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Chapter 21. CUPS Printing Support

Kurt Pfeifle

Danka Deutschland GmbH

Ciprian Vizitiu

drawings

Jelmer R. Vernooij

drawings
The Samba Team

(27 Jan 2004)

Table of Contents

Introduction
Features and Benefits
Overview
Basic CUPS Support Configuration
Linking smbd with libcups.so
Simple smb.conf Settings for CUPS
More Complex CUPS smb.conf Settings
Advanced Configuration
Central Spooling vs. “Peer-to-Peer” Printing
Raw Print Serving Vendor Drivers on Windows Clients
Installation of Windows Client Drivers
Explicitly Enable “raw” Printing for application/octet-stream
Driver Upload Methods
Advanced Intelligent Printing with PostScript Driver Download
GDI on Windows -- PostScript on UNIX
Windows Drivers, GDI and EMF
UNIX Printfile Conversion and GUI Basics
PostScript and Ghostscript
Ghostscript the Software RIP for Non-PostScript Printers
PostScript Printer Description (PPD) Specification
Using Windows-Formatted Vendor PPDs
CUPS Also Uses PPDs for Non-PostScript Printers
The CUPS Filtering Architecture
MIME Types and CUPS Filters
MIME Type Conversion Rules
Filtering Overview
Prefilters
pstops
pstoraster
imagetops and imagetoraster
rasterto [printers specific]
CUPS Backends
The Role of cupsomatic/foomatic
The Complete Picture
mime.convs
Raw” Printing
application/octet-stream Printing
PostScript Printer Descriptions (PPDs) for Non-PS Printers
cupsomatic/foomatic-rip Versus native CUPS Printing
Examples for Filtering Chains
Sources of CUPS Drivers/PPDs
Printing with Interface Scripts
Network Printing (Purely Windows)
From Windows Clients to an NT Print Server
Driver Execution on the Client
Driver Execution on the Server
Network Printing (Windows Clients UNIX/Samba Print Servers)
From Windows Clients to a CUPS/Samba Print Server
Samba Receiving Job-files and Passing Them to CUPS
Network PostScript RIP
PPDs for Non-PS Printers on UNIX
PPDs for Non-PS Printers on Windows
Windows Terminal Servers (WTS) as CUPS Clients
Printer Drivers Running in “Kernel Mode” Cause Many Problems
Workarounds Impose Heavy Limitations
CUPS: A “Magical Stone”?
PostScript Drivers with No Major Problems Even in Kernel Mode
Configuring CUPS for Driver Download
cupsaddsmb: The Unknown Utility
Prepare Your smb.conf for cupsaddsmb
CUPS “PostScript Driver for Windows NT/200x/XP
Recognizing Different Driver Files
Acquiring the Adobe Driver Files
ESP Print Pro PostScript Driver for Windows NT/200x/XP
Caveats to be Considered
Windows CUPS PostScript Driver Versus Adobe Driver
Run cupsaddsmb (Quiet Mode)
Run cupsaddsmb with Verbose Output
Understanding cupsaddsmb
How to Recognize If cupsaddsmb Completed Successfully
cupsaddsmb with a Samba PDC
cupsaddsmb Flowchart
Installing the PostScript Driver on a Client
Avoiding Critical PostScript Driver Settings on the Client
Installing PostScript Driver Files Manually Using rpcclient
A Check of the rpcclient man Page
Understanding the rpcclient man Page
Producing an Example by Querying a Windows Box
Requirements for adddriver and setdriver to Succeed
Manual Driver Installation in 15 Steps
Troubleshooting Revisited
The Printing *.tdb Files
Trivial Database Files
Binary Format
Losing *.tdb Files
Using tdbbackup
CUPS Print Drivers from Linuxprinting.org
foomatic-rip and Foomatic Explained
foomatic-rip and Foomatic-PPD Download and Installation
Page Accounting with CUPS
Setting Up Quotas
Correct and Incorrect Accounting
Adobe and CUPS PostScript Drivers for Windows Clients
The page_log File Syntax
Possible Shortcomings
Future Developments
Additional Material
Auto-Deletion or Preservation of CUPS Spool Files
CUPS Configuration Settings Explained
Pre-Conditions
Manual Configuration
Printing from CUPS to Windows Attached Printers
More CUPS-Filtering Chains
Common Errors
Windows 9x/ME Client Can't Install Driver
cupsaddsmb” Keeps Asking for Root Password in Never-ending Loop
cupsaddsmb” or “rpcclient addriver” Keeps Giving WERR_BAD_PASSWORD
cupsaddsmb” Errors
Client Can't Connect to Samba Printer
New Account Reconnection from Windows 200x/XP Troubles
Avoid Being Connected to the Samba Server as the Wrong User
Upgrading to CUPS Drivers from Adobe Drivers
Can't Use “cupsaddsmb” on Samba Server Which Is a PDC
Deleted Windows 200x Printer Driver Is Still Shown
Windows 200x/XP "Local Security Policies"
Administrator Cannot Install Printers for All Local Users
Print Change Notify Functions on NT-clients
Win XP-SP1
Print Options for All Users Can't Be Set on Windows 200x/XP
Most Common Blunders in Driver Settings on Windows Clients
cupsaddsmb Does Not Work with Newly Installed Printer
Permissions on /var/spool/samba/ Get Reset After Each Reboot
Print Queue Called “lp” Mis-handles Print Jobs
Location of Adobe PostScript Driver Files for “cupsaddsmb
Overview of the CUPS Printing Processes

Introduction

Features and Benefits

The Common UNIX Print System (CUPS) has become quite popular. All major Linux distributions now ship it as their default printing system. To many, it is still a mystical tool. Mostly, it just works. People tend to regard it as a “black box” that they do not want to look into as long as it works. But once there is a little problem, they are in trouble to find out where to start debugging it. Refer to the chapter “Classical Printing” that contains a lot of information that is relevant for CUPS.

CUPS sports quite a few unique and powerful features. While their basic functions may be grasped quite easily, they are also new. Because they are different from other, more traditional printing systems, it is best not to try and apply any prior knowledge about printing to this new system. Rather, try to understand CUPS from the beginning. This documentation will lead you to a complete understanding of CUPS. Let's start with the most basic things first.

Overview

CUPS is more than just a print spooling system. It is a complete printer management system that complies with the new Internet Printing Protocol (IPP). IPP is an industry and Internet Engineering Task Force (IETF) standard for network printing. Many of its functions can be managed remotely (or locally) via a Web browser (giving you a platform-independent access to the CUPS print server). Additionally, it has the traditional command line and several more modern GUI interfaces (GUI interfaces developed by third parties, like KDE's overwhelming KDEPrint).

CUPS allows creation of “raw” printers (i.e., no print file format translation) as well as “smart” printers (i.e., CUPS does file format conversion as required for the printer). In many ways this gives CUPS similar capabilities to the MS Windows print monitoring system. Of course, if you are a CUPS advocate, you would argue that CUPS is better! In any case, let us now move on to explore how one may configure CUPS for interfacing with MS Windows print clients via Samba.

Basic CUPS Support Configuration

Printing with CUPS in the most basic smb.conf setup in Samba-3.0 (as was true for 2.2.x) only needs two settings: printing = cups and printcap = cups. CUPS does not need a printcap file. However, the cupsd.conf configuration file knows of two related directives that control how such a file will be automatically created and maintained by CUPS for the convenience of third-party applications (example: Printcap /etc/printcap and PrintcapFormat BSD). Legacy programs often require the existence of a printcap file containing printer names or they will refuse to print. Make sure CUPS is set to generate and maintain a printcap file. For details, see man cupsd.conf and other CUPS-related documentation, like the wealth of documents on your CUPS server itself: http://localhost:631/documentation.html.

Linking smbd with libcups.so

Samba has a special relationship to CUPS. Samba can be compiled with CUPS library support. Most recent installations have this support enabled. Per default, CUPS linking is compiled into smbd and other Samba binaries. Of course, you can use CUPS even if Samba is not linked against libcups.so but there are some differences in required or supported configuration.

When Samba is compiled against libcups, printcap = cups uses the CUPS API to list printers, submit jobs, query queues, and so on. Otherwise it maps to the System V commands with an additional -oraw option for printing. On a Linux system, you can use the ldd utility to find out details (ldd may not be present on other OS platforms, or its function may be embodied by a different command):

root# ldd `which smbd`
libssl.so.0.9.6 => /usr/lib/libssl.so.0.9.6 (0x4002d000)
libcrypto.so.0.9.6 => /usr/lib/libcrypto.so.0.9.6 (0x4005a000)
libcups.so.2 => /usr/lib/libcups.so.2 (0x40123000)
[....]

The line libcups.so.2 => /usr/lib/libcups.so.2 (0x40123000) shows there is CUPS support compiled into this version of Samba. If this is the case, and printing = cups is set, then any otherwise manually set print command in smb.conf is ignored. This is an important point to remember!

Tip

Should it be necessary, for any reason, to set your own print commands, you can do this by setting printing = sysv. However, you will lose all the benefits of tight CUPS/Samba integration. When you do this you must manually configure the printing system commands (most important: print command; other commands are lppause command, lpresume command, lpq command, lprm command, queuepause command and queue resume command).

Simple smb.conf Settings for CUPS

To summarize, following example shows simplest printing-related setup for smb.conf to enable basic CUPS support:

Example 21.1. Simplest printing-related smb.conf

[global]
load printers = yes
printing = cups
printcap name = cups
[printers]
comment = All Printers
path = /var/spool/samba
browseable = no
public = yes
guest ok = yes
writable = no
printable = yes
printer admin = root, @ntadmins

This is all you need for basic printing setup for CUPS. It will print all graphic, text, PDF, and PostScript files submitted from Windows clients. However, most of your Windows users would not know how to send these kinds of files to print without opening a GUI application. Windows clients tend to have local printer drivers installed, and the GUI application's print buttons start a printer driver. Your users also rarely send files from the command line. Unlike UNIX clients, they hardly submit graphic, text or PDF formatted files directly to the spooler. They nearly exclusively print from GUI applications with a “printer driver” hooked in between the application's native format and the print-data-stream. If the backend printer is not a PostScript device, the print data stream is “binary,” sensible only for the target printer. Read on to learn which problem this may cause and how to avoid it.

More Complex CUPS smb.conf Settings

Next configuration is a slightly more complex printing-related setup for smb.conf. It enables general CUPS printing support for all printers, but defines one printer share, which is set up differently.

Example 21.2. Overriding global CUPS settings for one printer

[global]
printing = cups
printcap name = cups
load printers = yes
[printers]
comment = All Printers
path = /var/spool/samba
public = yes
guest ok = yes
writable = no
printable = yes
printer admin = root, @ntadmins
[special_printer]
comment = A special printer with his own settings
path = /var/spool/samba-special
printing = sysv
printcap = lpstat
print command = echo "NEW: `date`: printfile %f" \
>> /tmp/smbprn.log ; \
echo " `date`: p-%p s-%s f-%f" >> /tmp/smbprn.log ; \
echo " `date`: j-%j J-%J z-%z c-%c" >> /tmp/smbprn.log ; rm %f
public = no
guest ok = no
writable = no
printable = yes
printer admin = kurt
hosts deny = 0.0.0.0
hosts allow = turbo_xp, 10.160.50.23, 10.160.51.60

This special share is only there for testing purposes. It does not write the print job to a file. It just logs the job parameters known to Samba into the /tmp/smbprn.log file and deletes the job-file. Moreover, the printer admin of this share is “kurt” (not the “@ntadmins” group), guest access is not allowed, the share isn't published to the Network Neighborhood (so you need to know it is there), and it only allows access from only three hosts. To prevent CUPS kicking in and taking over the print jobs for that share, we need to set printing = sysv and printcap = lpstat.

Advanced Configuration

Before we delve into all the configuration options, let us clarify a few points. Network printing needs to be organized and setup correctly. This frequently doesn't happen. Legacy systems or small business LAN environments often lack design and good housekeeping.

Central Spooling vs. “Peer-to-Peer” Printing

Many small office or home networks, as well as badly organized larger environments, allow each client a direct access to available network printers. This is generally a bad idea. It often blocks one client's access to the printer when another client's job is printing. It might freeze the first client's application while it is waiting to get rid of the job. Also, there are frequent complaints about various jobs being printed with their pages mixed with each other. A better concept is the usage of a print server: it routes all jobs through one central system, which responds immediately, takes jobs from multiple concurrent clients at the same time, and in turn transfers them to the printer(s) in the correct order.

Raw Print Serving Vendor Drivers on Windows Clients

Most traditionally configured UNIX print servers acting on behalf of Samba's Windows clients represented a really simple setup. Their only task was to manage the “raw” spooling of all jobs handed to them by Samba. This approach meant that the Windows clients were expected to prepare the print job file that its ready to be sent to the printing device. Here a native (vendor-supplied) Windows printer driver needs to be installed on each and every client for the target device.

It is possible to configure CUPS, Samba and your Windows clients in the same traditional and simple way. When CUPS printers are configured for RAW print-through mode operation, it is the responsibility of the Samba client to fully render the print job (file). The file must be sent in a format that is suitable for direct delivery to the printer. Clients need to run the vendor-provided drivers to do this. In this case, CUPS will not do any print file format conversion work.

The easiest printing configuration possible is to use raw print-through. This is achieved by installation of the printer as if it was physically attached to the Windows client. You then redirect output to a raw network print queue. The following procedure may be followed to achieve this:

  1. Edit /etc/cups/mime.types to uncomment the line near the end of the file that has:

    #application/octet-...
    

  2. Do the same for the file /etc/cups/mime.convs.

  3. Add a raw printer using the Web interface. Point your browser at http://localhost:631. Enter Administration, add the printer following the prompts. Do not install any drivers for it. Choose Raw. Choose queue name Raw Queue.

  4. In the smb.conf file [printers] section add use client driver = Yes, and in the [global] section add printing = CUPS, plus printcap = CUPS.

  5. Install the printer as if it is a local printer. i.e.: Printing to LPT1:.

  6. Edit the configuration under the Detail tab, create a local port that points to the raw printer queue that you have configured above. Example: \\server\raw_q. Here, the name raw_q is the name you gave the print queue in the CUPS environment.

Installation of Windows Client Drivers

The printer drivers on the Windows clients may be installed in two functionally different ways:

  • Manually install the drivers locally on each client, one by one; this yields the old LanMan style printing and uses a \\sambaserver\printershare type of connection.

  • Deposit and prepare the drivers (for later download) on the print server (Samba); this enables the clients to use “Point'n'Print” to get drivers semi-automatically installed the first time they access the printer; with this method NT/200x/XP clients use the SPOOLSS/MS-RPC type printing calls.

The second method is recommended for use over the first.

Explicitly Enable “raw” Printing for application/octet-stream

If you use the first option (drivers are installed on the client side), there is one setting to take care of: CUPS needs to be told that it should allow “raw” printing of deliberate (binary) file formats. The CUPS files that need to be correctly set for RAW mode printers to work are:

  • /etc/cups/mime.types

  • /etc/cups/mime.convs

Both contain entries (at the end of the respective files) which must be uncommented to allow RAW mode operation. In /etc/cups/mime.types, make sure this line is present:

	 application/octet-stream
	

In /etc/cups/mime.convs, have this line:

		application/octet-stream   application/vnd.cups-raw   0   - 
	

If these two files are not set up correctly for raw Windows client printing, you may encounter the dreaded Unable to convert file 0 in your CUPS error_log file.

Note

Editing the mime.convs and the mime.types file does not enforceraw” printing, it only allows it.

Background.  CUPS being a more security-aware printing system than traditional ones does not by default allow a user to send deliberate (possibly binary) data to printing devices. This could be easily abused to launch a “Denial of Service” attack on your printer(s), causing at least the loss of a lot of paper and ink. “Unknown” data are tagged by CUPS as MIME type: application/octet-stream and not allowed to go to the printer. By default, you can only send other (known) MIME types “raw”. Sending data “raw” means that CUPS does not try to convert them and passes them to the printer untouched (see the next chapter for even more background explanations).

This is all you need to know to get the CUPS/Samba combo printing “raw” files prepared by Windows clients, which have vendor drivers locally installed. If you are not interested in background information about more advanced CUPS/Samba printing, simply skip the remaining sections of this chapter.

Driver Upload Methods

This section describes three familiar methods, plus one new one, by which printer drivers may be uploaded.

If you want to use the MS-RPC type printing, you must upload the drivers onto the Samba server first ([print$] share). For a discussion on how to deposit printer drivers on the Samba host (so the Windows clients can download and use them via “Point'n'Print”), please refer to the previous chapter of this HOWTO Collection. There you will find a description or reference to three methods of preparing the client drivers on the Samba server:

  • The GUI, “Add Printer Wizardupload-from-a-Windows-client method.

  • The command line, “smbclient/rpcclient” upload-from-a-UNIX-workstation method.

  • The Imprints Toolset method.

These three methods apply to CUPS all the same. A new and more convenient way to load the Windows drivers into Samba is provided if you use CUPS:

  • the cupsaddsmb utility.

cupsaddsmb is discussed in much detail further below. But we first explore the CUPS filtering system and compare the Windows and UNIX printing architectures.

Advanced Intelligent Printing with PostScript Driver Download

We now know how to set up a “dump” printserver, that is, a server which is spooling print-jobs “raw”, leaving the print data untouched.

Possibly you need to setup CUPS in a smarter way. The reasons could be manifold:

  • Maybe your boss wants to get monthly statistics: Which printer did how many pages? What was the average data size of a job? What was the average print run per day? What are the typical hourly peaks in printing? Which department prints how much?

  • Maybe you are asked to setup a print quota system: Users should not be able to print more jobs, once they have surpassed a given limit per period.

  • Maybe your previous network printing setup is a mess and must be re-organized from a clean beginning.

  • Maybe you have experiencing too many “blue screens” originating from poorly debugged printer drivers running in NT “kernel mode”?

