9.3. 基礎設定

要用印表機搭配 LPD 多工緩衝系統,您需要有印表機這個硬體以及 LPD 這套軟體。 本手冊提供了兩階段的設定說明:

9.3.1. 簡易印表機設定

本章節會告訴您如何設定印表機設備和 LPD 軟體以使用印表機, 基本教學內容:

  • 硬體設定 會提示如何將印表機接上電腦的連接埠。

  • 軟體設定 會示範如何寫 LPD 緩衝器設定檔 (/etc/printcap)。

如果您要把印表機設定接收網路列印資料而不是本機端的話,請參考 印表機及網路資料傳輸介面

這個章節雖然叫做簡易印表機設定, 實際上還是有點複雜的。 最困難的部份是讓你的印表機和電腦上的 LPD 緩衝器能夠正常運作。 一旦印表機可以正常工作之後, 像是印首頁或是做列印統計這些進階的功能就不難做到了。

9.3.1.1. 硬體設定

本章節討論各種連接印表機到 PC 的方式。 這裡會提到不同種類的連接埠和連接線, 以及為了讓 FreeBSD 能和印表機溝通您可能會需要開啟的核心參數等。

如果您已經把印表機接上電腦, 而且在其他作業系統上有成功列印過的話,可以直接跳至 軟體設定

9.3.1.1.1. 連接埠和排線

市售個人電腦印表機一般來說不出這三種界面:

  • 序列 (Serial) 界面,又稱為 RS-232 或 COM 埠, 用您電腦上的序列埠傳送資料到印表機。 序列界面廣泛的為電腦業界所採用, 所以排線容易取得,要設定連線並不困難。 然而序列介面有時候會需要使用較特別的排線, 這時候就有可能需要設定一些較為複雜的通訊參數了。 大部份 PC 序列埠的傳輸速度最高只到 115200 bps, 因此想要用序列埠來列印大圖是不切實際的。

  • 並列 (Parallel) 界面利用電腦的並列埠將資料送到印表機。 並列埠比 RS-232 序列埠還快,也是一種電腦業界常用的界面。 這種界面的排線非常容易取得,但是較難用手工打造。 通常來說並列界面並沒有什麼通訊參數需要指定, 所以設定起來超級容易。

    並列埠界面有時候也會被稱為 Centronics 界面,這是印表機的接頭的名稱。

  • USB 界面,也就是通用序列匯流排,傳輸速率比並列界面或是 RS-232 序列界面都來得快,而且 USB 排線單純又便宜。 對列印工作而言,USB 比 RS-232 序列埠或是並列埠都來得好,但是在 UNIX® 系統上的支援度較差。 購買同時具有 USB 及並列埠兩種界面的印表機可以避免掉這種問題。

一般而言,並列界面只能提供單向傳輸 (電腦至印表機),而要用 USB 才能提供雙向。 然而在 FreeBSD 下,使用較新的並列埠 (EPP 和 ECP) 以及印表機,再配合使用 IEEE-1284 相容排線也可以做到雙向溝通。

電腦和印表機之間藉由並列埠行進雙向溝通的方式有兩種。 第一種是使用特製的、能和特定印表機溝通的 FreeBSD 印表機驅動程式。 這種方式在噴墨印表機上很常見,用來回報墨水存量以及其他狀態資訊等。 第二種方法是用 PostScript®,如果印表機有支援的話。

PostScript® jobs are actually programs sent to the printer; they need not produce paper at all and may return results directly to the computer. PostScript® also uses two-way communication to tell the computer about problems, such as errors in the PostScript® program or paper jams. Your users may be appreciative of such information. Furthermore, the best way to do effective accounting with a PostScript® printer requires two-way communication: you ask the printer for its page count (how many pages it has printed in its lifetime), then send the user's job, then ask again for its page count. Subtract the two values and you know how much paper to charge to the user.

9.3.1.1.2. Parallel Ports

To hook up a printer using a parallel interface, connect the Centronics cable between the printer and the computer. The instructions that came with the printer, the computer, or both should give you complete guidance.

