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PrintingContributed by &a.kelly;, 30 September 1995.
Restructured and updated by &a.jim;, March 2000.SynopsisLPD spooling systemprintingIn order to use printers with FreeBSD, you will need to set them
up to work with the Berkeley line printer spooling system, also
known as the LPD spooling system. It is the standard printer
control system in FreeBSD. This chapter introduces the LPD spooling
system, often simply called LPD, and will guide you through its
configuration.If you are already familiar with LPD or another printer spooling
system, you may wish to skip to section Setting up the spooling
system.IntroductionLPD controls everything about a host's printers. It is
responsible for a number of things:It controls access to attached printers and printers
attached to other hosts on the network.print jobsIt enables users to submit files to be printed; these
submissions are known as jobs.It prevents multiple users from accessing a printer at the
same time by maintaining a queue for each
printer.It can print header pages (also known
as banner or burst
pages) so users can easily find jobs they have printed in a
stack of printouts.It takes care of communications parameters for printers
connected on serial ports.It can send jobs over the network to a LPD spooler on
another host.It can run special filters to format jobs to be printed for
various printer languages or printer capabilities.It can account for printer usage.Through a configuration file
(/etc/printcap), and by providing the special
filter programs, you can enable the LPD system to do all or some
subset of the above for a great variety of printer hardware.Why You Should Use the SpoolerIf you are the sole user of your system, you may be wondering
why you should bother with the spooler when you do not need access
control, header pages, or printer accounting. While it is
possible to enable direct access to a printer, you should use the
spooler anyway since:LPD prints jobs in the background; you do not have to wait
for data to be copied to the printer.TeXLPD can conveniently run a job to be printed through
filters to add date/time headers or convert a special file
format (such as a TeX DVI file) into a format the printer will
understand. You will not have to do these steps
manually.Many free and commercial programs that provide a print
feature usually expect to talk to the spooler on your system.
By setting up the spooling system, you will more easily
support other software you may later add or already
have.Basic SetupTo use printers with the LPD spooling system, you will need to
set up both your printer hardware and the LPD software. This
document describes two levels of setup:See section Simple Printer
Setup to learn how to connect a printer, tell LPD how to
communicate with it, and print plain text files to the
printer.See section Advanced
Printer Setup to find out how to print a variety of
special file formats, to print header pages, to print across a
network, to control access to printers, and to do printer
accounting.Simple Printer SetupThis section tells how to configure printer hardware and the
LPD software to use the printer. It teaches the basics:Section Hardware
Setup gives some hints on connecting the printer to a
port on your computer.Section Software
Setup shows how to setup the LPD spooler configuration
file (/etc/printcap).If you are setting up a printer that uses a network protocol
to accept data to print instead of a serial or parallel interface,
see Printers With
Networked Data Stream Interfaces.Although this section is called Simple Printer
Setup, it is actually fairly complex. Getting the printer
to work with your computer and the LPD spooler is the hardest
part. The advanced options like header pages and accounting are
fairly easy once you get the printer working.Hardware SetupThis section tells about the various ways you can connect a
printer to your PC. It talks about the kinds of ports and
cables, and also the kernel configuration you may need to enable
FreeBSD to speak to the printer.If you have already connected your printer and have
successfully printed with it under another operating system, you
can probably skip to section Software Setup.Ports and CablesNearly all printers you can get for a PC today support one
or both of the following interfaces:printerserialSerial interfaces use a serial
port on your computer to send data to the printer. Serial
interfaces are common in the computer industry and cables
are readily available and also easy to construct. Serial
interfaces sometimes need special cables and might require
you to configure somewhat complex communications
options.printerparallelParallel interfaces use a
parallel port on your computer to send data to the
printer. Parallel interfaces are common in the PC market.
Cables are readily available but more difficult to
construct by hand. There are usually no communications
options with parallel interfaces, making their
configuration exceedingly simple.centronics (see parallel printers)Parallel interfaces are sometimes known as
Centronics interfaces, named after the
connector type on the printer.In general, serial interfaces are slower than parallel
interfaces. Parallel interfaces usually offer just
one-way communication (computer to printer) while serial
gives you two-way. Many newer parallel ports and printers
can communicate in both directions under FreeBSD when a
IEEE1284 compliant cable is used.PostScriptUsually, the only time you need two-way communication with
the printer is if the printer speaks PostScript. PostScript
printers can be very verbose. In fact, 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 the
user.Parallel PortsTo 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 /dev/lpt0 to
FreeBSD; the second is /dev/lpt1, and so
on.Serial PortsTo 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.null-modem cableA 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.baud rateparityflow control protocolYou 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) 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.Software SetupThis section describes the software setup necessary to print
with the LPD spooling system in FreeBSD.Here is an outline of the steps involved:Configure your kernel, if necessary, for the port you
are using for the printer; section Kernel Configuration tells
you what you need to do.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.Test if the operating system can send data to the printer.
Section Checking Printer
Communications gives some suggestions on how to do
this.Set up LPD for the printer by modifying the file
/etc/printcap. You will find out how
to do this later in this chapter.Kernel ConfigurationThe 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:&prompt.root; dmesg | grep sioNWhere N is the number of the
serial port, starting from zero. If you see output similar to
the following:sio2 at 0x3e8-0x3ef irq 5 on isa
sio2: type 16550Athen the kernel supports the port.To find out if the kernel supports a parallel interface,
type:&prompt.root; dmesg | grep lptNWhere N is the number of the
parallel port, starting from zero. If you see output similar
to the following lpt0 at 0x378-0x37f on isa
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.Adding /dev Entries for the
PortsEven though the kernel may support communication along a
serial or parallel port, you will still need a software
interface through which programs running on the system can
send and receive data. That is what entries in the
/dev directory are for.To add a /dev entry for a
port:Become root with the &man.su.1; command. Enter the
root password when prompted.Change to the /dev
directory:&prompt.root; cd /devType:&prompt.root; ./MAKEDEV portWhere port is the device
entry for the port you want to make. Use
lpt0 for the first parallel port,
lpt1 for the second, and so on; use
ttyd0 for the first serial port,
ttyd1 for the second, and so on.Type:&prompt.root; ls -l portto make sure the device entry got created.Setting the Communication Mode for the Parallel
PortWhen you are using the parallel interface, you can choose
whether FreeBSD should use interrupt-driven or polled
communication with the printer.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 somewhat faster but uses up
a precious IRQ line. You should use whichever one
works.You can set the communications mode in two ways: by
configuring the kernel or by using the &man.lptcontrol.8;
program.To set the communications mode by configuring
the kernel:Edit your kernel configuration file. Look for or add
an lpt0 entry. If you are setting up
the second parallel port, use lpt1
instead. Use lpt2 for the third port,
and so on.If you want interrupt-driven mode, add the
irq specifier:device lpt0 at isa? port? tty irq N vector lptintrWhere N is the IRQ
number for your computer's parallel port.If you want polled mode, do not add the
irq specifier:device lpt0 at isa? port? tty vector lptintrSave the file. Then configure, build, and install the
kernel, then reboot. See kernel configuration for
more details.To set the communications mode with
&man.lptcontrol.8;:Type:&prompt.root; lptcontrol -i -u Nto set interrupt-driven mode for
lptN.Type:&prompt.root; lptcontrol -p -u Nto 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 &man.lptcontrol.8; for more
information.Checking Printer CommunicationsBefore 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 &man.lptest.1; is perfect: it generates all 96
printable ASCII characters in 96 lines.PostScriptFor 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
showpageThe above PostScript code can be placed into a file and
used as shown in the examples appearing in the following
sections.PCLWhen 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.Checking a Parallel PrinterprinterparallelThis 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:Become root with &man.su.1;.Send data to the printer.If the printer can print plain text, then use
&man.lptest.1;. Type:&prompt.root; lptest > /dev/lptNWhere 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:&prompt.root; cat > /dev/lptNThen, 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:&prompt.root; cat file > /dev/lptNWhere 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.Checking a Serial PrinterprinterserialThis 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:Become root with &man.su.1;.Edit the file /etc/remote. Add
the following entry:printer:dv=/dev/port:br#bps-rate:pa=paritybits-per-secondserial portparityWhere 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=noneConnect to the printer with &man.tip.1;.
Type:&prompt.root; tip printerIf this step does not work, edit the file
/etc/remote again and try using
/dev/cuaaN
instead of
/dev/ttydN.Send data to the printer.If the printer can print plain text, then use
&man.lptest.1;. Type:~$lptestIf 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:~>fileWhere file is the
name of the file containing the program. After
&man.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.Enabling the Spooler: The /etc/printcap
FileAt 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.printercapabilitiesThe format of the &man.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 &man.cgetent.3;.The simple spooler configuration consists of the following
steps: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.header pagesTurn off header pages (which are on by default) by
inserting the sh capability; see the
Suppressing Header
Pages section for more information.Make a spooling directory, and specify its location with
the sd capability; see the Making the Spooling
Directory section for more information.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 fs, fc,
xs, and xc
capabilities; which is discussed in the Configuring Spooler
Communications Parameters section.Install a plain text input filter; see the Installing the Text
Filter section for details.Test the setup by printing something with the
&man.lpr.1; command. More details are available in the
Trying It Out and
Troubleshooting
sections.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.Naming the PrinterThe 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.Suppressing Header Pagesprintingheader pagesThe 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 with
a single TAB. Every line in an entry except the last ends in
a backslash character.Making the Spooling Directoryprinter spoolprint jobsThe 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 &man.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:&prompt.root; mkdir /var/spool/printer-nameHowever, 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:&prompt.root; mkdir /var/spool/lpd
&prompt.root; mkdir /var/spool/lpd/rattan
&prompt.root; mkdir /var/spool/lpd/bambooIf 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:&prompt.root; chown daemon:daemon /var/spool/lpd/rattan
&prompt.root; chown daemon:daemon /var/spool/lpd/bamboo
&prompt.root; chmod 770 /var/spool/lpd/rattan
&prompt.root; chmod 770 /var/spool/lpd/bambooFinally, 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 with a tab and each line 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.Identifying the Printer DeviceIn the Adding
/dev 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.Configuring Spooler Communication ParametersprinterserialFor 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-rateSets 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, or 38400 bits-per-second.fc#clear-bitsClears the flag bits
clear-bits in the
sgttyb structure after
opening the device.fs#set-bitsSets the flag bits
set-bits in the
sgttyb structure.xc#clear-bitsClears local mode bits
clear-bits after opening the
device.xs#set-bitsSets local mode bits
set-bits.For more information on the bits for the
fc, fs,
xc, and xs capabilities,
see the file
/usr/include/sys/ioctl_compat.h.When LPD opens the device specified by the
lp capability, it reads the flag bits in
the sgttyb structure; it clears any bits in
the fc capability, then sets bits in the
fs capability, then applies the resultant
setting. It does the same for the local mode bits as
well.Let us add to our example printer on the sixth serial
port. We will set the bps rate to 38400. For the flag bits,
we will set the TANDEM,
ANYP, LITOUT,
FLUSHO, and PASS8 flags.
For the local mode bits, we will set the
LITOUT and PASS8
flags:bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
:sh:sd=/var/spool/lpd/bamboo:\
:lp=/dev/ttyd5:fs#0x82000c1:xs#0x820:Installing the Text Filterprint filtersWe 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 2Make the file executable:&prompt.root; chmod 555 /usr/local/libexec/if-simpleAnd 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:fs#0x82000e1:xs#0x820:\
:if=/usr/local/libexec/if-simple:Turn on LPD&man.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 &man.lpd.8;.&prompt.root; lpdTrying It OutYou 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 &man.lpr.1;,
which submits a job for printing.You can combine &man.lpr.1; with the &man.lptest.1;
program, introduced in section Checking Printer
Communications to generate some test text.To test the simple LPD setup:Type:&prompt.root; lptest 20 5 | lpr -Pprinter-nameWhere printer-name is a the
name of a printer (or an alias) specified in
/etc/printcap. To test the default
printer, type &man.lpr.1; without any
argument. Again, if you are testing a printer that expects
PostScript, send a PostScript program in that language instead
of using &man.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 &man.lptest.1;, then your
results should look like the following:!"#$%&'()*+,-./01234
"#$%&'()*+,-./012345
#$%&'()*+,-./0123456
$%&'()*+,-./01234567
%&'()*+,-./012345678To further test the printer, try downloading larger
programs (for language-based printers) or running
&man.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.Advanced Printer SetupThis section describes filters for printing specially formatted
files, header pages, printing across networks, and restricting and
accounting for printer usage.Filtersprint filtersAlthough LPD handles network protocols, queuing, access control,
and other aspects of printing, most of the real
work happens in the filters. Filters are
programs that communicate with the printer and handle its device
dependencies and special requirements. In the simple printer setup,
we installed a plain text filter—an extremely simple one that
should work with most printers (section Installing the Text
Filter).However, in order to take advantage of format conversion, printer
accounting, specific printer quirks, and so on, you should understand
how filters work. It will ultimately be the filter's responsibility
to handle these aspects. And the bad news is that most of the time
you have to provide filters yourself. The good
news is that many are generally available; when they are not, they are
usually easy to write.Also, FreeBSD comes with one,
/usr/libexec/lpr/lpf, that works with many
printers that can print plain text. (It handles backspacing and tabs
in the file, and does accounting, but that is about all it does.)
There are also several filters and filter components in the FreeBSD
ports collection.Here is what you will find in this section:Section How Filters
Work, tries to give an overview of a filter's role in the
printing process. You should read this section to get an
understanding of what is happening under the hood
when LPD uses filters. This knowledge could help you anticipate
and debug problems you might encounter as you install more and
more filters on each of your printers.LPD expects every printer to be able to print plain text by
default. This presents a problem for PostScript (or other
language-based printers) which cannot directly print plain text.
