docs/docbook/projdoc/printer_driver2.sgml

   1 <chapter id="printing">
   2
   3
   4 <chapterinfo>
   5         <author>
   6                 <firstname>Gerald (Jerry)</firstname><surname>Carter</surname>
   7                 <affiliation>
   8                         <orgname>Samba Team</orgname>
   9                         <address>
  10                                 <email>jerry@samba.org</email>
  11                         </address>
  12                 </affiliation>
  13         </author>
  14
  15
  16         <pubdate> (3 May 2001) </pubdate>
  17 </chapterinfo>
  18
  19 <title>Printing Support in Samba 2.2.x</title>
  20
  21 <sect1>
  22 <title>Introduction</title>
  23
  24 <para>Beginning with the 2.2.0 release, Samba supports
  25 the native Windows NT printing mechanisms implemented via
  26 MS-RPC (i.e. the SPOOLSS named pipe).  Previous versions of
  27 Samba only supported LanMan printing calls.</para>
  28
  29 <para>The additional functionality provided by the new
  30 SPOOLSS support includes:</para>
  31
  32 <itemizedlist>
  33         <listitem><para>Support for downloading printer driver
  34         files to Windows 95/98/NT/2000 clients upon demand.
  35         </para></listitem>
  36
  37         <listitem><para>Uploading of printer drivers via the
  38         Windows NT Add Printer Wizard (APW) or the
  39         Imprints tool set (refer to <ulink
  40         url="http://imprints.sourceforge.net">http://imprints.sourceforge.net</ulink>).
  41         </para></listitem>
  42
  43         <listitem><para>Support for the native MS-RPC printing
  44         calls such as StartDocPrinter, EnumJobs(), etc...  (See
  45         the MSDN documentation at <ulink
  46         url="http://msdn.microsoft.com/">http://msdn.microsoft.com/</ulink>
  47         for more information on the Win32 printing API)
  48         </para></listitem>
  49
  50         <listitem><para>Support for NT Access Control Lists (ACL)
  51         on printer objects</para></listitem>
  52
  53         <listitem><para>Improved support for printer queue manipulation
  54         through the use of an internal databases for spooled job
  55         information</para></listitem>
  56 </itemizedlist>
  57
  58 <para>
  59 There has been some initial confusion about what all this means
  60 and whether or not it is a requirement for printer drivers to be
  61 installed on a Samba host in order to support printing from Windows
  62 clients.  A bug existed in Samba 2.2.0 which made Windows NT/2000 clients
  63 require that the Samba server possess a valid driver for the printer.
  64 This is fixed in Samba 2.2.1 and once again, Windows NT/2000 clients
  65 can use the local APW for installing drivers to be used with a Samba
  66 served printer.  This is the same behavior exhibited by Windows 9x clients.
  67 As a side note, Samba does not use these drivers in any way to process
  68 spooled files.  They are utilized entirely by the clients.
  69 </para>
  70
  71 <para>
  72 The following MS KB article, may be of some help if you are dealing with
  73 Windows 2000 clients:  <emphasis>How to Add Printers with No User
  74 Interaction in Windows 2000</emphasis>
  75 </para>
  76
  77 <para>
  78 <ulink url="http://support.microsoft.com/support/kb/articles/Q189/1/05.ASP">http://support.microsoft.com/support/kb/articles/Q189/1/05.ASP</ulink>
  79 </para>
  80
  81 </sect1>
  82
  83
  84 <sect1>
  85 <title>Configuration</title>
  86
  87 <warning>
  88 <title>[print$] vs. [printer$]</title>
  89
  90 <para>
  91 Previous versions of Samba recommended using a share named [printer$].
  92 This name was taken from the printer$ service created by Windows 9x
  93 clients when a printer was shared.  Windows 9x printer servers always have
  94 a printer$ service which provides read-only access via no
  95 password in order to support printer driver downloads.
  96 </para>
  97
  98 <para>
  99 However, the initial implementation allowed for a
 100 parameter named <parameter>printer driver location</parameter>
 101 to be used on a per share basis to specify the location of
 102 the driver files associated with that printer.  Another
 103 parameter named <parameter>printer driver</parameter> provided
 104 a means of defining the printer driver name to be sent to
 105 the client.