These goals cannot be achieved by a raw print server. To build a server meeting these requirements, you'll first need to learn about how CUPS works and how you can enable its features.

What follows is the comparison of some fundamental concepts for Windows and UNIX printing; then follows a description of the CUPS filtering system, how it works and how you can tweak it.

GDI on Windows -- PostScript on UNIX

Network printing is one of the most complicated and error-prone day-to-day tasks any user or administrator may encounter. This is true for all OS platforms. And there are reasons for this.

You can't expect most file formats to just throw them toward printers and they get printed. There needs to be a file format conversion in between. The problem is that there is no common standard for print file formats across all manufacturers and printer types. While PostScript (trademark held by Adobe) and, to an extent, PCL (trademark held by HP) have developed into semi-official “standards” by being the most widely used PDLs Page Description Languages (PDLs), there are still many manufacturers who “roll their own” (their reasons may be unacceptable license fees for using printer-embedded PostScript interpreters, and so on).

Windows Drivers, GDI and EMF

In Windows OS, the format conversion job is done by the printer drivers. On MS Windows OS platforms all application programmers have at their disposal a built-in API, the Graphical Device Interface (GDI), as part and parcel of the OS itself to base themselves on. This GDI core is used as one common unified ground for all Windows programs to draw pictures, fonts and documents on screen as well as on paper (print). Therefore, printer driver developers can standardize on a well-defined GDI output for their own driver input. Achieving WYSIWYG (“What You See Is What You Get”) is relatively easy, because the on-screen graphic primitives, as well as the on-paper drawn objects, come from one common source. This source, the GDI, often produces a file format called Enhanced MetaFile (EMF). The EMF is processed by the printer driver and converted to the printer-specific file format.

Note

To the GDI foundation in MS Windows, Apple has chosen to put paper and screen output on a common foundation for their (BSD-UNIX-based, did you know?) Mac OS X and Darwin Operating Systems. Their Core Graphic Engine uses a PDF derivative for all display work.

Figure 21.1. Windows printing to a local printer.

Windows printing to a local printer.

UNIX Printfile Conversion and GUI Basics

In UNIX and Linux, there is no comparable layer built into the OS kernel(s) or the X (screen display) server. Every application is responsible for itself to create its print output. Fortunately, most use PostScript and that at least gives some common ground. Unfortunately, there are many different levels of quality for this PostScript. And worse, there is a huge difference (and no common root) in the way the same document is displayed on screen and how it is presented on paper. WYSIWYG is more difficult to achieve. This goes back to the time, decades ago, when the predecessors of X.org, designing the UNIX foundations and protocols for Graphical User Interfaces, refused to take responsibility for “paper output” also, as some had demanded at the time, and restricted itself to “on-screen only.” (For some years now, the “Xprint” project has been under development, attempting to build printing support into the X framework, including a PostScript and a PCL driver, but it is not yet ready for prime time.) You can see this unfavorable inheritance up to the present day by looking into the various “font” directories on your system; there are separate ones for fonts used for X display and fonts to be used on paper.

Background.  The PostScript programming language is an “invention” by Adobe Inc., but its specifications have been published to the full. Its strength lies in its powerful abilities to describe graphical objects (fonts, shapes, patterns, lines, curves, and dots), their attributes (color, linewidth) and the way to manipulate (scale, distort, rotate, shift) them. Because of its open specification, anybody with the skill can start writing his own implementation of a PostScript interpreter and use it to display PostScript files on screen or on paper. Most graphical output devices are based on the concept of “raster images” or “pixels” (one notable exception is pen plotters). Of course, you can look at a PostScript file in its textual form and you will be reading its PostScript code, the language instructions which need to be interpreted by a rasterizer. Rasterizers produce pixel images, which may be displayed on screen by a viewer program or on paper by a printer.

PostScript and Ghostscript

So, UNIX is lacking a common ground for printing on paper and displaying on screen. Despite this unfavorable legacy for UNIX, basic printing is fairly easy if you have PostScript printers at your disposal. The reason is these devices have a built-in PostScript language “interpreter,” also called a Raster Image Processor (RIP) (which makes them more expensive than other types of printers); throw PostScript toward them, and they will spit out your printed pages. Their RIP is doing all the hard work of converting the PostScript drawing commands into a bitmap picture as you see it on paper, in a resolution as done by your printer. This is no different to PostScript printing a file from a Windows origin.

Note

Traditional UNIX programs and printing systems while using PostScript are largely not PPD-aware. PPDs are “PostScript Printer Description” files. They enable you to specify and control all options a printer supports: duplexing, stapling and punching. Therefore, UNIX users for a long time couldn't choose many of the supported device and job options, unlike Windows or Apple users. But now there is CUPS.

Figure 21.2. Printing to a PostScript printer.

Printing to a PostScript printer.

However, there are other types of printers out there. These do not know how to print PostScript. They use their own Page Description Language (PDL, often proprietary). To print to them is much more demanding. Since your UNIX applications mostly produce PostScript, and since these devices do not understand PostScript, you need to convert the print files to a format suitable for your printer on the host before you can send it away.

Ghostscript the Software RIP for Non-PostScript Printers

Here is where Ghostscript kicks in. Ghostscript is the traditional (and quite powerful) PostScript interpreter used on UNIX platforms. It is a RIP in software, capable of doing a lot of file format conversions for a very broad spectrum of hardware devices as well as software file formats. Ghostscript technology and drivers are what enable PostScript printing to non-PostScript hardware.

Figure 21.3. Ghostscript as a RIP for non-postscript printers.

Ghostscript as a RIP for non-postscript printers.

Tip

Use the “gs -h” command to check for all built-in “devices” of your Ghostscript version. If you specify a parameter of -sDEVICE=png256 on your Ghostscript command line, you are asking Ghostscript to convert the input into a PNG file. Naming a “device” on the command line is the most important single parameter to tell Ghostscript exactly how it should render the input. New Ghostscript versions are released at fairly regular intervals, now by artofcode LLC. They are initially put under the “AFPL” license, but re-released under the GNU GPL as soon as the next AFPL version appears. GNU Ghostscript is probably the version installed on most Samba systems. But it has some deficiencies. Therefore, ESP Ghostscript was developed as an enhancement over GNU Ghostscript, with lots of bug-fixes, additional devices and improvements. It is jointly maintained by developers from CUPS, Gimp-Print, MandrakeSoft, SuSE, Red Hat, and Debian. It includes the “cups” device (essential to print to non-PS printers from CUPS).

PostScript Printer Description (PPD) Specification

While PostScript in essence is a Page Description Language (PDL) to represent the page layout in a device-independent way, real-world print jobs are always ending up being output on hardware with device-specific features. To take care of all the differences in hardware and to allow for innovations, Adobe has specified a syntax and file format for PostScript Printer Description (PPD) files. Every PostScript printer ships with one of these files.

PPDs contain all the information about general and special features of the given printer model: Which different resolutions can it handle? Does it have a Duplexing Unit? How many paper trays are there? What media types and sizes does it take? For each item, it also names the special command string to be sent to the printer (mostly inside the PostScript file) in order to enable it.

Information from these PPDs is meant to be taken into account by the printer drivers. Therefore, installed as part of the Windows PostScript driver for a given printer is the printer's PPD. Where it makes sense, the PPD features are presented in the drivers' UI dialogs to display to the user a choice of print options. In the end, the user selections are somehow written (in the form of special PostScript, PJL, JCL or vendor-dependent commands) into the PostScript file created by the driver.

Warning

A PostScript file that was created to contain device-specific commands for achieving a certain print job output (e.g., duplex-ed, stapled and punched) on a specific target machine, may not print as expected, or may not be printable at all on other models; it also may not be fit for further processing by software (e.g., by a PDF distilling program).

Using Windows-Formatted Vendor PPDs

CUPS can handle all spec-compliant PPDs as supplied by the manufacturers for their PostScript models. Even if a vendor might not have mentioned our favorite OS in his manuals and brochures, you can safely trust this: If you get the Windows NT version of the PPD, you can use it unchanged in CUPS and thus access the full power of your printer just like a Windows NT user could!

Tip

To check the spec compliance of any PPD online, go to http://www.cups.org/testppd.php and upload your PPD. You will see the results displayed immediately. CUPS in all versions after 1.1.19 has a much more strict internal PPD parsing and checking code enabled; in case of printing trouble, this online resource should be one of your first pit-stops.

Warning

For real PostScript printers, do not use the Foomatic or cupsomatic PPDs from Linuxprinting.org. With these devices, the original vendor-provided PPDs are always the first choice!

Tip

If you are looking for an original vendor-provided PPD of a specific device, and you know that an NT4 box (or any other Windows box) on your LAN has the PostScript driver installed, just use smbclient //NT4-box/print\$ -U username to access the Windows directory where all printer driver files are stored. First look in the W32X86/2 subdir for the PPD you are seeking.

CUPS Also Uses PPDs for Non-PostScript Printers

CUPS also uses specially crafted PPDs to handle non-PostScript printers. These PPDs are usually not available from the vendors (and no, you can't just take the PPD of a PostScript printer with the same model name and hope it works for the non-PostScript version too). To understand how these PPDs work for non-PS printers, we first need to dive deeply into the CUPS filtering and file format conversion architecture. Stay tuned.

The CUPS Filtering Architecture

The core of the CUPS filtering system is based on Ghostscript. In addition to Ghostscript, CUPS uses some other filters of its own. You (or your OS vendor) may have plugged in even more filters. CUPS handles all data file formats under the label of various MIME types. Every incoming printfile is subjected to an initial auto-typing. The auto-typing determines its given MIME type. A given MIME type implies zero or more possible filtering chains relevant to the selected target printer. This section discusses how MIME types recognition and conversion rules interact. They are used by CUPS to automatically setup a working filtering chain for any given input data format.

If CUPS rasterizes a PostScript file natively to a bitmap, this is done in two stages:

  • The first stage uses a Ghostscript device named “cups” (this is since version 1.1.15) and produces a generic raster format called “CUPS raster”.

  • The second stage uses a “raster driver” that converts the generic CUPS raster to a device-specific raster.

Make sure your Ghostscript version has the “cups” device compiled in (check with gs -h | grep cups). Otherwise you may encounter the dreaded Unable to convert file 0 in your CUPS error_log file. To have “cups” as a device in your Ghostscript, you either need to patch GNU Ghostscript and re-compile, or use ESP Ghostscript. The superior alternative is ESP Ghostscript. It supports not just CUPS, but 300 other devices too (while GNU Ghostscript supports only about 180). Because of this broad output device support, ESP Ghostscript is the first choice for non-CUPS spoolers, too. It is now recommended by Linuxprinting.org for all spoolers.

CUPS printers may be setup to use external rendering paths. One of the most common is provided by the Foomatic/cupsomatic concept from Linuxprinting.org. This uses the classical Ghostscript approach, doing everything in one step. It does not use the “cups” device, but one of the many others. However, even for Foomatic/cupsomatic usage, best results and broadest printer model support is provided by ESP Ghostscript (more about cupsomatic/Foomatic, particularly the new version called now foomatic-rip, follows below).

MIME Types and CUPS Filters

CUPS reads the file /etc/cups/mime.types (and all other files carrying a *.types suffix in the same directory) upon startup. These files contain the MIME type recognition rules that are applied when CUPS runs its auto-typing routines. The rule syntax is explained in the man page for mime.types and in the comments section of the mime.types file itself. A simple rule reads like this:

 application/pdf         pdf string(0,%PDF)

This means if a filename has either a .pdf suffix or if the magic string %PDF is right at the beginning of the file itself (offset 0 from the start), then it is a PDF file (application/pdf). Another rule is this:

 application/postscript  ai eps ps string(0,%!) string(0,<04>%!)

If the filename has one of the suffixes .ai, .eps, .ps or if the file itself starts with one of the strings %! or <04>%!, it is a generic PostScript file (application/postscript).

Warning

Don't confuse the other mime.types files your system might be using with the one in the /etc/cups/ directory.

Note

There is an important difference between two similar MIME types in CUPS: one is application/postscript, the other is application/vnd.cups-postscript. While application/postscript is meant to be device independent (job options for the file are still outside the PS file content, embedded in command line or environment variables by CUPS), application/vnd.cups-postscript may have the job options inserted into the PostScript data itself (where applicable). The transformation of the generic PostScript (application/postscript) to the device-specific version (application/vnd.cups-postscript) is the responsibility of the CUPS pstops filter. pstops uses information contained in the PPD to do the transformation.

CUPS can handle ASCII text, HP-GL, PDF, PostScript, DVI, and many image formats (GIF. PNG, TIFF, JPEG, Photo-CD, SUN-Raster, PNM, PBM, SGI-RGB, and more) and their associated MIME types with its filters.

MIME Type Conversion Rules

CUPS reads the file /etc/cups/mime.convs (and all other files named with a *.convs suffix in the same directory) upon startup. These files contain lines naming an input MIME type, an output MIME type, a format conversion filter that can produce the output from the input type and virtual costs associated with this conversion. One example line reads like this:

 application/pdf         application/postscript   33   pdftops

This means that the pdftops filter will take application/pdf as input and produce application/postscript as output; the virtual cost of this operation is 33 CUPS-$. The next filter is more expensive, costing 66 CUPS-$:

 application/vnd.hp-HPGL application/postscript   66   hpgltops

This is the hpgltops, which processes HP-GL plotter files to PostScript.

 application/octet-stream

Here are two more examples:

 application/x-shell     application/postscript   33    texttops
 text/plain              application/postscript   33    texttops

The last two examples name the texttops filter to work on text/plain as well as on application/x-shell. (Hint: This differentiation is needed for the syntax highlighting feature of texttops).

Filtering Overview

There are many more combinations named in mime.convs. However, you are not limited to use the ones pre-defined there. You can plug in any filter you like into the CUPS framework. It must meet, or must be made to meet, some minimal requirements. If you find (or write) a cool conversion filter of some kind, make sure it complies to what CUPS needs and put in the right lines in mime.types and mime.convs, then it will work seamlessly inside CUPS.

Filter requirements

The mentioned “CUPS requirements” for filters are simple. Take filenames or stdin as input and write to stdout. They should take these 5 or 6 arguments: printer job user title copies options [filename]

Printer

The name of the printer queue (normally this is the name of the filter being run).

job

The numeric job ID for the job being printed.

user

The string from the originating-user-name attribute.

title

The string from the job-name attribute.

copies

The numeric value from the number-copies attribute.

options

The job options.

filename

(Optionally) The print request file (if missing, filters expected data fed through stdin). In most cases, it is easy to write a simple wrapper script around existing filters to make them work with CUPS.

Prefilters

As previously stated, PostScript is the central file format to any UNIX-based printing system. From PostScript, CUPS generates raster data to feed non-PostScript printers.

But what happens if you send one of the supported non-PS formats to print? Then CUPS runs “pre-filters” on these input formats to generate PostScript first. There are pre-filters to create PS from ASCII text, PDF, DVI, or HP-GL. The outcome of these filters is always of MIME type application/postscript (meaning that any device-specific print options are not yet embedded into the PostScript by CUPS, and that the next filter to be called is pstops). Another pre-filter is running on all supported image formats, the imagetops filter. Its outcome is always of MIME type application/vnd.cups-postscript (not application/postscript), meaning it has the print options already embedded into the file.

Figure 21.4. Pre-filtering in CUPS to form PostScript.

Pre-filtering in CUPS to form PostScript.

pstops

pstops is the filter to convert application/postscript to application/vnd.cups-postscript. It was said above that this filter inserts all device-specific print options (commands to the printer to ask for the duplexing of output, or stapling and punching it, and so on) into the PostScript file.

Figure 21.5. Adding device-specific print options.

Adding device-specific print options.

This is not all. Other tasks performed by it are:

  • Selecting the range of pages to be printed (if you choose to print only pages “3, 6, 8-11, 16, 19-21”, or only the odd numbered ones).

  • Putting 2 or more logical pages on one sheet of paper (the so-called “number-up” function).

  • Counting the pages of the job to insert the accounting information into the /var/log/cups/page_log.

pstoraster

pstoraster is at the core of the CUPS filtering system. It is responsible for the first stage of the rasterization process. Its input is of MIME type application/vnd.cups-postscript; its output is application/vnd.cups-raster. This output format is not yet meant to be printable. Its aim is to serve as a general purpose input format for more specialized raster drivers that are able to generate device-specific printer data.

Figure 21.6. PostScript to intermediate raster format.

PostScript to intermediate raster format.

CUPS raster is a generic raster format with powerful features. It is able to include per-page information, color profiles, and more, to be used by the following downstream raster drivers. Its MIME type is registered with IANA and its specification is, of course, completely open. It is designed to make it quite easy and inexpensive for manufacturers to develop Linux and UNIX raster drivers for their printer models, should they choose to do so. CUPS always takes care for the first stage of rasterization so these vendors do not need to care about Ghostscript complications (in fact, there is currently more than one vendor financing the development of CUPS raster drivers).

Figure 21.7. CUPS-raster production using Ghostscript.

CUPS-raster production using Ghostscript.

CUPS versions before version 1.1.15 were shipping a binary (or source code) standalone filter, named pstoraster. pstoraster was derived from GNU Ghostscript 5.50, and could be installed besides and in addition to any GNU or AFPL Ghostscript package without conflicting.

>From version 1.1.15, this has changed. The functions for this have been integrated back into Ghostscript (now based on GNU Ghostscript version 7.05). The pstoraster filter is now a simple shell script calling gs with the -sDEVICE=cups parameter. If your Ghostscript does not show a success on asking for gs -h |grep cups, you might not be able to print. Update your Ghostscript.

imagetops and imagetoraster

In the section about pre-filters, we mentioned the pre-filter that generates PostScript from image formats. The imagetoraster filter is used to convert directly from image to raster, without the intermediate PostScript stage. It is used more often than the above mentioned pre-filters. We summarize flowchart of image file filtering on next picture.

Figure 21.8. Image format to CUPS-raster format conversion.

