888
hexadecimal code of the second command is given in the
1889
<tt class="literal">Com2</tt> field. In this case the command is
1890
<tt class="literal">0x75</tt>, which is the <tt class="literal">SMBtconX</tt>
1891
<tt class="literal">(</tt>Tree Connect and X) command. The
1892
<tt class="literal">SMBtconX</tt><a name="INDEX-121"/> message looks for the name of the
1893
resource in the <em class="emphasis">smb_buf</em> buffer. In this example,
1894
<em class="emphasis">smb_buf</em> contains the string
1895
<tt class="literal">\\TOLTEC\SPIRIT</tt>, which is the full pathname to a
1896
shared directory on <tt class="literal">toltec</tt>. Using the
1897
"and X" commands like this speeds
1898
up each transaction because the server doesn't have
1899
to wait on the client to make a second request.</p>
1901
<p>Note that the TID is still zero. Finally, the server returns a TID to
1902
the client, indicating that the user has been authorized access and
1903
that the resource is ready to be used:</p>
1905
<blockquote><pre class="code">>>> NBT Packet
1910
SMB PACKET: SMBsesssetupX (REPLY)
1924
[000] Unix Samba 2.2.6
1927
SMB PACKET: SMBtconX (REPLY) (CHAINED)
1932
ServiceType=A:</pre></blockquote>
1934
<p>The <em class="emphasis">ServiceType</em> field is set to
1935
"A" to indicate that this is a file
1936
service. Available service types are:</p>
1939
<p>"A" for a disk or file</p>
1941
<p>"LPT1" for a spooled output</p>
1943
<p>"COMM" for a direct-connect printer
1946
<p>"IPC" for a named pipe</p>
1948
<p>Now that a TID has been assigned, the client can use it as a handle
1949
to perform any operation that it would use on a local disk drive. It
1950
can open files, read and write to them, delete them, create new
1951
files, search for filenames, and so on. <a name="INDEX-122"/></p>
1961
<div class="sect1"><a name="samba2-CHP-1-SECT-5"/>
1963
<h2 class="head1">Windows Workgroups and Domains</h2>
1965
<p>Up to now, we've covered basic SMB technology, which
1966
is all you would need if you had nothing more advanced than MS-DOS
1967
clients on your network. We do assume you want to support Windows
1968
clients, especially the more recent versions, so next
1969
we'll describe the enhancements Microsoft has added
1970
to SMB networking—namely, Windows for Workgroups and Windows
1974
<div class="sect2"><a name="samba2-CHP-1-SECT-5.1"/>
1976
<h3 class="head2">Windows Workgroups</h3>
1978
<p><a name="INDEX-123"/><a name="INDEX-124"/>Windows
1979
Workgroups are very similar to the SMB groups already described. You
1980
need to know just a few additional things.</p>
1983
<div class="sect3"><a name="samba2-CHP-1-SECT-5.1.1"/>
1985
<h3 class="head3">Browsing</h3>
1987
<p><a name="INDEX-125"/>Browsing
1988
is the process of finding the other computers and shared resources in
1989
the Windows network. Note that there is no connection with a World
1990
Wide Web browser, apart from the general idea of
1991
"discovering what's
1992
there." On the other hand, browsing the Windows
1993
network is like the Web in that what's out there can
1994
change without warning.</p>
1996
<p>Before browsing existed, users had to know the name of the computer
1997
they wanted to connect to on the network and then manually enter a
1998
UNC such as the following into an application or file manager to
1999
access resources:</p>
2001
<blockquote><pre class="code">\\toltec\spirit\</pre></blockquote>
2003
<p>Browsing is much more convenient, making it possible to examine the
2004
contents of a network by using the point-and-click GUI interface of
2005
the Network Neighborhood (or My Network Places<a name="FNPTR-5"/><a href="#FOOTNOTE-5">[5]</a>) on a Windows client.</p>
2007
<p>You will encounter two types of browsing in an SMB network:</p>
2010
<p><a name="INDEX-129"/>Browsing a list
2011
of computers and shared resources</p>
2013
<p><a name="INDEX-130"/>Browsing the shared resource
2014
of a specific computer</p>
2016
<p>Let's look at the first one. On each LAN (or subnet)
2017
with a Windows workgroup or domain, one computer has the
2018
responsibility of maintaining a list of the computers that are
2019
currently accessible through the network. This computer is called the
2020
<em class="firstterm">local master
2021
browser</em><a name="INDEX-131"/><a name="INDEX-132"/>, and the list that it maintains is
2022
called the <em class="firstterm">browse
2023
list</em><a name="INDEX-133"/>. Computers on a subnet use the browse
2024
list to cut down on the amount of network traffic generated while
2025
browsing. Instead of each computer dynamically polling to determine a
2026
list of the currently available computers, the computer can simply
2027
query the local master browser to obtain a complete, up-to-date list.</p>
2029
<p>To browse the resources on a computer, a user must connect to the
2030
specific computer; this information cannot be obtained from the
2031
browse list. Browsing the list of resources on a computer can be done
2032
by double-clicking the computer's icon when it is
2033
presented in the Network Neighborhood. As you saw at the opening of
2034
the chapter, the computer will respond with a list of shared
2035
resources that can be accessed after the user is successfully
2038
<p>Each server on a Windows workgroup is required to announce its
2039
presence to the local master browser after it has registered a
2040
NetBIOS name, and (theoretically) announce that it is leaving the
2041
workgroup when it is shut down. It is the local master
2042
browser's responsibility to record what the servers
2044
<a name="samba2-CHP-1-NOTE-86"/><blockquote class="note"><h4 class="objtitle">WARNING</h4>
2045
<p>The Windows <a name="INDEX-134"/>Network Neighborhood can behave
2046
oddly: until you select a particular computer to browse, the Network
2047
Neighborhood window might contain data that is not up-to-date. That
2048
means the Network Neighborhood window can be showing computers that
2049
have crashed or can be missing computers that
2050
haven't been noticed yet. Put succinctly, once
2051
you've selected a server and connected to it, you
2052
can be a lot more confident that the shares and printers really exist
2056
<p>Unlike the roles you've seen earlier, almost any
2057
Windows system (including Windows for Workgroups and Windows 95/98/Me
2058
or NT/2000/XP) can act as a local master browser. The local master
2059
browser can have one or more
2060
<em class="firstterm"/><a name="INDEX-135"/><a name="INDEX-136"/>backup
2061
browsers</em> on the local subnet
2062
that will take over in the event that the local master browser fails
2063
or becomes inaccessible. To ensure fluid operation, the local backup
2064
browsers will frequently synchronize their browse list with the local
2067
<p>Here is how to calculate the minimum number of backup browsers that
2068
will be allocated on a workgroup:</p>
2071
<p>If up to 32 Windows NT/2000/XP workstations are on the network, or up
2072
to 16 Windows 95/98/Me computers are on the network, the local master
2073
browser allocates one backup browser in addition to the local master