 106 </para>
 107
 108 <para>
 109 These parameters, including <parameter>printer driver
 110 file</parameter> parameter, are being deprecated and should not
 111 be used in new installations.  For more information on this change,
 112 you should refer to the <link linkend="MIGRATION">Migration section</link>
 113 of this document.
 114 </para>
 115 </warning>
 116
 117 <sect2>
 118 <title>Creating [print$]</title>
 119
 120 <para>
 121 In order to support the uploading of printer driver
 122 files, you must first configure a file share named [print$].
 123 The name of this share is hard coded in Samba's internals so
 124 the name is very important (print$ is the service used by
 125 Windows NT print servers to provide support for printer driver
 126 download).
 127 </para>
 128
 129 <para>You should modify the server's smb.conf file to add the global
 130 parameters and to create the
 131 following file share (of course, some of the parameter values,
 132 such as 'path' are arbitrary and should be replaced with
 133 appropriate values for your site):</para>
 134
 135 <para><programlisting>
 136 [global]
 137     ; members of the ntadmin group should be able
 138     ; to add drivers and set printer properties
 139     ; root is implicitly a 'printer admin'
 140     printer admin = @ntadmin
 141
 142 [print$]
 143     path = /usr/local/samba/printers
 144     guest ok = yes
 145     browseable = yes
 146     read only = yes
 147     ; since this share is configured as read only, then we need
 148     ; a 'write list'.  Check the file system permissions to make
 149     ; sure this account can copy files to the share.  If this
 150     ; is setup to a non-root account, then it should also exist
 151     ; as a 'printer admin'
 152     write list = @ntadmin,root
 153 </programlisting></para>
 154
 155 <para>The <ulink url="smb.conf.5.html#WRITELIST"><parameter>
 156 write list</parameter></ulink> is used to allow administrative
 157 level user accounts to have write access in order to update files
 158 on the share.  See the <ulink url="smb.conf.5.html">smb.conf(5)
 159 man page</ulink> for more information on configuring file shares.</para>
 160
 161 <para>The requirement for <ulink url="smb.conf.5.html#GUESTOK"><command>guest
 162 ok = yes</command></ulink> depends upon how your
 163 site is configured.  If users will be guaranteed to have
 164 an account on the Samba host, then this is a non-issue.</para>
 165
 166 <note>
 167 <title>Author's Note</title>
 168
 169 <para>
 170 The non-issue is that if all your Windows NT users are guaranteed to be
 171 authenticated by the Samba server (such as a domain member server and the NT
 172 user has already been validated by the Domain Controller in
 173 order to logon to the Windows NT console), then guest access
 174 is not necessary.  Of course, in a workgroup environment where
 175 you just want to be able to print without worrying about
 176 silly accounts and security, then configure the share for
 177 guest access.  You'll probably want to add <ulink
 178 url="smb.conf.5.html#MAPTOGUEST"><command>map to guest = Bad User
 179 </command></ulink> in the [global] section as well.  Make sure
 180 you understand what this parameter does before using it
 181 though. --jerry
 182 </para>
 183 </note>
 184
 185 <para>In order for a Windows NT print server to support
 186 the downloading of driver files by multiple client architectures,
 187 it must create subdirectories within the [print$] service
 188 which correspond to each of the supported client architectures.