Section Accommodating
Plain Text Jobs on PostScript Printers tells you what you
should do to overcome this problem. You should read this
section if you have a PostScript printer.PostScript is a popular output format for many programs. Even
some people (myself included) write PostScript code directly. But
PostScript printers are expensive. Section Simulating PostScript on
Non-PostScript Printers tells how you can further modify
a printer's text filter to accept and print PostScript data on a
non-PostScript printer. You should read
this section if you do not have a PostScript printer.Section Conversion
Filters tells about a way you can automate the conversion
of specific file formats, such as graphic or typesetting data,
into formats your printer can understand. After reading this
section, you should be able to set up your printers such that
users can type lpr -t to print troff data, or
lpr -d to print TeX DVI data, or lpr
-v to print raster image data, and so forth. I
recommend reading this section.Section Output
Filters tells all about a not often used feature of LPD:
output filters. Unless you are printing header pages (see Header Pages),
you can probably skip that section altogether.Section lpf: a Text
Filter describes lpf, a fairly
complete if simple text filter for line printers (and laser
printers that act like line printers) that comes with FreeBSD. If
you need a quick way to get printer accounting working for plain
text, or if you have a printer which emits smoke when it sees
backspace characters, you should definitely consider
lpf.How Filters WorkAs mentioned before, a filter is an executable program started
by LPD to handle the device-dependent part of communicating with the
printer.When LPD wants to print a file in a job, it starts a filter
program. It sets the filter's standard input to the file to print,
its standard output to the printer, and its standard error to the
error logging file (specified in the lf
capability in /etc/printcap, or
/dev/console by default).troffWhich filter LPD starts and the filter's arguments depend on
what is listed in the /etc/printcap file and
what arguments the user specified for the job on the
&man.lpr.1; command line. For example, if the user typed
lpr -t, LPD would start the troff filter, listed
in the tf capability for the destination printer.
If the user wanted to print plain text, it would start the
if filter (this is mostly true: see Output Filters for
details).There are three kinds of filters you can specify in
/etc/printcap:The text filter, confusingly called the
input filter in LPD documentation, handles
regular text printing. Think of it as the default filter. LPD
expects every printer to be able to print plain text by default,
and it is the text filter's job to make sure backspaces, tabs,
or other special characters do not confuse the printer. If you
are in an environment where you have to account for printer
usage, the text filter must also account for pages printed,
usually by counting the number of lines printed and comparing
that to the number of lines per page the printer supports. The
text filter is started with the following argument list:
filter-name-c-wwidth-llength-iindent-n login-h hostacct-file
where
appears if the job's submitted with lpr
-lwidthis the value from the pw (page
width) capability specified in
/etc/printcap, default 132lengthis the value from the pl (page
length) capability, default 66indentis the amount of the indentation from lpr
-i, default 0loginis the account name of the user printing the
filehostis the host name from which the job was
submittedacct-fileis the name of the accounting file from the
af capability.printerfiltersA conversion filter converts a specific
file format into one the printer can render onto paper. For
example, ditroff typesetting data cannot be directly printed,
but you can install a conversion filter for ditroff files to
convert the ditroff data into a form the printer can digest and
print. Section Conversion
Filters tells all about them. Conversion filters also
need to do accounting, if you need printer accounting.
Conversion filters are started with the following arguments:
filter-name-xpixel-width-ypixel-height-n login-h hostacct-file
where pixel-width is the value
from the px capability (default 0) and
pixel-height is the value from the
py capability (default 0).The output filter is used only if there
is no text filter, or if header pages are enabled. In my
experience, output filters are rarely used. Section Output Filters describe
them. There are only two arguments to an output filter:
filter-name-wwidth-llength
which are identical to the text filters and
arguments.Filters should also exit with the
following exit status:exit 0If the filter printed the file successfully.exit 1If the filter failed to print the file but wants LPD to
try to print the file again. LPD will restart a filter if it
exits with this status.exit 2If the filter failed to print the file and does not want
LPD to try again. LPD will throw out the file.The text filter that comes with the FreeBSD release,
/usr/libexec/lpr/lpf, takes advantage of the
page width and length arguments to determine when to send a form
feed and how to account for printer usage. It uses the login, host,
and accounting file arguments to make the accounting entries.If you are shopping for filters, see if they are LPD-compatible.
If they are, they must support the argument lists described above.
If you plan on writing filters for general use, then have them
support the same argument lists and exit codes.Accommodating Plain Text Jobs on PostScript Printersprint jobsIf you are the only user of your computer and PostScript (or
other language-based) printer, and you promise to never send plain
text to your printer and to never use features of various programs
that will want to send plain text to your printer, then you do not
need to worry about this section at all.But, if you would like to send both PostScript and plain text
jobs to the printer, then you are urged to augment your printer
setup. To do so, we have the text filter detect if the arriving job
is plain text or PostScript. All PostScript jobs must start with
%! (for other printer languages, see your printer
documentation). If those are the first two characters in the job,
we have PostScript, and can pass the rest of the job directly. If
those are not the first two characters in the file, then the filter
will convert the text into PostScript and print the result.How do we do this?printerserialIf you have got a serial printer, a great way to do it is to
install lprps. lprps is a
PostScript printer filter which performs two-way communication with
the printer. It updates the printer's status file with verbose
information from the printer, so users and administrators can see
exactly what the state of the printer is (such as toner
low or paper jam). But more
importantly, it includes a program called psif
which detects whether the incoming job is plain text and calls
textps (another program that comes with
lprps) to convert it to PostScript. It then uses
lprps to send the job to the printer.lprps is part of the FreeBSD ports collection
(see The Ports Collection). You can
fetch, build and install it yourself, of course. After installing
lprps, just specify the pathname to the
psif program that is part of
lprps. If you installed lprps
from the ports collection, use the following in the serial
PostScript printer's entry in
/etc/printcap::if=/usr/local/libexec/psif:You should also specify the rw capability;
that tells LPD to open the printer in read-write mode.If you have a parallel PostScript printer (and therefore cannot
use two-way communication with the printer, which
lprps needs), you can use the following shell
script as the text filter:#!/bin/sh
#
# psif - Print PostScript or plain text on a PostScript printer
# Script version; NOT the version that comes with lprps
# Installed in /usr/local/libexec/psif
#
read first_line
first_two_chars=`expr "$first_line" : '\(..\)'`
if [ "$first_two_chars" = "%!" ]; then
#
# PostScript job, print it.
#
echo "$first_line" && cat && printf "\004" && exit 0
exit 2
else
#
# Plain text, convert it, then print it.
#
( echo "$first_line"; cat ) | /usr/local/bin/textps && printf "\004" && exit 0
exit 2
fiIn the above script, textps is a program we
installed separately to convert plain text to PostScript. You can
use any text-to-PostScript program you wish. The FreeBSD ports
collection (see The Ports Collection)
includes a full featured text-to-PostScript program called
a2ps that you might want to investigate.Simulating PostScript on Non-PostScript PrintersPostScriptemulatingGhostscriptPostScript is the de facto standard for
high quality typesetting and printing. PostScript is, however, an
expensive standard. Thankfully, Alladin
Enterprises has a free PostScript work-alike called
Ghostscript that runs with FreeBSD.
Ghostscript can read most PostScript files and can render their
pages onto a variety of devices, including many brands of
non-PostScript printers. By installing Ghostscript and using a
special text filter for your printer, you can make your
non-PostScript printer act like a real PostScript printer.Ghostscript is in the FreeBSD ports collection, if you
would like to install it from there. You can fetch, build, and
install it quite easily yourself, as well.To simulate PostScript, we have the text filter detect if it is
printing a PostScript file. If it is not, then the filter will pass
the file directly to the printer; otherwise, it will use Ghostscript
to first convert the file into a format the printer will
understand.Here is an example: the following script is a text filter
for Hewlett Packard DeskJet 500 printers. For other printers,
substitute the argument to the
gs (Ghostscript) command. (Type gs
-h to get a list of devices the current installation of
Ghostscript supports.)#!/bin/sh
#
# ifhp - Print Ghostscript-simulated PostScript on a DeskJet 500
# Installed in /usr/local/libexec/hpif
#
# Treat LF as CR+LF:
#
printf "\033&k2G" || exit 2
#
# Read first two characters of the file
#
read first_line
first_two_chars=`expr "$first_line" : '\(..\)'`
if [ "$first_two_chars" = "%!" ]; then
#
# It is PostScript; use Ghostscript to scan-convert and print it.
#
# Note that PostScript files are actually interpreted programs,
# and those programs are allowed to write to stdout, which will
# mess up the printed output. So, we redirect stdout to stderr
# and then make descriptor 3 go to stdout, and have Ghostscript
# write its output there. Exercise for the clever reader:
# capture the stderr output from Ghostscript and mail it back to
# the user originating the print job.
#
exec 3>&1 1>&2
/usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 \
-sOutputFile=/dev/fd/3 - && exit 0
#
/usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 -sOutputFile=- - \
&& exit 0
else
#
# Plain text or HP/PCL, so just print it directly; print a form
# at the end to eject the last page.
#
echo $first_line && cat && printf "\033&l0H" &&
exit 0
fi
exit 2Finally, you need to notify LPD of the filter via the
if capability::if=/usr/local/libexec/hpif:That is it. You can type lpr plain.text and
lpr whatever.ps and both should print
successfully.Conversion FiltersAfter completing the simple setup described in Simple Printer Setup, the first
thing you will probably want to do is install conversion filters for
your favorite file formats (besides plain ASCII text).Why Install Conversion Filters?TeXprinting dvi filesConversion filters make printing various kinds of files easy.
As an example, suppose we do a lot of work with the TeX
typesetting system, and we have a PostScript printer. Every time
we generate a DVI file from TeX, we cannot print it directly until
we convert the DVI file into PostScript. The command sequence
goes like this:&prompt.user; dvips seaweed-analysis.dvi
&prompt.user; lpr seaweed-analysis.psBy installing a conversion filter for DVI files, we can skip
the hand conversion step each time by having LPD do it for us.
Now, each time we get a DVI file, we are just one step away from
printing it:&prompt.user; lpr -d seaweed-analysis.dviWe got LPD to do the DVI file conversion for us by specifying
the option. Section Formatting and Conversion
Options lists the conversion options.For each of the conversion options you want a printer to
support, install a conversion filter and
specify its pathname in /etc/printcap. A
conversion filter is like the text filter for the simple printer
setup (see section Installing
the Text Filter) except that instead of printing plain
text, the filter converts the file into a format the printer can
understand.Which Conversions Filters Should I Install?You should install the conversion filters you expect to use.
If you print a lot of DVI data, then a DVI conversion filter is in
order. If you have got plenty of troff to print out, then you
probably want a troff filter.The following table summarizes the filters that LPD works
with, their capability entries for the
/etc/printcap file, and how to invoke them
with the lpr command:File type/etc/printcap capabilitylpr optioncifplotcfDVIdfplotgfditroffnfFORTRAN textrftroffrfrastervfplain textifnone, , or
In our example, using lpr -d means the
printer needs a df capability in its entry in
/etc/printcap.fortranDespite what others might contend, formats like FORTRAN text
and plot are probably obsolete. At your site, you can give new
meanings to these or any of the formatting options just by
installing custom filters. For example, suppose you would like to
directly print Printerleaf files (files from the Interleaf desktop
publishing program), but will never print plot files. You could
install a Printerleaf conversion filter under the
gf capability and then educate your users that
lpr -g mean print Printerleaf
files.Installing Conversion FiltersSince conversion filters are programs you install outside of
the base FreeBSD installation, they should probably go under
/usr/local. The directory
/usr/local/libexec is a popular location,
since they are specialized programs that only LPD will run;
regular users should not ever need to run them.To enable a conversion filter, specify its pathname under the
appropriate capability for the destination printer in
/etc/printcap.In our example, we will add the DVI conversion filter to the
entry for the printer named bamboo. Here is
the example /etc/printcap file again, with
the new df capability for the printer
bamboo.#
# /etc/printcap for host rose - added df filter for bamboo
#
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:fs#0x82000e1:xs#0x820:rw:\
:if=/usr/local/libexec/psif:\
:df=/usr/local/libexec/psdf:The DVI filter is a shell script named
/usr/local/libexec/psdf. Here is that
script:#!bin/sh
#
# psdf - DVI to PostScript printer filter
# Installed in /usr/local/libexec/psdf
#
# Invoked by lpd when user runs lpr -d
#
exec /usr/local/bin/dvips -f | /usr/local/libexec/lprps "$@"This script runs dvips in filter mode (the
argument) on standard input, which is the job
to print. It then starts the PostScript printer filter
lprps (see section Accommodating Plain
Text Jobs on PostScript Printers) with the arguments LPD
passed to this script. lprps will use those
arguments to account for the pages printed.More Conversion Filter ExamplesSince there is no fixed set of steps to install conversion
filters, let me instead provide more examples. Use these as
guidance to making your own filters. Use them directly, if
appropriate.This example script is a raster (well, GIF file, actually)
conversion filter for a Hewlett Packard LaserJet III-Si
printer:#!/bin/sh
#
# hpvf - Convert GIF files into HP/PCL, then print
# Installed in /usr/local/libexec/hpvf
PATH=/usr/X11R6/bin:$PATH; export PATH
giftopnm | ppmtopgm | pgmtopbm | pbmtolj -resolution 300 \
&& exit 0 \
|| exit 2It works by converting the GIF file into a portable anymap,
converting that into a portable graymap, converting that into a
portable bitmap, and converting that into LaserJet/PCL-compatible
data.Here is the /etc/printcap file with an
entry for a printer using the above filter:#
# /etc/printcap for host orchid
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
:lp=/dev/lpt0:sh:sd=/var/spool/lpd/teak:mx#0:\
:if=/usr/local/libexec/hpif:\
:vf=/usr/local/libexec/hpvf:The following script is a conversion filter for troff data
from the groff typesetting system for the PostScript printer named
bamboo:#!/bin/sh
#
# pstf - Convert groff's troff data into PS, then print.
# Installed in /usr/local/libexec/pstf
#
exec grops | /usr/local/libexec/lprps "$@"The above script makes use of lprps again
to handle the communication with the printer. If the printer were
on a parallel port, we would use this script instead:#!/bin/sh
#
# pstf - Convert groff's troff data into PS, then print.
# Installed in /usr/local/libexec/pstf
#
exec gropsThat is it. Here is the entry we need to add to
/etc/printcap to enable the filter::tf=/usr/local/libexec/pstf:Here is an example that might make old hands at FORTRAN blush.
It is a FORTRAN-text filter for any printer that can directly
print plain text. We will install it for the printer
teak:#!/bin/sh
#
# hprf - FORTRAN text filter for LaserJet 3si:
# Installed in /usr/local/libexec/hprf
#
printf "\033&k2G" && fpr && printf "\033&l0H" &&
exit 0
exit 2And we will add this line to the
/etc/printcap for the printer
teak to enable this filter::rf=/usr/local/libexec/hprf:Here is one final, somewhat complex example. We will add a
DVI filter to the LaserJet printer teak
introduced earlier. First, the easy part: updating
/etc/printcap with the location of the DVI
filter::df=/usr/local/libexec/hpdf:Now, for the hard part: making the filter. For that, we need
a DVI-to-LaserJet/PCL conversion program. The FreeBSD ports
collection (see The Ports Collection)
has one: dvi2xx is the name of the package.