Remember which parallel port you used on the computer. The first parallel port is ppc0 to FreeBSD; the second is ppc1, and so on. The printer device name uses the same scheme: /dev/lpt0 for the printer on the first parallel ports etc.

9.3.1.1.3. Serial Ports

To hook up a printer using a serial interface, connect the proper serial cable between the printer and the computer. The instructions that came with the printer, the computer, or both should give you complete guidance.

If you are unsure what the proper serial cable is, you may wish to try one of the following alternatives:

  • A modem cable connects each pin of the connector on one end of the cable straight through to its corresponding pin of the connector on the other end. This type of cable is also known as a DTE-to-DCE cable.

  • A null-modem cable connects some pins straight through, swaps others (send data to receive data, for example), and shorts some internally in each connector hood. This type of cable is also known as a DTE-to-DTE cable.

  • A serial printer cable, required for some unusual printers, is like the null-modem cable, but sends some signals to their counterparts instead of being internally shorted.

You should also set up the communications parameters for the printer, usually through front-panel controls or DIP switches on the printer. Choose the highest bps (bits per second, sometimes baud rate) that both your computer and the printer can support. Choose 7 or 8 data bits; none, even, or odd parity; and 1 or 2 stop bits. Also choose a flow control protocol: either none, or XON/XOFF (also known as in-band or software) flow control. Remember these settings for the software configuration that follows.

9.3.1.2. Software Setup

This section describes the software setup necessary to print with the LPD spooling system in FreeBSD.

Here is an outline of the steps involved:

  1. Configure your kernel, if necessary, for the port you are using for the printer; section Kernel Configuration tells you what you need to do.

  2. Set the communications mode for the parallel port, if you are using a parallel port; section Setting the Communication Mode for the Parallel Port gives details.

  3. Test if the operating system can send data to the printer. Section Checking Printer Communications gives some suggestions on how to do this.

  4. Set up LPD for the printer by modifying the file /etc/printcap. You will find out how to do this later in this chapter.

9.3.1.2.1. Kernel Configuration

The operating system kernel is compiled to work with a specific set of devices. The serial or parallel interface for your printer is a part of that set. Therefore, it might be necessary to add support for an additional serial or parallel port if your kernel is not already configured for one.

To find out if the kernel you are currently using supports a serial interface, type:

# grep sioN /var/run/dmesg.boot

Where N is the number of the serial port, starting from zero. If you see output similar to the following:

sio2 at port 0x3e8-0x3ef irq 5 on isa
sio2: type 16550A

then the kernel supports the port.

To find out if the kernel supports a parallel interface, type:

# grep ppcN /var/run/dmesg.boot

Where N is the number of the parallel port, starting from zero. If you see output similar to the following:

ppc0: <Parallel port> at port 0x378-0x37f irq 7 on isa0
ppc0: SMC-like chipset (ECP/EPP/PS2/NIBBLE) in COMPATIBLE mode
ppc0: FIFO with 16/16/8 bytes threshold

then the kernel supports the port.

You might have to reconfigure your kernel in order for the operating system to recognize and use the parallel or serial port you are using for the printer.

To add support for a serial port, see the section on kernel configuration. To add support for a parallel port, see that section and the section that follows.

9.3.1.3. Setting the Communication Mode for the Parallel Port

When you are using the parallel interface, you can choose whether FreeBSD should use interrupt-driven or polled communication with the printer. The generic printer device driver (lpt(4)) on FreeBSD uses the ppbus(4) system, which controls the port chipset with the ppc(4) driver.

  • The interrupt-driven method is the default with the GENERIC kernel. With this method, the operating system uses an IRQ line to determine when the printer is ready for data.

  • The polled method directs the operating system to repeatedly ask the printer if it is ready for more data. When it responds ready, the kernel sends more data.

The interrupt-driven method is usually somewhat faster but uses up a precious IRQ line. Some newer HP printers are claimed not to work correctly in interrupt mode, apparently due to some (not yet exactly understood) timing problem. These printers need polled mode. You should use whichever one works. Some printers will work in both modes, but are painfully slow in interrupt mode.