2076
<p>If the number of Windows NT/2000/XP workstations falls between 33 and
2077
64, or the number of Windows 95/98/Me workstations falls between 17
2078
and 32, the local master browser allocates two backup browsers.</p>
2080
<p>For each group of 32 NT/2000/XP workstations or 16 Windows 95/98/Me
2081
computers beyond this, the local master browser allocates another
2084
<p>There is currently no upper limit on the number of backup browsers
2085
that can be allocated by the local master browser.</p>
2092
<div class="sect3"><a name="samba2-CHP-1-SECT-5.1.2"/>
2094
<h3 class="head3">Browsing elections</h3>
2096
<p><a name="INDEX-137"/>Browsing
2097
is a critical aspect of any Windows workgroup. However, not
2098
everything runs perfectly on any network. For example,
2099
let's say that a computer running Windows on the
2100
desk of a small company's CEO is the local master
2101
browser—that is, until he switches it off while plugging in his
2102
massage chair. At this point the Windows NT Workstation in the spare
2103
parts department might agree to take over the job. However, that
2104
computer is currently running a large, poorly written program that
2105
has brought its processor to its knees. The moral: browsing has to be
2106
very tolerant of servers coming and going. Because nearly every
2107
Windows system can serve as a browser, there has to be a way of
2108
deciding at any time who will take on the job. This decision-making
2109
process is called an <em class="firstterm">election</em>.</p>
2111
<p>An election algorithm is built into nearly all Windows operating
2112
systems such that they can each agree who is going to be a local
2113
master browser and who will be local backup browsers. An election can
2114
be forced at any time. For example, let's assume
2115
that the CEO has finished his massage and reboots his server. As the
2116
server comes online, it will announce its presence, and an election
2117
will take place to see if the PC in the spare parts department should
2118
still be the master browser.</p>
2120
<p>When an election is performed, each computer broadcasts information
2121
about itself via datagrams. This information includes the following:</p>
2124
<p>The version of the election protocol used</p>
2126
<p>The operating system on the computer</p>
2128
<p>The amount of time the client has been on the network</p>
2130
<p>The hostname of the client</p>
2132
<p>These values determine which operating system has seniority and will
2133
fulfill the role of the local master browser. (<a href="ch07.html">Chapter 7</a> describes the election process in more
2134
detail.) The architecture developed to achieve this is not elegant
2135
and has built-in security problems. While a browsing domain can be
2136
integrated with domain security, the election algorithm does not take
2137
into consideration which computers become browsers. Thus it is
2138
possible for any computer running a browser service to register
2139
itself as participating in the browsing election and (after winning)
2140
being able to change the browse list. Nevertheless, browsing is a key
2141
feature of Windows networking, and backward-compatibility
2142
requirements will ensure that it is in use for years to come.
2143
<a name="INDEX-138"/></p>
2150
<div class="sect3"><a name="samba2-CHP-1-SECT-5.1.3"/>
2152
<h3 class="head3">Windows 95/98/Me authentication</h3>
2154
<p>Three types of passwords arise when
2155
<a name="INDEX-139"/><a name="INDEX-140"/>Windows
2156
95/98/Me is operating in a Windows workgroup:</p>
2159
<p>A Windows password</p>
2161
<p>A Windows Networking password</p>
2163
<p>A password for each shared resource that has been assigned password
2166
<p>The Windows <a name="INDEX-141"/>password functions in a manner
2167
that might be a source of confusion for Unix system administrators.
2168
It is not there to prevent unauthorized users from using the
2169
computer. (If you don't believe that, try clicking
2170
the Cancel button on the password dialog box and see what happens!)
2171
Instead, the Windows password is used to gain access to a file that
2172
contains the Windows Networking and network resource passwords. There
2173
is one such file per registered user of the system, and they can be
2174
found in the <em class="filename">C:\Windows</em> directory with a name
2175
composed of the user's account name, followed by a
2176
<em class="filename">.pwl</em><a name="INDEX-142"/><a name="INDEX-143"/><a name="INDEX-144"/> extension. For example, if the
2177
user's account name is
2178
"sarah," the file will be
2179
<em class="filename">C:\Windows\sarah.pwl</em>. This file is encrypted
2180
using the Windows password as the encryption key.</p>
2182
<a name="samba2-CHP-1-NOTE-87"/><blockquote class="note"><h4 class="objtitle">TIP</h4>
2183
<p>As a security measure, you might want to check for junk
2184
<em class="filename">.pwl</em> files on Windows 95/98/Me clients, which
2185
might have been created by mistakes users made while attempting to
2186
log on. A <em class="filename">.pwl</em> file is easily cracked and can
2187
contain valid passwords for Samba accounts and network shares.</p>
2190
<p>The first time the network is accessed, Windows attempts to use the
2191
Windows password as the Windows Networking password. If this is
2192
successful, the user will not be prompted for two separate passwords,
2193
and subsequent logins to the Windows system will automatically result
2194
in logging on to the Windows network as well, making things much
2195
simpler for the user.</p>
2197
<p>Shared network resources in the workgroup can also have passwords
2198
assigned to them to limit their accessibility. The first time a user
2199
attempts to access the resource, she is asked for its password, and a
2200
checkbox in the password dialog box gives the user the option to add
2201
the password to her password list. This is the default; if it is
2202
accepted, Windows will store the password in the
2203
user's <em class="filename">.pwl</em> file, and all
2204
further authentication to the resource will be handled automatically
2207
<p>Samba's approach to workgroup authentication is a
2208
little different, which is a result of blending the Windows workgroup
2209
model with that of the Unix host upon which Samba runs. This will be
2210
discussed further in <a href="ch09.html">Chapter 9</a>. <a name="INDEX-145"/></p>
2219
<div class="sect2"><a name="samba2-CHP-1-SECT-5.2"/>
2221
<h3 class="head2">Windows NT Domains</h3>
2223
<p><a name="INDEX-146"/>The
2224
peer-to-peer networking model of
2225
<a name="INDEX-147"/>workgroups functions fairly well as long as
2226
the number of computers on the network is small and there is a
2227
close-knit community of users. However, in larger networks the
2228
simplicity of workgroups becomes a limiting factor. Workgroups offer
2229
only the most basic level of security, and because each resource can
2230
have its own password, it is inconvenient (to say the least) for
2231
users to remember the password for each resource in a large network.
