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><H1
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><A
NAME="SPOOLERS"
>6. Spooling software</A
></H1
><P
> Until recently, the choice for free software users was simple -
everyone ran the same old lpd lifted mostly verbatim out of BSD's
Net-2 code. Even today, most vendors ship this software. But this
is beginning to change. SVR4-like systems including Sun's Solaris
come with a completely different print spooling package, centered
around lpsched.
</P
><P
> Today, there are a number of good systems to chose from. I
describe them all below; read the descriptions and make your own
choice. PDQ is the simplest modern system with a GUI; it is
suitable for both basic home users and (in a hybrid pdq/lprng
setup) people in many larger environments. For business
environments with mainly networked Postscript printers, a front-end
program like GPR with LPRng is a good alternative; it handles
PPD options directly and has a slightly nicer interface. In other
cases CUPS is a good option; it too has excellent Postscript
printer support, and offers IPP support, a web interface, and a
number of other features.
</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="LPD-WHICH-SPOOLER"
>6.1. LPD</A
></H2
><A
NAME="AEN1460"
></A
><A
NAME="AEN1463"
></A
><P
> LPD, the original BSD Unix Line Printer Daemon, has been the
standard on Unix for years. It is available for every style of
Unix, and offers a rather minimal feature set derived from the
needs of timesharing-era computing. Despite this somewhat
peculiar history, it is still useful today as a basic print
spooler. To be really useful with modern printer, a good deal of
extra work is needed in the form of companion filter scripts and
front-end programs. But these exist, and it does all work.
</P
><P
> LPD is also the name given to the network printing protocol by
<A
HREF="http://www.ietf.org/rfc/rfc1179.txt"
TARGET="_top"
>RFC
1179</A
>. This network protocol is spoken not only by
the LPD daemon itself, but by essentially every networked print
server, networked printer, and every other print spooler out
there; LPD is the least common denominator of standards-based
network printing.
</P
><P
> LPRng (see <A
HREF="spoolers.html#LPRNG-WHICH-SPOOLER"
>Section 6.3</A
>) is a far better
implementation of the basic LPD design than the regular one; if
you must use LPD, consider using LPRng instead. There is far less
voodoo involved in making it do what you want, and what voodoo
there is is well documented.
</P
><P
> There are a large number of LPD sources floating around in the
world. Arguably, some strain of BSD Unix is probably the official
owner, but everyone implements changes willy-nilly, and they all
cross-pollinate in unknown ways, such that it is difficult to say
with certainty exactly which LPD you might have. Of the readily
available LPDs, VA Linux offers one with a few minor modifications
that make the user interface much more flexible. The <A
HREF="http://sourceforge.net/project/?group_id=3800"
TARGET="_top"
>SourceForge
LPD</A
> supports command-line option specification with a
<TT
CLASS="OPTION"
>-o</TT
> flag; options are then passed through to
filters. This is similar to the features offered by a number of
traditional Unix vendors, and similar to (although incompatible
with) LPRng's <TT
CLASS="OPTION"
>-z</TT
> option mechanism.
</P
><DIV
CLASS="SIMPLESECT"
><H3
CLASS="SIMPLESECT"
><A
NAME="LPD-FRONT-ENDS"
>6.1.1. LPD front-ends</A
></H3
><P
> If you go with LPD, the best way to use it is via a front-end.
There are several to chose from; GPR (see <A
HREF="how.html#HOW-WITH-GUI-TOOLS"
>Section 3.3</A
>) and XPDQ (see <A
HREF="spoolers.html#PDQ-WHICH-SPOOLER"
>Section 6.2</A
>) are perhaps the two best. Others
exist; tell me about them.
</P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="PDQ-WHICH-SPOOLER"
>6.2. PDQ</A
></H2
><A
NAME="AEN1482"
></A
><A
NAME="AEN1484"
></A
><A
NAME="AEN1487"
></A
><P
> <A
HREF="http://feynman.tam.uiuc.edu/pdq/"
TARGET="_top"
>PDQ</A
> is a
non-daemon-centric print system which has a built-in, and
sensible, driver configuration syntax. This includes the ability
to declare printing options, and a GUI or command line tool for
users to specify these options with; users get a nice dialog box
in which to specify resolution, duplexing, paper type, etc (see
<A
HREF="spoolers.html#SNAPSHOT-XPDQ-OPTIONS"
>Figure 9</A
>).