You can set the communications mode in two ways: by configuring the kernel or by using the lptcontrol(8) program.

To set the communications mode by configuring the kernel:

  1. Edit your kernel configuration file. Look for an ppc0 entry. If you are setting up the second parallel port, use ppc1 instead. Use ppc2 for the third port, and so on.

    • If you want interrupt-driven mode, edit the following line:

      hint.ppc.0.irq="N"

      in the /boot/device.hints file and replace N with the right IRQ number. The kernel configuration file must also contain the ppc(4) driver:

      device ppc
    • If you want polled mode, remove in your /boot/device.hints file, the following line:

      hint.ppc.0.irq="N"

      In some cases, this is not enough to put the port in polled mode under FreeBSD. Most of time it comes from acpi(4) driver, this latter is able to probe and attach devices, and therefore, control the access mode to the printer port. You should check your acpi(4) configuration to correct this problem.

  2. Save the file. Then configure, build, and install the kernel, then reboot. See kernel configuration for more details.

To set the communications mode with lptcontrol(8):

  1. Type:

    # lptcontrol -i -d /dev/lptN

    to set interrupt-driven mode for lptN.

  2. Type:

    # lptcontrol -p -d /dev/lptN

    to set polled-mode for lptN.

You could put these commands in your /etc/rc.local file to set the mode each time your system boots. See lptcontrol(8) for more information.

9.3.1.4. Checking Printer Communications

Before proceeding to configure the spooling system, you should make sure the operating system can successfully send data to your printer. It is a lot easier to debug printer communication and the spooling system separately.

To test the printer, we will send some text to it. For printers that can immediately print characters sent to them, the program lptest(1) is perfect: it generates all 96 printable ASCII characters in 96 lines.

For a PostScript® (or other language-based) printer, we will need a more sophisticated test. A small PostScript® program, such as the following, will suffice:

%!PS
100 100 moveto 300 300 lineto stroke
310 310 moveto /Helvetica findfont 12 scalefont setfont
(Is this thing working?) show
showpage

The above PostScript® code can be placed into a file and used as shown in the examples appearing in the following sections.

注意:

When this document refers to a printer language, it is assuming a language like PostScript®, and not Hewlett Packard's PCL. Although PCL has great functionality, you can intermingle plain text with its escape sequences. PostScript® cannot directly print plain text, and that is the kind of printer language for which we must make special accommodations.

9.3.1.4.1. Checking a Parallel Printer

This section tells you how to check if FreeBSD can communicate with a printer connected to a parallel port.

To test a printer on a parallel port:

  1. Become root with su(1).

  2. Send data to the printer.

    • If the printer can print plain text, then use lptest(1). Type:

      # lptest > /dev/lptN

      Where N is the number of the parallel port, starting from zero.

    • If the printer understands PostScript® or other printer language, then send a small program to the printer. Type:

      # cat > /dev/lptN

      Then, line by line, type the program carefully as you cannot edit a line once you have pressed RETURN or ENTER. When you have finished entering the program, press CONTROL+D, or whatever your end of file key is.

      Alternatively, you can put the program in a file and type:

      # cat file > /dev/lptN

      Where file is the name of the file containing the program you want to send to the printer.

You should see something print. Do not worry if the text does not look right; we will fix such things later.

9.3.1.4.2. Checking a Serial Printer

This section tells you how to check if FreeBSD can communicate with a printer on a serial port.

To test a printer on a serial port:

  1. Become root with su(1).

  2. Edit the file /etc/remote. Add the following entry:

    printer:dv=/dev/port:br#bps-rate:pa=parity

    Where port is the device entry for the serial port (ttyd0, ttyd1, etc.), bps-rate is the bits-per-second rate at which the printer communicates, and parity is the parity required by the printer (either even, odd, none, or zero).

    Here is a sample entry for a printer connected via a serial line to the third serial port at 19200 bps with no parity:

    printer:dv=/dev/ttyd2:br#19200:pa=none
  3. Connect to the printer with tip(1). Type:

    # tip printer

    If this step does not work, edit the file /etc/remote again and try using /dev/cuaaN instead of /dev/ttydN.