Image format to CUPS-raster format conversion.

rasterto [printers specific]

CUPS ships with quite different raster drivers processing CUPS raster. On my system I find in /usr/lib/cups/filter/ these: rastertoalps, rastertobj, rastertoepson, rastertoescp, rastertopcl, rastertoturboprint, rastertoapdk, rastertodymo, rastertoescp, rastertohp, and rastertoprinter. Don't worry if you have less than this; some of these are installed by commercial add-ons to CUPS (like rastertoturboprint), others (like rastertoprinter) by third-party driver development projects (such as Gimp-Print) wanting to cooperate as closely as possible with CUPS.

Figure 21.9. Raster to printer-specific formats.

Raster to printer-specific formats.

CUPS Backends

The last part of any CUPS filtering chain is a backend. Backends are special programs that send the print-ready file to the final device. There is a separate backend program for any transfer protocol of sending print jobs over the network, or for every local interface. Every CUPS print queue needs to have a CUPS “device-URI” associated with it. The device URI is the way to encode the backend used to send the job to its destination. Network device-URIs are using two slashes in their syntax, local device URIs only one, as you can see from the following list. Keep in mind that local interface names may vary much from my examples, if your OS is not Linux:

usb

This backend sends print files to USB-connected printers. An example for the CUPS device-URI to use is: usb:/dev/usb/lp0.

serial

This backend sends print files to serially connected printers. An example for the CUPS device-URI to use is: serial:/dev/ttyS0?baud=11500.

parallel

This backend sends print files to printers connected to the parallel port. An example for the CUPS device-URI to use is: parallel:/dev/lp0.

SCSI

This backend sends print files to printers attached to the SCSI interface. An example for the CUPS device-URI to use is: scsi:/dev/sr1.

lpd

This backend sends print files to LPR/LPD connected network printers. An example for the CUPS device-URI to use is: lpd://remote_host_name/remote_queue_name.

AppSocket/HP JetDirect

This backend sends print files to AppSocket (a.k.a. "HP JetDirect") connected network printers. An example for the CUPS device-URI to use is: socket://10.11.12.13:9100.

ipp

This backend sends print files to IPP connected network printers (or to other CUPS servers). Examples for CUPS device-URIs to use are: ipp:://192.193.194.195/ipp (for many HP printers) or ipp://remote_cups_server/printers/remote_printer_name.

http

This backend sends print files to HTTP connected printers. (The http:// CUPS backend is only a symlink to the ipp:// backend.) Examples for the CUPS device-URIs to use are: http:://192.193.194.195:631/ipp (for many HP printers) or http://remote_cups_server:631/printers/remote_printer_name.

smb

This backend sends print files to printers shared by a Windows host. An example for CUPS device-URIs that may be used includes:

smb://workgroup/server/printersharename
smb://server/printersharename
smb://username:password@workgroup/server/printersharename
smb://username:password@server/printersharename

The smb:// backend is a symlink to the Samba utility smbspool (does not ship with CUPS). If the symlink is not present in your CUPS backend directory, have your root user create it: ln -s `which smbspool' /usr/lib/cups/backend/smb.

It is easy to write your own backends as shell or Perl scripts, if you need any modification or extension to the CUPS print system. One reason could be that you want to create “special” printers that send the print-jobs as email (through a “mailto:/” backend), convert them to PDF (through a “pdfgen:/” backend) or dump them to “/dev/null”. (In fact I have the system-wide default printer set up to be connected to a devnull:/ backend: there are just too many people sending jobs without specifying a printer, or scripts and programs which do not name a printer. The system-wide default deletes the job and sends a polite email back to the $USER asking him to always specify the correct printer name.)

Not all of the mentioned backends may be present on your system or usable (depending on your hardware configuration). One test for all available CUPS backends is provided by the lpinfo utility. Used with the -v parameter, it lists all available backends:

$ lpinfo -v

The Role of cupsomatic/foomatic

cupsomatic filters may be the most widely used on CUPS installations. You must be clear about the fact that these were not developed by the CUPS people. They are a third party add-on to CUPS. They utilize the traditional Ghostscript devices to render jobs for CUPS. When troubleshooting, you should know about the difference. Here the whole rendering process is done in one stage, inside Ghostscript, using an appropriate device for the target printer. cupsomatic uses PPDs that are generated from the Foomatic Printer & Driver Database at Linuxprinting.org.

You can recognize these PPDs from the line calling the cupsomatic filter:

 *cupsFilter: "application/vnd.cups-postscript  0  cupsomatic"

You may find this line among the first 40 or so lines of the PPD file. If you have such a PPD installed, the printer shows up in the CUPS Web interface with a foomatic namepart for the driver description. cupsomatic is a Perl script that runs Ghostscript with all the complicated command line options auto-constructed from the selected PPD and command line options give to the print-job.

However, cupsomatic is now deprecated. Its PPDs (especially the first generation of them, still in heavy use out there) are not meeting the Adobe specifications. You might also suffer difficulties when you try to download them with “Point'n'Print” to Windows clients. A better and more powerful successor is now in a stable beta-version: it is called foomatic-rip. To use foomatic-rip as a filter with CUPS, you need the new-type PPDs. These have a similar but different line:

 *cupsFilter: "application/vnd.cups-postscript  0  foomatic-rip"

The PPD generating engine at Linuxprinting.org has been revamped. The new PPDs comply to the Adobe spec. On top, they also provide a new way to specify different quality levels (hi-res photo, normal color, grayscale, and draft) with a single click, whereas before you could have required five or more different selections (media type, resolution, inktype and dithering algorithm). There is support for custom-size media built in. There is support to switch print-options from page to page in the middle of a job. And the best thing is the new foomatic-rip now works seamlessly with all legacy spoolers too (like LPRng, BSD-LPD, PDQ, PPR and so on), providing for them access to use PPDs for their printing.

The Complete Picture

If you want to see an overview of all the filters and how they relate to each other, the complete picture of the puzzle is at the end of this document.

mime.convs

CUPS auto-constructs all possible filtering chain paths for any given MIME type, and every printer installed. But how does it decide in favor or against a specific alternative? (There may often be cases where there is a choice of two or more possible filtering chains for the same target printer.) Simple. You may have noticed the figures in the third column of the mime.convs file. They represent virtual costs assigned to this filter. Every possible filtering chain will sum up to a total “filter cost.” CUPS decides for the most “inexpensive” route.

Tip

The setting of FilterLimit 1000 in cupsd.conf will not allow more filters to run concurrently than will consume a total of 1000 virtual filter cost. This is an efficient way to limit the load of any CUPS server by setting an appropriate “FilterLimit” value. A FilterLimit of 200 allows roughly one job at a time, while a FilterLimit of 1000 allows approximately five jobs maximum at a time.

Raw” Printing

You can tell CUPS to print (nearly) any file “raw”. “Raw” means it will not be filtered. CUPS will send the file to the printer “as is” without bothering if the printer is able to digest it. Users need to take care themselves that they send sensible data formats only. Raw printing can happen on any queue if the “-o raw” option is specified on the command line. You can also set up raw-only queues by simply not associating any PPD with it. This command:

$ lpadmin -P rawprinter -v socket://11.12.13.14:9100 -E

sets up a queue named “rawprinter”, connected via the “socket” protocol (a.k.a. “HP JetDirect”) to the device at IP address 11.12.1.3.14, using port 9100. (If you had added a PPD with -P /path/to/PPD to this command line, you would have installed a “normal” print queue.

CUPS will automatically treat each job sent to a queue as a “raw” one, if it can't find a PPD associated with the queue. However, CUPS will only send known MIME types (as defined in its own mime.types file) and refuse others.

application/octet-stream Printing

Any MIME type with no rule in the /etc/cups/mime.types file is regarded as unknown or application/octet-stream and will not be sent. Because CUPS refuses to print unknown MIME types per default, you will probably have experienced the fact that print jobs originating from Windows clients were not printed. You may have found an error message in your CUPS logs like:

Unable to convert file 0 to printable format for job

To enable the printing of application/octet-stream files, edit these two files:

  • /etc/cups/mime.convs

  • /etc/cups/mime.types

Both contain entries (at the end of the respective files) which must be uncommented to allow RAW mode operation for application/octet-stream. In /etc/cups/mime.types make sure this line is present:

application/octet-stream

This line (with no specific auto-typing rule set) makes all files not otherwise auto-typed a member of application/octet-stream. In /etc/cups/mime.convs, have this line:

application/octet-stream   application/vnd.cups-raw   0   -

This line tells CUPS to use the Null Filter (denoted as “-”, doing nothing at all) on application/octet-stream, and tag the result as application/vnd.cups-raw. This last one is always a green light to the CUPS scheduler to now hand the file over to the backend connecting to the printer and sending it over.

Note

Editing the mime.convs and the mime.types file does not enforceraw” printing, it only allows it.

Background.  CUPS being a more security-aware printing system than traditional ones does not by default allow one to send deliberate (possibly binary) data to printing devices. (This could be easily abused to launch a Denial of Service attack on your printer(s), causing at least the loss of a lot of paper and ink...) “Unknown” data are regarded by CUPS as MIME type application/octet-stream. While you can send data “raw”, the MIME type for these must be one that is known to CUPS and an allowed one. The file /etc/cups/mime.types defines the “rules” of how CUPS recognizes MIME types. The file /etc/cups/mime.convs decides which file conversion filter(s) may be applied to which MIME types.

PostScript Printer Descriptions (PPDs) for Non-PS Printers

Originally PPDs were meant to be used for PostScript printers only. Here, they help to send device-specific commands and settings to the RIP which processes the job file. CUPS has extended this scope for PPDs to cover non-PostScript printers too. This was not difficult, because it is a standardized file format. In a way it was logical too: CUPS handles PostScript and uses a PostScript RIP (Ghostscript) to process the job files. The only difference is: a PostScript printer has the RIP built-in, for other types of printers the Ghostscript RIP runs on the host computer.

PPDs for a non-PS printer have a few lines that are unique to CUPS. The most important one looks similar to this:

 *cupsFilter: application/vnd.cups-raster  66   rastertoprinter

It is the last piece in the CUPS filtering puzzle. This line tells the CUPS daemon to use as a last filter rastertoprinter. This filter should be served as input an application/vnd.cups-raster MIME type file. Therefore, CUPS should auto-construct a filtering chain, which delivers as its last output the specified MIME type. This is then taken as input to the specified rastertoprinter filter. After this the last filter has done its work (rastertoprinter is a Gimp-Print filter), the file should go to the backend, which sends it to the output device.

CUPS by default ships only a few generic PPDs, but they are good for several hundred printer models. You may not be able to control different paper trays, or you may get larger margins than your specific model supports. See PPDs shipped with CUPS for summary information.

Table 21.1. PPDs shipped with CUPS

PPD filePrinter type
deskjet.ppdolder HP inkjet printers and compatible
deskjet2.ppdnewer HP inkjet printers and compatible
dymo.ppdlabel printers
epson9.ppdEpson 24pin impact printers and compatible
epson24.ppdEpson 24pin impact printers and compatible
okidata9.ppdOkidata 9pin impact printers and compatible
okidat24.ppdOkidata 24pin impact printers and compatible
stcolor.ppdolder Epson Stylus Color printers
stcolor2.ppdnewer Epson Stylus Color printers
stphoto.ppdolder Epson Stylus Photo printers
stphoto2.ppdnewer Epson Stylus Photo printers
laserjet.ppdall PCL printers. Further below is a discussion of several other driver/PPD-packages suitable for use with CUPS.

cupsomatic/foomatic-rip Versus native CUPS Printing

Native CUPS rasterization works in two steps:

  • First is the pstoraster step. It uses the special CUPS device from ESP Ghostscript 7.05.x as its tool.

  • Second comes the rasterdriver step. It uses various device-specific filters; there are several vendors who provide good quality filters for this step. Some are free software, some are shareware/non-free and some are proprietary.

Often this produces better quality (and has several more advantages) than other methods.

Figure 21.10. cupsomatic/foomatic Processing versus Native CUPS.

cupsomatic/foomatic Processing versus Native CUPS.

One other method is the cupsomatic/foomatic-rip way. Note that cupsomatic is not made by the CUPS developers. It is an independent contribution to printing development, made by people from Linuxprinting.org [5]. cupsomatic is no longer developed and maintained and is no longer supported. It has now been replaced by foomatic-rip. foomatic-rip is a complete re-write of the old cupsomatic idea, but very much improved and generalized to other (non-CUPS) spoolers. An upgrade to foomatic-rip is strongly advised, especially if you are upgrading to a recent version of CUPS, too.

Both the cupsomatic (old) and the foomatic-rip (new) methods from Linuxprinting.org use the traditional Ghostscript print file processing, doing everything in a single step. It therefore relies on all the other devices built into Ghostscript. The quality is as good (or bad) as Ghostscript rendering is in other spoolers. The advantage is that this method supports many printer models not supported (yet) by the more modern CUPS method.

Of course, you can use both methods side by side on one system (and even for one printer, if you set up different queues) and find out which works best for you.

cupsomatic kidnaps the printfile after the application/vnd.cups-postscript stage and deviates it through the CUPS-external, system-wide Ghostscript installation. Therefore the printfile bypasses the pstoraster filter (and also bypasses the CUPS-raster-drivers rastertosomething). After Ghostscript finished its rasterization, cupsomatic hands the rendered file directly to the CUPS backend. The flowchart in cupsomatic/foomatic processing versus Native CUPS illustrates the difference between native CUPS rendering and the Foomatic/cupsomatic method.

Examples for Filtering Chains

Here are a few examples of commonly occurring filtering chains to illustrate the workings of CUPS.

Assume you want to print a PDF file to an HP JetDirect-connected PostScript printer, but you want to print the pages 3-5, 7, 11-13 only, and you want to print them “two-up” and “duplex”:

  • Your print options (page selection as required, two-up, duplex) are passed to CUPS on the command line.

  • The (complete) PDF file is sent to CUPS and auto-typed as application/pdf.

  • The file therefore must first pass the pdftops pre-filter, which produces PostScript MIME type application/postscript (a preview here would still show all pages of the original PDF).

  • The file then passes the pstops filter that applies the command line options: it selects the pages 2-5, 7 and 11-13, creates an imposed layout “2 pages on 1 sheet” and inserts the correct “duplex” command (as defined in the printer's PPD) into the new PostScript file; the file is now of PostScript MIME type application/vnd.cups-postscript.

  • The file goes to the socket backend, which transfers the job to the printers.

The resulting filter chain, therefore, is as drawn in PDF to socket chain.

Figure 21.11. PDF to socket chain.

PDF to socket chain.

Assume you want to print the same filter to an USB-connected Epson Stylus Photo printer installed with the CUPS stphoto2.ppd. The first few filtering stages are nearly the same:

  • Your print options (page selection as required, two-up, duplex) are passed to CUPS on the command-line.

  • The (complete) PDF file is sent to CUPS and auto-typed as application/pdf.

  • The file must first pass the pdftops pre-filter, which produces PostScript MIME type application/postscript (a preview here would still show all pages of the original PDF).

  • The file then passes the “pstops” filter that applies the command-line options: it selects the pages 2-5, 7 and 11-13, creates an imposed layout “two pages on one sheet” and inserts the correct “duplex” command... (Oops this printer and PPD do not support duplex printing at all so this option will be ignored) into the new PostScript file; the file is now of PostScript MIME type application/vnd.cups-postscript.

  • The file then passes the pstoraster stage and becomes MIME type application/ cups-raster.

  • Finally, the rastertoepson filter does its work (as indicated in the printer's PPD), creating the printer-specific raster data and embedding any user-selected print-options into the print data stream.

  • The file goes to the usb backend, which transfers the job to the printers.

The resulting filter chain therefore is as drawn in this figure.

Figure 21.12. PDF to USB chain.

PDF to USB chain.

Sources of CUPS Drivers/PPDs

On the Internet you can now find many thousands of CUPS-PPD files (with their companion filters), in many national languages supporting more than thousand non-PostScript models.

  • ESP PrintPro (commercial, non-free) is packaged with more than three thousand PPDs, ready for successful use “out of the box” on Linux, Mac OS X, IBM-AIX, HP-UX, Sun-Solaris, SGI-IRIX, Compaq Tru64, Digital UNIX, and some more commercial Unices (it is written by the CUPS developers themselves and its sales help finance the further development of CUPS, as they feed their creators).

  • The Gimp-Print-Project (GPL, free software) provides around 140 PPDs (supporting nearly 400 printers, many driven to photo quality output), to be used alongside the Gimp-Print CUPS filters.

  • TurboPrint (shareware, non-free) supports roughly the same amount of printers in excellent quality.

  • OMNI (LPGL, free) is a package made by IBM, now containing support for more than 400 printers, stemming from the inheritance of IBM OS/2 Know-How ported over to Linux (CUPS support is in a beta-stage at present).

  • HPIJS (BSD-style licenses, free) supports around 150 of HP's own printers and is also providing excellent print quality now (currently available only via the Foomatic path).

  • Foomatic/cupsomatic (LPGL, free) from Linuxprinting.org are providing PPDs for practically every Ghostscript filter known to the world (including Omni, Gimp-Print and HPIJS).

Printing with Interface Scripts

CUPS also supports the usage of “interface scripts” as known from System V AT&T printing systems. These are often used for PCL printers, from applications that generate PCL print jobs. Interface scripts are specific to printer models. They have a similar role as PPDs for PostScript printers. Interface scripts may inject the Escape sequences as required into the print data stream, if the user has chosen to select a certain paper tray, or print landscape, or use A3 paper, etc. Interfaces scripts are practically unknown in the Linux realm. On HP-UX platforms they are more often used. You can use any working interface script on CUPS too. Just install the printer with the -i option:

root# lpadmin -p pclprinter -v socket://11.12.13.14:9100 \
  -i /path/to/interface-script

Interface scripts might be the “unknown animal” to many. However, with CUPS they provide the easiest way to plug in your own custom-written filtering script or program into one specific print queue (some information about the traditional usage of interface scripts is to be found at http://playground.sun.com/printing/documentation/interface.html).