Installing this package gives us the program we need,
dvilj2p, which converts DVI into LaserJet IIp,
LaserJet III, and LaserJet 2000 compatible codes.dvilj2p makes the filter
hpdf quite complex since
dvilj2p cannot read from standard input. It
wants to work with a filename. What is worse, the filename has to
end in .dvi so using
/dev/fd/0 for standard input is problematic.
We can get around that problem by linking (symbolically) a
temporary file name (one that ends in .dvi)
to /dev/fd/0, thereby forcing
dvilj2p to read from standard input.The only other fly in the ointment is the fact that we cannot
use /tmp for the temporary link. Symbolic
links are owned by user and group bin. The
filter runs as user daemon. And the
/tmp directory has the sticky bit set. The
filter can create the link, but it will not be able clean up when
done and remove it since the link will belong to a different
user.Instead, the filter will make the symbolic link in the current
working directory, which is the spooling directory (specified by
the sd capability in
/etc/printcap). This is a perfect place for
filters to do their work, especially since there is (sometimes)
more free disk space in the spooling directory than under
/tmp.Here, finally, is the filter:#!/bin/sh
#
# hpdf - Print DVI data on HP/PCL printer
# Installed in /usr/local/libexec/hpdf
PATH=/usr/local/bin:$PATH; export PATH
#
# Define a function to clean up our temporary files. These exist
# in the current directory, which will be the spooling directory
# for the printer.
#
cleanup() {
rm -f hpdf$$.dvi
}
#
# Define a function to handle fatal errors: print the given message
# and exit 2. Exiting with 2 tells LPD to do not try to reprint the
# job.
#
fatal() {
echo "$@" 1>&2
cleanup
exit 2
}
#
# If user removes the job, LPD will send SIGINT, so trap SIGINT
# (and a few other signals) to clean up after ourselves.
#
trap cleanup 1 2 15
#
# Make sure we are not colliding with any existing files.
#
cleanup
#
# Link the DVI input file to standard input (the file to print).
#
ln -s /dev/fd/0 hpdf$$.dvi || fatal "Cannot symlink /dev/fd/0"
#
# Make LF = CR+LF
#
printf "\033&k2G" || fatal "Cannot initialize printer"
#
# Convert and print. Return value from dvilj2p does not seem to be
# reliable, so we ignore it.
#
dvilj2p -M1 -q -e- dfhp$$.dvi
#
# Clean up and exit
#
cleanup
exit 0Automated Conversion: An Alternative To Conversion
FiltersAll these conversion filters accomplish a lot for your
printing environment, but at the cost forcing the user to specify
(on the &man.lpr.1; command line) which one to use.
If your users are not particularly computer literate, having to
specify a filter option will become annoying. What is worse,
though, is that an incorrectly specified filter option may run a
filter on the wrong type of file and cause your printer to spew
out hundreds of sheets of paper.Rather than install conversion filters at all, you might want
to try having the text filter (since it is the default filter)
detect the type of file it has been asked to print and then
automatically run the right conversion filter. Tools such as
file can be of help here. Of course, it will
be hard to determine the differences between
some file types—and, of course, you can
still provide conversion filters just for them.apsfilterprinterfiltersapsfilterThe FreeBSD ports collection has a text filter that performs
automatic conversion called apsfilter. It can
detect plain text, PostScript, and DVI files, run the proper
conversions, and print.Output FiltersThe LPD spooling system supports one other type of filter that
we have not yet explored: an output filter. An output filter is
intended for printing plain text only, like the text filter, but
with many simplifications. If you are using an output filter but no
text filter, then:LPD starts an output filter once for the entire job instead
of once for each file in the job.LPD does not make any provision to identify the start or the
end of files within the job for the output filter.LPD does not pass the user's login or host to the filter, so
it is not intended to do accounting. In fact, it gets only two
arguments:filter-name-wwidth-llengthWhere width is from the
pw capability and
length is from the
pl capability for the printer in
question.Do not be seduced by an output filter's simplicity. If you
would like each file in a job to start on a different page an output
filter will not work. Use a text filter (also
known as an input filter); see section Installing the Text Filter.
Furthermore, an output filter is actually more
complex in that it has to examine the byte stream being
sent to it for special flag characters and must send signals to
itself on behalf of LPD.However, an output filter is necessary if
you want header pages and need to send escape sequences or other
initialization strings to be able to print the header page. (But it
is also futile if you want to charge header
pages to the requesting user's account, since LPD does not give any
user or host information to the output filter.)On a single printer, LPD allows both an output filter and text
or other filters. In such cases, LPD will start the output filter
to print the header page (see section Header Pages)
only. LPD then expects the output filter to stop
itself by sending two bytes to the filter: ASCII 031
followed by ASCII 001. When an output filter sees these two bytes
(031, 001), it should stop by sending SIGSTOP to itself. When LPD's
done running other filters, it will restart the output filter by
sending SIGCONT to it.If there is an output filter but no text
filter and LPD is working on a plain text job, LPD uses the output
filter to do the job. As stated before, the output filter will
print each file of the job in sequence with no intervening form
feeds or other paper advancement, and this is probably
not what you want. In almost all cases, you
need a text filter.The program lpf, which we introduced earlier
as a text filter, can also run as an output filter. If you need a
quick-and-dirty output filter but do not want to write the byte
detection and signal sending code, try lpf. You
can also wrap lpf in a shell script to handle any
initialization codes the printer might require.lpf: a Text FilterThe program /usr/libexec/lpr/lpf that comes
with FreeBSD binary distribution is a text filter (input filter)
that can indent output (job submitted with lpr
-i), allow literal characters to pass (job submitted
with lpr -l), adjust the printing position for
backspaces and tabs in the job, and account for pages printed. It
can also act like an output filter.lpf is suitable for many printing
environments. And although it has no capability to send
initialization sequences to a printer, it is easy to write a shell
script to do the needed initialization and then execute
lpf.page accountingaccountingprinterIn order for lpf to do page accounting
correctly, it needs correct values filled in for the
pw and pl capabilities in the
/etc/printcap file. It uses these values to
determine how much text can fit on a page and how many pages were in
a user's job. For more information on printer accounting, see Accounting for Printer
Usage.Header PagesIf you have lots of users, all of them using
various printers, then you probably want to consider header
pages as a necessary evil.banner pages (see header pages)header pagesHeader pages, also known as banner or
burst pages identify to whom jobs belong after
they are printed. They are usually printed in large, bold letters,
perhaps with decorative borders, so that in a stack of printouts they
stand out from the real documents that comprise users' jobs. They
enable users to locate their jobs quickly. The obvious drawback to a
header page is that it is yet one more sheet that has to be printed
for every job, their ephemeral usefulness lasting not more than a few
minutes, ultimately finding themselves in a recycling bin or rubbish
heap. (Note that header pages go with each job, not each file in a
job, so the paper waste might not be that bad.)The LPD system can provide header pages automatically for your
printouts if your printer can directly print
plain text. If you have a PostScript printer, you will need an
external program to generate the header page; see Header Pages on
PostScript Printers.Enabling Header PagesIn the Simple Printer
Setup, we turned off header pages by specifying
sh (meaning suppress header) in the
/etc/printcap file. To enable header pages for
a printer, just remove the sh capability.Sounds too easy, right?You are right. You might have to provide
an output filter to send initialization strings to the printer.
Here is an example output filter for Hewlett Packard PCL-compatible
printers:#!/bin/sh
#
# hpof - Output filter for Hewlett Packard PCL-compatible printers
# Installed in /usr/local/libexec/hpof
printf "\033&k2G" || exit 2
exec /usr/libexec/lpr/lpfSpecify the path to the output filter in the
of capability. See Output Filters for more
information.Here is an example /etc/printcap file for
the printer teak that we introduced earlier; we
enabled header pages and added the above output filter:#
# /etc/printcap for host orchid
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
:lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:\
:if=/usr/local/libexec/hpif:\
:vf=/usr/local/libexec/hpvf:\
:of=/usr/local/libexec/hpof:Now, when users print jobs to teak, they get
a header page with each job. If users want to spend time searching
for their printouts, they can suppress header pages by submitting
the job with lpr -h; see Header Page Options for
more &man.lpr.1; options.LPD prints a form feed character after the header page. If
your printer uses a different character or sequence of characters
to eject a page, specify them with the ff
capability in /etc/printcap.Controlling Header PagesBy enabling header pages, LPD will produce a long
header, a full page of large letters identifying the
user, host, and job. Here is an example (kelly printed the job
named outline from host rose): k ll ll
k l l
k l l
k k eeee l l y y
k k e e l l y y
k k eeeeee l l y y
kk k e l l y y
k k e e l l y yy
k k eeee lll lll yyy y
y
y y
yyyy
ll
t l i
t l
oooo u u ttttt l ii n nnn eeee
o o u u t l i nn n e e
o o u u t l i n n eeeeee
o o u u t l i n n e
o o u uu t t l i n n e e
oooo uuu u tt lll iii n n eeee
r rrr oooo ssss eeee
rr r o o s s e e
r o o ss eeeeee
r o o ss e
r o o s s e e
r oooo ssss eeee
Job: outline
Date: Sun Sep 17 11:04:58 1995LPD appends a form feed after this text so the job starts on a
new page (unless you have sf (suppress form
feeds) in the destination printer's entry in
/etc/printcap).If you prefer, LPD can make a short header;
specify sb (short banner) in the
/etc/printcap file. The header page will look
like this:rose:kelly Job: outline Date: Sun Sep 17 11:07:51 1995Also by default, LPD prints the header page first, then the job.
To reverse that, specify hl (header last) in
/etc/printcap.Accounting for Header PagesUsing LPD's built-in header pages enforces a particular paradigm
when it comes to printer accounting: header pages must be
free of charge.Why?Because the output filter is the only external program that will
have control when the header page is printed that could do
accounting, and it is not provided with any user or
host information or an accounting file, so it has no
idea whom to charge for printer use. It is also not enough to just
add one page to the text filter or any of the
conversion filters (which do have user and host information) since
users can suppress header pages with lpr -h.
They could still be charged for header pages they did not print.
Basically, lpr -h will be the preferred option of
environmentally-minded users, but you cannot offer any incentive to
use it.It is still not enough to have each of the
filters generate their own header pages (thereby being able to
charge for them). If users wanted the option of suppressing the
header pages with lpr -h, they will still get
them and be charged for them since LPD does not pass any knowledge
of the option to any of the filters.So, what are your options?You can:Accept LPD's paradigm and make header pages free.Install an alternative to LPD, such as LPRng. Section
Alternatives to the
Standard Spooler tells more about other spooling
software you can substitute for LPD.Write a smart output filter. Normally,
an output filter is not meant to do anything more than
initialize a printer or do some simple character conversion. It
is suited for header pages and plain text jobs (when there is no
text (input) filter). But, if there is a text filter for the
plain text jobs, then LPD will start the output filter only for
the header pages. And the output filter can parse the header
page text that LPD generates to determine what user and host to
charge for the header page. The only other problem with this
method is that the output filter still does not know what
accounting file to use (it is not passed the name of the file
from the af capability), but if you have a
well-known accounting file, you can hard-code that into the
output filter. To facilitate the parsing step, use the
sh (short header) capability in
/etc/printcap. Then again, all that might
be too much trouble, and users will certainly appreciate the
more generous system administrator who makes header pages
free.Header Pages on PostScript PrintersAs described above, LPD can generate a plain text header page
suitable for many printers. Of course, PostScript cannot directly
print plain text, so the header page feature of LPD is
useless—or mostly so.One obvious way to get header pages is to have every conversion
filter and the text filter generate the header page. The filters
should use the user and host arguments to generate a suitable
header page. The drawback of this method is that users will always
get a header page, even if they submit jobs with lpr
-h.Let us explore this method. The following script takes three
arguments (user login name, host name, and job name) and makes a
simple PostScript header page:#!/bin/sh
#
# make-ps-header - make a PostScript header page on stdout
# Installed in /usr/local/libexec/make-ps-header
#
#
# These are PostScript units (72 to the inch). Modify for A4 or
# whatever size paper you are using:
#
page_width=612
page_height=792
border=72
#
# Check arguments
#
if [ $# -ne 3 ]; then
echo "Usage: `basename $0` <user> <host> <job>" 1>&2
exit 1
fi
#
# Save these, mostly for readability in the PostScript, below.
#
user=$1
host=$2
job=$3
date=`date`
#
# Send the PostScript code to stdout.
#
exec cat <<EOF
%!PS
%
% Make sure we do not interfere with user's job that will follow
%
save
%
% Make a thick, unpleasant border around the edge of the paper.
%
$border $border moveto
$page_width $border 2 mul sub 0 rlineto
0 $page_height $border 2 mul sub rlineto
currentscreen 3 -1 roll pop 100 3 1 roll setscreen
$border 2 mul $page_width sub 0 rlineto closepath
0.8 setgray 10 setlinewidth stroke 0 setgray
%
% Display user's login name, nice and large and prominent
%
/Helvetica-Bold findfont 64 scalefont setfont
$page_width ($user) stringwidth pop sub 2 div $page_height 200 sub moveto
($user) show
%
% Now show the boring particulars
%
/Helvetica findfont 14 scalefont setfont
/y 200 def
[ (Job:) (Host:) (Date:) ] {
200 y moveto show /y y 18 sub def }
forall
/Helvetica-Bold findfont 14 scalefont setfont
/y 200 def
[ ($job) ($host) ($date) ] {
270 y moveto show /y y 18 sub def
} forall
%
% That is it
%
restore
showpage
EOFNow, each of the conversion filters and the text filter can call
this script to first generate the header page, and then print the
user's job. Here is the DVI conversion filter from earlier in this
document, modified to make a header page:#!/bin/sh
#
# psdf - DVI to PostScript printer filter
# Installed in /usr/local/libexec/psdf
#
# Invoked by lpd when user runs lpr -d
#
orig_args="$@"
fail() {
echo "$@" 1>&2
exit 2
}
while getopts "x:y:n:h:" option; do
case $option in
x|y) ;; # Ignore
n) login=$OPTARG ;;
h) host=$OPTARG ;;
*) echo "LPD started `basename $0` wrong." 1>&2
exit 2
;;
esac
done
[ "$login" ] || fail "No login name"
[ "$host" ] || fail "No host name"
( /usr/local/libexec/make-ps-header $login $host "DVI File"
/usr/local/bin/dvips -f ) | eval /usr/local/libexec/lprps $orig_argsNotice how the filter has to parse the argument list in order to
determine the user and host name. The parsing for the other
conversion filters is identical. The text filter takes a slightly
different set of arguments, though (see section How Filters
Work).As we have mentioned before, the above scheme, though fairly
simple, disables the suppress header page option (the
option) to lpr. If users
wanted to save a tree (or a few pennies, if you charge for header
pages), they would not be able to do so, since every filter's going
to print a header page with every job.To allow users to shut off header pages on a per-job basis, you
will need to use the trick introduced in section Accounting for
Header Pages: write an output filter that parses the
LPD-generated header page and produces a PostScript version. If the
user submits the job with lpr -h, then LPD will
not generate a header page, and neither will your output filter.