  4. Send data to the printer.

    • If the printer can print plain text, then use lptest(1). Type:

      % $lptest
    • If the printer understands PostScript® or other printer language, then send a small program to the printer. Type the program, line by line, very carefully as backspacing or other editing keys may be significant to the printer. You may also need to type a special end-of-file key for the printer so it knows it received the whole program. For PostScript® printers, press CONTROL+D.

      Alternatively, you can put the program in a file and type:

      % >file

      Where file is the name of the file containing the program. After tip(1) sends the file, press any required end-of-file key.

You should see something print. Do not worry if the text does not look right; we will fix that later.

9.3.1.5. Enabling the Spooler: the /etc/printcap File

At this point, your printer should be hooked up, your kernel configured to communicate with it (if necessary), and you have been able to send some simple data to the printer. Now, we are ready to configure LPD to control access to your printer.

You configure LPD by editing the file /etc/printcap. The LPD spooling system reads this file each time the spooler is used, so updates to the file take immediate effect.

The format of the printcap(5) file is straightforward. Use your favorite text editor to make changes to /etc/printcap. The format is identical to other capability files like /usr/share/misc/termcap and /etc/remote. For complete information about the format, see the cgetent(3).

The simple spooler configuration consists of the following steps:

  1. Pick a name (and a few convenient aliases) for the printer, and put them in the /etc/printcap file; see the Naming the Printer section for more information on naming.

  2. Turn off header pages (which are on by default) by inserting the sh capability; see the Suppressing Header Pages section for more information.

  3. Make a spooling directory, and specify its location with the sd capability; see the Making the Spooling Directory section for more information.

  4. Set the /dev entry to use for the printer, and note it in /etc/printcap with the lp capability; see the Identifying the Printer Device for more information. Also, if the printer is on a serial port, set up the communication parameters with the ms# capability which is discussed in the Configuring Spooler Communications Parameters section.

  5. Install a plain text input filter; see the Installing the Text Filter section for details.

  6. Test the setup by printing something with the lpr(1) command. More details are available in the Trying It Out and Troubleshooting sections.

注意:

Language-based printers, such as PostScript® printers, cannot directly print plain text. The simple setup outlined above and described in the following sections assumes that if you are installing such a printer you will print only files that the printer can understand.

Users often expect that they can print plain text to any of the printers installed on your system. Programs that interface to LPD to do their printing usually make the same assumption. If you are installing such a printer and want to be able to print jobs in the printer language and print plain text jobs, you are strongly urged to add an additional step to the simple setup outlined above: install an automatic plain-text-to-PostScript® (or other printer language) conversion program. The section entitled Accommodating Plain Text Jobs on PostScript® Printers tells how to do this.

9.3.1.5.1. Naming the Printer

The first (easy) step is to pick a name for your printer. It really does not matter whether you choose functional or whimsical names since you can also provide a number of aliases for the printer.

At least one of the printers specified in the /etc/printcap should have the alias lp. This is the default printer's name. If users do not have the PRINTER environment variable nor specify a printer name on the command line of any of the LPD commands, then lp will be the default printer they get to use.

Also, it is common practice to make the last alias for a printer be a full description of the printer, including make and model.

Once you have picked a name and some common aliases, put them in the /etc/printcap file. The name of the printer should start in the leftmost column. Separate each alias with a vertical bar and put a colon after the last alias.

In the following example, we start with a skeletal /etc/printcap that defines two printers (a Diablo 630 line printer and a Panasonic KX-P4455 PostScript® laser printer):

#
#  /etc/printcap for host rose
#
rattan|line|diablo|lp|Diablo 630 Line Printer:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:

In this example, the first printer is named rattan and has as aliases line, diablo, lp, and Diablo 630 Line Printer. Since it has the alias lp, it is also the default printer. The second is named bamboo, and has as aliases ps, PS, S, panasonic, and Panasonic KX-P4455 PostScript v51.4.