 189 Samba follows this model as well.</para>
 190
 191 <para>Next create the directory tree below the [print$] share
 192 for each architecture you wish to support.</para>
 193
 194 <para><programlisting>
 195 [print$]-----
 196         |-W32X86           ; "Windows NT x86"
 197         |-WIN40            ; "Windows 95/98"
 198         |-W32ALPHA         ; "Windows NT Alpha_AXP"
 199         |-W32MIPS          ; "Windows NT R4000"
 200         |-W32PPC           ; "Windows NT PowerPC"
 201 </programlisting></para>
 202
 203 <warning>
 204 <title>ATTENTION!  REQUIRED PERMISSIONS</title>
 205
 206 <para>
 207 In order to currently add a new driver to you Samba host,
 208 one of two conditions must hold true:
 209 </para>
 210
 211 <itemizedlist>
 212         <listitem><para>The account used to connect to the Samba host
 213         must have a uid of 0 (i.e. a root account)</para></listitem>
 214
 215         <listitem><para>The account used to connect to the Samba host
 216         must be a member of the <ulink
 217         url="smb.conf.5.html#PRINTERADMIN"><parameter>printer
 218         admin</parameter></ulink> list.</para></listitem>
 219 </itemizedlist>
 220
 221 <para>
 222 Of course, the connected account must still possess access
 223 to add files to the subdirectories beneath [print$]. Remember
 224 that all file shares are set to 'read only' by default.
 225 </para>
 226 </warning>
 227
 228
 229 <para>
 230 Once you have created the required [print$] service and
 231 associated subdirectories, simply log onto the Samba server using
 232 a root (or <parameter>printer admin</parameter>) account
 233 from a Windows NT 4.0/2k client.  Open "Network Neighbourhood" or
 234 "My Network Places" and browse for the Samba host.  Once you have located
 235 the server, navigate to the "Printers..." folder.
 236 You should see an initial listing of printers
 237 that matches the printer shares defined on your Samba host.
 238 </para>
 239 </sect2>
 240
 241 <sect2>
 242 <title>Setting Drivers for Existing Printers</title>
 243
 244 <para>The initial listing of printers in the Samba host's
 245 Printers folder will have no real printer driver assigned
 246 to them.  By default, in Samba 2.2.0 this driver name was set to
 247 <emphasis>NO PRINTER DRIVER AVAILABLE FOR THIS PRINTER</emphasis>.
 248 Later versions changed this to a NULL string to allow the use
 249 tof the local Add Printer Wizard on NT/2000 clients.
 250 Attempting to view the printer properties for a printer
 251 which has this default driver assigned will result in
 252 the error message:</para>
 253
 254 <para>
 255 <emphasis>Device settings cannot be displayed.  The driver
 256 for the specified printer is not installed, only spooler
 257 properties will be displayed.  Do you want to install the
 258 driver now?</emphasis>
 259 </para>
 260
 261 <para>
 262 Click "No" in the error dialog and you will be presented with
 263 the printer properties window.  The way to assign a driver to a
 264 printer is to either
 265 </para>
 266
 267 <itemizedlist>
 268         <listitem><para>Use the "New Driver..." button to install
 269         a new printer driver, or</para></listitem>
 270
 271         <listitem><para>Select a driver from the popup list of
 272         installed drivers.  Initially this list will be empty.</para>
 273         </listitem>
 274 </itemizedlist>
 275
 276 <para>If you wish to install printer drivers for client
 277 operating systems other than "Windows NT x86", you will need
 278 to use the "Sharing" tab of the printer properties dialog.</para>
 279
 280 <para>Assuming you have connected with a root account, you
 281 will also be able modify other printer properties such as
 282 ACLs and device settings using this dialog box.</para>
 283
 284 <para>A few closing comments for this section, it is possible
 285 on a Windows NT print server to have printers
 286 listed in the Printers folder which are not shared.  Samba does
 287 not make this distinction.  By definition, the only printers of
 288 which Samba is aware are those which are specified as shares in
 289 <filename>smb.conf</filename>.</para>
 290
 291 <para>Another interesting side note is that Windows NT clients do
 292 not use the SMB printer share, but rather can print directly
 293 to any printer on another Windows NT host using MS-RPC.  This
 294 of course assumes that the printing client has the necessary
 295 privileges on the remote host serving the printer.  The default
 296 permissions assigned by Windows NT to a printer gives the "Print"
 297 permissions to the "Everyone" well-known group.