Otherwise, your output filter will read the text from LPD and send
the appropriate header page PostScript code to the printer.If you have a PostScript printer on a serial line, you can make
use of lprps, which comes with an output filter,
psof, which does the above. Note that
psof does not charge for header pages.Networked Printingprinternetworknetwork printingFreeBSD supports networked printing: sending jobs to remote
printers. Networked printing generally refers to two different
things:Accessing a printer attached to a remote host. You install a
printer that has a conventional serial or parallel interface on
one host. Then, you set up LPD to enable access to the printer
from other hosts on the network. Section Printers Installed on
Remote Hosts tells how to do this.Accessing a printer attached directly to a network. The
printer has a network interface in addition (or in place of) a
more conventional serial or parallel interface. Such a printer
might work as follows:It might understand the LPD protocol and can even queue
jobs from remote hosts. In this case, it acts just like a
regular host running LPD. Follow the same procedure in
section Printers
Installed on Remote Hosts to set up such a
printer.It might support a data stream network connection. In this
case, you attach the printer to one host on the
network by making that host responsible for spooling jobs and
sending them to the printer. Section Printers with
Networked Data Stream Interfaces gives some
suggestions on installing such printers.Printers Installed on Remote HostsThe LPD spooling system has built-in support for sending jobs to
other hosts also running LPD (or are compatible with LPD). This
feature enables you to install a printer on one host and make it
accessible from other hosts. It also works with printers that have
network interfaces that understand the LPD protocol.To enable this kind of remote printing, first install a printer
on one host, the printer host, using the simple
printer setup described in Simple
Printer Setup. Do any advanced setup in Advanced Printer Setup that you
need. Make sure to test the printer and see if it works with the
features of LPD you have enabled. Also ensure that the
local host has authorization to use the LPD
service in the remote host (see Restricting Jobs
from Remote Printers).printernetworknetwork printingIf you are using a printer with a network interface that is
compatible with LPD, then the printer host in
the discussion below is the printer itself, and the
printer name is the name you configured for the
printer. See the documentation that accompanied your printer and/or
printer-network interface.If you are using a Hewlett Packard Laserjet then the printer
name text will automatically perform the LF to
CRLF conversion for you, so you will not require the
hpif script.Then, on the other hosts you want to have access to the printer,
make an entry in their /etc/printcap files with
the following:Name the entry anything you want. For simplicity, though,
you probably want to use the same name and aliases as on the
printer host.Leave the lp capability blank, explicitly
(:lp=:).Make a spooling directory and specify its location in the
sd capability. LPD will store jobs here
before they get sent to the printer host.Place the name of the printer host in the
rm capability.Place the printer name on the printer
host in the rp
capability.That is it. You do not need to list conversion filters, page
dimensions, or anything else in the
/etc/printcap file.Here is an example. The host rose has two
printers, bamboo and rattan.
We will enable users on the host orchid to print to those printers.
Here is the /etc/printcap file for
orchid (back from section Enabling Header
Pages). It already had the entry for the printer
teak; we have added entries for the two printers
on the host rose:#
# /etc/printcap for host orchid - added (remote) printers on rose
#
#
# teak is local; it is connected directly to orchid:
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
:lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:\
:if=/usr/local/libexec/ifhp:\
:vf=/usr/local/libexec/vfhp:\
:of=/usr/local/libexec/ofhp:
#
# rattan is connected to rose; send jobs for rattan to rose:
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
:lp=:rm=rose:rp=rattan:sd=/var/spool/lpd/rattan:
#
# bamboo is connected to rose as well:
#
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
:lp=:rm=rose:rp=bamboo:sd=/var/spool/lpd/bamboo:Then, we just need to make spooling directories on
orchid:&prompt.root; mkdir -p /var/spool/lpd/rattan /var/spool/lpd/bamboo
&prompt.root; chmod 770 /var/spool/lpd/rattan /var/spool/lpd/bamboo
&prompt.root; chown daemon:daemon /var/spool/lpd/rattan /var/spool/lpd/bambooNow, users on orchid can print to
rattan and bamboo. If, for
example, a user on orchid typed
&prompt.user; lpr -P bamboo -d sushi-review.dvi
the LPD system on orchid would copy the job to the spooling
directory /var/spool/lpd/bamboo and note that
it was a DVI job. As soon as the host rose has room in its
bamboo spooling directory, the two LPDs would
transfer the file to rose. The file would wait in rose's queue
until it was finally printed. It would be converted from DVI to
PostScript (since bamboo is a PostScript printer) on rose.Printers with Networked Data Stream InterfacesOften, when you buy a network interface card for a printer, you
can get two versions: one which emulates a spooler (the more
expensive version), or one which just lets you send data to it as if
you were using a serial or parallel port (the cheaper version).
This section tells how to use the cheaper version. For the more
expensive one, see the previous section Printers Installed on
Remote Hosts.The format of the /etc/printcap file lets
you specify what serial or parallel interface to use, and (if you
are using a serial interface), what baud rate, whether to use flow
control, delays for tabs, conversion of newlines, and more. But
there is no way to specify a connection to a printer that is
listening on a TCP/IP or other network port.To send data to a networked printer, you need to develop a
communications program that can be called by the text and conversion
filters. Here is one such example: the script
netprint takes all data on standard input and
sends it to a network-attached printer. We specify the hostname of
the printer as the first argument and the port number to which to
connect as the second argument to netprint. Note
that this supports one-way communication only (FreeBSD to printer);
many network printers support two-way communication, and you might
want to take advantage of that (to get printer status, perform
accounting, etc.).#!/usr/bin/perl
#
# netprint - Text filter for printer attached to network
# Installed in /usr/local/libexec/netprint
#
$#ARGV eq 1 || die "Usage: $0 <printer-hostname> <port-number>";
$printer_host = $ARGV[0];
$printer_port = $ARGV[1];
require 'sys/socket.ph';
($ignore, $ignore, $protocol) = getprotobyname('tcp');
($ignore, $ignore, $ignore, $ignore, $address)
= gethostbyname($printer_host);
$sockaddr = pack('S n a4 x8', &AF_INET, $printer_port, $address);
socket(PRINTER, &PF_INET, &SOCK_STREAM, $protocol)
|| die "Can't create TCP/IP stream socket: $!";
connect(PRINTER, $sockaddr) || die "Can't contact $printer_host: $!";
while (<STDIN>) { print PRINTER; }
exit 0;We can then use this script in various filters. Suppose we had
a Diablo 750-N line printer connected to the network. The printer
accepts data to print on port number 5100. The host name of the
printer is scrivener. Here is the text filter for the
printer:#!/bin/sh
#
# diablo-if-net - Text filter for Diablo printer `scrivener' listening
# on port 5100. Installed in /usr/local/libexec/diablo-if-net
#
exec /usr/libexec/lpr/lpf "$@" | /usr/local/libexec/netprint scrivener 5100Restricting Printer UsageThis section gives information on restricting printer usage. The
printerrestricting
access to
LPD system lets you control who can access a printer, both locally or
remotely, whether they can print multiple copies, how large their jobs
can be, and how large the printer queues can get.Restricting Multiple CopiesThe LPD system makes it easy for users to print multiple copies
of a file. Users can print jobs with lpr -#5
(for example) and get five copies of each file in the job. Whether
this is a good thing is up to you.If you feel multiple copies cause unnecessary wear and tear on
your printers, you can disable the option to
&man.lpr.1; by adding the sc capability to the
/etc/printcap file. When users submit jobs
with the option, they will see:lpr: multiple copies are not allowedNote that if you have set up access to a printer remotely (see
section Printers
Installed on Remote Hosts), you need the
sc capability on the remote
/etc/printcap files as well, or else users will
still be able to submit multiple-copy jobs by using another
host.Here is an example. This is the
/etc/printcap file for the host
rose. The printer rattan is
quite hearty, so we will allow multiple copies, but the laser
printer bamboo's a bit more delicate, so we will
disable multiple copies by adding the sc
capability:#
# /etc/printcap for host rose - restrict multiple copies on bamboo
#
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:sc:\
:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\
:if=/usr/local/libexec/psif:\
:df=/usr/local/libexec/psdf:Now, we also need to add the sc capability on
the host orchid's
/etc/printcap (and while we are at it, let us
disable multiple copies for the printer
teak):#
# /etc/printcap for host orchid - no multiple copies for local
# printer teak or remote printer bamboo
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
:lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:sc:\
:if=/usr/local/libexec/ifhp:\
:vf=/usr/local/libexec/vfhp:\
:of=/usr/local/libexec/ofhp:
rattan|line|diablo|lp|Diablo 630 Line Printer:\
:lp=:rm=rose:rp=rattan:sd=/var/spool/lpd/rattan:
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
:lp=:rm=rose:rp=bamboo:sd=/var/spool/lpd/bamboo:sc:By using the sc capability, we prevent the
use of lpr -#, but that still does not prevent
users from running &man.lpr.1;
multiple times, or from submitting the same file multiple times in
one job like this:&prompt.user; lpr forsale.sign forsale.sign forsale.sign forsale.sign forsale.signThere are many ways to prevent this abuse (including ignoring
it) which you are free to explore.Restricting Access To PrintersYou can control who can print to what printers by using the UNIX
group mechanism and the rg capability in
/etc/printcap. Just place the users you want
to have access to a printer in a certain group, and then name that
group in the rg capability.Users outside the group (including root) will be greeted with
lpr: Not a member of the restricted group
if they try to print to the controlled printer.As with the sc (suppress multiple copies)
capability, you need to specify rg on remote
hosts that also have access to your printers, if you feel it is
appropriate (see section Printers Installed on
Remote Hosts).For example, we will let anyone access the printer
rattan, but only those in group
artists can use bamboo. Here
is the familiar /etc/printcap for host
rose:#
# /etc/printcap for host rose - restricted group for bamboo
#
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:sc:rg=artists:\
:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\
:if=/usr/local/libexec/psif:\
:df=/usr/local/libexec/psdf:Let us leave the other example
/etc/printcap file (for the host
orchid) alone. Of course, anyone on
orchid can print to bamboo. It
might be the case that we only allow certain logins on
orchid anyway, and want them to have access to the
printer. Or not.There can be only one restricted group per printer.Controlling Sizes of Jobs Submittedprint jobsIf you have many users accessing the printers, you probably need
to put an upper limit on the sizes of the files users can submit to
print. After all, there is only so much free space on the
filesystem that houses the spooling directories, and you also need
to make sure there is room for the jobs of other users.print jobscontrollingLPD enables you to limit the maximum byte size a file in a job
can be with the mx capability. The units are in
BUFSIZ blocks, which are 1024 bytes. If you put a zero for this
capability, there will be no limit on file size; however, if no
mx capability is specified, then a default limit
of 1000 blocks will be used.The limit applies to files in a job, and
not the total job size.LPD will not refuse a file that is larger than the limit you
place on a printer. Instead, it will queue as much of the file up
to the limit, which will then get printed. The rest will be
discarded. Whether this is correct behavior is up for
debate.Let us add limits to our example printers
rattan and bamboo. Since
those artists' PostScript files tend to be large, we will limit them
to five megabytes. We will put no limit on the plain text line
printer:#
# /etc/printcap for host rose
#
#
# No limit on job size:
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
:sh:mx#0:sd=/var/spool/lpd/rattan:\
:lp=/dev/lpt0:\
:if=/usr/local/libexec/if-simple:
#
# Limit of five megabytes:
#
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
:sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:mx#5000:\
:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\
:if=/usr/local/libexec/psif:\
:df=/usr/local/libexec/psdf:Again, the limits apply to the local users only. If you have
set up access to your printers remotely, remote users will not get
those limits. You will need to specify the mx
capability in the remote /etc/printcap files as
well. See section Printers Installed on
Remote Hosts for more information on remote
printing.There is another specialized way to limit job sizes from remote
printers; see section Restricting Jobs
from Remote Printers.Restricting Jobs from Remote PrintersThe LPD spooling system provides several ways to restrict print
jobs submitted from remote hosts:Host restrictionsYou can control from which remote hosts a local LPD
accepts requests with the files
/etc/hosts.equiv and
/etc/hosts.lpd. LPD checks to see if an
incoming request is from a host listed in either one of these
files. If not, LPD refuses the request.The format of these files is simple: one host name per
line. Note that the file
/etc/hosts.equiv is also used by the
&man.ruserok.3; protocol, and affects programs like
&man.rsh.1; and &man.rcp.1;, so be careful.For example, here is the
/etc/hosts.lpd file on the host
rose:orchid
violet
madrigal.fishbaum.deThis means rose will accept requests from
the hosts orchid, violet,
and madrigal.fishbaum.de. If any
other host tries to access rose's
LPD, the job will be refused.Size restrictionsYou can control how much free space there needs to remain
on the filesystem where a spooling directory resides. Make a
file called minfree in the spooling
directory for the local printer. Insert in that file a number
representing how many disk blocks (512 bytes) of free space
there has to be for a remote job to be accepted.This lets you insure that remote users will not fill your
filesystem. You can also use it to give a certain priority to
local users: they will be able to queue jobs long after the
free disk space has fallen below the amount specified in the
minfree file.For example, let us add a minfree
file for the printer bamboo. We examine
/etc/printcap to find the spooling
directory for this printer; here is bamboo's
entry:bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
:sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:mx#5000:\
:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:mx#5000:\
:if=/usr/local/libexec/psif:\
:df=/usr/local/libexec/psdf:The spooling directory is the given in the
sd capability. We will make three
megabytes (which is 6144 disk blocks) the amount of free disk
space that must exist on the filesystem for LPD to accept
remote jobs:&prompt.root; echo 6144 > /var/spool/lpd/bam
boo/minfreeUser restrictionsYou can control which remote users can print to local
printers by specifying the rs capability in
/etc/printcap. When
rs appears in the entry for a
locally-attached printer, LPD will accept jobs from remote
hosts if the user submitting the job also
has an account of the same login name on the local host.