Network Printing (Purely Windows)

Network printing covers a lot of ground. To understand what exactly goes on with Samba when it is printing on behalf of its Windows clients, let's first look at a “purely Windows” setup: Windows clients with a Windows NT print server.

From Windows Clients to an NT Print Server

Windows clients printing to an NT-based print server have two options. They may:

  • Execute the driver locally and render the GDI output (EMF) into the printer-specific format on their own.

  • Send the GDI output (EMF) to the server, where the driver is executed to render the printer specific output.

Both print paths are shown in the flowcharts Print driver execution on the client and Print driver execution on the server.

Driver Execution on the Client

In the first case the print server must spool the file as raw, meaning it shouldn't touch the jobfile and try to convert it in any way. This is what a traditional UNIX-based print server can do too, and at a better performance and more reliably than an NT print server. This is what most Samba administrators probably are familiar with. One advantage of this setup is that this “spooling-only” print server may be used even if no driver(s) for UNIX are available it is sufficient to have the Windows client drivers available; and installed on the clients.

Figure 21.13. Print driver execution on the client.

Print driver execution on the client.

Driver Execution on the Server

The other path executes the printer driver on the server. The client transfers print files in EMF format to the server. The server uses the PostScript, PCL, ESC/P or other driver to convert the EMF file into the printer-specific language. It is not possible for UNIX to do the same. Currently, there is no program or method to convert a Windows client's GDI output on a UNIX server into something a printer could understand.

Figure 21.14. Print driver execution on the server.

Print driver execution on the server.

However, there is something similar possible with CUPS. Read on.

Network Printing (Windows Clients UNIX/Samba Print Servers)

Since UNIX print servers cannot execute the Win32 program code on their platform, the picture is somewhat different. However, this does not limit your options all that much. On the contrary, you may have a way here to implement printing features that are not possible otherwise.

From Windows Clients to a CUPS/Samba Print Server

Here is a simple recipe showing how you can take advantage of CUPS' powerful features for the benefit of your Windows network printing clients:

  • Let the Windows clients send PostScript to the CUPS server.

  • Let the CUPS server render the PostScript into device-specific raster format.

This requires the clients to use a PostScript driver (even if the printer is a non-PostScript model. It also requires that you have a driver on the CUPS server.

First, to enable CUPS-based printing through Samba the following options should be set in your smb.conf file [global] section:

printing = cups
printcap = cups

When these parameters are specified, all manually set print directives (like print command, or lppause command) in smb.conf (as well as in Samba itself) will be ignored. Instead, Samba will directly interface with CUPS through its application program interface (API), as long as Samba has been compiled with CUPS library (libcups) support. If Samba has not been compiled with CUPS support, and if no other print commands are set up, then printing will use the System V AT&T command set, with the -oraw option automatically passing through (if you want your own defined print commands to work with a Samba that has CUPS support compiled in, simply use printing = sysv).

Figure 21.15. Printing via CUPS/Samba server.

Printing via CUPS/Samba server.

Samba Receiving Job-files and Passing Them to CUPS

Samba must use its own spool directory (it is set by a line similar to path = /var/spool/samba, in the [printers] or [printername] section of smb.conf). Samba receives the job in its own spool space and passes it into the spool directory of CUPS (the CUPS spooling directory is set by the RequestRoot directive, in a line that defaults to RequestRoot /var/spool/cups). CUPS checks the access rights of its spool dir and resets it to healthy values with every restart. We have seen quite a few people who had used a common spooling space for Samba and CUPS, and were struggling for weeks with this “problem.

A Windows user authenticates only to Samba (by whatever means is configured). If Samba runs on the same host as CUPS, you only need to allow “localhost” to print. If they run on different machines, you need to make sure the Samba host gets access to printing on CUPS.

Network PostScript RIP

This section discusses the use of CUPS filters on the server configuration where clients make use of a PostScript driver with CUPS-PPDs.

PPDs can control all print device options. They are usually provided by the manufacturer, if you own a PostScript printer, that is. PPD files (PostScript Printer Descriptions) are always a component of PostScript printer drivers on MS Windows or Apple Mac OS systems. They are ASCII files containing user-selectable print options, mapped to appropriate PostScript, PCL or PJL commands for the target printer. Printer driver GUI dialogs translate these options “on-the-fly” into buttons and drop-down lists for the user to select.

CUPS can load, without any conversions, the PPD file from any Windows (NT is recommended) PostScript driver and handle the options. There is a Web browser interface to the print options (select http://localhost:631/printers/ and click on one Configure Printer button to see it), or a command line interface (see man lpoptions or see if you have lphelp on your system). There are also some different GUI front-ends on Linux/UNIX, which can present PPD options to users. PPD options are normally meant to be evaluated by the PostScript RIP on the real PostScript printer.

PPDs for Non-PS Printers on UNIX

CUPS does not limit itself to “real” PostScript printers in its usage of PPDs. The CUPS developers have extended the scope of the PPD concept to also describe available device and driver options for non-PostScript printers through CUPS-PPDs.

This is logical, as CUPS includes a fully featured PostScript interpreter (RIP). This RIP is based on Ghostscript. It can process all received PostScript (and additionally many other file formats) from clients. All CUPS-PPDs geared to non-PostScript printers contain an additional line, starting with the keyword *cupsFilter. This line tells the CUPS print system which printer-specific filter to use for the interpretation of the supplied PostScript. Thus CUPS lets all its printers appear as PostScript devices to its clients, because it can act as a PostScript RIP for those printers, processing the received PostScript code into a proper raster print format.

PPDs for Non-PS Printers on Windows

CUPS-PPDs can also be used on Windows-Clients, on top of a “core” PostScript driver (now recommended is the "CUPS PostScript Driver for Windows NT/200x/XP"; you can also use the Adobe one, with limitations). This feature enables CUPS to do a few tricks no other spooler can do:

  • Act as a networked PostScript RIP (Raster Image Processor), handling print files from all client platforms in a uniform way.

  • Act as a central accounting and billing server, since all files are passed through the pstops filter and are, therefore, logged in the CUPS page_log file. Note: this cannot happen with “raw” print jobs, which always remain unfiltered per definition.

  • Enable clients to consolidate on a single PostScript driver, even for many different target printers.

Using CUPS PPDs on Windows clients enables these to control all print job settings just as a UNIX client can do.

Windows Terminal Servers (WTS) as CUPS Clients

This setup may be of special interest to people experiencing major problems in WTS environments. WTS often need a multitude of non-PostScript drivers installed to run their clients' variety of different printer models. This often imposes the price of much increased instability.

Printer Drivers Running in “Kernel Mode” Cause Many Problems

In Windows NT printer drivers which run in “Kernel Mode”, introduces a high risk for the stability of the system if the driver is not really stable and well-tested. And there are a lot of bad drivers out there! Especially notorious is the example of the PCL printer driver that had an additional sound module running, to notify users via sound-card of their finished jobs. Do I need to say that this one was also reliably causing “blue screens of death” on a regular basis?

PostScript drivers are generally well tested. They are not known to cause any problems, even though they also run in kernel mode. This might be because there have been so far only two different PostScript drivers: the ones from Adobe and the one from Microsoft. Both are well tested and are as stable as you can imagine on Windows. The CUPS driver is derived from the Microsoft one.

Workarounds Impose Heavy Limitations

In many cases, in an attempt to work around this problem, site administrators have resorted to restricting the allowed drivers installed on their WTS to one generic PCL and one PostScript driver. This, however, restricts the clients in the number of printer options available for them. Often they can't get out more than simplex prints from one standard paper tray, while their devices could do much better, if driven by a different driver!

CUPS: A “Magical Stone”?

Using a PostScript driver, enabled with a CUPS-PPD, seems to be a very elegant way to overcome all these shortcomings. There are, depending on the version of Windows OS you use, up to three different PostScript drivers available: Adobe, Microsoft and CUPS PostScript drivers. None of them is known to cause major stability problems on WTS (even if used with many different PPDs). The clients will be able to (again) chose paper trays, duplex printing and other settings. However, there is a certain price for this too: a CUPS server acting as a PostScript RIP for its clients requires more CPU and RAM than when just acting as a “raw spooling” device. Plus, this setup is not yet widely tested, although the first feedbacks look very promising.

PostScript Drivers with No Major Problems Even in Kernel Mode

More recent printer drivers on W200x and XP no longer run in kernel mode (unlike Windows NT). However, both operating systems can still use the NT drivers, running in kernel mode (you can roughly tell which is which as the drivers in subdirectory “2” of “W32X86” are “old” ones). As was said before, the Adobe as well as the Microsoft PostScript drivers are not known to cause any stability problems. The CUPS driver is derived from the Microsoft one. There is a simple reason for this: The MS DDK (Device Development Kit) for Windows NT (which used to be available at no cost to licensees of Visual Studio) includes the source code of the Microsoft driver, and licensees of Visual Studio are allowed to use and modify it for their own driver development efforts. This is what the CUPS people have done. The license does not allow them to publish the whole of the source code. However, they have released the “diff” under the GPL, and if you are the owner of an “MS DDK for Windows NT,” you can check the driver yourself.

Configuring CUPS for Driver Download

As we have said before, all previously known methods to prepare client printer drivers on the Samba server for download and Point'n'Print convenience of Windows workstations are working with CUPS, too. These methods were described in the previous chapter. In reality, this is a pure Samba business and only relates to the Samba/Windows client relationship.

cupsaddsmb: The Unknown Utility

The cupsaddsmb utility (shipped with all current CUPS versions) is an alternate method to transfer printer drivers into the Samba [print$] share. Remember, this share is where clients expect drivers deposited and setup for download and installation. It makes the sharing of any (or all) installed CUPS printers quite easy. cupsaddsmb can use the Adobe PostScript driver as well as the newly developed CUPS PostScript Driver for Windows NT/200x/XP. cupsaddsmb does not work with arbitrary vendor printer drivers, but only with the exact driver files that are named in its man page.

The CUPS printer driver is available from the CUPS download site. Its package name is cups-samba-[version].tar.gz . It is preferred over the Adobe drivers since it has a number of advantages:

  • It supports a much more accurate page accounting.

  • It supports banner pages, and page labels on all printers.

  • It supports the setting of a number of job IPP attributes (such as job-priority, page-label and job-billing).

However, currently only Windows NT, 2000 and XP are supported by the CUPS drivers. You will also need to get the respective part of Adobe driver if you need to support Windows 95, 98 and ME clients.

Prepare Your smb.conf for cupsaddsmb

Prior to running cupsaddsmb, you need the settings in smb.conf as shown in the next example:

Example 21.3. smb.conf for cupsaddsmb usage

[global]
load printers = yes
printing = cups
printcap name = cups
[printers]
comment = All Printers
path = /var/spool/samba
browseable = no
public = yes
# setting depends on your requirements
guest ok = yes
writable = no
printable = yes
printer admin = root
[print$]
comment = Printer Drivers
path = /etc/samba/drivers
browseable = yes
guest ok = no
read only = yes
write list = root

CUPS “PostScript Driver for Windows NT/200x/XP

CUPS users may get the exact same packages from http://www.cups.org/software.html. It is a separate package from the CUPS base software files, tagged as CUPS 1.1.x Windows NT/200x/XP Printer Driver for Samba (tar.gz, 192k). The filename to download is cups-samba-1.1.x.tar.gz. Upon untar and unzipping, it will reveal these files:

root# tar xvzf cups-samba-1.1.19.tar.gz
cups-samba.install
cups-samba.license
cups-samba.readme
cups-samba.remove
cups-samba.ss

These have been packaged with the ESP meta packager software EPM. The *.install and *.remove files are simple shell scripts, which untars the *.ss (the *.ss is nothing else but a tar-archive, which can be untarred by “tar” too). Then it puts the content into /usr/share/cups/drivers/. This content includes three files:

root# tar tv cups-samba.ss
cupsdrvr.dll
cupsui.dll
cups.hlp  

The cups-samba.install shell scripts are easy to handle:

root# ./cups-samba.install
[....]
Installing software...
Updating file permissions...
Running post-install commands...
Installation is complete.       

The script should automatically put the driver files into the /usr/share/cups/drivers/ directory.

Warning

Due to a bug, one recent CUPS release puts the cups.hlp driver file into/usr/share/drivers/ instead of /usr/share/cups/drivers/. To work around this, copy/move the file (after running the ./cups-samba.install script) manually to the correct place.

root# cp /usr/share/drivers/cups.hlp /usr/share/cups/drivers/

This new CUPS PostScript driver is currently binary-only, but free of charge. No complete source code is provided (yet). The reason is that it has been developed with the help of the Microsoft Driver Developer Kit (DDK) and compiled with Microsoft Visual Studio 6. Driver developers are not allowed to distribute the whole of the source code as free software. However, CUPS developers released the “diff” in source code under the GPL, so anybody with a license of Visual Studio and a DDK will be able to compile for him/herself.

Recognizing Different Driver Files

The CUPS drivers do not support the older Windows 95/98/Me, but only the Windows NT/2000/XP client.

Windows NT, 2000 and XP are supported by:

  • cups.hlp

  • cupsdrvr.dll

  • cupsui.dll

Adobe drivers are available for the older Windows 95/98/Me as well as the Windows NT/2000/XP clients. The set of files is different from the different platforms.

Windows 95, 98 and ME are supported by:

  • ADFONTS.MFM

  • ADOBEPS4.DRV

  • ADOBEPS4.HLP

  • DEFPRTR2.PPD

  • ICONLIB.DLL

  • PSMON.DLL

Windows NT, 2000 and XP are supported by:

  • ADOBEPS5.DLL

  • ADOBEPSU.DLL

  • ADOBEPSU.HLP

Note

If both the Adobe driver files and the CUPS driver files for the support of Windows NT/200x/XP are present in FIXME, the Adobe ones will be ignored and the CUPS ones will be used. If you prefer for whatever reason to use Adobe-only drivers, move away the three CUPS driver files. The Windows 9x/Me clients use the Adobe drivers in any case.

Acquiring the Adobe Driver Files

Acquiring the Adobe driver files seems to be unexpectedly difficult for many users. They are not available on the Adobe Web site as single files and the self-extracting and/or self-installing Windows-.exe is not easy to locate either. Probably you need to use the included native installer and run the installation process on one client once. This will install the drivers (and one Generic PostScript printer) locally on the client. When they are installed, share the Generic PostScript printer. After this, the client's [print$] share holds the Adobe files, from where you can get them with smbclient from the CUPS host.

ESP Print Pro PostScript Driver for Windows NT/200x/XP

Users of the ESP Print Pro software are able to install their Samba drivers package for this purpose with no problem. Retrieve the driver files from the normal download area of the ESP Print Pro software at http://www.easysw.com/software.html. You need to locate the link labeled “SAMBA” among the Download Printer Drivers for ESP Print Pro 4.x area and download the package. Once installed, you can prepare any driver by simply highlighting the printer in the Printer Manager GUI and select Export Driver... from the menu. Of course you need to have prepared Samba beforehand to handle the driver files; i.e., setup the [print$] share, and so on. The ESP Print Pro package includes the CUPS driver files as well as a (licensed) set of Adobe drivers for the Windows 95/98/Me client family.

Caveats to be Considered

Once you have run the install script (and possibly manually moved the cups.hlp file to /usr/share/cups/drivers/), the driver is ready to be put into Samba's [print$] share (which often maps to /etc/samba/drivers/ and contains a subdirectory tree with WIN40 and W32X86 branches). You do this by running cupsaddsmb (see also man cupsaddsmb for CUPS since release 1.1.16).

Tip

You may need to put root into the smbpasswd file by running smbpasswd; this is especially important if you should run this whole procedure for the first time, and are not working in an environment where everything is configured for single sign on to a Windows Domain Controller.

Once the driver files are in the [print$] share and are initialized, they are ready to be downloaded and installed by the Windows NT/200x/XP clients.

Note

Win 9x/Me clients will not work with the CUPS PostScript driver. For these you still need to use the ADOBE*.* drivers as previously stated.

Note

It is not harmful if you still have the ADOBE*.* driver files from previous installations in the /usr/share/cups/drivers/ directory. The new cupsaddsmb (from 1.1.16) will automatically prefer its own drivers if it finds both.

Note

Should your Windows clients have had the old ADOBE*.* files for the Adobe PostScript driver installed, the download and installation of the new CUPS PostScript driver for Windows NT/200x/XP will fail at first. You need to wipe the old driver from the clients first. It is not enough to “delete” the printer, as the driver files will still be kept by the clients and re-used if you try to re-install the printer. To really get rid of the Adobe driver files on the clients, open the Printers folder (possibly via Start > Settings > Control Panel > Printers), right-click on the folder background and select Server Properties. When the new dialog opens, select the Drivers tab. On the list select the driver you want to delete and click the Delete button. This will only work if there is not one single printer left that uses that particular driver. You need to “delete” all printers using this driver in the Printers folder first. You will need Administrator privileges to do this.

Note

Once you have successfully downloaded the CUPS PostScript driver to a client, you can easily switch all printers to this one by proceeding as described in Classical Printing Support. Either change a driver for an existing printer by running the Printer Properties dialog, or use rpcclient with the setdriver subcommand.

Windows CUPS PostScript Driver Versus Adobe Driver

Are you interested in a comparison between the CUPS and the Adobe PostScript drivers? For our purposes these are the most important items that weigh in favor of the CUPS ones:

  • No hassle with the Adobe EULA.

  • No hassle with the question “Where do I get the ADOBE*.* driver files from?

  • The Adobe drivers (on request of the printer PPD associated with them) often put a PJL header in front of the main PostScript part of the print file. Thus, the printfile starts with <1B >%-12345X or <escape>%-12345X instead of %!PS). This leads to the CUPS daemon auto-typing the incoming file as a print-ready file, not initiating a pass through the pstops filter (to speak more technically, it is not regarded as the generic MIME-type application/postscript, but as the more special MIME type application/cups.vnd-postscript), which therefore also leads to the page accounting in /var/log/cups/page_log not receiving the exact number of pages; instead the dummy page number of “1” is logged in a standard setup).