2232
Even if that were not a problem, many people find it frustrating to
2233
have to interrupt their creative workflow to enter a shared password
2234
into a dialog box every time another network resource is accessed.</p>
2236
<p>To support the needs of larger networks, such as those found in
2237
departmental computing environments, Microsoft introduced domains
2238
with Windows NT 3.51. A <em class="firstterm">Windows NT domain</em> is
2239
essentially a workgroup of SMB computers that has one addition: a
2240
server acting as a <em class="firstterm">domain
2241
controller</em><a name="INDEX-148"/> (see <a href="ch01.html#samba2-CHP-1-FIG-12">Figure 1-12</a>).</p>
2243
<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>
2246
<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.1"/>
2248
<h3 class="head3">Domain controllers</h3>
2250
<p>A domain controller in a Windows NT domain functions much like a
2251
<a name="INDEX-149"/><a name="INDEX-150"/>Network
2252
Information Service (NIS) server in a Unix network, maintaining a
2253
domain-wide database of user and group information, as well as
2254
performing related services. The responsibilities of a domain
2255
controller are mainly centered around security, including
2256
<em class="firstterm">authentication</em><a name="INDEX-151"/>,
2257
the process of granting or denying a user access to the resources of
2258
the domain. This is typically done through the use of a username and
2259
password. The service that maintains the database on the domain
2260
controllers is called the <a name="INDEX-152"/><a name="INDEX-153"/>Security Account Manager (SAM).</p>
2262
<p>The <a name="INDEX-154"/>Windows NT security model revolves
2263
around <em class="firstterm">security
2264
identifiers</em><a name="INDEX-155"/><a name="INDEX-156"/> (SIDs) and <em class="firstterm">access
2265
control lists</em><a name="INDEX-157"/><a name="INDEX-158"/>
2266
(ACLs). Security identifiers are used to represent objects in the
2267
domain, which include (but are not limited to) users, groups,
2268
computers, and processes. SIDs are commonly written in ASCII form as
2269
hyphen-separated fields, like this:</p>
2271
<blockquote><pre class="code">S-1-5-21-1638239387-7675610646-9254035128-545</pre></blockquote>
2273
<p>The part of the SID starting with the
2274
"S" and leading up to the rightmost
2275
hyphen identifies a domain. The number after the rightmost hyphen is
2276
called a <a name="INDEX-159"/>relative identifier (RID) and is a unique
2277
number within the domain that identifies the user, group, computer,
2278
or other object. The RID is the analog of a <a name="INDEX-160"/>user ID (UID) or
2279
<a name="INDEX-161"/>group ID
2280
(GID) on a Unix system or within an NIS domain.</p>
2282
<p>ACLs supply the same function as
2284
<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
2285
systems. However, ACLs are more versatile. Unix file permissions only
2286
set permissions for the owner and group to which the file belongs,
2287
and "other," meaning everyone else.
2288
Windows NT/2000/XP ACLs allow permissions to be set individually for
2289
any number of arbitrary users and/or groups. ACLs are made up of one
2290
or more <em class="firstterm">access control
2291
entries</em><a name="INDEX-167"/> (ACEs), each of which contains an SID
2292
and the access rights associated with it.</p>
2294
<p>ACL support has been added as a standard feature for some Unix
2295
variants and is available as an add-on for others. Samba supports
2296
mappings between Windows and Unix ACLs, and this will be covered in
2297
<a href="ch08.html">Chapter 8</a>.</p>
2304
<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.2"/>
2306
<h3 class="head3">Primary and backup domain controllers</h3>
2308
<p>You've already read about master and backup
2309
browsers. Domain controllers are similar in that a domain has a
2310
<em class="firstterm">primary domain
2311
controller</em><a name="INDEX-168"/><a name="INDEX-169"/><a name="INDEX-170"/> (PDC) and can have
2312
one or more <em class="firstterm">backup domain
2313
controllers</em><a name="INDEX-171"/> (BDCs) as well. If the PDC fails or
2314
becomes inaccessible, its duties are automatically taken over by one
2315
of the BDCs. BDCs frequently synchronize their SAM data with the PDC
2316
so if the need arises, any one of them can immediately begin
2317
performing domain-controller services without impacting the clients.