</P
><DIV
CLASS="FIGURE"
><P
><B
>Figure 8. XPDQ Main Window</B
></P
><P
><IMG
SRC="snapshot-xpdq-main.gif"></P
></DIV
><P
> Running all of the filters as the user has a number of advantages:
the security problems possible from Postscript are mostly gone,
multi-file LaTeX jobs can be printed effectively as dvi files, and
so forth.
</P
><P
> This is what I now use; I've written driver spec files for my
printers, and there are several included with the distribution, so
there are plenty of examples to base yours on. I've also written
a few tools to automate driver spec generation to help the rest of
you.
</P
><P
> PDQ is not without flaws: most notably it processes the entire job
before sending it to the printer. This means that, for large
jobs, PDQ may simply be impractical—you can end up with
hundreds of megs being copied back and forth on your disk. Even
worse, for slow drivers like the better quality inkjet drivers,
the job will not start printing until Ghostscript and the driver
have finished processing. This may be many minutes after submission.
</P
><P
> If you have many users, many printers, or anything else complex
going on, I recommend using PDQ as a front-end to LPD-protocol
based network printing (you can print via the lpd protocol to the
local machine). In most such situations, rather than using the
traditional BSD lpd as the back-end, I recommend LPRng:
</P
><DIV
CLASS="FIGURE"
><A
NAME="SNAPSHOT-XPDQ-OPTIONS"
></A
><P
><B
>Figure 9. XPDQ Driver Options Window</B
></P
><P
><IMG
SRC="snapshot-xpdq-options.gif"></P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="LPRNG-WHICH-SPOOLER"
>6.3. LPRng</A
></H2
><A
NAME="AEN1504"
></A
><A
NAME="AEN1506"
></A
><P
> Some GNU/Linux vendors (including Caldera) provide LPRng, a far less
ancient LPD print spooling implementation. LPRng is far easier to
administer for large installations (read: more than one printer,
any serial printers, or any peculiar non-lpd network printers) and
has a less frightfully haphazard codebase than does stock lpd. It
can even honestly claim to be secure - there are no SUID binaries,
and it supports authentication via PGP or Kerberos.
</P
><P
> LPRng also includes some example setups for common network
printers - HP LaserJets, mainly, that include some accounting
abilities. If you'd like more information on LPRng, check out the
<A
HREF="http://www.astart.com/lprng/LPRng.html"
TARGET="_top"
>LPRng Web
Page</A
>. LPRng uses more or less the same basic filter model
as does BSD lpd, so the <A
HREF="http://www.linuxprinting.org/lpd-doc.html"
TARGET="_top"
>LPD
support</A
> offered by my website applies to LPRng as well.
This can help you effectively use free software drivers for many
printers.
</P
><P
> LPRng is distributed under either the GPL or an Artistic license.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="PPR-WHICH-SPOOLER"
>6.4. PPR</A
></H2
><A
NAME="AEN1516"
></A
><A
NAME="AEN1518"
></A
><P
> <A
HREF="http://ppr.trincoll.edu/"
TARGET="_top"
>PPR</A
> is a
Postscript-centric spooler which includes a rudimentary Postscript
parsing ability from which it derives several nice features. It
includes good accounting capabilities, good support for Appletalk,
SMB, and LPD clients, and much better error handling than lpd.
PPR, like every other spooler here, can call Ghostscript to handle
non-Postscript printers.
</P
><P
> I only recently found out about PPR; I don't know of anyone who
has tried it. It was written by, and is in use at, Trinity
College. The license is BSD-style; free for all use but credit is
due.
</P
><P
> According to the documentation, it's somewhat experimental.
Malformed Postscript jobs won't print; instead they bounce, and
it's up to the user to fix the Postscript. This may make it
unsuitable for some environments, although most users generate
Postscript with a small handful of well-characterized Postscript
generators, so it probably wouldn't be that big an issue.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="CUPS-WHICH-SPOOLER"
>6.5. CUPS</A
></H2
><A
NAME="AEN1527"
></A
><A
NAME="AEN1529"
></A
><A
NAME="AEN1533"
></A
><A
NAME="AEN1536"
></A
><P
> <A
NAME="AEN1540"
></A
>
<A
NAME="AEN1542"
></A
>
One interesting newcomer on the scene is <A
HREF="http://www.cups.org/"
TARGET="_top"
>CUPS</A
>, an implementation of the
Internet Printing Protocol (IPP), an HTTP-like RFC standard
replacement protocol for the venerable (and klunky) LPD protocol.