Otherwise, LPD refuses the job.This capability is particularly useful in an environment
where there are (for example) different departments sharing a
network, and some users transcend departmental boundaries. By
giving them accounts on your systems, they can use your
printers from their own departmental systems. If you would
rather allow them to use only your
printers and not your compute resources, you can give them
token accounts, with no home directory and a
useless shell like /usr/bin/false.Accounting for Printer UsageaccountingprinterSo, you need to charge for printouts. And why not? Paper and ink
cost money. And then there are maintenance costs—printers are
loaded with moving parts and tend to break down. You have examined
your printers, usage patterns, and maintenance fees and have come up
with a per-page (or per-foot, per-meter, or per-whatever) cost. Now,
how do you actually start accounting for printouts?Well, the bad news is the LPD spooling system does not provide
much help in this department. Accounting is highly dependent on the
kind of printer in use, the formats being printed, and
your requirements in charging for printer
usage.To implement accounting, you have to modify a printer's text
filter (to charge for plain text jobs) and the conversion filters (to
charge for other file formats), to count pages or query the printer
for pages printed. You cannot get away with using the simple output
filter, since it cannot do accounting. See section Filters.Generally, there are two ways to do accounting:Periodic accounting is the more common
way, possibly because it is easier. Whenever someone prints a
job, the filter logs the user, host, and number of pages to an
accounting file. Every month, semester, year, or whatever time
period you prefer, you collect the accounting files for the
various printers, tally up the pages printed by users, and charge
for usage. Then you truncate all the logging files, starting with
a clean slate for the next period.Timely accounting is less common,
probably because it is more difficult. This method has the
filters charge users for printouts as soon as they use the
printers. Like disk quotas, the accounting is immediate. You can
prevent users from printing when their account goes in the red,
and might provide a way for users to check and adjust their
print quotas. But this method requires some database
code to track users and their quotas.The LPD spooling system supports both methods easily: since you
have to provide the filters (well, most of the time), you also have to
provide the accounting code. But there is a bright side: you have
enormous flexibility in your accounting methods. For example, you
choose whether to use periodic or timely accounting. You choose what
information to log: user names, host names, job types, pages printed,
square footage of paper used, how long the job took to print, and so
forth. And you do so by modifying the filters to save this
information.Quick and Dirty Printer AccountingFreeBSD comes with two programs that can get you set up with
simple periodic accounting right away. They are the text filter
lpf, described in section lpf: a Text Filter, and
&man.pac.8;, a program to gather and total
entries from printer accounting files.As mentioned in the section on filters (Filters), LPD starts
the text and the conversion filters with the name of the accounting
file to use on the filter command line. The filters can use this
argument to know where to write an accounting file entry. The name
of this file comes from the af capability in
/etc/printcap, and if not specified as an
absolute path, is relative to the spooling directory.LPD starts lpf with page width and length
arguments (from the pw and pl
capabilities). lpf uses these arguments to
determine how much paper will be used. After sending the file to
the printer, it then writes an accounting entry in the accounting
file. The entries look like this:2.00 rose:andy
3.00 rose:kelly
3.00 orchid:mary
5.00 orchid:mary
2.00 orchid:zhangYou should use a separate accounting file for each printer, as
lpf has no file locking logic built into it, and
two lpfs might corrupt each other's entries if
they were to write to the same file at the same time. A easy way to
insure a separate accounting file for each printer is to use
af=acct in /etc/printcap.
Then, each accounting file will be in the spooling directory for a
printer, in a file named acct.When you are ready to charge users for printouts, run the
&man.pac.8; program. Just change to the spooling directory for
the printer you want to collect on and type pac.
You will get a dollar-centric summary like the following: Login pages/feet runs price
orchid:kelly 5.00 1 $ 0.10
orchid:mary 31.00 3 $ 0.62
orchid:zhang 9.00 1 $ 0.18
rose:andy 2.00 1 $ 0.04
rose:kelly 177.00 104 $ 3.54
rose:mary 87.00 32 $ 1.74
rose:root 26.00 12 $ 0.52
total 337.00 154 $ 6.74These are the arguments &man.pac.8; expects:Which printer to summarize.
This option works only if there is an absolute path in the
af capability in
/etc/printcap.Sort the output by cost instead of alphabetically by user
name.Ignore host name in the accounting files. With this
option, user smith on host
alpha is the same user
smith on host gamma.
Without, they are different users.Compute charges with price
dollars per page or per foot instead of the price from the
pc capability in
/etc/printcap, or two cents (the
default). You can specify price as
a floating point number.Reverse the sort order.Make an accounting summary file and truncate the
accounting file.name…Print accounting information for the given user
names only.In the default summary that &man.pac.8; produces, you see the
number of pages printed by each user from various hosts. If, at
your site, host does not matter (because users can use any host),
run pac -m, to produce the following
summary: Login pages/feet runs price
andy 2.00 1 $ 0.04
kelly 182.00 105 $ 3.64
mary 118.00 35 $ 2.36
root 26.00 12 $ 0.52
zhang 9.00 1 $ 0.18
total 337.00 154 $ 6.74To compute the dollar amount due,
&man.pac.8; uses the pc capability in the
/etc/printcap file (default of 200, or 2 cents
per page). Specify, in hundredths of cents, the price per page or
per foot you want to charge for printouts in this capability. You
can override this value when you run &man.pac.8; with the
option. The units for the
option are in dollars, though, not hundredths of cents. For
example,
&prompt.root; pac -p1.50
makes each page cost one dollar and fifty cents. You can really
rake in the profits by using this option.Finally, running pac -s will save the summary
information in a summary accounting file, which is named the same as
the printer's accounting file, but with _sum
appended to the name. It then truncates the accounting file. When
you run &man.pac.8; again, it rereads the
summary file to get starting totals, then adds information from the
regular accounting file.How Can You Count Pages Printed?In order to perform even remotely accurate accounting, you need
to be able to determine how much paper a job uses. This is the
essential problem of printer accounting.For plain text jobs, the problem is not that hard to solve: you
count how many lines are in a job and compare it to how many lines
per page your printer supports. Do not forget to take into account
backspaces in the file which overprint lines, or long logical lines
that wrap onto one or more additional physical lines.The text filter lpf (introduced in lpf: a Text Filter) takes
into account these things when it does accounting. If you are
writing a text filter which needs to do accounting, you might want
to examine lpf's source code.How do you handle other file formats, though?Well, for DVI-to-LaserJet or DVI-to-PostScript conversion, you
can have your filter parse the diagnostic output of
dvilj or dvips and look to see
how many pages were converted. You might be able to do similar
things with other file formats and conversion programs.But these methods suffer from the fact that the printer may not
actually print all those pages. For example, it could jam, run out
of toner, or explode—and the user would still get
charged.So, what can you do?There is only one sure way to do
accurate accounting. Get a printer that can
tell you how much paper it uses, and attach it via a serial line or
a network connection. Nearly all PostScript printers support this
notion. Other makes and models do as well (networked Imagen laser
printers, for example). Modify the filters for these printers to
get the page usage after they print each job and have them log
accounting information based on that value
only. There is no line counting nor
error-prone file examination required.Of course, you can always be generous and make all printouts
free.Using PrintersprinterusageThis section tells you how to use printers you have setup with
FreeBSD. Here is an overview of the user-level commands:&man.lpr.1;Print jobs&man.lpq.1;Check printer queues&man.lprm.1;Remove jobs from a printer's queueThere is also an administrative command, &man.lpc.8;, described in
the section Administrating the LPD
Spooler, used to control printers and their queues.All three of the commands &man.lpr.1;, &man.lprm.1;, and &man.lpq.1;
accept an option to specify on which
printer/queue to operate, as listed in the
/etc/printcap file. This enables you to submit,
remove, and check on jobs for various printers. If you do not use the
option, then these commands use the printer
specified in the PRINTER environment variable. Finally,
if you do not have a PRINTER environment variable, these
commands default to the printer named lp.Hereafter, the terminology default printer
means the printer named in the PRINTER environment
variable, or the printer named lp when there is no
PRINTER environment variable.Printing JobsTo print files, type:&prompt.user; lpr filename...printingThis prints each of the listed files to the default printer. If
you list no files, &man.lpr.1; reads data to
print from standard input. For example, this command prints some
important system files:&prompt.user; lpr /etc/host.conf /etc/hosts.equivTo select a specific printer, type:&prompt.user; lpr -P printer-namefilename...This example prints a long listing of the current directory to the
printer named rattan:&prompt.user; ls -l | lpr -P rattanBecause no files were listed for the
&man.lpr.1; command, lpr read the data to print
from standard input, which was the output of the ls
-l command.The &man.lpr.1; command can also accept a wide variety of options
to control formatting, apply file conversions, generate multiple
copies, and so forth. For more information, see the section Printing Options.Checking Jobsprint jobsWhen you print with &man.lpr.1;, the data you wish to print is put
together in a package called a print job, which is sent
to the LPD spooling system. Each printer has a queue of jobs, and
your job waits in that queue along with other jobs from yourself and
from other users. The printer prints those jobs in a first-come,
first-served order.To display the queue for the default printer, type &man.lpq.1;.
For a specific printer, use the option. For
example, the command
&prompt.user; lpq -P bamboo
shows the queue for the printer named bamboo. Here
is an example of the output of the lpq
command:bamboo is ready and printing
Rank Owner Job Files Total Size
active kelly 9 /etc/host.conf, /etc/hosts.equiv 88 bytes
2nd kelly 10 (standard input) 1635 bytes
3rd mary 11 ... 78519 bytesThis shows three jobs in the queue for bamboo.
The first job, submitted by user kelly, got assigned job
number 9. Every job for a printer gets a unique job number.
Most of the time you can ignore the job number, but you will need it
if you want to cancel the job; see section Removing Jobs for details.Job number nine consists of two files; multiple files given on the
&man.lpr.1; command line are treated as part of a single job. It
is the currently active job (note the word active
under the Rank column), which means the printer should
be currently printing that job. The second job consists of data
passed as the standard input to the &man.lpr.1; command. The third
job came from user mary; it is a much larger
job. The pathname of the files she's trying to print is too long to
fit, so the &man.lpq.1; command just shows three dots.The very first line of the output from &man.lpq.1; is also useful:
it tells what the printer is currently doing (or at least what LPD
thinks the printer is doing).The &man.lpq.1; command also support a option
to generate a detailed long listing. Here is an example of
lpq -l:waiting for bamboo to become ready (offline ?)
kelly: 1st [job 009rose]
/etc/host.conf 73 bytes
/etc/hosts.equiv 15 bytes
kelly: 2nd [job 010rose]
(standard input) 1635 bytes
mary: 3rd [job 011rose]
/home/orchid/mary/research/venus/alpha-regio/mapping 78519 bytesRemoving JobsIf you change your mind about printing a job, you can remove the
job from the queue with the &man.lprm.1; command. Often, you can
even use &man.lprm.1; to remove an active job, but some or all of the
job might still get printed.To remove a job from the default printer, first use
&man.lpq.1; to find the job number. Then type:&prompt.user; lprm job-numberTo remove the job from a specific printer, add the
option. The following command removes job number
10 from the queue for the printer bamboo:&prompt.user; lprm -P bamboo 10The &man.lprm.1; command has a few shortcuts:lprm -Removes all jobs (for the default printer) belonging to
you.lprm userRemoves all jobs (for the default printer) belonging to
user. The superuser can remove other
users' jobs; you can remove only your own jobs.lprmWith no job number, user name, or
appearing on the command line,
&man.lprm.1; removes the currently active job on the
default printer, if it belongs to you. The superuser can remove
any active job.Just use the option with the above shortcuts
to operate on a specific printer instead of the default. For example,
the following command removes all jobs for the current user in the
queue for the printer named rattan:&prompt.user; lprm -P rattan -If you are working in a networked environment, &man.lprm.1; will
let you remove jobs only from the
host from which the jobs were submitted, even if the same printer is
available from other hosts. The following command sequence
demonstrates this:&prompt.user; lpr -P rattan myfile
&prompt.user; rlogin orchid
&prompt.user; lpq -P rattan
Rank Owner Job Files Total Size
active seeyan 12 ... 49123 bytes
2nd kelly 13 myfile 12 bytes
&prompt.user; lprm -P rattan 13
rose: Permission denied
&prompt.user; logout
&prompt.user; lprm -P rattan 13
dfA013rose dequeued
cfA013rose dequeued
Beyond Plain Text: Printing OptionsThe &man.lpr.1; command supports a number of options that control
formatting text, converting graphic and other file formats, producing
multiple copies, handling of the job, and more. This section
describes the options.Formatting and Conversion OptionsThe following &man.lpr.1; options control formatting of the
files in the job. Use these options if the job does not contain
plain text or if you want plain text formatted through the
&man.pr.1; utility.TeXFor example, the following command prints a DVI file (from the
TeX typesetting system) named fish-report.dvi
to the printer named bamboo:&prompt.user; lpr -P bamboo -d fish-report.dviThese options apply to every file in the job, so you cannot mix
(say) DVI and ditroff files together in a job. Instead, submit the
files as separate jobs, using a different conversion option for each
job.All of these options except and
require conversion filters installed for the
destination printer. For example, the option
requires the DVI conversion filter. Section Conversion
Filters gives details.Print cifplot files.Print DVI files.Print FORTRAN text files.Print plot data.Indent the output by number
columns; if you omit number, indent
by 8 columns. This option works only with certain conversion
filters.Do not put any space between the and
the number.Print literal text data, including control
characters.Print ditroff (device independent troff) data.-pFormat plain text with &man.pr.1; before printing. See
&man.pr.1; for more information.Use title on the
&man.pr.1; header instead of the file name. This option has
effect only when used with the
option.Print troff data.Print raster data.Here is an example: this command prints a nicely formatted
version of the &man.ls.1; manual page on the default printer:&prompt.user; zcat /usr/share/man/man1/ls.1.gz | troff -t -man | lpr -tThe &man.zcat.1; command uncompresses the source of the
&man.ls.1; manual page and passes it to the &man.troff.1;
command, which formats that source and makes GNU troff
output and passes it to &man.lpr.1;, which submits the job
to the LPD spooler. Because we used the
option to &man.lpr.1;, the spooler will convert the GNU
troff output into a format the default printer can
understand when it prints the job.Job Handling OptionsThe following options to &man.lpr.1; tell LPD to handle the job
specially:-# copiesProduce a number of copies of
each file in the job instead of just one copy. An
administrator may disable this option to reduce printer
wear-and-tear and encourage photocopier usage. See section
Restricting
Multiple Copies.This example prints three copies of
parser.c followed by three copies of
parser.h to the default printer:&prompt.user; lpr -#3 parser.c parser.h-mSend mail after completing the print job. With this
option, the LPD system will send mail to your account when it
finishes handling your job. In its message, it will tell you
if the job completed successfully or if there was an error,
and (often) what the error was.-sDo not copy the files to the spooling directory, but make
symbolic links to them instead.If you are printing a large job, you probably want to use
this option. It saves space in the spooling directory (your
job might overflow the free space on the filesystem where the
spooling directory resides). It saves time as well since LPD
will not have to copy each and every byte of your job to the
spooling directory.There is a drawback, though: since LPD will refer to the
original files directly, you cannot modify or remove them
until they have been printed.If you are printing to a remote printer, LPD will
eventually have to copy files from the local host to the
remote host, so the option will save
space only on the local spooling directory, not the remote.