2318
However, note that BDCs have read-only copies of the SAM database;
2319
they can update their data only by synchronizing with a PDC. A server
2320
in a Windows domain can use the SAM of any PDC or BDC to authenticate
2321
a user who attempts to access its resources and log on to the domain.</p>
2323
<p>All recent versions of Windows can log on to a domain as clients to
2324
access the resources of the domain servers. The systems that are
2325
considered members of the domain are a more exclusive class, composed
2326
of the PDC and BDCs, as well as domain member servers, which are
2327
systems that have joined a domain as members, and are known to the
2328
domain controllers by having a computer account in the SAM database.</p>
2335
<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.3"/>
2337
<h3 class="head3">Authentication</h3>
2339
<p><a name="INDEX-172"/>When
2340
a user logs on to a Windows domain by typing in a username and
2341
password, a secure challenge and response protocol is invoked between
2342
the client computer and a domain controller to verify that the
2343
username and password are valid. Then the domain controller sends a
2344
SID back to the client, which uses it to create a
2345
<a name="INDEX-173"/>Security Access Token (SAT) that is valid
2346
only for that system, to be used for further authentication. This
2347
access token has information about the user coded into it, including
2348
the username, the group, and the rights the user has within the
2349
domain. At this point, the user is logged on to the domain.</p>
2351
<p>Subsequently, when the client attempts to access a shared resource
2352
within the domain, the client system enters into a secure challenge
2353
and response exchange with the server of the resource. The server
2354
then enters into another secure challenge and response conversation
2355
with a domain controller to check that the client is valid. (What
2356
actually happens is that the server uses information it gets from the
2357
client to pretend to be the client and authenticate itself with the
2358
domain controller. If the domain controller validates the
2359
credentials, it sends an SID back to the server, which uses the SID
2360
to create its own SAT for the client to enable access to its local
2361
resources on the client's behalf.) At this point,
2362
the client is authenticated for resources on the server and is
2363
allowed to access them. The server then uses the SID in the access
2364
token to determine what permissions the client has to use and modify
2365
the requested resource by comparing them to entries in the ACL of the
2368
<p>Although this method of authentication might seem overly complicated,
2369
it allows clients to authenticate without having plain-text passwords
2370
travel through the network, and it is much more difficult to crack
2371
than the relatively weak workgroup security we described earlier.</p>
2378
<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.4"/>
2380
<h3 class="head3">Name service with WINS and DNS</h3>
2382
<p>The <a name="INDEX-174"/><a name="INDEX-175"/>Windows
2383
Internet Name Service (WINS) is Microsoft's
2384
implementation of a NetBIOS name server (NBNS). As such, WINS
2385
inherits much of NetBIOS's characteristics. First,
2386
WINS is flat; you can have only simple machine names such as
2387
<tt class="literal">inca</tt>, <tt class="literal">mixtec</tt>, or
2388
<tt class="literal">navaho</tt>, and workgroups such as PERU, MEXICO, or
2389
USA. In addition, WINS is dynamic: when a client first comes online,
2390
it is required to report its hostname, its address, and its workgroup
2391
to the local WINS server. This WINS server will retain the
2392
information so long as the client periodically refreshes its WINS
2393
registration, which indicates that it's still
2394
connected to the network. Note that WINS servers are not workgroup-
2395
or domain-specific; they can contain information for multiple domains
2396
and/or workgroups, which might exist on more than one subnet.</p>
2398
<p>Multiple <a name="INDEX-176"/>WINS
2399
servers can be set to synchronize with each other. This allows
2400
entries for computers that come online and go offline in the network
2401
to propagate from one WINS server to another. While in theory this
2402
seems efficient, it can quickly become cumbersome if several WINS
2403
servers are covering a network. Because WINS services can cross
2404
multiple subnets (you'll either hardcode the address
2405
of a WINS server in each of your clients or obtain it via DHCP), it
2406
is often more efficient to have each Windows client, regardless of
2407
the number of Windows domains, point themselves to the same WINS
2408
server. That way, only one authoritative WINS server will have the
2409
correct information, instead of several WINS servers continually
2410
struggling to synchronize themselves with the most recent changes.</p>
2412
<p>The currently active WINS server is known as the <em class="firstterm">primary
2413
WINS server</em><a name="INDEX-177"/><a name="INDEX-178"/>. You can also install a secondary WINS
2414
server, which will take over if the primary WINS server fails or
2415
becomes inaccessible. Both the primary and any other WINS servers
2416
will synchronize their address databases on a periodic basis.</p>
2418
<p>In the Windows family of operating systems, only a server edition of
2419
Windows NT/2000 can act as a WINS server. Samba 2.2 can function as a
2420
primary WINS server, but cannot <a name="INDEX-179"/><a name="INDEX-180"/>synchronize
2421
its database with other WINS servers. It therefore cannot act as a
2422
secondary WINS server or as a primary WINS server for a Windows
2423
secondary WINS server.</p>
2425
<p>WINS handles name service by default, although Microsoft added DNS
2426
starting with Windows NT 4 Server. It is compatible with DNS that is
2427
standard on virtually every Unix system, and a Unix server (such as
2428
the Samba host) can also be used for DNS.</p>
2435
<div class="sect3"><a name="samba2-CHP-1-SECT-5.2.5"/>
2437
<h3 class="head3">Trust relationships</h3>
2439
<p>One additional aspect of Windows NT domains not yet supported in
2440
Samba 2.2 is that it is possible to set up a <em class="emphasis">trust
2441
relationship</em><a name="INDEX-181"/><a name="INDEX-182"/><a name="INDEX-183"/> between domains, allowing clients
2442
within one domain to access the resources within another without the
2443
user having to go through additional authentication. The protocol
2444
that is followed is called <em class="emphasis">pass-through authentication</em>,
2445
<a name="INDEX-184"/><a name="INDEX-185"/>in which the
2446
user's credentials are passed from the client system
2447
in the first domain to the server in the second domain, which
2448
consults a domain controller in the first (trusted) domain to check
2449
that the user is valid before granting access to the resource.</p>
2451
<p>Note that in many aspects, the behaviors of a Windows workgroup and a
2452
Windows NT domain overlap. For example, the master and backup
2453
browsers in a domain are always the PDC and BDC, respectively.