  • The Adobe driver has more options to mis-configure the PostScript generated by it (like setting it inadvertently to Optimize for Speed, instead of Optimize for Portability, which could lead to CUPS being unable to process it).

  • The CUPS PostScript driver output sent by Windows clients to the CUPS server is guaranteed to auto-type as the generic MIME type application/postscript, thus passing through the CUPS pstops filter and logging the correct number of pages in the page_log for accounting and quota purposes.

  • The CUPS PostScript driver supports the sending of additional standard (IPP) print options by Windows NT/200x/XP clients. Such additional print options are: naming the CUPS standard banner pages (or the custom ones, should they be installed at the time of driver download), using the CUPS page-label option, setting a job-priority, and setting the scheduled time of printing (with the option to support additional useful IPP job attributes in the future).

  • The CUPS PostScript driver supports the inclusion of the new *cupsJobTicket comments at the beginning of the PostScript file (which could be used in the future for all sort of beneficial extensions on the CUPS side, but which will not disturb any other applications as they will regard it as a comment and simply ignore it).

  • The CUPS PostScript driver will be the heart of the fully fledged CUPS IPP client for Windows NT/200x/XP to be released soon (probably alongside the first beta release for CUPS 1.2).

Run cupsaddsmb (Quiet Mode)

The cupsaddsmb command copies the needed files into your [print$] share. Additionally, the PPD associated with this printer is copied from /etc/cups/ppd/ to [print$]. There the files wait for convenient Windows client installations via Point'n'Print. Before we can run the command successfully, we need to be sure that we can authenticate toward Samba. If you have a small network, you are probably using user-level security (security = user).

Here is an example of a successfully run cupsaddsmb command:

root# cupsaddsmb -U root infotec_IS2027
Password for root required to access localhost via Samba: ['secret']

To share all printers and drivers, use the -a parameter instead of a printer name. Since cupsaddsmbexports” the printer drivers to Samba, it should be obvious that it only works for queues with a CUPS driver associated.

Run cupsaddsmb with Verbose Output

Probably you want to see what's going on. Use the -v parameter to get a more verbose output. The output below was edited for better readability: all “\” at the end of a line indicate that I inserted an artificial line break plus some indentation here:

Warning

You will see the root password for the Samba account printed on screen.

root# cupsaddsmb -U root -v infotec_2105
Password for root required to access localhost via GANDALF:
Running command: smbclient //localhost/print\$ -N -U'root%secret' \
    -c 'mkdir W32X86; \
    put /var/spool/cups/tmp/3e98bf2d333b5 W32X86/infotec_2105.ppd; \
	put /usr/share/cups/drivers/cupsdrvr.dll W32X86/cupsdrvr.dll; \
    put /usr/share/cups/drivers/cupsui.dll W32X86/cupsui.dll; \
    put /usr/share/cups/drivers/cups.hlp W32X86/cups.hlp'
added interface ip=10.160.51.60 bcast=10.160.51.255 nmask=255.255.252.0
Domain=[CUPS-PRINT] OS=[UNIX] Server=[Samba 2.2.7a]
NT_STATUS_OBJECT_NAME_COLLISION making remote directory \W32X86
putting file /var/spool/cups/tmp/3e98bf2d333b5 as \W32X86/infotec_2105.ppd
putting file /usr/share/cups/drivers/cupsdrvr.dll as \W32X86/cupsdrvr.dll
putting file /usr/share/cups/drivers/cupsui.dll as \W32X86/cupsui.dll
putting file /usr/share/cups/drivers/cups.hlp as \W32X86/cups.hlp
  
Running command: rpcclient localhost -N -U'root%secret' 
   -c 'adddriver "Windows NT x86"   \
   "infotec_2105:cupsdrvr.dll:infotec_2105.ppd:cupsui.dll:cups.hlp:NULL: \
    RAW:NULL"'
cmd = adddriver "Windows NT x86" \
   "infotec_2105:cupsdrvr.dll:infotec_2105.ppd:cupsui.dll:cups.hlp:NULL: \
	RAW:NULL"
Printer Driver infotec_2105 successfully installed.
  
Running command: smbclient //localhost/print\$ -N -U'root%secret' \
-c 'mkdir WIN40; \
    put /var/spool/cups/tmp/3e98bf2d333b5 WIN40/infotec_2105.PPD; \
	put /usr/share/cups/drivers/ADFONTS.MFM WIN40/ADFONTS.MFM;   \
    put /usr/share/cups/drivers/ADOBEPS4.DRV WIN40/ADOBEPS4.DRV; \
    put /usr/share/cups/drivers/ADOBEPS4.HLP WIN40/ADOBEPS4.HLP; \
    put /usr/share/cups/drivers/DEFPRTR2.PPD WIN40/DEFPRTR2.PPD; \
	put /usr/share/cups/drivers/ICONLIB.DLL WIN40/ICONLIB.DLL; \
	put /usr/share/cups/drivers/PSMON.DLL WIN40/PSMON.DLL;'
  added interface ip=10.160.51.60 bcast=10.160.51.255 nmask=255.255.252.0
  Domain=[CUPS-PRINT] OS=[UNIX] Server=[Samba 2.2.7a]
  NT_STATUS_OBJECT_NAME_COLLISION making remote directory \WIN40
  putting file /var/spool/cups/tmp/3e98bf2d333b5 as \WIN40/infotec_2105.PPD
  putting file /usr/share/cups/drivers/ADFONTS.MFM as \WIN40/ADFONTS.MFM
  putting file /usr/share/cups/drivers/ADOBEPS4.DRV as \WIN40/ADOBEPS4.DRV
  putting file /usr/share/cups/drivers/ADOBEPS4.HLP as \WIN40/ADOBEPS4.HLP
  putting file /usr/share/cups/drivers/DEFPRTR2.PPD as \WIN40/DEFPRTR2.PPD
  putting file /usr/share/cups/drivers/ICONLIB.DLL as \WIN40/ICONLIB.DLL
  putting file /usr/share/cups/drivers/PSMON.DLL as \WIN40/PSMON.DLL
  
  Running command: rpcclient localhost -N -U'root%secret' \
   -c 'adddriver "Windows 4.0"      \
   "infotec_2105:ADOBEPS4.DRV:infotec_2105.PPD:NULL:ADOBEPS4.HLP: \
   PSMON.DLL:RAW:ADOBEPS4.DRV,infotec_2105.PPD,ADOBEPS4.HLP,PSMON.DLL, \
    ADFONTS.MFM,DEFPRTR2.PPD,ICONLIB.DLL"'
	cmd = adddriver "Windows 4.0" "infotec_2105:ADOBEPS4.DRV:\
	infotec_2105.PPD:NULL:ADOBEPS4.HLP:PSMON.DLL:RAW:ADOBEPS4.DRV,\
	infotec_2105.PPD,ADOBEPS4.HLP,PSMON.DLL,ADFONTS.MFM,DEFPRTR2.PPD,\
	ICONLIB.DLL"
  Printer Driver infotec_2105 successfully installed.
  
  Running command: rpcclient localhost -N -U'root%secret'  \
   -c 'setdriver infotec_2105 infotec_2105'
  cmd = setdriver infotec_2105 infotec_2105
  Successfully set infotec_2105 to driver infotec_2105.

If you look closely, you'll discover your root password was transferred unencrypted over the wire, so beware! Also, if you look further, you'll discover error messages like NT_STATUS_OBJECT_NAME_COLLISION in between. They occur, because the directories WIN40 and W32X86 already existed in the [print$] driver download share (from a previous driver installation). They are harmless here.

Understanding cupsaddsmb

What has happened? What did cupsaddsmb do? There are five stages of the procedure:

  1. Call the CUPS server via IPP and request the driver files and the PPD file for the named printer.

  2. Store the files temporarily in the local TEMPDIR (as defined in cupsd.conf).

  3. Connect via smbclient to the Samba server's [print$] share and put the files into the share's WIN40 (for Windows 9x/Me) and W32X86/ (for Windows NT/200x/XP) subdirectories.

  4. Connect via rpcclient to the Samba server and execute the adddriver command with the correct parameters.

  5. Connect via rpcclient to the Samba server a second time and execute the setdriver command.

Note

You can run the cupsaddsmb utility with parameters to specify one remote host as Samba host and a second remote host as CUPS host. Especially if you want to get a deeper understanding, it is a good idea to try it and see more clearly what is going on (though in real life most people will have their CUPS and Samba servers run on the same host):

root# cupsaddsmb -H sambaserver -h cupsserver -v printer

How to Recognize If cupsaddsmb Completed Successfully

You must always check if the utility completed successfully in all fields. You need as a minimum these three messages among the output:

  1. Printer Driver infotec_2105 successfully installed. # (for the W32X86 == Windows NT/200x/XP architecture).

  2. Printer Driver infotec_2105 successfully installed. # (for the WIN40 == Windows 9x/Me architecture).

  3. Successfully set [printerXPZ] to driver [printerXYZ].

These messages are probably not easily recognized in the general output. If you run cupsaddsmb with the -a parameter (which tries to prepare all active CUPS printer drivers for download), you might miss if individual printers drivers had problems installing properly. Here a redirection of the output will help you analyze the results in retrospective.

If you get:

SetPrinter call failed!
result was WERR_ACCESS_DENIED

It means that you might have set use client driver = yes for this printer. Set it to “no” will solve the problem. Refer to man samba(5) for explanantion on use client driver.

Note

It is impossible to see any diagnostic output if you do not run cupsaddsmb in verbose mode. Therefore, we strongly recommend to not use the default quiet mode. It will hide any problems from you that might occur.

cupsaddsmb with a Samba PDC

Can't get the standard cupsaddsmb command to run on a Samba PDC? Are you asked for the password credential all over again and again and the command just will not take off at all? Try one of these variations:

root# cupsaddsmb -U MIDEARTH\\root -v printername
root# cupsaddsmb -H SAURON -U MIDEARTH\\root -v printername
root# cupsaddsmb -H SAURON -U MIDEARTH\\root -h cups-server -v printername

(Note the two backslashes: the first one is required to “escape” the second one).

cupsaddsmb Flowchart

cupsaddsmb flowchart shows a chart about the procedures, command-flows and data-flows of the cupaddsmb command. Note again: cupsaddsmb is not intended to, and does not work with, raw queues!

Figure 21.16. cupsaddsmb flowchart.

cupsaddsmb flowchart.

Installing the PostScript Driver on a Client

After cupsaddsmb is completed, your driver is prepared for the clients to use. Here are the steps you must perform to download and install it via Point'n'Print. From a Windows client, browse to the CUPS/Samba server:

  • Open the Printers share of Samba in Network Neighborhood.

  • Right-click on the printer in question.

  • From the opening context-menu select Install... or Connect... (depending on the Windows version you use).

After a few seconds, there should be a new printer in your client's local Printers folder. On Windows XP it will follow a naming convention of PrinterName on SambaServer. (In my current case it is "infotec_2105 on kde-bitshop"). If you want to test it and send your first job from an application like Winword, the new printer appears in a \\SambaServer\PrinterName entry in the drop-down list of available printers.

cupsaddsmb will only reliably work with CUPS version 1.1.15 or higher and Samba from 2.2.4. If it does not work, or if the automatic printer driver download to the clients does not succeed, you can still manually install the CUPS printer PPD on top of the Adobe PostScript driver on clients. Then point the client's printer queue to the Samba printer share for a UNC type of connection:

C:\> net use lpt1: \\sambaserver\printershare /user:ntadmin

should you desire to use the CUPS networked PostScript RIP functions. (Note that user “ntadmin” needs to be a valid Samba user with the required privileges to access the printershare.) This sets up the printer connection in the traditional LanMan way (not using MS-RPC).

Avoiding Critical PostScript Driver Settings on the Client

Printing works, but there are still problems. Most jobs print well, some do not print at all. Some jobs have problems with fonts, which do not look very good. Some jobs print fast and some are dead-slow. Many of these problems can be greatly reduced or even completely eliminated if you follow a few guidelines. Remember, if your print device is not PostScript-enabled, you are treating your Ghostscript installation on your CUPS host with the output your client driver settings produce. Treat it well:

  • Avoid the PostScript Output Option: Optimize for Speed setting. Use the Optimize for Portability instead (Adobe PostScript driver).

  • Don't use the Page Independence: NO setting. Instead, use Page Independence YES (CUPS PostScript Driver).

  • Recommended is the True Type Font Downloading Option: Native True Type over Automatic and Outline; you should by all means avoid Bitmap (Adobe PostScript Driver).

  • Choose True Type Font: Download as Softfont into Printer over the default Replace by Device Font (for exotic fonts, you may need to change it back to get a printout at all) (Adobe).

  • Sometimes you can choose PostScript Language Level: In case of problems try 2 instead of 3 (the latest ESP Ghostscript package handles Level 3 PostScript very well) (Adobe).

  • Say Yes to PostScript Error Handler (Adobe).

Installing PostScript Driver Files Manually Using rpcclient

Of course, you can run all the commands that are embedded into the cupsaddsmb convenience utility yourself, one by one, and hereby upload and prepare the driver files for future client downloads.

  1. Prepare Samba (A CUPS print queue with the name of the printer should be there. We are providing the driver now).

  2. Copy all files to [print$].

  3. Run rpcclient adddriver (for each client architecture you want to support).

  4. Run rpcclient setdriver.

We are going to do this now. First, read the man page on rpcclient to get a first idea. Look at all the printing related subcommands. enumprinters, enumdrivers, enumports, adddriver, setdriver are among the most interesting ones. rpcclient implements an important part of the MS-RPC protocol. You can use it to query (and command) a Windows NT (or 200x/XP) PC, too. MS-RPC is used by Windows clients, among other things, to benefit from the Point'n'Print features. Samba can now mimic this as well.

A Check of the rpcclient man Page

First let's check the rpcclient man page. Here are two relevant passages:

adddriver <arch> <config> Execute an AddPrinterDriver() RPC to install the printer driver information on the server. The driver files should already exist in the directory returned by getdriverdir. Possible values for arch are the same as those for the getdriverdir command. The config parameter is defined as follows:

Long Printer Name:\
Driver File Name:\
Data File Name:\
Config File Name:\
Help File Name:\
Language Monitor Name:\
Default Data Type:\
Comma Separated list of Files

Any empty fields should be enter as the string “NULL”.

Samba does not need to support the concept of Print Monitors since these only apply to local printers whose driver can make use of a bi-directional link for communication. This field should be “NULL”. On a remote NT print server, the Print Monitor for a driver must already be installed prior to adding the driver or else the RPC will fail.

setdriver <printername> <drivername> Execute a SetPrinter() command to update the printer driver associated with an installed printer. The printer driver must already be correctly installed on the print server.

See also the enumprinters and enumdrivers commands for obtaining a list of installed printers and drivers.

Understanding the rpcclient man Page

The exact format isn't made too clear by the man page, since you have to deal with some parameters containing spaces. Here is a better description for it. We have line-broken the command and indicated the breaks with “\”. Usually you would type the command in one line without the line-breaks:

 adddriver "Architecture" \
           "LongPrinterName:DriverFile:DataFile:ConfigFile:HelpFile:\
           LanguageMonitorFile:DataType:ListOfFiles,Comma-separated"

What the man pages denote as a simple <config> keyword, in reality consists of eight colon-separated fields. The last field may take multiple (in some very insane cases, even 20 different additional) files. This might sound confusing at first. What the man pages names the “LongPrinterName” in reality should be called the “Driver Name”. You can name it anything you want, as long as you use this name later in the rpcclient ... setdriver command. For practical reasons, many name the driver the same as the printer.

It isn't simple at all. I hear you asking: “How do I know which files are "Driver File”, “Data File”, “Config File”, “Help File” and “Language Monitor File" in each case?” For an answer, you may want to have a look at how a Windows NT box with a shared printer presents the files to us. Remember, that this whole procedure has to be developed by the Samba team by overhearing the traffic caused by Windows computers on the wire. We may as well turn to a Windows box now and access it from a UNIX workstation. We will query it with rpcclient to see what it tells us and try to understand the man page more clearly that we've read just now.

Producing an Example by Querying a Windows Box

We could run rpcclient with a getdriver or a getprinter subcommand (in level 3 verbosity) against it. Just sit down at a UNIX or Linux workstation with the Samba utilities installed, then type the following command:

root# rpcclient -U'user%secret' NT-SERVER -c 'getdriver printername 3'

From the result it should become clear which is which. Here is an example from my installation:

root# rpcclient -U'Danka%xxxx' W200xSERVER \
	-c'getdriver "DANKA InfoStream Virtual Printer" 3'
 cmd = getdriver "DANKA InfoStream Virtual Printer" 3

 [Windows NT x86]
 Printer Driver Info 3:
         Version: [2]
         Driver Name: [DANKA InfoStream]
         Architecture: [Windows NT x86]
         Driver Path: [C:\WINNT\System32\spool\DRIVERS\W32X86\2\PSCRIPT.DLL]
         Datafile: [C:\WINNT\System32\spool\DRIVERS\W32X86\2\INFOSTRM.PPD]
         Configfile: [C:\WINNT\System32\spool\DRIVERS\W32X86\2\PSCRPTUI.DLL]
         Helpfile: [C:\WINNT\System32\spool\DRIVERS\W32X86\2\PSCRIPT.HLP]
 
         Dependentfiles: []
         Dependentfiles: []
         Dependentfiles: []
         Dependentfiles: []
         Dependentfiles: []
         Dependentfiles: []
         Dependentfiles: []
 
         Monitorname: []
         Defaultdatatype: []

Some printer drivers list additional files under the label Dependentfiles and these would go into the last field ListOfFiles,Comma-separated. For the CUPS PostScript drivers, we do not need any (nor would we for the Adobe PostScript driver), therefore, the field will get a “NULL” entry.