It is still useful, though.-rRemove the files in the job after copying them to the
spooling directory, or after printing them with the
option. Be careful with this
option!Header Page OptionsThese options to &man.lpr.1; adjust the text that normally
appears on a job's header page. If header pages are suppressed for
the destination printer, these options have no effect. See section
Header Pages
for information about setting up header pages.-C textReplace the hostname on the header page with
text. The hostname is normally the
name of the host from which the job was submitted.-J textReplace the job name on the header page with
text. The job name is normally the
name of the first file of the job, or
stdin if you are printing standard
input.-hDo not print any header page.At some sites, this option may have no effect due to the
way header pages are generated. See Header
Pages for details.Administrating PrintersAs an administrator for your printers, you have had to install,
set up, and test them. Using the &man.lpc.8; command, you
can interact with your printers in yet more ways. With &man.lpc.8;,
you canStart and stop the printersEnable and disable their queuesRearrange the order of the jobs in each queue.First, a note about terminology: if a printer is
stopped, it will not print anything in its queue.
Users can still submit jobs, which will wait in the queue until the
printer is started or the queue is
cleared.If a queue is disabled, no user (except root)
can submit jobs for the printer. An enabled
queue allows jobs to be submitted. A printer can be
started for a disabled queue, in which case it
will continue to print jobs in the queue until the queue is
empty.In general, you have to have root privileges to use the
&man.lpc.8; command. Ordinary users can use the &man.lpc.8; command
to get printer status and to restart a hung printer only.Here is a summary of the &man.lpc.8; commands. Most of the
commands takes a printer-name argument to
tell on which printer to operate. You can use all
for the printer-name to mean all printers
listed in /etc/printcap.abort
printer-nameCancel the current job and stop the printer. Users can
still submit jobs if the queue's enabled.clean
printer-nameRemove old files from the printer's spooling directory.
Occasionally, the files that make up a job are not properly
removed by LPD, particularly if there have been errors during
printing or a lot of administrative activity. This command
finds files that do not belong in the spooling directory and
removes them.disable
printer-nameDisable queuing of new jobs. If the printer's started, it
will continue to print any jobs remaining in the queue. The
superuser (root) can always submit jobs, even to a disabled
queue.This command is useful while you are testing a new printer
or filter installation: disable the queue and submit jobs as
root. Other users will not be able to submit jobs until you
complete your testing and re-enable the queue with the
enable command.down printer-namemessageTake a printer down. Equivalent to
disable followed by stop.
The message appears as the printer's
status whenever a user checks the printer's queue with
&man.lpq.1; or status with lpc
status.enable
printer-nameEnable the queue for a printer. Users can submit jobs but
the printer will not print anything until it is started.help
command-namePrint help on the command
command-name. With no
command-name, print a summary of the
commands available.restart
printer-nameStart the printer. Ordinary users can use this command if
some extraordinary circumstance hangs LPD, but they cannot start
a printer stopped with either the stop or
down commands. The
restart command is equivalent to
abort followed by
start.start
printer-nameStart the printer. The printer will print jobs in its
queue.stop
printer-nameStop the printer. The printer will finish the current job
and will not print anything else in its queue. Even though the
printer is stopped, users can still submit jobs to an enabled
queue.topq printer-namejob-or-usernameRearrange the queue for
printer-name by placing the jobs with
the listed job numbers or the jobs
belonging to username at the top of
the queue. For this command, you cannot use
all as the
printer-name.up
printer-nameBring a printer up; the opposite of the
down command. Equivalent to
start followed by
enable.&man.lpc.8; accepts the above commands on the command line. If
you do not enter any commands, &man.lpc.8; enters an interactive mode,
where you can enter commands until you type exit,
quit, or end-of-file.Alternatives to the Standard SpoolerIf you have been reading straight through this manual, by now you
have learned just about everything there is to know about the LPD
spooling system that comes with FreeBSD. You can probably appreciate
many of its shortcomings, which naturally leads to the question:
What other spooling systems are out there (and work with
FreeBSD)?LPRngLPRngLPRng, which purportedly means LPR: the Next
Generation is a complete rewrite of PLP. Patrick Powell
and Justin Mason (the principal maintainer of PLP) collaborated to
make LPRng. The main site for LPRng is http://www.astart.com/lprng/LPRng.html.TroubleshootingAfter performing the simple test with &man.lptest.1;, you might
have gotten one of the following results instead of the correct
printout:It worked, after awhile; or, it did not eject a full
sheet.The printer printed the above, but it sat for awhile and
did nothing. In fact, you might have needed to press a
PRINT REMAINING or FORM FEED button on the printer to get any
results to appear.If this is the case, the printer was probably waiting to
see if there was any more data for your job before it printed
anything. To fix this problem, you can have the text filter
send a FORM FEED character (or whatever is necessary) to the
printer. This is usually sufficient to have the printer
immediately print any text remaining in its internal buffer.
It is also useful to make sure each print job ends on a full
sheet, so the next job does not start somewhere on the middle
of the last page of the previous job.The following replacement for the shell script
/usr/local/libexec/if-simple prints a
form feed after it sends the job to the printer:#!/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.
# Writes a form feed character (\f) after printing job.
/bin/cat && printf "\f" && exit 0
exit 2It produced the staircase effect.You got the following on paper:!"#$%&'()*+,-./01234
"#$%&'()*+,-./012345
#$%&'()*+,-./0123456
- DOS
+ MS-DOSOS/2ASCIIYou have become another victim of the staircase
effect, caused by conflicting interpretations of
what characters should indicate a new line. UNIX-style
operating systems use a single character: ASCII code 10, the
line feed (LF). MS-DOS, OS/2, and others uses a pair of
characters, ASCII code 10 and ASCII code
13 (the carriage return or CR). Many printers use the MS-DOS
convention for representing new-lines.When you print with FreeBSD, your text used just the line
feed character. The printer, upon seeing a line feed
character, advanced the paper one line, but maintained the
same horizontal position on the page for the next character
to print. That is what the carriage return is for: to move
the location of the next character to print to the left edge
of the paper.Here is what FreeBSD wants your printer to do:Printer received CRPrinter prints CRPrinter received LFPrinter prints CR + LFHere are some ways to achieve this:Use the printer's configuration switches or control
panel to alter its interpretation of these characters.
Check your printer's manual to find out how to do
this.If you boot your system into other operating systems
besides FreeBSD, you may have to
reconfigure the printer to use a an
interpretation for CR and LF characters that those other
operating systems use. You might prefer one of the other
solutions, below.Have FreeBSD's serial line driver automatically
convert LF to CR+LF. Of course, this works with printers
on serial ports only. To enable this
feature, set the CRMOD bit in fs
capability in the /etc/printcap file
for the printer.Send an escape code to the
printer to have it temporarily treat LF characters
differently. Consult your printer's manual for escape
codes that your printer might support. When you find the
proper escape code, modify the text filter to send the
code first, then send the print job.PCLHere is an example text filter for printers that
understand the Hewlett-Packard PCL escape codes. This
filter makes the printer treat LF characters as a LF and
CR; then it sends the job; then it sends a form feed to
eject the last page of the job. It should work with
nearly all Hewlett Packard printers.#!/bin/sh
#
# hpif - Simple text input filter for lpd for HP-PCL based printers
# Installed in /usr/local/libexec/hpif
#
# Simply copies stdin to stdout. Ignores all filter arguments.
# Tells printer to treat LF as CR+LF. Ejects the page when done.
printf "\033&k2G" && cat && printf "\033&l0H" && exit 0
exit 2Here is an example /etc/printcap
from a host called orchid. It has a single printer
attached to its first parallel port, a Hewlett Packard
LaserJet 3Si named teak. It is using the
above script as its text filter:#
# /etc/printcap for host orchid
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
:lp=/dev/lpt0:sh:sd=/var/spool/lpd/teak:mx#0:\
:if=/usr/local/libexec/hpif:It overprinted each line.The printer never advanced a line. All of the lines of
text were printed on top of each other on one line.This problem is the opposite of the
staircase effect, described above, and is much rarer.
Somewhere, the LF characters that FreeBSD uses to end a line
are being treated as CR characters to return the print
location to the left edge of the paper, but not also down a
line.Use the printer's configuration switches or control panel
to enforce the following interpretation of LF and CR
characters:Printer receivesPrinter printsCRCRLFCR + LFThe printer lost characters.While printing, the printer did not print a few characters
in each line. The problem might have gotten worse as the
printer ran, losing more and more characters.The problem is that the printer cannot keep up with the
speed at which the computer sends data over a serial line
(this problem should not occur with printers on parallel
ports). There are two ways to overcome the problem:If the printer supports XON/XOFF flow control, have
FreeBSD use it by specifying the TANDEM bit in the
fs capability.If the printer supports carrier flow control, specify
the MDMBUF bit in the fs capability.
Make sure the cable connecting the printer to the computer
is correctly wired for carrier flow control.If the printer does not support any flow control, use
some combination of the NLDELAY, TBDELAY, CRDELAY, VTDELAY,
and BSDELAY bits in the fs capability
to add appropriate delays to the stream of data sent to
the printer.It printed garbage.The printer printed what appeared to be random garbage,
but not the desired text.This is usually another symptom of incorrect
communications parameters with a serial printer. Double-check
the bps rate in the br capability, and the
parity bits in the fs and
fc capabilities; make sure the printer is
using the same settings as specified in the
/etc/printcap file.Nothing happened.If nothing happened, the problem is probably within
FreeBSD and not the hardware. Add the log file
(lf) capability to the entry for the
printer you are debugging in the
/etc/printcap file. For example, here is
the entry for rattan, with the
lf capability:rattan|line|diablo|lp|Diablo 630 Line Printer:\
:sh:sd=/var/spool/lpd/rattan:\
:lp=/dev/lpt0:\
:if=/usr/local/libexec/if-simple:\
:lf=/var/log/rattan.logThen, try printing again. Check the log file (in our
example, /var/log/rattan.log) to see any
error messages that might appear. Based on the messages you
see, try to correct the problem.If you do not specify a lf capability,
LPD uses /dev/console as a
default.
diff --git a/en_US.ISO8859-1/books/handbook/security/chapter.sgml b/en_US.ISO8859-1/books/handbook/security/chapter.sgml
index 83894eefd6..bca6ced3a6 100644
--- a/en_US.ISO8859-1/books/handbook/security/chapter.sgml
+++ b/en_US.ISO8859-1/books/handbook/security/chapter.sgml
@@ -1,3033 +1,3037 @@
SecuritysecurityMuch of this chapter has been taken from the
&man.security.7; man page, originally written by
&a.dillon;.SynopsisThe following chapter will provide a basic introduction to
system security concepts, some general good rules of thumb, and some
advanced topics such as S/Key, OpenSSL, Kerberos, and others.IntroductionSecurity is a function that begins and ends with the system
administrator. While all BSD UNIX multi-user systems have some
inherent security, the job of building and maintaining additional
security mechanisms to keep those users honest is
probably one of the single largest undertakings of the sysadmin.
Machines are only as secure as you make them, and security concerns
are ever competing with the human necessity for convenience. UNIX
systems, in general, are capable of running a huge number of
simultaneous processes and many of these processes operate as
servers – meaning that external entities can connect and talk
to them. As yesterday's mini-computers and mainframes become
today's desktops, and as computers become networked and
internetworked, security becomes an ever bigger issue.Security is best implemented through a layered
onion approach. In a nutshell, what you want to do is
to create as many layers of security as are convenient and then
carefully monitor the system for intrusions. You do not want to
overbuild your security or you will interfere with the detection
side, and detection is one of the single most important aspects of
any security mechanism. For example, it makes little sense to set
the schg flags (see &man.chflags.1;) on every system binary because
while this may temporarily protect the binaries, it prevents an
attacker who has broken in from making an easily detectable change
that may result in your security mechanisms not detecting the attacker
at all.System security also pertains to dealing with various forms of
attack, including attacks that attempt to crash or otherwise make a
system unusable but do not attempt to break root. Security concerns
can be split up into several categories:Denial of service attacks.User account compromises.Root compromise through accessible servers.Root compromise via user accounts.Backdoor creation.DOS attackssecurityDOS attacksDenial of ServiceA denial of service attack is an action that deprives the
machine of needed resources. Typically, D.O.S. attacks are
brute-force mechanisms that attempt to crash or otherwise make a
machine unusable by overwhelming its servers or network stack. Some
D.O.S. attacks try to take advantages of bugs in the networking
stack to crash a machine with a single packet. The latter can only
be fixed by applying a bug fix to the kernel. Attacks on servers
can often be fixed by properly specifying options to limit the load
the servers incur on the system under adverse conditions.
Brute-force network attacks are harder to deal with. A
spoofed-packet attack, for example, is nearly impossible to stop
short of cutting your system off from the Internet. It may not be
able to take your machine down, but it can saturate your
Internet connection.securityaccount compromisesA user account compromise is even more common than a D.O.S.
attack. Many sysadmins still run standard telnetd, rlogind, rshd,
and ftpd servers on their machines. These servers, by default, do
not operate over encrypted connections. The result is that if you
have any moderate-sized user base, one or more of your users logging
into your system from a remote location (which is the most common
and convenient way to login to a system) will have his or her
password sniffed. The attentive system admin will analyze his
remote access logs looking for suspicious source addresses even for
successful logins.One must always assume that once an attacker has access to a
user account, the attacker can break root. However, the reality is
that in a well secured and maintained system, access to a user
account does not necessarily give the attacker access to root. The
distinction is important because without access to root the attacker
cannot generally hide his tracks and may, at best, be able to do
nothing more than mess with the user's files or crash the machine.