9.3.1.5.2. Suppressing Header Pages

The LPD spooling system will by default print a header page for each job. The header page contains the user name who requested the job, the host from which the job came, and the name of the job, in nice large letters. Unfortunately, all this extra text gets in the way of debugging the simple printer setup, so we will suppress header pages.

To suppress header pages, add the sh capability to the entry for the printer in /etc/printcap. Here is an example /etc/printcap with sh added:

#
#  /etc/printcap for host rose - no header pages anywhere
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
        :sh:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
        :sh:

Note how we used the correct format: the first line starts in the leftmost column, and subsequent lines are indented. Every line in an entry except the last ends in a backslash character.

9.3.1.5.3. Making the Spooling Directory

The next step in the simple spooler setup is to make a spooling directory, a directory where print jobs reside until they are printed, and where a number of other spooler support files live.

Because of the variable nature of spooling directories, it is customary to put these directories under /var/spool. It is not necessary to backup the contents of spooling directories, either. Recreating them is as simple as running mkdir(1).

It is also customary to make the directory with a name that is identical to the name of the printer, as shown below:

# mkdir /var/spool/printer-name

However, if you have a lot of printers on your network, you might want to put the spooling directories under a single directory that you reserve just for printing with LPD. We will do this for our two example printers rattan and bamboo:

# mkdir /var/spool/lpd
# mkdir /var/spool/lpd/rattan
# mkdir /var/spool/lpd/bamboo

注意:

If you are concerned about the privacy of jobs that users print, you might want to protect the spooling directory so it is not publicly accessible. Spooling directories should be owned and be readable, writable, and searchable by user daemon and group daemon, and no one else. We will do this for our example printers:

# chown daemon:daemon /var/spool/lpd/rattan
# chown daemon:daemon /var/spool/lpd/bamboo
# chmod 770 /var/spool/lpd/rattan
# chmod 770 /var/spool/lpd/bamboo

Finally, you need to tell LPD about these directories using the /etc/printcap file. You specify the pathname of the spooling directory with the sd capability:

#
#  /etc/printcap for host rose - added spooling directories
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
        :sh:sd=/var/spool/lpd/rattan:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
        :sh:sd=/var/spool/lpd/bamboo:

Note that the name of the printer starts in the first column but all other entries describing the printer should be indented and each line end escaped with a backslash.

If you do not specify a spooling directory with sd, the spooling system will use /var/spool/lpd as a default.

9.3.1.5.4. Identifying the Printer Device

In the Entries for the Ports section, we identified which entry in the /dev directory FreeBSD will use to communicate with the printer. Now, we tell LPD that information. When the spooling system has a job to print, it will open the specified device on behalf of the filter program (which is responsible for passing data to the printer).

List the /dev entry pathname in the /etc/printcap file using the lp capability.

In our running example, let us assume that rattan is on the first parallel port, and bamboo is on a sixth serial port; here are the additions to /etc/printcap:

#
#  /etc/printcap for host rose - identified what devices to use
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
        :sh:sd=/var/spool/lpd/rattan:\
        :lp=/dev/lpt0:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
        :sh:sd=/var/spool/lpd/bamboo:\
        :lp=/dev/ttyd5:

If you do not specify the lp capability for a printer in your /etc/printcap file, LPD uses /dev/lp as a default. /dev/lp currently does not exist in FreeBSD.

If the printer you are installing is connected to a parallel port, skip to the section entitled, Installing the Text Filter. Otherwise, be sure to follow the instructions in the next section.

9.3.1.5.5. Configuring Spooler Communication Parameters

For printers on serial ports, LPD can set up the bps rate, parity, and other serial communication parameters on behalf of the filter program that sends data to the printer. This is advantageous since:

  • It lets you try different communication parameters by simply editing the /etc/printcap file; you do not have to recompile the filter program.

  • It enables the spooling system to use the same filter program for multiple printers which may have different serial communication settings.

The following /etc/printcap capabilities control serial communication parameters of the device listed in the lp capability:

br#bps-rate

Sets the communications speed of the device to bps-rate, where bps-rate can be 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, or 115200 bits-per-second.

ms#stty-mode

Sets the options for the terminal device after opening the device. stty(1) explains the available options.