Requirements for adddriver and setdriver to Succeed

>From the man page (and from the quoted output of cupsaddsmb above) it becomes clear that you need to have certain conditions in order to make the manual uploading and initializing of the driver files succeed. The two rpcclient subcommands (adddriver and setdriver) need to encounter the following preconditions to complete successfully:

  • You are connected as printer admin or root (this is not the “Printer Operators” group in NT, but the printer admin group as defined in the [global] section of smb.conf).

  • Copy all required driver files to \\SAMBA\print$\w32x86 and \\SAMBA\print$\win40 as appropriate. They will end up in the “0” respective “2” subdirectories later. For now, do not put them there, they'll be automatically used by the adddriver subcommand. (If you use smbclient to put the driver files into the share, note that you need to escape the “$”: smbclient //sambaserver/print\$ -U root.)

  • The user you're connecting as must be able to write to the [print$] share and create subdirectories.

  • The printer you are going to setup for the Windows clients needs to be installed in CUPS already.

  • The CUPS printer must be known to Samba, otherwise the setdriver subcommand fails with an NT_STATUS_UNSUCCESSFUL error. To check if the printer is known by Samba, you may use the enumprinters subcommand to rpcclient. A long-standing bug prevented a proper update of the printer list until every smbd process had received a SIGHUP or was restarted. Remember this in case you've created the CUPS printer just recently and encounter problems: try restarting Samba.

Manual Driver Installation in 15 Steps

We are going to install a printer driver now by manually executing all required commands. As this may seem a rather complicated process at first, we go through the procedure step by step, explaining every single action item as it comes up.

Procedure 21.2. Manual Driver Installation

  1. Install the printer on CUPS.

    root# lpadmin -p mysmbtstprn -v socket://10.160.51.131:9100 -E \
    			-P canonIR85.ppd
    

    This installs a printer with the name mysmbtstprn to the CUPS system. The printer is accessed via a socket (a.k.a. JetDirect or Direct TCP/IP) connection. You need to be root for this step.

  2. (Optional) Check if the printer is recognized by Samba.

    	root# rpcclient -Uroot%xxxx -c 'enumprinters' localhost \
      | grep -C2 mysmbtstprn
    flags:[0x800000]
    name:[\\kde-bitshop\mysmbtstprn]
    description:[\\kde-bitshop\mysmbtstprn,,mysmbtstprn]
    comment:[mysmbtstprn]
    

    This should show the printer in the list. If not, stop and restart the Samba daemon (smbd), or send a HUP signal:

    root# kill -HUP `pidof smbd`
    

    Check again. Troubleshoot and repeat until successful. Note the “empty” field between the two commas in the “description” line. The driver name would appear here if there was one already. You need to know root's Samba password (as set by the smbpasswd command) for this step and most of the following steps. Alternately, you can authenticate as one of the users from the “write list” as defined in smb.conf for [print$].

  3. (Optional) Check if Samba knows a driver for the printer.

    root# rpcclient -Uroot%xxxx -c 'getprinter mysmbtstprn 2' localhost \
    			| grep driver 
    drivername:[]
    
    root# rpcclient -Uroot%xxxx -c 'getprinter mysmbtstprn 2' localhost \
    	| grep -C4 driv
    servername:[\\kde-bitshop]
    printername:[\\kde-bitshop\mysmbtstprn]
    sharename:[mysmbtstprn]
    portname:[Samba Printer Port]
    drivername:[]
    comment:[mysmbtstprn]
    location:[]
    sepfile:[]
    printprocessor:[winprint]
     
    root# rpcclient -U root%xxxx -c 'getdriver mysmbtstprn' localhost
     result was WERR_UNKNOWN_PRINTER_DRIVER
    
    

    None of the three commands shown above should show a driver. This step was done for the purpose of demonstrating this condition. An attempt to connect to the printer at this stage will prompt the message along the lines of: “The server does not have the required printer driver installed.

  4. Put all required driver files into Samba's [print$].

    root# smbclient //localhost/print\$ -U 'root%xxxx' \
    	-c 'cd W32X86; \
    	put /etc/cups/ppd/mysmbtstprn.ppd mysmbtstprn.PPD; \ 
    	put /usr/share/cups/drivers/cupsui.dll cupsui.dll; \
    	put /usr/share/cups/drivers/cupsdrvr.dll cupsdrvr.dll; \
    	put /usr/share/cups/drivers/cups.hlp cups.hlp'
    

    (This command should be entered in one long single line. Line-breaks and the line-end indicated by “\” have been inserted for readability reasons.) This step is required for the next one to succeed. It makes the driver files physically present in the [print$] share. However, clients would still not be able to install them, because Samba does not yet treat them as driver files. A client asking for the driver would still be presented with a “not installed here” message.

  5. Verify where the driver files are now.

    root# ls -l /etc/samba/drivers/W32X86/
    total 669
    drwxr-sr-x    2 root     ntadmin       532 May 25 23:08 2
    drwxr-sr-x    2 root     ntadmin       670 May 16 03:15 3
    -rwxr--r--    1 root     ntadmin     14234 May 25 23:21 cups.hlp
    -rwxr--r--    1 root     ntadmin    278380 May 25 23:21 cupsdrvr.dll
    -rwxr--r--    1 root     ntadmin    215848 May 25 23:21 cupsui.dll
    -rwxr--r--    1 root     ntadmin    169458 May 25 23:21 mysmbtstprn.PPD
    

    The driver files now are in the W32X86 architecture “root” of [print$].

  6. Tell Samba that these are driver files (adddriver).

    root# rpcclient -Uroot%xxxx -c 'adddriver "Windows NT x86" \
    	"mydrivername:cupsdrvr.dll:mysmbtstprn.PPD: \
      cupsui.dll:cups.hlp:NULL:RAW:NULL"' \
      localhost
    Printer Driver mydrivername successfully installed.
    

    You cannot repeat this step if it fails. It could fail even as a result of a simple typo. It will most likely have moved a part of the driver files into the “2” subdirectory. If this step fails, you need to go back to the fourth step and repeat it before you can try this one again. In this step, you need to choose a name for your driver. It is normally a good idea to use the same name as is used for the printer name; however, in big installations you may use this driver for a number of printers that obviously have different names, so the name of the driver is not fixed.

  7. Verify where the driver files are now.

    root# ls -l /etc/samba/drivers/W32X86/
    total 1
    drwxr-sr-x    2 root     ntadmin       532 May 25 23:22 2
    drwxr-sr-x    2 root     ntadmin       670 May 16 03:15 3
    
    root# ls -l /etc/samba/drivers/W32X86/2
    total 5039
    [....]
    -rwxr--r--    1 root     ntadmin     14234 May 25 23:21 cups.hlp
    -rwxr--r--    1 root     ntadmin    278380 May 13 13:53 cupsdrvr.dll
    -rwxr--r--    1 root     ntadmin    215848 May 13 13:53 cupsui.dll
    -rwxr--r--    1 root     ntadmin    169458 May 25 23:21 mysmbtstprn.PPD
    

    Notice how step 6 also moved the driver files to the appropriate subdirectory. Compare this with the situation after step 5.

  8. (Optional) Verify if Samba now recognizes the driver.

    root# rpcclient -Uroot%xxxx -c 'enumdrivers 3' \
    	localhost | grep -B2 -A5 mydrivername
    Printer Driver Info 3:
    Version: [2]
    Driver Name: [mydrivername]
    Architecture: [Windows NT x86]
    Driver Path: [\\kde-bitshop\print$\W32X86\2\cupsdrvr.dll]
    Datafile: [\\kde-bitshop\print$\W32X86\2\mysmbtstprn.PPD]
    Configfile: [\\kde-bitshop\print$\W32X86\2\cupsui.dll]
    Helpfile: [\\kde-bitshop\print$\W32X86\2\cups.hlp]
    

    Remember, this command greps for the name you chose for the driver in step 6. This command must succeed before you can proceed.

  9. Tell Samba which printer should use these driver files (setdriver).

    root# rpcclient -Uroot%xxxx -c 'setdriver mysmbtstprn mydrivername' \
    	localhost
    Successfully set mysmbtstprn to driver mydrivername
    

    Since you can bind any printername (print queue) to any driver, this is a convenient way to setup many queues that use the same driver. You do not need to repeat all the previous steps for the setdriver command to succeed. The only preconditions are: enumdrivers must find the driver and enumprinters must find the printer.

  10. (Optional) Verify if Samba has recognized this association.

    root# rpcclient -Uroot%xxxx -c 'getprinter mysmbtstprn 2' localhost \
      | grep driver
    drivername:[mydrivername]
     
    root# rpcclient -Uroot%xxxx -c 'getprinter mysmbtstprn 2' localhost \
      | grep -C4 driv
    servername:[\\kde-bitshop]
    printername:[\\kde-bitshop\mysmbtstprn]
    sharename:[mysmbtstprn]
    portname:[Done]
    drivername:[mydrivername]
    comment:[mysmbtstprn]
    location:[]
    sepfile:[]
    printprocessor:[winprint]
     
    root# rpcclient -U root%xxxx -c 'getdriver mysmbtstprn' localhost
    [Windows NT x86]
    Printer Driver Info 3:
         Version: [2]
         Driver Name: [mydrivername]
         Architecture: [Windows NT x86]
         Driver Path: [\\kde-bitshop\print$\W32X86\2\cupsdrvr.dll]
         Datafile: [\\kde-bitshop\print$\W32X86\2\mysmbtstprn.PPD]
         Configfile: [\\kde-bitshop\print$\W32X86\2\cupsui.dll]
         Helpfile: [\\kde-bitshop\print$\W32X86\2\cups.hlp]
         Monitorname: []
         Defaultdatatype: [RAW]
         Monitorname: []
         Defaultdatatype: [RAW]
     
    root# rpcclient -Uroot%xxxx -c 'enumprinters' localhost \
    	| grep mysmbtstprn
         name:[\\kde-bitshop\mysmbtstprn]
         description:[\\kde-bitshop\mysmbtstprn,mydrivername,mysmbtstprn]
         comment:[mysmbtstprn]
    
    

    Compare these results with the ones from steps 2 and 3. Every one of these commands show the driver is installed. Even the enumprinters command now lists the driver on the “description” line.

  11. (Optional) Tickle the driver into a correct device mode.

    You certainly know how to install the driver on the client. In case you are not particularly familiar with Windows, here is a short recipe: Browse the Network Neighborhood, go to the Samba server, and look for the shares. You should see all shared Samba printers. Double-click on the one in question. The driver should get installed and the network connection set up. An alternate way is to open the Printers (and Faxes) folder, right-click on the printer in question and select Connect or Install. As a result, a new printer should have appeared in your client's local Printers (and Faxes) folder, named something like printersharename on Sambahostname.

    It is important that you execute this step as a Samba printer admin (as defined in smb.conf). Here is another method to do this on Windows XP. It uses a command line, which you may type into the “DOS box” (type root's smbpassword when prompted):

    C:\> runas /netonly /user:root "rundll32 printui.dll,PrintUIEntry \
    	/in /n \\sambaserver\mysmbtstprn"
    

    Change any printer setting once (like changing portrait to landscape), click on Apply; change the setting back.

  12. Install the printer on a client (Point'n'Print).

    C:\> rundll32 printui.dll,PrintUIEntry /in /n "\\sambaserver\mysmbtstprn"
    

    If it does not work it could be a permission problem with the [print$] share.

  13. (Optional) Print a test page.

    C:\> rundll32 printui.dll,PrintUIEntry /p /n "\\sambaserver\mysmbtstprn"
    

    Then hit [TAB] five times, [ENTER] twice, [TAB] once and [ENTER] again and march to the printer.

  14. (Recommended) Study the test page.

    Hmmm.... just kidding! By now you know everything about printer installations and you do not need to read a word. Just put it in a frame and bolt it to the wall with the heading "MY FIRST RPCCLIENT-INSTALLED PRINTER" why not just throw it away!

  15. (Obligatory) Enjoy. Jump. Celebrate your success.

    root# echo "Cheeeeerioooooo! Success..." >> /var/log/samba/log.smbd
    

Troubleshooting Revisited

The setdriver command will fail, if in Samba's mind the queue is not already there. You had promising messages about the:

 Printer Driver ABC successfully installed.

after the adddriver parts of the procedure? But you are also seeing a disappointing message like this one?

result was NT_STATUS_UNSUCCESSFUL

It is not good enough that you can see the queue in CUPS, using the lpstat -p ir85wm command. A bug in most recent versions of Samba prevents the proper update of the queue-list. The recognition of newly installed CUPS printers fails unless you restart Samba or send a HUP to all smbd processes. To verify if this is the reason why Samba does not execute the setdriver command successfully, check if Samba “sees” the printer:

root# rpcclient transmeta -N -U'root%xxxx' -c 'enumprinters 0'|grep ir85wm
        printername:[ir85wm]

An alternate command could be this:

root# rpcclient transmeta -N -U'root%secret' -c 'getprinter ir85wm' 
        cmd = getprinter ir85wm
        flags:[0x800000]
        name:[\\transmeta\ir85wm]
        description:[\\transmeta\ir85wm,ir85wm,DPD]
        comment:[CUPS PostScript-Treiber for Windows NT/200x/XP]

By the way, you can use these commands, plus a few more, of course, to install drivers on remote Windows NT print servers too!

The Printing *.tdb Files

Some mystery is associated with the series of files with a tdb suffix appearing in every Samba installation. They are connections.tdb, printing.tdb, share_info.tdb, ntdrivers.tdb, unexpected.tdb, brlock.tdb, locking.tdb, ntforms.tdb, messages.tdb , ntprinters.tdb, sessionid.tdb and secrets.tdb. What is their purpose?

Trivial Database Files

A Windows NT (print) server keeps track of all information needed to serve its duty toward its clients by storing entries in the Windows registry. Client queries are answered by reading from the registry, Administrator or user configuration settings that are saved by writing into the registry. Samba and UNIX obviously do not have such a Registry. Samba instead keeps track of all client related information in a series of *.tdb files. (TDB = Trivial Data Base). These are often located in /var/lib/samba/ or /var/lock/samba/. The printing related files are ntprinters.tdb, printing.tdb,ntforms.tdb and ntdrivers.tdb.

Binary Format

*.tdb files are not human readable. They are written in a binary format. “Why not ASCII?”, you may ask. “After all, ASCII configuration files are a good and proven tradition on UNIX.” The reason for this design decision by the Samba team is mainly performance. Samba needs to be fast; it runs a separate smbd process for each client connection, in some environments many thousands of them. Some of these smbds might need to write-access the same *.tdb file at the same time. The file format of Samba's *.tdb files allows for this provision. Many smbd processes may write to the same *.tdb file at the same time. This wouldn't be possible with pure ASCII files.

Losing *.tdb Files

It is very important that all *.tdb files remain consistent over all write and read accesses. However, it may happen that these files do get corrupted. (A kill -9 `pidof smbd' while a write access is in progress could do the damage as well as a power interruption, etc.). In cases of trouble, a deletion of the old printing-related *.tdb files may be the only option. After that you need to re-create all print-related setup or you have made a backup of the *.tdb files in time.

Using tdbbackup

Samba ships with a little utility that helps the root user of your system to backup your *.tdb files. If you run it with no argument, it prints a usage message:

root# tdbbackup
 Usage: tdbbackup [options] <fname...>
 
 Version:3.0a
   -h            this help message
   -s suffix     set the backup suffix
   -v            verify mode (restore if corrupt)

Here is how I backed up my printing.tdb file:

root# ls
.              browse.dat     locking.tdb     ntdrivers.tdb printing.tdb
..             share_info.tdb connections.tdb messages.tdb  ntforms.tdb
printing.tdbkp unexpected.tdb brlock.tdb      gmon.out      namelist.debug  
ntprinters.tdb sessionid.tdb
 
root# tdbbackup -s .bak printing.tdb
 printing.tdb : 135 records
 
root# ls -l printing.tdb*
 -rw-------    1 root     root        40960 May  2 03:44 printing.tdb
 -rw-------    1 root     root        40960 May  2 03:44 printing.tdb.bak

CUPS Print Drivers from Linuxprinting.org

CUPS ships with good support for HP LaserJet-type printers. You can install the generic driver as follows:

root# lpadmin -p laserjet4plus -v parallel:/dev/lp0 -E -m laserjet.ppd

The -m switch will retrieve the laserjet.ppd from the standard repository for not-yet-installed-PPDs, which CUPS typically stores in /usr/share/cups/model. Alternately, you may use -P /path/to/your.ppd.

The generic laserjet.ppd, however, does not support every special option for every LaserJet-compatible model. It constitutes a sort of “least common denominator” of all the models. If for some reason you must pay for the commercially available ESP Print Pro drivers, your first move should be to consult the database on the Linuxprinting web site. Linuxprinting.org has excellent recommendations about which driver is best used for each printer. Its database is kept current by the tireless work of Till Kamppeter from MandrakeSoft, who is also the principal author of the foomatic-rip utility.

Note

The former cupsomatic concept is now being replaced by the new successor, a much more powerful foomatic-rip. cupsomatic is no longer maintained. Here is the new URL to the Foomatic-3.0 database. If you upgrade to foomatic-rip, remember to also upgrade to the new-style PPDs for your Foomatic-driven printers. foomatic-rip will not work with PPDs generated for the old cupsomatic. The new-style PPDs are 100% compliant to the Adobe PPD specification. They are also intended to be used by Samba and the cupsaddsmb utility, to provide the driver files for the Windows clients!

foomatic-rip and Foomatic Explained

Nowadays, most Linux distributions rely on the utilities of Linuxprinting.org to create their printing-related software (which, by the way, works on all UNIXes and on Mac OS X or Darwin, too). It is not known as well as it should be, that it also has a very end-user-friendly interface that allows for an easy update of drivers and PPDs for all supported models, all spoolers, all operating systems, and all package formats (because there is none). Its history goes back a few years.