The implementation of CUPS has been driven by Michael Sweet of
Easy Software Products; CUPS is distributed under the GPL.
</P
><P
> <A
NAME="AEN1547"
></A
>
I've finally done some work with CUPS, and it does
work as advertised. There are a number of very good features in
it, including sensible option handling; web, gui, and command-line
interfaces; and a mime-based filtering system with strong support
for Postscript. Since it is so new, however, it does have a
number of quirks, and it is hard to recommend for large or secure
installations at this time (as of version 1.1). It is a fine
solution, however, for smaller installations or especially larger
installatons with trusted users.
</P
><P
> Like other systems, CUPS can be used with most existing drivers.
Unfortunately, it's a bit tricky to configure an arbitrary driver
for use with CUPS—at least if you want all the options to
work—so it's best to find a preexisting PPD file and filter
script to make your driver go. There are at least four sets of
drivers which you can use with CUPS:
<P
></P
><DL
><DT
><A
HREF="http://www.linuxprinting.org/foomatic.html"
TARGET="_top"
>Foomatic</A
></DT
><DD
><A
NAME="AEN1556"
></A
><A
NAME="AEN1559"
></A
><P
>My web-based CUPS-O-Matic system can generate a suitable
PPD for use with any printer driver that has full details
entered in the LinuxPrinting.org Database. The PPD gets used
together with a backend script named
<B
CLASS="COMMAND"
>cupsomatic</B
>. CUPS-O-Matic uses free
software drivers. At the moment there is support for a rather
large number of printers in this system, and both XPP and
QtCUPS (graphical front-ends for CUPS users) have added
special support for several of the many styles of adjustments
useful with Foomatic's free drivers but not supported by CUPS
itself. Foomatic forms a basis for non-Postscript printer
support in a number of GNU/Linux distributions.
</P
></DD
><DT
><A
HREF="http://cups.sourceforge.net/"
TARGET="_top"
>CUPS Drivers
and KUPS</A
></DT
><DD
><P
>The CUPS Drivers project is accumulating PPD files
useable with either Postscript printers or the backend filter
<B
CLASS="COMMAND"
>ps2gs2raw</B
>. These PPD files use free
software drivers. KUPS is a companion setup program. The
driver project has mostly stalled with the advent of Foomatic,
but KUPS is a nifty setup tool shipped standard in a number of
distributions.
</P
></DD
><DT
>Postscript PPDs</DT
><DD
><P
>CUPS can use vendor-supplied PPD files for Postscript
printers directly. Often these come with the Windows drivers
for a printer, or can be found on the printer vendor's
website. <A
HREF="http://www.adobe.com/products/printerdrivers/winppd.html"
TARGET="_top"
>Adobe</A
> also distributes PPD files for many Postscript
printers.
</P
></DD
><DT
>ESP Print Pro</DT
><DD
><P
><A
HREF="http://www.easysw.com/"
TARGET="_top"
>Easy Software
Products, Inc.</A
> sells CUPS bundled with a collection of
proprietary drivers. Although they are not free software,
they do drive many common printers. The bundle is somewhat
expensive measured against the price of a single supported
printer, but it certainly has a place. These drivers are
reputedly not terribly good, but they are somewhat more
comprehensive than the coverage from free software, and even
mediocre quality is preferable to a paperweight. The package
includes graphical front-end tools which are reputedly not as
good as XPP or QtCUPS.
</P
></DD
></DL
>
</P
><P
> The third-party program <B
CLASS="COMMAND"
><A
HREF="http://cups.sourceforge.net/xpp/"
TARGET="_top"
>XPP</A
></B
> (see <A
HREF="how.html#SNAPSHOT-XPP-MAIN"
>Figure 5</A
>) offers a
very nice graphical interface to the user functionality of CUPS,
including an marvelous interface to print-time options (shown in
<A
HREF="how.html#SNAPSHOT-XPP-OPTIONS"
>Figure 6</A
>). For information on using
XPP, see <A
HREF="how.html#XPP-SECT"
>Section 3.3.3</A
>.
</P
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