 298 </para>
 299
 300 </sect2>
 301
 302
 303 <sect2>
 304 <title>Support a large number of printers</title>
 305
 306 <para>One issue that has arisen during the development
 307 phase of Samba 2.2 is the need to support driver downloads for
 308 100's of printers.  Using the Windows NT APW is somewhat
 309 awkward to say the list.  If more than one printer are using the
 310 same driver, the <ulink url="rpcclient.1.html"><command>rpcclient's
 311 setdriver command</command></ulink> can be used to set the driver
 312 associated with an installed driver.  The following is example
 313 of how this could be accomplished:</para>
 314
 315 <para><programlisting>
 316 <prompt>$ </prompt>rpcclient pogo -U root%secret -c "enumdrivers"
 317 Domain=[NARNIA] OS=[Unix] Server=[Samba 2.2.0-alpha3]
 318
 319 [Windows NT x86]
 320 Printer Driver Info 1:
 321      Driver Name: [HP LaserJet 4000 Series PS]
 322
 323 Printer Driver Info 1:
 324      Driver Name: [HP LaserJet 2100 Series PS]
 325
 326 Printer Driver Info 1:
 327      Driver Name: [HP LaserJet 4Si/4SiMX PS]
 328
 329 <prompt>$ </prompt>rpcclient pogo -U root%secret -c "enumprinters"
 330 Domain=[NARNIA] OS=[Unix] Server=[Samba 2.2.0-alpha3]
 331      flags:[0x800000]
 332      name:[\\POGO\hp-print]
 333      description:[POGO\\POGO\hp-print,NO DRIVER AVAILABLE FOR THIS PRINTER,]
 334      comment:[]
 335
 336 <prompt>$ </prompt>rpcclient pogo -U root%secret \
 337 <prompt>&gt; </prompt> -c "setdriver hp-print \"HP LaserJet 4000 Series PS\""
 338 Domain=[NARNIA] OS=[Unix] Server=[Samba 2.2.0-alpha3]
 339 Successfully set hp-print to driver HP LaserJet 4000 Series PS.
 340 </programlisting></para>
 341 </sect2>
 342
 343
 344
 345 <sect2>
 346 <title>Adding New Printers via the Windows NT APW</title>
 347
 348 <para>
 349 By default, Samba offers all printer shares defined in <filename>smb.conf</filename>
 350 in the "Printers..." folder.  Also existing in this folder is the Windows NT
 351 Add Printer Wizard icon.  The APW will be show only if
 352 </para>
 353
 354 <itemizedlist>
 355         <listitem><para>The connected user is able to successfully
 356         execute an OpenPrinterEx(\\server) with administrative
 357         privileges (i.e. root or <parameter>printer admin</parameter>).
 358         </para></listitem>
 359
 360         <listitem><para><ulink url="smb.conf.5.html#SHOWADDPRINTERWIZARD"><parameter>show
 361         add printer wizard = yes</parameter></ulink> (the default).
 362         </para></listitem>
 363 </itemizedlist>
 364
 365 <para>
 366 In order to be able to use the APW to successfully add a printer to a Samba
 367 server, the <ulink url="smb.conf.5.html#ADDPRINTERCOMMAND"><parameter>add
 368 printer command</parameter></ulink> must have a defined value.  The program
 369 hook must successfully add the printer to the system (i.e.
 370 <filename>/etc/printcap</filename> or appropriate files) and
 371 <filename>smb.conf</filename> if necessary.
 372 </para>
 373
 374 <para>
 375 When using the APW from a client, if the named printer share does
 376 not exist, <command>smbd</command> will execute the <parameter>add printer
 377 command</parameter> and reparse to the <filename>smb.conf</filename>
 378 to attempt to locate the new printer share.  If the share is still not defined,
 379 an error of "Access Denied" is returned to the client.  Note that the
 380 <parameter>add printer program</parameter> is executed under the context
 381 of the connected user, not necessarily a root account.
 382 </para>
 383
 384 <para>
 385 There is a complementing <ulink url="smb.conf.5.html#DELETEPRINTERCOMMAND"><parameter>delete
 386 printer command</parameter></ulink> for removing entries from the "Printers..."
 387 folder.