Recently, Foomatic has achieved the astonishing milestone of 1000 listed printer models. Linuxprinting.org keeps all the important facts about printer drivers, supported models and which options are available for the various driver/printer combinations in its Foomatic database. Currently there are 245 drivers in the database. Many drivers support various models, and many models may be driven by different drivers its your choice!

690 “Perfect” Printers

At present, there are 690 devices dubbed as working perfectly, 181 mostly, 96 partially, and 46 are paperweights. Keeping in mind that most of these are non-PostScript models (PostScript printers are automatically supported by CUPS to perfection, by using their own manufacturer-provided Windows-PPD), and that a multi-functional device never qualifies as working perfectly if it does not also scan and copy and fax under GNU/Linux then this is a truly astonishing achievement! Three years ago the number was not more than 500, and Linux or UNIX printing at the time wasn't anywhere near the quality it is today.

How the Printing HOWTO Started It All

A few years ago Grant Taylor started it all. The roots of today's Linuxprinting.org are in the first Linux Printing HOWTO that he authored. As a side-project to this document, which served many Linux users and Admins to guide their first steps in this complicated and delicate setup (to a scientist, printing is “applying a structured deposition of distinct patterns of ink or toner particles on paper substrates”, he started to build in a little Postgres database with information about the hardware and driver zoo that made up Linux printing of the time. This database became the core component of today's Foomatic collection of tools and data. In the meantime, it has moved to an XML representation of the data.

Foomatic's Strange Name

Why the funny name?” you ask. When it really took off, around spring 2000, CUPS was far less popular than today, and most systems used LPD, LPRng or even PDQ to print. CUPS shipped with a few generic drivers (good for a few hundred different printer models). These didn't support many device-specific options. CUPS also shipped with its own built-in rasterization filter (pstoraster, derived from Ghostscript). On the other hand, CUPS provided brilliant support for controlling all printer options through standardized and well-defined PPD files (PostScript Printers Description files). Plus, CUPS was designed to be easily extensible.

Taylor already had in his database a respectable compilation of facts about many more printers and the Ghostscript “drivers” they run with. His idea, to generate PPDs from the database information and use them to make standard Ghostscript filters work within CUPS, proved to work very well. It also killed several birds with one stone:

  • It made all current and future Ghostscript filter developments available for CUPS.

  • It made available a lot of additional printer models to CUPS users (because often the traditional Ghostscript way of printing was the only one available).

  • It gave all the advanced CUPS options (Web interface, GUI driver configurations) to users wanting (or needing) to use Ghostscript filters.

cupsomatic, pdqomatic, lpdomatic, directomatic

CUPS worked through a quickly-hacked up filter script named cupsomatic. cupsomatic ran the printfile through Ghostscript, constructing automatically the rather complicated command line needed. It just needed to be copied into the CUPS system to make it work. To configure the way cupsomatic controls the Ghostscript rendering process, it needs a CUPS-PPD. This PPD is generated directly from the contents of the database. For CUPS and the respective printer/filter combo, another Perl script named CUPS-O-Matic did the PPD generation. After that was working, Taylor implemented within a few days a similar thing for two other spoolers. Names chosen for the config-generator scripts were PDQ-O-Matic (for PDQ) and LPD-O-Matic (for you guessed it LPD); the configuration here didn't use PPDs but other spooler-specific files.

From late summer of that year, Till Kamppeter started to put work into the database. Kamppeter had been newly employed by MandrakeSoft to convert its printing system over to CUPS, after they had seen his FLTK-based XPP (a GUI front-end to the CUPS lp-command). He added a huge amount of new information and new printers. He also developed the support for other spoolers, like PPR (via ppromatic), GNUlpr and LPRng (both via an extended lpdomatic) and spooler-less printing (directomatic).

So, to answer your question: “Foomatic” is the general name for all the overlapping code and data behind the “*omatic” scripts. Foomatic, up to versions 2.0.x, required (ugly) Perl data structures attached to Linuxprinting.org PPDs for CUPS. It had a different “*omatic” script for every spooler, as well as different printer configuration files.

The Grand Unification Achieved

This has all changed in Foomatic versions 2.9 (beta) and released as “stable” 3.0. It has now achieved the convergence of all *omatic scripts and is called the foomatic-rip. This single script is the unification of the previously different spooler-specific *omatic scripts. foomatic-rip is used by all the different spoolers alike and because it can read PPDs (both the original PostScript printer PPDs and the Linuxprinting.org-generated ones), all of a sudden all supported spoolers can have the power of PPDs at their disposal. Users only need to plug foomatic-rip into their system. For users there is improved media type and source support paper sizes and trays are easier to configure.

Also, the New Generation of Linuxprinting.org PPDs no longer contains Perl data structures. If you are a distro maintainer and have used the previous version of Foomatic, you may want to give the new one a spin, but remember to generate a new-version set of PPDs via the new foomatic-db-engine! Individual users just need to generate a single new PPD specific to their model by following the steps outlined in the Foomatic tutorial or in this chapter. This new development is truly amazing.

foomatic-rip is a very clever wrapper around the need to run Ghostscript with a different syntax, options, device selections, and/or filters for each different printer or spooler. At the same time it can read the PPD associated with a print queue and modify the print job according to the user selections. Together with this comes the 100% compliance of the new Foomatic PPDs with the Adobe spec. Some innovative features of the Foomatic concept may surprise users. It will support custom paper sizes for many printers and will support printing on media drawn from different paper trays within the same job (in both cases, even where there is no support for this from Windows-based vendor printer drivers).

Driver Development Outside

Most driver development itself does not happen within Linuxprinting.org. Drivers are written by independent maintainers. Linuxprinting.org just pools all the information and stores it in its database. In addition, it also provides the Foomatic glue to integrate the many drivers into any modern (or legacy) printing system known to the world.

Speaking of the different driver development groups, most of the work is currently done in three projects. These are:

  • Omni a free software project by IBM that tries to convert their printer driver knowledge from good-ol' OS/2 times into a modern, modular, universal driver architecture for Linux/UNIX (still beta). This currently supports 437 models.

  • HPIJS a free software project by HP to provide the support for their own range of models (very mature, printing in most cases is perfect and provides true photo quality). This currently supports 369 models.

  • Gimp-Print a free software effort, started by Michael Sweet (also lead developer for CUPS), now directed by Robert Krawitz, which has achieved an amazing level of photo print quality (many Epson users swear that its quality is better than the vendor drivers provided by Epson for the Microsoft platforms). This currently supports 522 models.

Forums, Downloads, Tutorials, Howtos also for Mac OS X and Commercial UNIX

Linuxprinting.org today is the one-stop shop to download printer drivers. Look for printer information and tutorials or solve printing problems in its popular forums. This forum it's not just for GNU/Linux users, but admins of commercial UNIX systems are also going there, and the relatively new Mac OS X forum has turned out to be one of the most frequented forums after only a few weeks.

Linuxprinting.org and the Foomatic driver wrappers around Ghostscript are now a standard tool-chain for printing on all the important distros. Most of them also have CUPS underneath. While in recent years most printer data had been added by Kamppeter (who works at Mandrake), many additional contributions came from engineers with SuSE, Red Hat, Conectiva, Debian, and others. Vendor-neutrality is an important goal of the Foomatic project.

Note

Till Kamppeter from MandrakeSoft is doing an excellent job in his spare time to maintain Linuxprinting.org and Foomatic. So if you use it often, please send him a note showing your appreciation.

Foomatic Database-Generated PPDs

The Foomatic database is an amazing piece of ingenuity in itself. Not only does it keep the printer and driver information, but it is organized in a way that it can generate PPD files on the fly from its internal XML-based datasets. While these PPDs are modeled to the Adobe specification of PostScript Printer Descriptions (PPDs), the Linuxprinting.org/Foomatic-PPDs do not normally drive PostScript printers. They are used to describe all the bells and whistles you could ring or blow on an Epson Stylus inkjet, or a HP Photosmart, or what-have-you. The main trick is one little additional line, not envisaged by the PPD specification, starting with the *cupsFilter keyword. It tells the CUPS daemon how to proceed with the PostScript print file (old-style Foomatic-PPDs named the cupsomatic filter script, while the new-style PPDs are now call foomatic-rip). This filter script calls Ghostscript on the host system (the recommended variant is ESP Ghostscript) to do the rendering work. foomatic-rip knows which filter or internal device setting it should ask from Ghostscript to convert the PostScript print job into a raster format ready for the target device. This usage of PPDs to describe the options of non-PS printers was the invention of the CUPS developers. The rest is easy. GUI tools (like KDE's marvelous kprinter, or the GNOME gtklp, xpp and the CUPS Web interface) read the PPD as well and use this information to present the available settings to the user as an intuitive menu selection.

foomatic-rip and Foomatic-PPD Download and Installation

Here are the steps to install a foomatic-rip driven LaserJet 4 Plus-compatible printer in CUPS (note that recent distributions of SuSE, UnitedLinux and Mandrake may ship with a complete package of Foomatic-PPDs plus the foomatic-rip utility. Going directly to Linuxprinting.org ensures that you get the latest driver/PPD files):

  • Open your browser at the Linuxprinting.org printer listpage.

  • Check the complete list of printers in the database..

  • Select your model and click on the link.

  • You'll arrive at a page listing all drivers working with this model (for all printers, there will always be one recommended driver. Try this one first).

  • In our case (HP LaserJet 4 Plus), we'll arrive at the default driver for the HP-LaserJet 4 Plus.

  • The recommended driver is ljet4.

  • Several links are provided here. You should visit them all if you are not familiar with the Linuxprinting.org database.

  • There is a link to the database page for the ljet4. On the driver's page, you'll find important and detailed information about how to use that driver within the various available spoolers.

  • Another link may lead you to the home-page of the driver author or the driver.

  • Important links are the ones that provide hints with setup instructions for CUPS, PDQ, LPD, LPRng and GNUlpr) as well as PPR or “spooler-lessprinting.

  • You can view the PPD in your browser through this link: http://www.linuxprinting.org/ppd-o-matic.cgi?driver=ljet4&printer=HP-LaserJet_4_Plus&show=1

  • Most importantly, you can also generate and download the PPD.

  • The PPD contains all the information needed to use our model and the driver; once installed, this works transparently for the user. Later you'll only need to choose resolution, paper size, and so on from the Web-based menu, or from the print dialog GUI, or from the command line.

  • If you ended up on the drivers page you can choose to use the “PPD-O-Matic” online PPD generator program.

  • Select the exact model and check either Download or Display PPD file and click Generate PPD file.

  • If you save the PPD file from the browser view, please do not use cut and paste (since it could possibly damage line endings and tabs, which makes the PPD likely to fail its duty), but use Save as... in your browsers menu. (It is best to use the Download option directly from the Web page).

  • Another interesting part on each driver page is the Show execution details button. If you select your printer model and click on that button, a complete Ghostscript command line will be displayed, enumerating all options available for that combination of driver and printer model. This is a great way to “learn Ghostscript by doing”. It is also an excellent cheat sheet for all experienced users who need to re-construct a good command line for that damn printing script, but can't remember the exact syntax.

  • Some time during your visit to Linuxprinting.org, save the PPD to a suitable place on your hard-disk, say /path/to/my-printer.ppd (if you prefer to install your printers with the help of the CUPS Web interface, save the PPD to the /usr/share/cups/model/ path and restart cupsd).

  • Then install the printer with a suitable command line, like this:

    root# lpadmin -p laserjet4plus -v parallel:/dev/lp0 -E \
    	-P path/to/my-printer.ppd
    
  • For all the new-style “Foomatic-PPDs” from Linuxprinting.org, you also need a special CUPS filter named foomatic-rip.

  • The foomatic-rip Perl script itself also makes some interesting reading because it is well documented by Kamppeter's in-line comments (even non-Perl hackers will learn quite a bit about printing by reading it).

  • Save foomatic-rip either directly in /usr/lib/cups/filter/foomatic-rip or somewhere in your $PATH (and remember to make it world-executable). Again, do not save by copy and paste but use the appropriate link or the Save as... menu item in your browser.

  • If you save foomatic-rip in your $PATH, create a symlink:

    root# cd /usr/lib/cups/filter/ ; ln -s `which foomatic-rip'
    

    CUPS will discover this new available filter at startup after restarting cupsd.

Once you print to a print queue set up with the Foomatic-PPD, CUPS will insert the appropriate commands and comments into the resulting PostScript jobfile. foomatic-rip is able to read and act upon these and uses some specially encoded Foomatic comments embedded in the jobfile. These in turn are used to construct (transparently for you, the user) the complicated Ghostscript command line telling the printer driver exactly how the resulting raster data should look and which printer commands to embed into the data stream. You need:

  • A “foomatic+something” PPD but this is not enough to print with CUPS (it is only one important component).

  • The foomatic-rip filter script (Perl) in /usr/lib/cups/filters/.

  • Perl to make foomatic-rip run.

  • Ghostscript (because it is doing the main work, controlled by the PPD/foomatic-rip combo) to produce the raster data fit for your printer model's consumption.

  • Ghostscript must (depending on the driver/model) contain support for a certain device representing the selected driver for your model (as shown by gs -h).

  • foomatic-rip needs a new version of PPDs (PPD versions produced for cupsomatic do not work with foomatic-rip).

Page Accounting with CUPS

Often there are questions regarding print quotas where Samba users (that is, Windows clients) should not be able to print beyond a certain number of pages or data volume per day, week or month. This feature is dependent on the real print subsystem you're using. Samba's part is always to receive the job files from the clients (filtered or unfiltered) and hand it over to this printing subsystem.

Of course one could hack things with one's own scripts. But then there is CUPS. CUPS supports quotas that can be based on the size of jobs or on the number of pages or both, and span any time period you want.

Setting Up Quotas

This is an example command of how root would set a print quota in CUPS, assuming an existing printer named “quotaprinter”:

root# lpadmin -p quotaprinter -o job-quota-period=604800 \
	-o job-k-limit=1024 -o job-page-limit=100

This would limit every single user to print 100 pages or 1024 KB of data (whichever comes first) within the last 604,800 seconds ( = 1 week).

Correct and Incorrect Accounting

For CUPS to count correctly, the printfile needs to pass the CUPS pstops filter, otherwise it uses a dummy count of “one”. Some print files do not pass it (e.g., image files) but then those are mostly one- page jobs anyway. This also means that proprietary drivers for the target printer running on the client computers and CUPS/Samba, which then spool these files as “raw” (i.e., leaving them untouched, not filtering them), will be counted as one-pagers too!

You need to send PostScript from the clients (i.e., run a PostScript driver there) to have the chance to get accounting done. If the printer is a non-PostScript model, you need to let CUPS do the job to convert the file to a print-ready format for the target printer. This is currently working for about a thousand different printer models. Linuxprinting has a driver list.

Adobe and CUPS PostScript Drivers for Windows Clients

Before CUPS 1.1.16, your only option was to use the Adobe PostScript Driver on the Windows clients. The output of this driver was not always passed through the pstops filter on the CUPS/Samba side, and therefore was not counted correctly (the reason is that it often, depending on the PPD being used, wrote a PJL-header in front of the real PostScript which caused CUPS to skip pstops and go directly to the pstoraster stage).

From CUPS 1.1.16 onward, you can use the CUPS PostScript Driver for Windows NT/200x/XP clients (which is tagged in the download area of http://www.cups.org/ as the cups-samba-1.1.16.tar.gz package). It does not work for Windows 9x/ME clients, but it guarantees:

  • To not write a PJL-header.

  • To still read and support all PJL-options named in the driver PPD with its own means.

  • That the file will pass through the pstops filter on the CUPS/Samba server.

  • To page-count correctly the print file.

You can read more about the setup of this combination in the man page for cupsaddsmb (which is only present with CUPS installed, and only current from CUPS 1.1.16).

The page_log File Syntax

These are the items CUPS logs in the page_log for every page of a job:

  • Printer name

  • User name

  • Job ID

  • Time of printing

  • The page number

  • The number of copies

  • A billing information string (optional)

  • The host that sent the job (included since version 1.1.19)

Here is an extract of my CUPS server's page_log file to illustrate the format and included items:

tec_IS2027 kurt 401 [22/Apr/2003:10:28:43 +0100] 1 3 #marketing 10.160.50.13
tec_IS2027 kurt 401 [22/Apr/2003:10:28:43 +0100] 2 3 #marketing 10.160.50.13
tec_IS2027 kurt 401 [22/Apr/2003:10:28:43 +0100] 3 3 #marketing 10.160.50.13
tec_IS2027 kurt 401 [22/Apr/2003:10:28:43 +0100] 4 3 #marketing 10.160.50.13
Dig9110 boss 402 [22/Apr/2003:10:33:22 +0100] 1 440 finance-dep 10.160.51.33

This was job ID 401, printed on tec_IS2027 by user kurt, a 64-page job printed in three copies and billed to #marketing, sent from IP address 10.160.50.13. The next job had ID 402, was sent by user boss from IP address 10.160.51.33, printed from one page 440 copies and is set to be billed to finance-dep.

Possible Shortcomings

What flaws or shortcomings are there with this quota system?

  • The ones named above (wrongly logged job in case of printer hardware failure, and so on).

  • In reality, CUPS counts the job pages that are being processed in software (that is, going through the RIP) rather than the physical sheets successfully leaving the printing device. Thus if there is a jam while printing the fifth sheet out of a thousand and the job is aborted by the printer, the page count will still show the figure of a thousand for that job.

  • All quotas are the same for all users (no flexibility to give the boss a higher quota than the clerk) and no support for groups.

  • No means to read out the current balance or the “used-up” number of current quota.

  • A user having used up 99 sheets of a 100 quota will still be able to send and print a thousand sheet job.

  • A user being denied a job because of a filled-up quota does not get a meaningful error message from CUPS other than “client-error-not-possible”.

Future Developments

This is the best system currently available, and there are huge improvements under development for CUPS 1.2:

  • Page counting will go into the backends (these talk directly to the printer and will increase the count in sync with the actual printing process; thus, a jam at the fifth sheet will lead to a stop in the counting).