2454
Let's update our Windows domain diagram to include
2455
both a local master and local backup browser. The result is shown in
2456
<a href="ch01.html#samba2-CHP-1-FIG-13">Figure 1-13</a>.</p>
2458
<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>
2460
<p>The similarity between workgroups and NT domains is not accidental
2461
because the concept of Windows domains did not evolve until Windows
2462
NT 3.5 was introduced, and Windows domains were forced to remain
2463
backward-compatible with the workgroups present in Windows for
2466
<p>Samba can function as a primary domain controller for Windows
2467
95/98/Me and Windows NT/2000/XP clients with the limitation that it
2468
can act as a PDC only, and not as a BDC.</p>
2470
<p>Samba can also function as a <em class="firstterm">domain member
2471
server</em><a name="INDEX-187"/><a name="INDEX-188"/>, meaning that it has a computer account
2472
in the PDC's account database and is therefore
2473
recognized as being part of the domain. A domain member server does
2474
not authenticate users logging on to the domain, but still handles
2475
security functions (such as file permissions) for domain users
2476
accessing its resources.</p>
2485
<div class="sect2"><a name="samba2-CHP-1-SECT-5.3"/>
2487
<h3 class="head2">Active Directory Domains</h3>
2489
<p>Starting with Windows 2000, Microsoft has introduced
2490
<a name="INDEX-189"/><a name="INDEX-190"/>Active
2491
Directory, the next step beyond Windows NT domains. We
2492
won't go into much detail concerning Active
2493
Directory because it is a huge topic. <a name="INDEX-191"/>Samba 2.2 doesn't
2494
support Active Directory at all, and support in Samba 3.0 is limited
2495
to acting as a client. For now, be aware that with Active Directory,
2496
the authentication model is centered around
2497
<a name="INDEX-192"/>Lightweight Directory
2498
Access Protocol (LDAP), and name service is provided by DNS instead
2499
of WINS. Domains in Active Directory can be organized in a
2500
hierarchical tree structure, in which each domain controller operates
2501
as a peer, with no distinction between primary and backup controllers
2502
as in Windows NT domains.</p>
2504
<p>Windows 2000/XP systems can be set up as simple workgroup or Windows
2505
NT domain clients (which will function with Samba). The server
2506
editions of Windows 2000 can be set up to run Active Directory and
2507
support Windows NT domains for backward compatibility
2508
(<em class="firstterm">mixed mode</em>). In this case, Samba 2.2 works
2509
with Windows 2000 servers in the same way it works with Windows NT
2510
4.0 servers. When set up to operate in <em class="firstterm">native mode,
2511
</em><a name="INDEX-193"/>Windows 2000 servers support only
2512
Active Directory. Even so, <a name="INDEX-194"/>Samba 2.2 can operate as a server
2513
in a domain hosted by a native-mode Windows 2000 server, using the
2514
<a name="INDEX-195"/>Windows 2000 server's
2515
<em class="firstterm">PDC emulation mode</em>. However, it is not
2516
possible for Samba 2.2 or 3.0 to operate as a domain controller in a
2517
Windows 2000 Active Directory domain.</p>
2519
<p>If you want to know more about Active Directory, we encourage you to
2520
obtain a copy of the O'Reilly book,
2521
<em class="emphasis">Windows 2000 Active Directory</em>. <a name="INDEX-196"/></p>
2527
<div class="sect2"><a name="samba2-CHP-1-SECT-5.4"/>
2529
<h3 class="head2">Can a Windows Workgroup Span Multiple Subnets?</h3>
2531
<p><a name="INDEX-197"/><a name="INDEX-198"/>Yes, but most people who have
2532
done it have had their share of headaches. Spanning multiple subnets
2533
was not part of the initial design of Windows NT 3.5 or Windows for
2534
Workgroups. As a result, a Windows domain that spans two or more
2535
subnets is, in reality, the
2536
"gluing" together of two or more
2537
workgroups that share an identical name. The good news is that you
2538
can still use a PDC to control authentication across each subnet. The
2539
bad news is that things are not as simple with browsing.</p>
2541
<p>As mentioned previously, each subnet must have its own local master
2542
browser. When a Windows domain spans multiple subnets, a system
2543
administrator will have to assign one of the computers as the
2544
<em class="firstterm">domain master
2545
browser</em><a name="INDEX-199"/><a name="INDEX-200"/>. The domain master browser will keep a
2546
browse list for the entire Windows domain. This browse list is
2547
created by periodically synchronizing the browse lists of each local
2548
master browser with the browse list of the domain master browser.
2549
After the synchronization, the local master browser and the domain
2550
master browser should contain identical entries. See <a href="ch01.html#samba2-CHP-1-FIG-14">Figure 1-14</a> for an illustration.</p>
2552
<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>
2554
<p>Sound good? <a name="INDEX-201"/>Well, it's not quite
2555
nirvana for the following reasons:</p>
2558
<p>If it exists, a PDC always plays the role of the domain master
2559
browser. By Microsoft design, the two always share the NetBIOS
2560
resource type <tt class="literal"><1B></tt> and (unfortunately)
2561
cannot be separated.</p>
2563
<p>Windows 95/98/Me computers cannot become <em class="emphasis">or</em>
2564
<em class="emphasis">even contact</em> a domain master browser. This means
2565
that it is necessary to have at least one Windows NT/2000/XP system
2566
(or Samba server) on each subnet of a multisubnet workgroup.</p>
2568
<p>Each subnet's local master browser continues to
2569
maintain the browse list for its subnet, for which it becomes
2570
authoritative. So if a computer wants to see a list of servers within
2571
its own subnet, the local master browser of that subnet will be
2572
queried. If a computer wants to see a list of servers outside the
2573
subnet, it can still go only as far as the local master browser. This
2574
works because at appointed intervals, the authoritative browse list
2575
of a subnet's local master browser is synchronized
2576
with the domain master browser, which is synchronized with the local
2577
master browser of the other subnets in the domain. This is called
2578
<em class="firstterm">browse list propagation</em>.</p>
2580
<p>Samba can act as a domain master browser in a Windows NT domain, or
2581
it can act as a local master browser for a subnet, synchronizing its
2582
browse list with the domain master browser.</p>
2592
<div class="sect1"><a name="samba2-CHP-1-SECT-6"/>
2594
<h2 class="head1">What's New in Samba 2.2?</h2>