 388 </para>
 389
 390 </sect2>
 391
 392
 393 <sect2>
 394 <title>Samba and Printer Ports</title>
 395
 396 <para>
 397 Windows NT/2000 print servers associate a port with each printer.  These normally
 398 take the form of LPT1:, COM1:, FILE:, etc...  Samba must also support the
 399 concept of ports associated with a printer.  By default, only one printer port,
 400 named "Samba Printer Port", exists on a system.  Samba does not really a port in
 401 order to print, rather it is a requirement of Windows clients.
 402 </para>
 403
 404 <para>
 405 Note that Samba does not support the concept of "Printer Pooling" internally
 406 either.  This is when a logical printer is assigned to multiple ports as
 407 a form of load balancing or fail over.
 408 </para>
 409
 410 <para>
 411 If you require that multiple ports be defined for some reason,
 412 <filename>smb.conf</filename> possesses a <ulink
 413 url="smb.conf.5.html#ENUMPORTSCOMMAND"><parameter>enumports
 414 command</parameter></ulink> which can be used to define an external program
 415 that generates a listing of ports on a system.
 416 </para>
 417
 418 </sect2>
 419
 420 </sect1>
 421
 422
 423 <sect1>
 424         <title>The Imprints Toolset</title>
 425
 426         <para>The Imprints tool set provides a UNIX equivalent of the
 427         Windows NT Add Printer Wizard.  For complete information, please
 428         refer to the Imprints web site at <ulink url="http://imprints.sourceforge.net/">
 429         http://imprints.sourceforge.net/</ulink> as well as the documentation
 430         included with the imprints source distribution.  This section will
 431         only provide a brief introduction to the features of Imprints.</para>
 432
 433
 434         <sect2>
 435                 <title>What is Imprints?</title>
 436
 437                 <para>Imprints is a collection of tools for supporting the goals
 438                 of</para>
 439
 440                 <itemizedlist>
 441                         <listitem><para>Providing a central repository information
 442                         regarding Windows NT and 95/98 printer driver packages</para>
 443                         </listitem>
 444
 445                         <listitem><para>Providing the tools necessary for creating
 446                         the Imprints printer driver packages.</para></listitem>
 447
 448                         <listitem><para>Providing an installation client which
 449                         will obtain and install printer drivers on remote Samba
 450                         and Windows NT 4 print servers.</para></listitem>
 451                 </itemizedlist>
 452
 453         </sect2>
 454
 455
 456         <sect2>
 457                 <title>Creating Printer Driver Packages</title>
 458
 459                 <para>The process of creating printer driver packages is beyond
 460                 the scope of this document (refer to Imprints.txt also included
 461                 with the Samba distribution for more information).  In short,
 462                 an Imprints driver package is a gzipped tarball containing the
 463                 driver files, related INF files, and a control file needed by the
 464                 installation client.</para>
 465         </sect2>
 466
 467
 468         <sect2>
 469                 <title>The Imprints server</title>
 470
 471                 <para>The Imprints server is really a database server that
 472                 may be queried via standard HTTP mechanisms.  Each printer
 473                 entry in the database has an associated URL for the actual
 474                 downloading of the package.  Each package is digitally signed
 475                 via GnuPG which can be used to verify that package downloaded
 476                 is actually the one referred in the Imprints database.  It is
 477                 <emphasis>not</emphasis> recommended that this security check
 478                 be disabled.</para>
 479         </sect2>
 480
 481         <sect2>
 482                 <title>The Installation Client</title>
 483
 484                 <para>More information regarding the Imprints installation client
 485                 is available in the <filename>Imprints-Client-HOWTO.ps</filename>
 486                 file included with the imprints source package.</para>
 487
 488                 <para>The Imprints installation client comes in two forms.</para>
 489
 490                 <itemizedlist>
 491                         <listitem><para>a set of command line Perl scripts</para>
 492                         </listitem>
 493
 494                         <listitem><para>a GTK+ based graphical interface to
 495                         the command line perl scripts</para></listitem>
 496                 </itemizedlist>
 497