  • Quotas will be handled more flexibly.

  • Probably there will be support for users to inquire about their accounts in advance.

  • Probably there will be support for some other tools around this topic.

Additional Material

A printer queue with no PPD associated to it is a “raw” printer and all files will go directly there as received by the spooler. The exceptions are file types application/octet-stream that need pass-through feature enabled. “Raw” queues do not do any filtering at all, they hand the file directly to the CUPS backend. This backend is responsible for sending the data to the device (as in the “device URI” notation: lpd://, socket://, smb://, ipp://, http://, parallel:/, serial:/, usb:/, and so on).

cupsomatic/Foomatic are not native CUPS drivers and they do not ship with CUPS. They are a third party add-on developed at Linuxprinting.org. As such, they are a brilliant hack to make all models (driven by Ghostscript drivers/filters in traditional spoolers) also work via CUPS, with the same (good or bad!) quality as in these other spoolers. cupsomatic is only a vehicle to execute a Ghostscript command-line at that stage in the CUPS filtering chain, where normally the native CUPS pstoraster filter would kick in. cupsomatic bypasses pstoraster, kidnaps the printfile from CUPS away and redirects it to go through Ghostscript. CUPS accepts this, because the associated cupsomatic/foomatic-PPD specifies:

  *cupsFilter:  "application/vnd.cups-postscript 0 cupsomatic"

This line persuades CUPS to hand the file to cupsomatic, once it has successfully converted it to the MIME type application/vnd.cups-postscript. This conversion will not happen for Jobs arriving from Windows that are auto-typed application/octet-stream, with the according changes in /etc/cups/mime.types in place.

CUPS is widely configurable and flexible, even regarding its filtering mechanism. Another workaround in some situations would be to have in /etc/cups/mime.types entries as follows:

 application/postscript           application/vnd.cups-raw  0  -
 application/vnd.cups-postscript  application/vnd.cups-raw  0  -

This would prevent all PostScript files from being filtered (rather, they will through the virtual nullfilter denoted with “-”). This could only be useful for PS printers. If you want to print PS code on non-PS printers (provided they support ASCII text printing), an entry as follows could be useful:

 */*           application/vnd.cups-raw  0  -

and would effectively send all files to the backend without further processing.

You could have the following entry:

application/vnd.cups-postscript application/vnd.cups-raw 0 \
	my_PJL_stripping_filter

You will need to write a my_PJL_stripping_filter (which could be a shell script) that parses the PostScript and removes the unwanted PJL. This needs to conform to CUPS filter design (mainly, receive and pass the parameters printername, job-id, username, jobtitle, copies, print options and possibly the filename). It is installed as world executable into /usr/lib/cups/filters/ and is called by CUPS if it encounters a MIME type application/vnd.cups-postscript.

CUPS can handle -o job-hold-until=indefinite. This keeps the job in the queue on hold. It will only be printed upon manual release by the printer operator. This is a requirement in many central reproduction departments, where a few operators manage the jobs of hundreds of users on some big machine, where no user is allowed to have direct access (such as when the operators often need to load the proper paper type before running the 10,000 page job requested by marketing for the mailing, and so on).

Auto-Deletion or Preservation of CUPS Spool Files

Samba print files pass through two spool directories. One is the incoming directory managed by Samba, (set in the path = /var/spool/samba directive in the [printers] section of smb.conf). The other is the spool directory of your UNIX print subsystem. For CUPS it is normally /var/spool/cups/, as set by the cupsd.conf directive RequestRoot /var/spool/cups.

CUPS Configuration Settings Explained

Some important parameter settings in the CUPS configuration file cupsd.conf are:

PreserveJobHistory Yes

This keeps some details of jobs in cupsd's mind (well it keeps the c12345, c12346, and so on, files in the CUPS spool directory, which do a similar job as the old-fashioned BSD-LPD control files). This is set to “Yes” as a default.

PreserveJobFiles Yes

This keeps the job files themselves in cupsd's mind (it keeps the d12345, d12346 etc. files in the CUPS spool directory). This is set to “No” as the CUPS default.

MaxJobs 500

This directive controls the maximum number of jobs that are kept in memory. Once the number of jobs reaches the limit, the oldest completed job is automatically purged from the system to make room for the new one. If all of the known jobs are still pending or active, then the new job will be rejected. Setting the maximum to 0 disables this functionality. The default setting is 0.

(There are also additional settings for MaxJobsPerUser and MaxJobsPerPrinter...)

Pre-Conditions

For everything to work as announced, you need to have three things:

  • A Samba-smbd that is compiled against libcups (check on Linux by running ldd `which smbd').

  • A Samba-smb.conf setting of printing = cups.

  • Another Samba-smb.conf setting of printcap = cups.

Note

In this case, all other manually set printing-related commands (like print command, lpq command, lprm command, lppause command or lpresume command) are ignored and they should normally have no influence whatsoever on your printing.

Manual Configuration

If you want to do things manually, replace the printing = cups by printing = bsd. Then your manually set commands may work (I haven't tested this), and a print command = lp -d %P %s; rm %s" may do what you need.

Printing from CUPS to Windows Attached Printers

>From time to time the question arises, how can you print to a Windows attached printer from Samba? Normally the local connection from Windows host to printer would be done by USB or parallel cable, but this does not matter to Samba. From here only an SMB connection needs to be opened to the Windows host. Of course, this printer must be shared first. As you have learned by now, CUPS uses backends to talk to printers and other servers. To talk to Windows shared printers, you need to use the smb (surprise, surprise!) backend. Check if this is in the CUPS backend directory. This usually resides in /usr/lib/cups/backend/. You need to find an smb file there. It should be a symlink to smbspool and the file must exist and be executable:

root# ls -l /usr/lib/cups/backend/
total 253
drwxr-xr-x    3 root   root     720 Apr 30 19:04 .
drwxr-xr-x    6 root   root     125 Dec 19 17:13 ..
-rwxr-xr-x    1 root   root   10692 Feb 16 21:29 canon
-rwxr-xr-x    1 root   root   10692 Feb 16 21:29 epson
lrwxrwxrwx    1 root   root       3 Apr 17 22:50 http -> ipp
-rwxr-xr-x    1 root   root   17316 Apr 17 22:50 ipp
-rwxr-xr-x    1 root   root   15420 Apr 20 17:01 lpd
-rwxr-xr-x    1 root   root    8656 Apr 20 17:01 parallel
-rwxr-xr-x    1 root   root    2162 Mar 31 23:15 pdfdistiller
lrwxrwxrwx    1 root   root      25 Apr 30 19:04 ptal -> /usr/sbin/ptal-cups
-rwxr-xr-x    1 root   root    6284 Apr 20 17:01 scsi
lrwxrwxrwx    1 root   root      17 Apr  2 03:11 smb -> /usr/bin/smbspool
-rwxr-xr-x    1 root   root    7912 Apr 20 17:01 socket
-rwxr-xr-x    1 root   root    9012 Apr 20 17:01 usb

root# ls -l `which smbspool`
-rwxr-xr-x    1 root   root  563245 Dec 28 14:49 /usr/bin/smbspool

If this symlink does not exist, create it:

root# ln -s `which smbspool` /usr/lib/cups/backend/smb

smbspool has been written by Mike Sweet from the CUPS folks. It is included and ships with Samba. It may also be used with print subsystems other than CUPS, to spool jobs to Windows printer shares. To set up printer winprinter on CUPS, you need to have a driver for it. Essentially this means to convert the print data on the CUPS/Samba host to a format that the printer can digest (the Windows host is unable to convert any files you may send). This also means you should be able to print to the printer if it were hooked directly at your Samba/CUPS host. For troubleshooting purposes, this is what you should do to determine if that part of the process chain is in order. Then proceed to fix the network connection/authentication to the Windows host, and so on.

To install a printer with the smb backend on CUPS, use this command:

root# lpadmin -p winprinter -v smb://WINDOWSNETBIOSNAME/printersharename \
  -P /path/to/PPD

The PPD must be able to direct CUPS to generate the print data for the target model. For PostScript printers, just use the PPD that would be used with the Windows NT PostScript driver. But what can you do if the printer is only accessible with a password? Or if the printer's host is part of another workgroup? This is provided for: You can include the required parameters as part of the smb:// device-URI like this:

  • smb://WORKGROUP/WINDOWSNETBIOSNAME/printersharename

  • smb://username:password@WORKGROUP/WINDOWSNETBIOSNAME/printersharename

  • smb://username:password@WINDOWSNETBIOSNAME/printersharename

Note that the device-URI will be visible in the process list of the Samba server (e.g., when someone uses the ps -aux command on Linux), even if the username and passwords are sanitized before they get written into the log files. So this is an inherently insecure option, however, it is the only one. Don't use it if you want to protect your passwords. Better share the printer in a way that does not require a password! Printing will only work if you have a working netbios name resolution up and running. Note that this is a feature of CUPS and you do not necessarily need to have smbd running.

More CUPS-Filtering Chains

The following diagrams reveal how CUPS handles print jobs.

Figure 21.17. Filtering chain 1.

Filtering chain 1.

Figure 21.18. Filtering chain with cupsomatic

Filtering chain with cupsomatic

Common Errors

Windows 9x/ME Client Can't Install Driver

For Windows 9x/ME, clients require the printer names to be eight characters (or “8 plus 3 chars suffix”) max; otherwise, the driver files will not get transferred when you want to download them from Samba.

cupsaddsmb” Keeps Asking for Root Password in Never-ending Loop

Have you security = user? Have you used smbpasswd to give root a Samba account? You can do two things: open another terminal and execute smbpasswd -a root to create the account and continue entering the password into the first terminal. Or break out of the loop by pressing ENTER twice (without trying to type a password).

If the error is: “tree connect failed: NT_STATUS_BAD_NETWORK_NAME”, you may have forgotten to create the /etc/samba/drivers directory.

cupsaddsmb” or “rpcclient addriver” Keeps Giving WERR_BAD_PASSWORD

See the previous common error.

cupsaddsmb” Errors

The use of “cupsaddsmb” gives “No PPD file for printer...” Message While PPD File Is Present. What might the problem be?

Have you enabled printer sharing on CUPS? This means: Do you have a <Location /printers>....</Location> section in CUPS server's cupsd.conf that does not deny access to the host you run “cupsaddsmb” from? It could be an issue if you use cupsaddsmb remotely, or if you use it with a -h parameter: cupsaddsmb -H sambaserver -h cupsserver -v printername.

Is your TempDir directive in cupsd.conf set to a valid value and is it writable?

Client Can't Connect to Samba Printer

Use smbstatus to check which user you are from Samba's point of view. Do you have the privileges to write into the [print$] share?

New Account Reconnection from Windows 200x/XP Troubles

Once you are connected as the wrong user (for example, as nobody, which often occurs if you have map to guest = bad user), Windows Explorer will not accept an attempt to connect again as a different user. There will not be any byte transfered on the wire to Samba, but still you'll see a stupid error message that makes you think Samba has denied access. Use smbstatus to check for active connections. Kill the PIDs. You still can't re-connect and you get the dreaded You can't connect with a second account from the same machine message, as soon as you are trying. And you do not see any single byte arriving at Samba (see logs; use “ethereal”) indicating a renewed connection attempt. Shut all Explorer Windows. This makes Windows forget what it has cached in its memory as established connections. Then reconnect as the right user. The best method is to use a DOS terminal window and first do net use z: \\GANDALF\print$ /user:root. Check with smbstatus that you are connected under a different account. Now open the Printers folder (on the Samba server in the Network Neighborhood), right-click on the printer in question and select Connect...

Avoid Being Connected to the Samba Server as the Wrong User

You see per smbstatus that you are connected as user nobody; while you want to be root or printer admin. This is probably due to map to guest = bad user, which silently connects you under the guest account when you gave (maybe by accident) an incorrect username. Remove map to guest, if you want to prevent this.

Upgrading to CUPS Drivers from Adobe Drivers

This information came from a mailing list posting regarding problems experienced when upgrading from Adobe drivers to CUPS drivers on Microsoft Windows NT/200x/XP Clients.

First delete all old Adobe-using printers. Then delete all old Adobe drivers. (On Windows 200x/XP, right-click in the background of Printers folder, select Server Properties..., select tab Drivers and delete here).

Can't Use “cupsaddsmb” on Samba Server Which Is a PDC

Do you use the “naked” root user name? Try to do it this way: cupsaddsmb -U DOMAINNAME\\root -v printername> (note the two backslashes: the first one is required to “escape” the second one).

Deleted Windows 200x Printer Driver Is Still Shown

Deleting a printer on the client will not delete the driver too (to verify, right-click on the white background of the Printers folder, select Server Properties and click on the Drivers tab). These same old drivers will be re-used when you try to install a printer with the same name. If you want to update to a new driver, delete the old ones first. Deletion is only possible if no other printer uses the same driver.

Windows 200x/XP "Local Security Policies"

Local Security Policies may not allow the installation of unsigned drivers. “Local Security Policies” may not allow the installation of printer drivers at all.

Administrator Cannot Install Printers for All Local Users

Windows XP handles SMB printers on a “per-user” basis. This means every user needs to install the printer himself. To have a printer available for everybody, you might want to use the built-in IPP client capabilities of Win XP. Add a printer with the print path of http://cupsserver:631/printers/printername. We're still looking into this one. Maybe a logon script could automatically install printers for all users.

Print Change Notify Functions on NT-clients

For print change, notify functions on NT++ clients. These need to run the Server service first (renamed to File & Print Sharing for MS Networks in XP).

Win XP-SP1

Win XP-SP1 introduced a Point and Print Restriction Policy (this restriction does not apply to “Administrator” or “Power User” groups of users). In Group Policy Object Editor, go to User Configuration -> Administrative Templates -> Control Panel -> Printers. The policy is automatically set to Enabled and the Users can only Point and Print to machines in their Forest . You probably need to change it to Disabled or Users can only Point and Print to these servers to make driver downloads from Samba possible.

Print Options for All Users Can't Be Set on Windows 200x/XP

How are you doing it? I bet the wrong way (it is not easy to find out, though). There are three different ways to bring you to a dialog that seems to set everything. All three dialogs look the same, yet only one of them does what you intend. You need to be Administrator or Print Administrator to do this for all users. Here is how I do in on XP:

  1. The first wrong way:

    1. Open the Printers folder.

    2. Right-click on the printer (remoteprinter on cupshost) and select in context menu Printing Preferences...

    3. Look at this dialog closely and remember what it looks like.

  2. The second wrong way:

    1. Open the Printers folder.

    2. Right-click on the printer (remoteprinter on cupshost) and select the context menu Properties.

    3. Click on the General tab.

    4. Click on the button Printing Preferences...

    5. A new dialog opens. Keep this dialog open and go back to the parent dialog.

  3. The third, and the correct way:

    1. Open the Printers folder.

    2. Click on the Advanced tab. (If everything is “grayed out,” then you are not logged in as a user with enough privileges).

    3. Click on the Printing Defaults... button.

    4. On any of the two new tabs, click on the Advanced... button.

    5. A new dialog opens. Compare this one to the other identical looking one from “B.5” or A.3".

Do you see any difference? I don't either. However, only the last one, which you arrived at with steps “C.1.-6.”, will save any settings permanently and be the defaults for new users. If you want all clients to get the same defaults, you need to conduct these steps as Administrator (printer admin in smb.conf) before a client downloads the driver (the clients can later set their own per-user defaults by following the procedures A or B above).

Most Common Blunders in Driver Settings on Windows Clients

Don't use Optimize for Speed, but use Optimize for Portability instead (Adobe PS Driver). Don't use Page Independence: No: always settle with Page Independence: Yes (Microsoft PS Driver and CUPS PS Driver for Windows NT/200x/XP). If there are problems with fonts, use Download as Softfont into printer (Adobe PS Driver). For TrueType Download Options choose Outline. Use PostScript Level 2, if you are having trouble with a non-PS printer and if there is a choice.

cupsaddsmb Does Not Work with Newly Installed Printer

Symptom: The last command of cupsaddsmb does not complete successfully: cmd = setdriver printername printername result was NT_STATUS_UNSUCCESSFUL then possibly the printer was not yet recognized by Samba. Did it show up in Network Neighborhood? Did it show up i n rpcclient hostname -c `enumprinters'? Restart smbd (or send a kill -HUP to all processes listed by smbstatus and try again.

Permissions on /var/spool/samba/ Get Reset After Each Reboot

Have you ever by accident set the CUPS spool directory to the same location? (RequestRoot /var/spool/samba/ in cupsd.conf or the other way round: /var/spool/cups/ is set as path> in the [printers] section). These must be different. Set RequestRoot /var/spool/cups/ in cupsd.conf and path = /var/spool/samba in the [printers] section of smb.conf. Otherwise cupsd will sanitize permissions to its spool directory with each restart and printing will not work reliably.

Print Queue Called “lp” Mis-handles Print Jobs

In this case a print queue called “lp” intermittently swallows jobs and spits out completely different ones from what was sent.

It is a bad idea to name any printer “lp”. This is the traditional UNIX name for the default printer. CUPS may be set up to do an automatic creation of Implicit Classes. This means, to group all printers with the same name to a pool of devices, and load-balancing the jobs across them in a round-robin fashion. Chances are high that someone else has a printer named “lp” too. You may receive his jobs and send your own to his device unwittingly. To have tight control over the printer names, set BrowseShortNames No. It will present any printer as printername@cupshost and then gives you better control over what may happen in a large networked environment.

Location of Adobe PostScript Driver Files for “cupsaddsmb

Use smbclient to connect to any Windows box with a shared PostScript printer: smbclient //windowsbox/print\$ -U guest. You can navigate to the W32X86/2 subdir to mget ADOBE* and other files or to WIN40/0 to do the same. Another option is to download the *.exe packaged files from the Adobe Web site.

Overview of the CUPS Printing Processes

A complete overview of the CUPS printing processes can be found in the next flowchart.

Figure 21.19. CUPS printing overview.

CUPS printing overview.