2596
<p><a name="INDEX-202"/><a name="INDEX-203"/>In
2597
Version 2.2, Samba has more advanced support for Windows networking,
2598
including the ability to perform the more important tasks necessary
2599
for acting in a Windows NT domain. In addition, Samba 2.2 has some
2600
support for technologies that Microsoft introduced in Windows 2000,
2601
although the Samba team has saved Active Directory support for
2605
<div class="sect2"><a name="samba2-CHP-1-SECT-6.1"/>
2607
<h3 class="head2">PDC Support for Windows 2000/XP Clients</h3>
2609
<p>Samba previously could act as a PDC to authenticate Windows 95/98/Me
2610
and Windows NT 4 systems. This functionality has been extended in
2611
Release 2.2 to include Windows 2000 and Windows XP. Thus, it is
2612
possible to have a Samba server supporting domain logons for a
2613
network of Windows clients, including the most recent releases from
2614
Microsoft. This can result in a very stable, high-performance, and
2615
more secure network, and gives you the added benefit of not having to
2616
purchase per-seat Windows CALs from Microsoft.</p>
2622
<div class="sect2"><a name="samba2-CHP-1-SECT-6.2"/>
2624
<h3 class="head2">Microsoft Dfs Support</h3>
2626
<p><a name="INDEX-204"/>Microsoft Dfs allows shared resources that
2627
are dispersed among a number of servers in the network to be gathered
2628
together and appear to users as if they all exist in a single
2629
directory tree on one server. This method of organization makes life
2630
much simpler for users. Instead of having to browse around the
2631
network on a treasure hunt to locate the resource they want to use,
2632
they can go directly to the Dfs server and grab what they want. Samba
2633
2.2 offers support for serving Dfs, so a Windows server is no longer
2634
needed for this purpose.</p>
2640
<div class="sect2"><a name="samba2-CHP-1-SECT-6.3"/>
2642
<h3 class="head2">Windows NT/2000/XP Printing Support</h3>
2644
<p>Windows NT/2000/XP has a different Remote Procedure Call (RPC)-based
2645
printer interface than Windows 95/98/Me does. In Samba 2.2, the
2646
Windows NT/2000/XP interface is supported. Along with this, the Samba
2647
team has been adding support for automatically downloading the
2648
printer driver from the Samba server while adding a new printer to a
2655
<div class="sect2"><a name="samba2-CHP-1-SECT-6.4"/>
2657
<h3 class="head2">ACLs</h3>
2659
<p>Samba now supports
2660
<a name="INDEX-205"/>ACLs on its Unix host for Unix variants
2661
that support them. The list includes Solaris 2.6, 7, and 8, Irix,
2662
AIX, Linux (with either the ACL patch for the
2663
<a name="INDEX-206"/>ext2/ext3 filesystem from <a href="http://acl.bestbits.at">http://acl.bestbits.at</a> or when using the
2664
<a name="INDEX-207"/>XFS
2665
filesystem), and FreeBSD (Version 5.0 and later). When using ACL
2666
support, Samba translates between Unix ACLs and Windows NT/2000/XP
2667
ACLs, making the Samba host look and act more like a Windows
2668
NT/2000/XP server from the point of view of Windows clients.</p>
2674
<div class="sect2"><a name="samba2-CHP-1-SECT-6.5"/>
2676
<h3 class="head2">Support for Windows Client Administration Tools</h3>
2678
<p>Windows comes with tools that can be used from a client to manage
2679
shared resources remotely on a Windows server. Samba 2.2 allows these
2680
tools to operate on shares on the Samba server as well.</p>
2686
<div class="sect2"><a name="samba2-CHP-1-SECT-6.6"/>
2688
<h3 class="head2">Integration with Winbind</h3>
2690
<p><a name="INDEX-208"/>Winbind is a
2691
facility that allows users whose account information is stored in a
2692
Windows domain database to authenticate on a Unix system. The result
2693
is a unified logon environment, in which a user account can be kept
2694
on either the Unix system or a Windows NT/2000 domain controller.
2695
This greatly facilitates account management because administrators no
2696
longer need to keep the two systems synchronized, and it is possible
2697
for users whose accounts are held in a Windows domain to authenticate
2698
when accessing Samba shares.</p>
2704
<div class="sect2"><a name="samba2-CHP-1-SECT-6.7"/>
2706
<h3 class="head2">Unix CIFS Extensions</h3>
2708
<p>The <a name="INDEX-209"/><a name="INDEX-210"/>Unix CIFS extensions were developed
2709
at Hewlett-Packard and introduced in Samba 2.2.4. They allow Samba
2710
servers to support Unix filesystem attributes, such as links and
2711
permissions, when sharing files with other Unix systems. This allows
2712
Samba to be used as an alternative to network file sharing (NFS) for
2713
Unix-to-Unix file sharing. An advantage of using Samba is that it
2714
authenticates individual users, whereas NFS authenticates only
2715
clients (based on their IP addresses, which is a poor security
2716
model). This gives Samba an edge in the area of security, along with
2717
its much greater configurability. See <a href="ch05.html">Chapter 5</a>
2718
for information on how to operate Unix systems as Samba clients.</p>
2724
<div class="sect2"><a name="samba2-CHP-1-SECT-6.8"/>
2726
<h3 class="head2">And More...</h3>
2728
<p>As usual, the code has numerous improvements that do not show up at
2729
the administrative level in an immediate or obvious way. Samba now
2730
functions better on systems that employ <a name="INDEX-211"/>PAM
2731
(Pluggable Authentication Modules), and there is new support for
2732
profiling. Samba's support for oplocks has been
2733
strengthened, offering better integration with NFS server-terminated
2734
leases (currently on Irix and Linux only) and in the local filesystem
2735
with SMB locks mapped to POSIX locks (which is dependent on each Unix
2736
variant's implementation of POSIX locks). And of
2737
course there have been the usual bug fixes.</p>
2747
<div class="sect1"><a name="samba2-CHP-1-SECT-7"/>
2749
<h2 class="head1">What's New in Samba 3.0?</h2>
2751
<p>The main distinguishing feature of <a name="INDEX-212"/><a name="INDEX-213"/>Samba 3.0
2752
is that it includes support for <a name="INDEX-214"/>Kerberos 5 authentication and
2753
<a name="INDEX-215"/>LDAP, which are
2754
required to act as clients in an Active Directory domain. Another
2755
feature that appeared in Samba 3.0 is support for Unicode, which
2756
greatly simplifies supporting international languages.</p>
2758
<p>In later Version 3 releases, the Samba team plans to develop support
2760
<a name="INDEX-216"/>WINS
2761
replication, allowing Samba to act as a secondary WINS server or as a
2762
primary WINS server with Windows or Samba secondary WINS servers.