User account compromises are very common because users tend not to
take the precautions that sysadmins take.securitybackdoorsSystem administrators must keep in mind that there are
potentially many ways to break root on a machine. The attacker
may know the root password, the attacker may find a bug in a
root-run server and be able to break root over a network
connection to that server, or the attacker may know of a bug in
an suid-root program that allows the attacker to break root once
he has broken into a user's account. If an attacker has found
a way to break root on a machine, the attacker may not have a need
to install a backdoor. Many of the root holes
found and closed to date involve a considerable amount of work
by the attacker to cleanup after himself, so most attackers install
backdoors. Backdoors provide the attacker with a way to easily
regain root access to the system, but it also gives the smart
system administrator a convenient way to detect the intrusion.
Making it impossible for an attacker to install a backdoor may
actually be detrimental to your security because it will not
close off the hole the attacker found to break in the first
place.Security remedies should always be implemented with a
multi-layered onion peel approach and can be
categorized as follows:Securing root and staff accounts.Securing root – root-run servers and suid/sgid
binaries.Securing user accounts.Securing the password file.Securing the kernel core, raw devices, and
filesystems.Quick detection of inappropriate changes made to the
system.Paranoia.The next section of this chapter will cover the above bullet
items in greater depth.securitysecuringSecuring FreeBSDThe sections that follow will cover the methods of securing your
FreeBSD system that were mentioned in the last section of this chapter.Securing the root account and staff accountssuFirst off, do not bother securing staff accounts if you have
not secured the root account. Most systems have a password
assigned to the root account. The first thing you do is assume
that the password is always compromised.
This does not mean that you should remove the password. The
password is almost always necessary for console access to the
machine. What it does mean is that you should not make it
possible to use the password outside of the console or possibly
even with the &man.su.1; command. For example, make sure that
your pty's are specified as being unsecure in the
/etc/ttys file so that direct root logins
via telnet or rlogin are
disallowed. If using other login services such as
sshd, make sure that direct root logins
are disabled there as well. Consider every access method –
services such as FTP often fall through the cracks. Direct root
logins should only be allowed via the system console.wheelOf course, as a sysadmin you have to be able to get to root,
so we open up a few holes. But we make sure these holes require
additional password verification to operate. One way to make root
accessible is to add appropriate staff accounts to the
wheel group (in
/etc/group). The staff members placed in the
wheel group are allowed to
su to root. You should never give staff
members native wheel access by putting them in the
wheel group in their password entry. Staff
accounts should be placed in a staff group, and
then added to the wheel group via the
/etc/group file. Only those staff members
who actually need to have root access should be placed in the
wheel group. It is also possible, when using
an authentication method such as kerberos, to use kerberos'
.k5login file in the root account to allow a
&man.ksu.1; to root without having to place anyone at all in the
wheel group. This may be the better solution
since the wheel mechanism still allows an
intruder to break root if the intruder has gotten hold of your
password file and can break into a staff account. While having
the wheel mechanism is better than having
nothing at all, it is not necessarily the safest option.An indirect way to secure staff accounts, and ultimately
root access is to use an alternative login access method and
do what is known as *'ing out the crypted
password for the staff accounts. Using the &man.vipw.8;
command, one can replace each instance of a crypted password
with a single * character. This command
will update the /etc/master.passwd file
and user/password database to disable password-authenticated
logins.A staff account entry such as:foobar:R9DT/Fa1/LV9U:1000:1000::0:0:Foo Bar:/home/foobar:/usr/local/bin/tcshShould be changed to this :foobar:*:1000:1000::0:0:Foo Bar:/home/foobar:/usr/local/bin/tcshThis change will prevent normal logins from occurring,
since the encrypted password will never match
*. With this done, staff members must use
another mechanism to authenticate themselves such as
&man.kerberos.1; or &man.ssh.1; using a public/private key
pair. When using something like kerberos, one generally must
secure the machines which run the kerberos servers and your
desktop workstation. When using a public/private key pair
with ssh, one must generally secure
the machine used to login from (typically
one's workstation). An additional layer of protection can be
added to the key pair by password protecting the key pair when
creating it with &man.ssh-keygen.1;. Being able to
* out the passwords for staff accounts also
guarantees that staff members can only login through secure
access methods that you have setup. This forces all staff
members to use secure, encrypted connections for all of their
sessions which closes an important hole used by many
intruders: That of sniffing the network from an unrelated,
less secure machine.The more indirect security mechanisms also assume that you are
logging in from a more restrictive server to a less restrictive
server. For example, if your main box is running all sorts of
servers, your workstation should not be running any. In order for
your workstation to be reasonably secure you should run as few
servers as possible, up to and including no servers at all, and
you should run a password-protected screen blanker. Of course,
given physical access to a workstation an attacker can break any
sort of security you put on it. This is definitely a problem that
you should consider but you should also consider the fact that the
vast majority of break-ins occur remotely, over a network, from
people who do not have physical access to your workstation or
servers.KerberosUsing something like kerberos also gives you the ability to
disable or change the password for a staff account in one place
and have it immediately effect all the machine the staff member
may have an account on. If a staff member's account gets
compromised, the ability to instantly change his password on all
machines should not be underrated. With discrete passwords,
changing a password on N machines can be a mess. You can also
impose re-passwording restrictions with kerberos: not only can a
kerberos ticket be made to timeout after a while, but the kerberos
system can require that the user choose a new password after a
certain period of time (say, once a month).Securing Root-run Servers and SUID/SGID BinariesntalkcomsatfingersandboxessshdtelnetdrshdrlogindThe prudent sysadmin only runs the servers he needs to, no
more, no less. Be aware that third party servers are often the
most bug-prone. For example, running an old version of imapd or
popper is like giving a universal root ticket out to the entire
world. Never run a server that you have not checked out
carefully. Many servers do not need to be run as root. For
example, the ntalk,
comsat, and
finger daemons can be run in special
user sandboxes. A sandbox isn't perfect unless
you go to a large amount of trouble, but the onion approach to
security still stands: If someone is able to break in through
a server running in a sandbox, they still have to break out of the
sandbox. The more layers the attacker must break through, the
lower the likelihood of his success. Root holes have historically
been found in virtually every server ever run as root, including
basic system servers. If you are running a machine through which
people only login via sshd and never
login via telnetd or
rshd or
rlogind, then turn off those
services!FreeBSD now defaults to running
ntalkd,
comsat, and
finger in a sandbox. Another program
which may be a candidate for running in a sandbox is &man.named.8;.
/etc/defaults/rc.conf includes the arguments
necessary to run named in a sandbox in a
commented-out form. Depending on whether you are installing a new
system or upgrading an existing system, the special user accounts
used by these sandboxes may not be installed. The prudent
sysadmin would research and implement sandboxes for servers
whenever possible.sendmailThere are a number of other servers that typically do not run
in sandboxes: sendmail,
popper,
imapd, ftpd,
and others. There are alternatives to some of these, but
installing them may require more work than you are willing to
perform (the convenience factor strikes again). You may have to
run these servers as root and rely on other mechanisms to detect
break-ins that might occur through them.The other big potential root hole in a system are the
suid-root and sgid binaries installed on the system. Most of
these binaries, such as rlogin, reside
in /bin, /sbin,
/usr/bin, or /usr/sbin.
While nothing is 100% safe, the system-default suid and sgid
binaries can be considered reasonably safe. Still, root holes are
occasionally found in these binaries. A root hole was found in
Xlib in 1998 that made
xterm (which is typically suid)
vulnerable. It is better to be safe than sorry and the prudent
sysadmin will restrict suid binaries that only staff should run to
a special group that only staff can access, and get rid of
(chmod 000) any suid binaries that nobody uses.
A server with no display generally does not need an
xterm binary. Sgid binaries can be
almost as dangerous. If an intruder can break an sgid-kmem binary
the intruder might be able to read /dev/kmem
and thus read the crypted password file, potentially compromising
any passworded account. Alternatively an intruder who breaks
group kmem can monitor keystrokes sent through
pty's, including pty's used by users who login through secure
methods. An intruder that breaks the tty group can write to
almost any user's tty. If a user is running a terminal program or
emulator with a keyboard-simulation feature, the intruder can
potentially generate a data stream that causes the user's terminal
to echo a command, which is then run as that user.Securing User AccountsUser accounts are usually the most difficult to secure. While
you can impose Draconian access restrictions on your staff and
* out their passwords, you may not be able to
do so with any general user accounts you might have. If you do
have sufficient control then you may win out and be able to secure
the user accounts properly. If not, you simply have to be more
vigilant in your monitoring of those accounts. Use of
ssh and kerberos for user accounts is
more problematic due to the extra administration and technical
support required, but still a very good solution compared to a
crypted password file.Securing the Password FileThe only sure fire way is to * out as many
passwords as you can and use ssh or
kerberos for access to those accounts. Even though the crypted
password file (/etc/spwd.db) can only be read
by root, it may be possible for an intruder to obtain read access
to that file even if the attacker cannot obtain root-write
access.Your security scripts should always check for and report
changes to the password file (see Checking file integrity
below).Securing the Kernel Core, Raw Devices, and
FilesystemsIf an attacker breaks root he can do just about anything, but
there are certain conveniences. For example, most modern kernels
have a packet sniffing device driver built in. Under FreeBSD it
is called the bpf device. An intruder
will commonly attempt to run a packet sniffer on a compromised
machine. You do not need to give the intruder the capability and
most systems should not have the bpf device compiled in.sysctlBut even if you turn off the bpf device, you still have
/dev/mem and /dev/kmem
to worry about. For that matter, the intruder can still write to
raw disk devices. Also, there is another kernel feature called
the module loader, &man.kldload.8;. An enterprising intruder can
use a KLD module to install his own bpf device or other sniffing
device on a running kernel. To avoid these problems you have to
run the kernel at a higher secure level, at least securelevel 1.
The securelevel can be set with a sysctl on
the kern.securelevel variable. Once you have
set the securelevel to 1, write access to raw devices will be
denied and special chflags flags, such as schg,
will be enforced. You must also ensure that the
schg flag is set on critical startup binaries,
directories, and script files – everything that gets run up
to the point where the securelevel is set. This might be overdoing
it, and upgrading the system is much more difficult when you
operate at a higher secure level. You may compromise and run the
system at a higher secure level but not set the
schg flag for every system file and directory
under the sun. Another possibility is to simply mount
/ and /usr read-only.
It should be noted that being too draconian in what you attempt to
protect may prevent the all-important detection of an
intrusion.Checking File Integrity: Binaries, Configuration Files,
Etc.When it comes right down to it, you can only protect your core
system configuration and control files so much before the
convenience factor rears its ugly head. For example, using
chflags to set the schg bit
on most of the files in / and
/usr is probably counterproductive because
while it may protect the files, it also closes a detection window.
The last layer of your security onion is perhaps the most
important – detection. The rest of your security is pretty
much useless (or, worse, presents you with a false sense of
safety) if you cannot detect potential incursions. Half the job
of the onion is to slow down the attacker rather than stop him in
order to give the detection side of the equation a chance to catch
him in the act.The best way to detect an incursion is to look for modified,
missing, or unexpected files. The best way to look for modified
files is from another (often centralized) limited-access system.
Writing your security scripts on the extra-secure limited-access
system makes them mostly invisible to potential attackers, and this
is important. In order to take maximum advantage you generally
have to give the limited-access box significant access to the
other machines in the business, usually either by doing a
read-only NFS export of the other machines to the limited-access
box, or by setting up ssh key-pairs to
allow the limit-access box to ssh to
the other machines. Except for its network traffic, NFS is the
least visible method – allowing you to monitor the
filesystems on each client box virtually undetected. If your
limited-access server is connected to the client boxes through a
switch, the NFS method is often the better choice. If your
limited-access server is connected to the client boxes through a
hub or through several layers of routing, the NFS method may be
too insecure (network-wise) and using
ssh may be the better choice even with
the audit-trail tracks that ssh
lays.Once you give a limit-access box at least read access to the
client systems it is supposed to monitor, you must write scripts
to do the actual monitoring. Given an NFS mount, you can write
scripts out of simple system utilities such as &man.find.1; and
&man.md5.1;. It is best to physically md5 the client-box files
boxes at least once a day, and to test control files such as those
found in /etc and
/usr/local/etc even more often. When
mismatches are found relative to the base md5 information the
limited-access machine knows is valid, it should scream at a
sysadmin to go check it out. A good security script will also
check for inappropriate suid binaries and for new or deleted files
on system partitions such as / and
/usr.When using ssh rather than NFS,
writing the security script is much more difficult. You
essentially have to scp the scripts to the client box in order to
run them, making them visible, and for safety you also need to
scp the binaries (such as find) that those
scripts use. The ssh daemon on the
client box may already be compromised. All in all, using
ssh may be necessary when running over
unsecure links, but it's also a lot harder to deal with.A good security script will also check for changes to user and
staff members access configuration files:
.rhosts, .shosts,
.ssh/authorized_keys and so forth…
files that might fall outside the purview of the
MD5 check.If you have a huge amount of user disk space it may take too
long to run through every file on those partitions. In this case,
setting mount flags to disallow suid binaries and devices on those
partitions is a good idea. The nodev and
nosuid options (see &man.mount.8;) are what you
want to look into. You should probably scan them anyway at least
once a week, since the object of this layer is to detect a break-in
whether or not the break-in is effective.Process accounting (see &man.accton.8;) is a relatively
low-overhead feature of the operating system which might help
as a post-break-in evaluation mechanism. It is especially
useful in tracking down how an intruder has actually broken into
a system, assuming the file is still intact after the break-in
occurs.Finally, security scripts should process the log files and the
logs themselves should be generated in as secure a manner as
possible – remote syslog can be very useful. An intruder
tries to cover his tracks, and log files are critical to the
sysadmin trying to track down the time and method of the initial
break-in. One way to keep a permanent record of the log files is
to run the system console to a serial port and collect the
information on a continuing basis through a secure machine
monitoring the consoles.ParanoiaA little paranoia never hurts. As a rule, a sysadmin can add
any number of security features as long as they do not effect
convenience, and can add security features that do effect
convenience with some added thought. Even more importantly, a
security administrator should mix it up a bit – if you use
recommendations such as those given by this document verbatim, you
give away your methodologies to the prospective attacker who also
has access to this document.Denial of Service AttacksDOS attacksThis section covers Denial of Service attacks. A DOS attack
is typically a packet attack. While there is not much you can do
about modern spoofed packet attacks that saturate your network,
you can generally limit the damage by ensuring that the attacks
cannot take down your servers.Limiting server forks.Limiting springboard attacks (ICMP response attacks, ping
broadcast, etc.).Kernel Route Cache.A common DOS attack is against a forking server that attempts
to cause the server to eat processes, file descriptors, and memory
until the machine dies. Inetd (see &man.inetd.8;) has several
options to limit this sort of attack. It should be noted that
while it is possible to prevent a machine from going down it is
not generally possible to prevent a service from being disrupted
by the attack. Read the inetd manual page carefully and pay
specific attention to the , ,
and options. Note that spoofed-IP attacks
will circumvent the option to inetd, so
typically a combination of options must be used. Some standalone
servers have self-fork-limitation parameters.Sendmail has its
option which tends to work
much better than trying to use sendmail's load limiting options
due to the load lag. You should specify a
MaxDaemonChildren parameter when you start
sendmail high enough to handle your
expected load but no so high that the computer cannot handle that
number of sendmails without falling on
its face. It is also prudent to run sendmail in queued mode
() and to run the daemon
(sendmail -bd) separate from the queue-runs
(sendmail -q15m). If you still want real-time
delivery you can run the queue at a much lower interval, such as
, but be sure to specify a reasonable
MaxDaemonChildren option for that sendmail to
prevent cascade failures.Syslogd can be attacked directly
and it is strongly recommended that you use the
option whenever possible, and the option
otherwise.You should also be fairly careful with connect-back services
such as tcpwrapper's reverse-identd,
which can be attacked directly. You generally do not want to use
the reverse-ident feature of
tcpwrappers for this reason.It is a very good idea to protect internal services from
external access by firewalling them off at your border routers.