 498                 <para>The installation client (in both forms) provides a means
 499                 of querying the Imprints database server for a matching
 500                 list of known printer model names as well as a means to
 501                 download and install the drivers on remote Samba and Windows
 502                 NT print servers.</para>
 503
 504                 <para>The basic installation process is in four steps and
 505                 perl code is wrapped around <command>smbclient</command>
 506                 and <command>rpcclient</command>.</para>
 507
 508 <para><programlisting>
 509 foreach (supported architecture for a given driver)
 510 {
 511      1.  rpcclient: Get the appropriate upload directory
 512          on the remote server
 513      2.  smbclient: Upload the driver files
 514      3.  rpcclient: Issues an AddPrinterDriver() MS-RPC
 515 }
 516
 517 4.  rpcclient: Issue an AddPrinterEx() MS-RPC to actually
 518     create the printer
 519 </programlisting></para>
 520
 521                 <para>One of the problems encountered when implementing
 522                 the Imprints tool set was the name space issues between
 523                 various supported client architectures.  For example, Windows
 524                 NT includes a driver named "Apple LaserWriter II NTX v51.8"
 525                 and Windows 95 calls its version of this driver "Apple
 526                 LaserWriter II NTX"</para>
 527
 528                 <para>The problem is how to know what client drivers have
 529                 been uploaded for a printer.  As astute reader will remember
 530                 that the Windows NT Printer Properties dialog only includes
 531                 space for one printer driver name.  A quick look in the
 532                 Windows NT 4.0 system registry at</para>
 533
 534                 <para><filename>HKLM\System\CurrentControlSet\Control\Print\Environment
 535                 </filename></para>
 536
 537                 <para>will reveal that Windows NT always uses the NT driver
 538                 name.  This is ok as Windows NT always requires that at least
 539                 the Windows NT version of the printer driver is present.
 540                 However, Samba does not have the requirement internally.
 541                 Therefore, how can you use the NT driver name if is has not
 542                 already been installed?</para>
 543
 544                 <para>The way of sidestepping this limitation is to require
 545                 that all Imprints printer driver packages include both the Intel
 546                 Windows NT and 95/98 printer drivers and that NT driver is
 547                 installed first.</para>
 548         </sect2>
 549
 550 </sect1>
 551
 552
 553 <sect1>
 554 <title><anchor id="MIGRATION">Migration to from Samba 2.0.x to 2.2.x</title>
 555
 556 <para>
 557 Given that printer driver management has changed (we hope improved) in
 558 2.2 over prior releases, migration from an existing setup to 2.2 can
 559 follow several paths. Here are the possible scenarios for
 560 migration:
 561 </para>
 562
 563 <itemizedlist>
 564         <listitem><para>If you do not desire the new Windows NT
 565         print driver support, nothing needs to be done.
 566         All existing parameters work the same.</para></listitem>
 567
 568         <listitem><para>If you want to take advantage of NT printer
 569         driver support but do not want to migrate the
 570         9x drivers to the new setup, the leave the existing
 571         <filename>printers.def</filename> file.  When smbd attempts
 572         to locate a
 573         9x driver for the printer in the TDB and fails it
 574         will drop down to using the printers.def (and all
 575         associated parameters).  The <command>make_printerdef</command>
 576         tool will also remain for backwards compatibility but will
 577         be removed in the next major release.</para></listitem>
 578
 579         <listitem><para>If you install a Windows 9x driver for a printer
 580         on your Samba host (in the printing TDB), this information will
 581         take precedence and the three old printing parameters
 582         will be ignored (including print driver location).</para></listitem>
 583
 584         <listitem><para>If you want to migrate an existing <filename>printers.def</filename>
 585         file into the new setup, the current only solution is to use the Windows
 586         NT APW to install the NT drivers and the 9x  drivers.  This can be scripted
 587         using <command>smbclient</command> and <command>rpcclient</command>.  See the
 588         Imprints installation client at <ulink
 589         url="http://imprints.sourceforge.net/">http://imprints.sourceforge.net/</ulink>
 590         for an example.