2763
Also planned are support for acting as a Windows NT BDC and support
2764
for Windows NT domain trust relationships.</p>
2771
<div class="sect1"><a name="samba2-CHP-1-SECT-8"/>
2773
<h2 class="head1">What Can Samba Do?</h2>
2775
<p>Now let's wrap up by showing where Samba can help
2776
out and where it is limited. <a href="ch01.html#samba2-CHP-1-TABLE-9">Table 1-9</a> summarizes
2777
which roles Samba can and cannot play in a Windows NT or Active
2778
Directory domain or a Windows workgroup. Many of the Windows domain
2779
protocols are proprietary and have not been documented by Microsoft
2780
and therefore must be reverse-engineered by the Samba team before
2781
Samba can support them. As of Version 3.0, Samba cannot act as a
2782
backup in most roles and does not yet fully support Active Directory.</p>
2784
<a name="samba2-CHP-1-TABLE-9"/><h4 class="head4">Table 1-9. Samba roles (as of Version 3.0)</h4><table border="1">
2800
<p><a name="INDEX-217"/>File server</p>
2808
<p>Printer server</p>
2816
<p>Microsoft Dfs server</p>
2824
<p>Primary domain controller</p>
2832
<p>Backup domain controller</p>
2840
<p>Active Directory domain controller</p>
2848
<p>Windows 95/98/Me authentication</p>
2856
<p>Windows NT/2000/XP authentication</p>
2864
<p>Local master browser</p>
2872
<p>Local backup browser</p>
2880
<p>Domain master browser</p>
2888
<p>Primary WINS server</p>
2896
<p>Secondary WINS server</p>
2910
<div class="sect1"><a name="samba2-CHP-1-SECT-9"/>
2912
<h2 class="head1">An Overview of the Samba Distribution</h2>
2914
<p><a name="INDEX-218"/>As mentioned earlier, Samba actually
2915
contains several programs that serve different but related purposes.
2916
These programs are documented more fully in <a href="appc.html">Appendix C</a>. For now, we will introduce each of them
2917
briefly and describe how they work together.</p>
2919
<p>The majority of the programs that come with Samba center on its two
2920
daemons. Let's take a refined look at the
2921
responsibilities of each daemon:</p>
2924
<dt><b><em class="emphasis">nmbd</em></b></dt>
2926
<p>The <em class="emphasis">nmbd</em><a name="INDEX-219"/> daemon is a simple name server that
2927
supplies WINS functionality. This daemon listens for name-server
2928
requests and provides the appropriate IP addresses when called upon.
2929
It also provides browse lists for the Network Neighborhood and
2930
participates in browsing elections.</p>
2935
<dt><b><em class="emphasis">smbd</em></b></dt>
2937
<p>The <em class="emphasis">smbd</em><a name="INDEX-220"/> daemon manages the shared resources
2938
between the Samba server and its clients. It provides file, print,
2939
and browse services to <span class="acronym">SMB</span> clients across one or
2940
more networks and handles all notifications between the Samba server
2941
and the network clients. In addition, it is responsible for user
2942
authentication, resource locking, and data sharing through the
2943
<span class="acronym">SMB</span> protocol.</p>
2948
<p>New with Version 2.2, there is an additional daemon:</p>
2951
<dt><b><a name="INDEX-221"/><em class="emphasis">winbindd</em></b></dt>
2953
<p>This daemon is used along with the name service switch to get
2954
information on users and groups from a Windows NT server and allows
2955
Samba to authorize users through a Windows NT/2000 server.</p>
2960
<p>The Samba distribution also comes with a small set of Unix
2961
command-line tools:</p>
2964
<dt><b><em class="emphasis">findsmb</em><a name="INDEX-222"/></b></dt>
2966
<p>A program that searches the local network for computers that respond
2967
to SMB protocol and prints information on them.</p>
2972
<dt><b><em class="emphasis">make_smbcodepage</em><a name="INDEX-223"/></b></dt>
2974
<p>A program used when working with Samba's
2975
internationalization features for telling Samba how to convert
2976
between upper- and lowercase in different character sets.</p>
2981
<dt><b><em class="emphasis">make_unicodemap</em><a name="INDEX-224"/></b></dt>
2983
<p>Another internationalization program used with Samba for compiling
2984
Unicode map files that Samba uses to translate DOS codepages or Unix
2985
character sets into 16-bit unicode.</p>
2990
<dt><b><a name="INDEX-225"/><em class="emphasis">net</em></b></dt>
2992
<p>A new program distributed with Samba 3.0 that can be used to perform
2993
remote administration of servers.</p>
2998
<dt><b><em class="emphasis">nmblookup</em><a name="INDEX-226"/></b></dt>
3000
<p>A program that provides NBT name lookups to find a
3001
computer's IP address when given its machine name.</p>
3006
<dt><b><a name="INDEX-227"/><em class="emphasis">pdbedit</em></b></dt>
3008
<p>A new program distributed with Samba 3.0 that is helpful for managing
3009
user accounts held in SAM databases.</p>
3014
<dt><b><em class="emphasis">rpcclient</em><a name="INDEX-228"/></b></dt>
3016
<p>A program that can be used to run MS-RPC functions on Windows clients.</p>
3021
<dt><b><em class="emphasis">smbcacls</em><a name="INDEX-229"/></b></dt>
3023
<p>A program that is used to set or show ACLs on Windows NT filesystems.</p>
3028
<dt><b><em class="emphasis">smbclient</em><a name="INDEX-230"/></b></dt>
3030
<p>An <em class="emphasis">ftp</em>-like Unix client that can be used to connect to
3031
SMB shares and operate on them. The <em class="emphasis">smbclient</em>