When LPD opens the device specified by the lp capability, it sets the characteristics of the device to those specified with the ms# capability. Of particular interest will be the parenb, parodd, cs5, cs6, cs7, cs8, cstopb, crtscts, and ixon modes, which are explained in the stty(1) manual page.

Let us add to our example printer on the sixth serial port. We will set the bps rate to 38400. For the mode, we will set no parity with -parenb, 8-bit characters with cs8, no modem control with clocal and hardware flow control with crtscts:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
        :sh:sd=/var/spool/lpd/bamboo:\
        :lp=/dev/ttyd5:ms#-parenb cs8 clocal crtscts:
9.3.1.5.6. Installing the Text Filter

We are now ready to tell LPD what text filter to use to send jobs to the printer. A text filter, also known as an input filter, is a program that LPD runs when it has a job to print. When LPD runs the text filter for a printer, it sets the filter's standard input to the job to print, and its standard output to the printer device specified with the lp capability. The filter is expected to read the job from standard input, perform any necessary translation for the printer, and write the results to standard output, which will get printed. For more information on the text filter, see the Filters section.

For our simple printer setup, the text filter can be a small shell script that just executes /bin/cat to send the job to the printer. FreeBSD comes with another filter called lpf that handles backspacing and underlining for printers that might not deal with such character streams well. And, of course, you can use any other filter program you want. The filter lpf is described in detail in section entitled lpf: a Text Filter.

First, let us make the shell script /usr/local/libexec/if-simple be a simple text filter. Put the following text into that file with your favorite text editor:

#!/bin/sh
#
# if-simple - Simple text input filter for lpd
# Installed in /usr/local/libexec/if-simple
#
# Simply copies stdin to stdout.  Ignores all filter arguments.

/bin/cat && exit 0
exit 2

Make the file executable:

# chmod 555 /usr/local/libexec/if-simple

And then tell LPD to use it by specifying it with the if capability in /etc/printcap. We will add it to the two printers we have so far in the example /etc/printcap:

#
#  /etc/printcap for host rose - added text filter
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
        :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0:\
        :if=/usr/local/libexec/if-simple:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
        :sh:sd=/var/spool/lpd/bamboo:\
        :lp=/dev/ttyd5:ms#-parenb cs8 clocal crtscts:\
        :if=/usr/local/libexec/if-simple:

注意:

A copy of the if-simple script can be found in the /usr/share/examples/printing directory.

9.3.1.5.7. Turn on LPD

lpd(8) is run from /etc/rc, controlled by the lpd_enable variable. This variable defaults to NO. If you have not done so already, add the line:

lpd_enable="YES"

to /etc/rc.conf, and then either restart your machine, or just run lpd(8).

# lpd
9.3.1.5.8. Trying It Out

You have reached the end of the simple LPD setup. Unfortunately, congratulations are not quite yet in order, since we still have to test the setup and correct any problems. To test the setup, try printing something. To print with the LPD system, you use the command lpr(1), which submits a job for printing.

You can combine lpr(1) with the lptest(1) program, introduced in section Checking Printer Communications to generate some test text.

To test the simple LPD setup:

Type:

# lptest 20 5 | lpr -Pprinter-name

Where printer-name is a the name of a printer (or an alias) specified in /etc/printcap. To test the default printer, type lpr(1) without any -P argument. Again, if you are testing a printer that expects PostScript®, send a PostScript® program in that language instead of using lptest(1). You can do so by putting the program in a file and typing lpr file.

For a PostScript® printer, you should get the results of the program. If you are using lptest(1), then your results should look like the following:

!"#$%&'()*+,-./01234
"#$%&'()*+,-./012345
#$%&'()*+,-./0123456
$%&'()*+,-./01234567
%&'()*+,-./012345678

To further test the printer, try downloading larger programs (for language-based printers) or running lptest(1) with different arguments. For example, lptest 80 60 will produce 60 lines of 80 characters each.

If the printer did not work, see the Troubleshooting section.

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