 591         </para></listitem>
 592 </itemizedlist>
 593
 594
 595 <warning>
 596 <title>Achtung!</title>
 597
 598 <para>
 599 The following <filename>smb.conf</filename> parameters are considered to
 600 be deprecated and will be removed soon.  Do not use them in new
 601 installations
 602 </para>
 603
 604 <itemizedlist>
 605         <listitem><para><parameter>printer driver file (G)</parameter>
 606         </para></listitem>
 607
 608         <listitem><para><parameter>printer driver (S)</parameter>
 609         </para></listitem>
 610
 611         <listitem><para><parameter>printer driver location (S)</parameter>
 612         </para></listitem>
 613 </itemizedlist>
 614 </warning>
 615
 616
 617 <para>
 618 The have been two new parameters add in Samba 2.2.2 to for
 619 better support of Samba 2.0.x backwards capability (<parameter>disable
 620 spoolss</parameter>) and for using local printers drivers on Windows
 621 NT/2000 clients (<parameter>use client driver</parameter>). Both of
 622 these options are described in the smb.coinf(5) man page and are
 623 disabled by default.
 624 </para>
 625
 626
 627 </sect1>
 628
 629
 630 <!--
 631
 632   This comment from rpc_server/srv_spoolss_nt.c:_spoolss_open_printer_ex()
 633   needs to be added into a section probably.  This is to remind me it needs
 634   to be done.  -jerry
 635
 636                 /*
 637                  * If the openprinterex rpc call contains a devmode,
 638                  * it's a per-user one. This per-user devmode is derivated
 639                  * from the global devmode. Openprinterex() contains a per-user
 640                  * devmode for when you do EMF printing and spooling.
 641                  * In the EMF case, the NT workstation is only doing half the job
 642                  * of rendering the page. The other half is done by running the printer
 643                  * driver on the server.
 644                  * The EMF file doesn't contain the page description (paper size, orientation, ...).
 645                  * The EMF file only contains what is to be printed on the page.
 646                  * So in order for the server to know how to print, the NT client sends
 647                  * a devicemode attached to the openprinterex call.
 648                  * But this devicemode is short lived, it's only valid for the current print job.
 649                  *
 650                  * If Samba would have supported EMF spooling, this devicemode would
 651                  * have been attached to the handle, to sent it to the driver to correctly
 652                  * rasterize the EMF file.
 653                  *
 654                  * As Samba only supports RAW spooling, we only receive a ready-to-print file,
 655                  * we just act as a pass-thru between windows and the printer.
 656                  *
 657                  * In order to know that Samba supports only RAW spooling, NT has to call
 658                  * getprinter() at level 2 (attribute field) or NT has to call startdoc()
 659                  * and until NT sends a RAW job, we refuse it.
 660                  *
 661                  * But to call getprinter() or startdoc(), you first need a valid handle,
 662                  * and to get an handle you have to call openprintex(). Hence why you have
 663                  * a devicemode in the openprinterex() call.
 664                  *
 665                  *
 666                  * Differences between NT4 and NT 2000.
 667                  * NT4:
 668                  *
 669                  * On NT4, you only have a global devicemode. This global devicemode can be changed
 670                  * by the administrator (or by a user with enough privs). Every time a user
 671                  * wants to print, the devicemode is reset to the default. In Word, every time
 672                  * you print, the printer's characteristics are always reset to the global devicemode.
 673                  *
 674                  * NT 2000:
 675                  *
 676                  * In W2K, there is the notion of per-user devicemode. The first time you use
 677                  * a printer, a per-user devicemode is build from the global devicemode.
 678                  * If you change your per-user devicemode, it is saved in the registry, under the
 679                  * H_KEY_CURRENT_KEY sub_tree. So that every time you print, you have your default
 680                  * printer preferences available.
 681                  *
 682                  * To change the per-user devicemode: it's the "Printing Preferences ..." button
 683                  * on the General Tab of the printer properties windows.
 684                  *
 685                  * To change the global devicemode: it's the "Printing Defaults..." button
 686                  * on the Advanced Tab of the printer properties window.
 687 -->
 688
 689 </chapter>