3032
command is discussed in detail in <a href="ch05.html">Chapter 5</a>.</p>
3037
<dt><b><em class="emphasis">smbcontrol</em><a name="INDEX-231"/></b></dt>
3039
<p>A simple administrative utility that sends messages to <em class="emphasis">nmbd</em>
3040
or <em class="emphasis">smbd</em>.</p>
3045
<dt><b><a name="INDEX-232"/><em class="emphasis">smbgroupedit</em></b></dt>
3047
<p>A command that can be used to define mappings between Windows NT
3048
groups and Unix groups. It is new in Samba 3.0.</p>
3053
<dt><b><em class="emphasis">smbmnt</em><a name="INDEX-233"/></b></dt>
3055
<p>A helper utility used along with <em class="emphasis">smbmount.</em></p>
3060
<dt><b><em class="emphasis">smbmount</em><a name="INDEX-234"/></b></dt>
3062
<p>A program that mounts an smbfs filesystem, allowing remote SMB shares
3063
to be mounted in the filesystem of the Samba host.</p>
3068
<dt><b><em class="emphasis">smbpasswd</em><a name="INDEX-235"/></b></dt>
3070
<p>A program that allows an administrator to change the passwords used
3076
<dt><b><em class="emphasis">smbsh</em><a name="INDEX-236"/></b></dt>
3078
<p>A tool that functions like a command shell to allow access to a
3079
remote SMB filesystem and allow Unix utilities to operate on it. This
3080
command is covered in <a href="ch05.html">Chapter 5</a>.</p>
3085
<dt><b><em class="emphasis">smbspool</em><a name="INDEX-237"/></b></dt>
3087
<p>A print-spooling program used to send files to remote printers that
3088
are shared on the SMB network.</p>
3093
<dt><b><em class="emphasis">smbstatus</em><a name="INDEX-238"/></b></dt>
3095
<p>A program that reports the current network connections to the shares
3096
on a Samba server.</p>
3101
<dt><b><em class="emphasis">smbtar</em><a name="INDEX-239"/></b></dt>
3103
<p>A program similar to the Unix <em class="filename">tar</em> command, for
3104
backing up data in SMB shares.</p>
3109
<dt><b><em class="emphasis">smbumount</em><a name="INDEX-240"/></b></dt>
3111
<p>A program that works along with <em class="emphasis">smbmount</em> to unmount
3112
smbfs filesystems.</p>
3117
<dt><b><em class="emphasis">testparm</em><a name="INDEX-241"/></b></dt>
3119
<p>A simple program for checking the Samba configuration file.</p>
3124
<dt><b><em class="emphasis">testprns</em><a name="INDEX-242"/></b></dt>
3126
<p>A program that tests whether printers on the Samba host are
3127
recognized by the <em class="filename">smbd</em> daemon.</p>
3132
<dt><b><em class="emphasis">wbinfo</em><a name="INDEX-243"/></b></dt>
3134
<p>A utility used to query the <em class="filename">winbindd
3135
</em><a name="INDEX-244"/>daemon.</p>
3140
<p>Each major release of Samba goes through an exposure test before
3141
it's announced. In addition, it is quickly updated
3142
afterward if problems or unwanted side effects are found. The latest
3143
stable distribution as of this writing is Samba 2.2.6, and this book
3144
focuses mainly on the functionality supported in Samba 2.2.6, as
3145
opposed to older versions of Samba.</p>
3152
<div class="sect1"><a name="samba2-CHP-1-SECT-10"/>
3154
<h2 class="head1">How Can I Get Samba?</h2>
3156
<p><a name="INDEX-245"/><a name="INDEX-246"/>Source
3157
and binary distributions of Samba are available from mirror sites
3158
across the Internet. The primary web site for Samba is located at
3159
<a href="http://www.samba.org/">http://www.samba.org/</a>. From there, you
3160
can select a mirror site that is geographically near you.</p>
3162
<p>Most Linux and many Unix vendors provide binary packages. These can
3163
be more convenient to install and maintain than the Samba
3164
team's source or binary packages, due to the
3165
vendor's efforts to supply a package that matches
3166
its specific products. <a name="INDEX-247"/></p>
3171
<hr/><h4 class="head4">Footnotes</h4><blockquote><a name="FOOTNOTE-1"/> <p><a href="#FNPTR-1">[1]</a> You
3172
can also right-click the shared resource in the Network Neighborhood
3173
and then select the Map Network Drive menu item.</p> <a name="FOOTNOTE-2"/> <p><a href="#FNPTR-2">[2]</a> Be
3174
warned that many end-user license agreements forbid installing a
3175
program on a network so that multiple clients can access it. Check
3176
the legal agreements that accompany the product to be absolutely
3177
sure.</p> <a name="FOOTNOTE-3"/> <p><a href="#FNPTR-3">[3]</a> You
3178
might also see the abbreviation NetBT, which is common in Microsoft
3179
literature.</p> <a name="FOOTNOTE-4"/>
3180
<p><a href="#FNPTR-4">[4]</a> See
3181
<a href="http://www.samba.org/cifs/docs/what-is-smb.html">http://www.samba.org/cifs/docs/what-is-smb.html</a>
3182
for Richard's excellent summary of
3183
<a name="INDEX-93"/>SMB.</p> <a name="FOOTNOTE-5"/> <p><a href="#FNPTR-5">[5]</a> This
3184
was originally called <a name="INDEX-126"/><a name="INDEX-127"/><a name="INDEX-128"/>Network Neighborhood in Windows 95/98/NT,
3185
but Microsoft has changed the name to My Network Places in the more
3186
recent Windows Me/2000/XP. We will continue to call it Network
3187
Neighborhood, and if you're using a new version of
3188
Windows, be aware that My Network Places can act a little differently
3189
in some ways.</p> </blockquote>
3192
<hr/><h4 class="head4"><a href="toc.html">TOC</a></h4>
added
removed
docs/htmldocs/using_samba/ch01.html