The idea here is to prevent saturation attacks from outside your
LAN, not so much to protect internal services from network-based
root compromise. Always configure an exclusive firewall, i.e.,
firewall everything except ports A, B,
C, D, and M-Z. This way you can firewall off all of your
low ports except for certain specific services such as
named (if you are primary for a zone),
ntalkd,
sendmail, and other Internet-accessible
services. If you try to configure the firewall the other way
– as an inclusive or permissive firewall, there is a good
chance that you will forget to close a couple of
services or that you will add a new internal service and forget
to update the firewall. You can still open up the high-numbered
port range on the firewall to allow permissive-like operation
without compromising your low ports. Also take note that FreeBSD
allows you to control the range of port numbers used for dynamic
binding via the various net.inet.ip.portrangesysctl's (sysctl -a | fgrep
portrange), which can also ease the complexity of your
firewall's configuration. For example, you might use a normal
first/last range of 4000 to 5000, and a hiport range of 49152 to
65535, then block everything under 4000 off in your firewall
(except for certain specific Internet-accessible ports, of
course).ICMP_BANDLIMAnother common DOS attack is called a springboard attack
– to attack a server in a manner that causes the server to
generate responses which then overload the server, the local
network, or some other machine. The most common attack of this
nature is the ICMP ping broadcast attack.
The attacker spoofs ping packets sent to your LAN's broadcast
address with the source IP address set to the actual machine they
wish to attack. If your border routers are not configured to
stomp on ping's to broadcast addresses, your LAN winds up
generating sufficient responses to the spoofed source address to
saturate the victim, especially when the attacker uses the same
trick on several dozen broadcast addresses over several dozen
different networks at once. Broadcast attacks of over a hundred
and twenty megabits have been measured. A second common
springboard attack is against the ICMP error reporting system.
By constructing packets that generate ICMP error responses, an
attacker can saturate a server's incoming network and cause the
server to saturate its outgoing network with ICMP responses. This
type of attack can also crash the server by running it out of
mbuf's, especially if the server cannot drain the ICMP responses
it generates fast enough. The FreeBSD kernel has a new kernel
compile option called ICMP_BANDLIM which limits the effectiveness
of these sorts of attacks. The last major class of springboard
attacks is related to certain internal inetd services such as the
udp echo service. An attacker simply spoofs a UDP packet with the
source address being server A's echo port, and the destination
address being server B's echo port, where server A and B are both
on your LAN. The two servers then bounce this one packet back and
forth between each other. The attacker can overload both servers
and their LANs simply by injecting a few packets in this manner.
Similar problems exist with the internal chargen port. A
competent sysadmin will turn off all of these inetd-internal test
services.Spoofed packet attacks may also be used to overload the kernel
route cache. Refer to the net.inet.ip.rtexpire,
rtminexpire, and rtmaxcachesysctl parameters. A spoofed packet attack
that uses a random source IP will cause the kernel to generate a
temporary cached route in the route table, viewable with
netstat -rna | fgrep W3. These routes
typically timeout in 1600 seconds or so. If the kernel detects
that the cached route table has gotten too big it will dynamically
reduce the rtexpire but will never decrease it to less than
rtminexpire. There are two problems:The kernel does not react quickly enough when a lightly
loaded server is suddenly attacked.The rtminexpire is not low enough for
the kernel to survive a sustained attack.If your servers are connected to the Internet via a T3 or
better it may be prudent to manually override both
rtexpire and rtminexpire
via &man.sysctl.8;. Never set either parameter to zero (unless
you want to crash the machine :-). Setting both
parameters to 2 seconds should be sufficient to protect the route
table from attack.Access Issues with Kerberos and SSHSSHKerberosThere are a few issues with both kerberos and
ssh that need to be addressed if
you intend to use them. Kerberos V is an excellent
authentication protocol but there are bugs in the kerberized
telnet and
rlogin applications that make them
unsuitable for dealing with binary streams. Also, by default
kerberos does not encrypt a session unless you use the
option. ssh
encrypts everything by default.ssh works quite well in every
respect except that it forwards encryption keys by default. What
this means is that if you have a secure workstation holding keys
that give you access to the rest of the system, and you
ssh to an unsecure machine, your keys
becomes exposed. The actual keys themselves are not exposed, but
ssh installs a forwarding port for the
duration of your login and if a attacker has broken root on the
unsecure machine he can utilize that port to use your keys to gain
access to any other machine that your keys unlock.We recommend that you use ssh in
combination with kerberos whenever possible for staff logins.
ssh can be compiled with kerberos
support. This reduces your reliance on potentially exposable
ssh keys while at the same time
protecting passwords via kerberos. ssh
keys should only be used for automated tasks from secure machines
(something that kerberos is unsuited to). We also recommend that
you either turn off key-forwarding in the
ssh configuration, or that you make use
of the from=IP/DOMAIN option that
ssh allows in its
authorized_keys file to make the key only
usable to entities logging in from specific machines.DES, MD5, and CryptsecuritycryptcryptDESMD5Parts rewritten and updated by &a.unfurl;, 21 March
2000.Every user on a UNIX system has a password associated with
their account. It seems obvious that these passwords need to be
known only to the user and the actual operating system. In
order to keep these passwords secret, they are encrypted with
what is known as a one-way hash, that is, they can
only be easily encrypted but not decrypted. In other words, what
we told you a moment ago was obvious is not even true: the
operating system itself does not really know
the password. It only knows the encrypted
form of the password. The only way to get the
plain-text password is by a brute force search of the
space of possible passwords.Unfortunately the only secure way to encrypt passwords when
UNIX came into being was based on DES, the Data Encryption
Standard. This is not such a problem for users that live in
the US, but since the source code for DES could not be exported
outside the US, FreeBSD had to find a way to both comply with
US law and retain compatibility with all the other UNIX
variants that still use DES.The solution was to divide up the encryption libraries
so that US users could install the DES libraries and use
DES but international users still had an encryption method
that could be exported abroad. This is how FreeBSD came to
use MD5 as its default encryption method. MD5 is believed to
be more secure than DES, so installing DES is offered primarily
for compatibility reasons.Recognizing your crypt mechanismIt is pretty easy to identify which encryption method
FreeBSD is set up to use. Examining the encrypted passwords in
the /etc/master.passwd file is one way.
Passwords encrypted with the MD5 hash are longer than those with
encrypted with the DES hash and also begin with the characters
$1$. DES password strings do not
have any particular identifying characteristics, but they are
shorter than MD5 passwords, and are coded in a 64-character
alphabet which does not include the $
character, so a relatively short string which does not begin with
a dollar sign is very likely a DES password.The libraries can identify the passwords this way as well.
As a result, the DES libraries are able to identify MD5
passwords, and use MD5 to check passwords that were encrypted
that way, and DES for the rest. They are able to do this
because the DES libraries also contain MD5. Unfortunately, the
reverse is not true, so the MD5 libraries cannot authenticate
passwords that were encrypted with DES.Identifying which library is being used by the programs on
your system is easy as well. Any program that uses crypt is linked
against libcrypt which for each type of library is a symbolic link
to the appropriate implementation. For example, on a system using
the DES versions:&prompt.user; ls -l /usr/lib/libcrypt*
lrwxr-xr-x 1 root wheel 13 Mar 19 06:56 libcrypt.a -> libdescrypt.a
lrwxr-xr-x 1 root wheel 18 Mar 19 06:56 libcrypt.so.2.0 -> libdescrypt.so.2.0
lrwxr-xr-x 1 root wheel 15 Mar 19 06:56 libcrypt_p.a -> libdescrypt_p.aOn a system using the MD5-based libraries, the same links will
be present, but the target will be libscrypt
rather than libdescrypt.If you have installed the DES-capable crypt library
libdescrypt (e.g. by installing the
"crypto" distribution), then which password format will be used
for new passwords is controlled by the
passwd_format login capability in
/etc/login.conf, which takes values of
either des or md5. See the
&man.login.conf.5; manpage for more information about login
capabilities.S/KeyS/KeysecurityS/KeyS/Key is a one-time password scheme based on a one-way hash
function. FreeBSD uses the MD4 hash for compatibility but other
systems have used MD5 and DES-MAC. S/Key has been part of the
FreeBSD base system since version 1.1.5 and is also used on a
growing number of other operating systems. S/Key is a registered
trademark of Bell Communications Research, Inc.There are three different sorts of passwords which we will talk
about in the discussion below. The first is your usual UNIX-style or
Kerberos password; we will call this a UNIX password.
The second sort is the one-time password which is generated by the
S/Key key program and accepted by the
keyinit program and the login prompt; we will
call this a one-time password. The final sort of
password is the secret password which you give to the
key program (and sometimes the
keyinit program) which it uses to generate
one-time passwords; we will call it a secret password
or just unqualified password.The secret password does not have anything to do with your UNIX
password; they can be the same but this is not recommended. S/Key
secret passwords are not limited to 8 characters like UNIX passwords,
they can be as long as you like. Passwords of six or seven word
long phrases are fairly common. For the most part, the S/Key system
operates completely independently of the UNIX password
system.Besides the password, there are two other pieces of data that
are important to S/Key. One is what is known as the
seed or key and consists of two letters
and five digits. The other is what is called the iteration
count and is a number between 1 and 100. S/Key creates the
one-time password by concatenating the seed and the secret password,
then applying the MD4 hash as many times as specified by the
iteration count and turning the result into six short English words.
These six English words are your one-time password. The
login and su programs keep
track of the last one-time password used, and the user is
authenticated if the hash of the user-provided password is equal to
the previous password. Because a one-way hash is used it is
impossible to generate future one-time passwords if a successfully
used password is captured; the iteration count is decremented after
each successful login to keep the user and the login program in
sync. When the iteration count gets down to 1 S/Key must be
reinitialized.There are four programs involved in the S/Key system which we
will discuss below. The key program accepts an
iteration count, a seed, and a secret password, and generates a
one-time password. The keyinit program is used
to initialized S/Key, and to change passwords, iteration counts, or
seeds; it takes either a secret password, or an iteration count,
seed, and one-time password. The keyinfo program
examines the /etc/skeykeys file and prints out
the invoking user's current iteration count and seed. Finally, the
login and su programs contain
the necessary logic to accept S/Key one-time passwords for
authentication. The login program is also
capable of disallowing the use of UNIX passwords on connections
coming from specified addresses.There are four different sorts of operations we will cover. The
first is using the keyinit program over a secure
connection to set up S/Key for the first time, or to change your
password or seed. The second operation is using the
keyinit program over an insecure connection, in
conjunction with the key program over a secure
connection, to do the same. The third is using the
key program to log in over an insecure
connection. The fourth is using the key program
to generate a number of keys which can be written down or printed
out to carry with you when going to some location without secure
connections to anywhere.Secure connection initializationTo initialize S/Key for the first time, change your password,
or change your seed while logged in over a secure connection
(e.g., on the console of a machine or via ssh), use the
keyinit command without any parameters while
logged in as yourself:&prompt.user; keyinit
Adding unfurl:
Reminder - Only use this method if you are directly connected.
If you are using telnet or rlogin exit with no password and use keyinit -s.
Enter secret password:
Again secret password:
ID unfurl s/key is 99 to17757
DEFY CLUB PRO NASH LACE SOFTAt the Enter secret password: prompt you
should enter a password or phrase. Remember, this is not the
password that you will use to login with, this is used to generate
your one-time login keys. The ID line gives the
parameters of your particular S/Key instance; your login name, the
iteration count, and seed. When logging in with S/Key, the system
will remember these parameters and present them back to you so you
do not have to remember them. The last line gives the particular
one-time password which corresponds to those parameters and your
secret password; if you were to re-login immediately, this
one-time password is the one you would use.Insecure connection initializationTo initialize S/Key or change your secret password over an
insecure connection, you will need to already have a secure
connection to some place where you can run the
key program; this might be in the form of a
desk accessory on a Macintosh, or a shell prompt on a machine you
trust. You will also need to make up an iteration count (100 is
probably a good value), and you may make up your own seed or use a
randomly-generated one. Over on the insecure connection (to the
machine you are initializing), use the keyinit
-s command:&prompt.user; keyinit -s
Updating unfurl:
Old key: to17758
Reminder you need the 6 English words from the key command.
Enter sequence count from 1 to 9999: 100
Enter new key [default to17759]:
s/key 100 to 17759
s/key access password:To accept the default seed (which the
keyinit program confusingly calls a
key), press return. Then before entering an
access password, move over to your secure connection or S/Key desk
accessory, and give it the same parameters:&prompt.user; key 100 to17759
Reminder - Do not use this program while logged in via telnet or rlogin.
Enter secret password: <secret password>
CURE MIKE BANE HIM RACY GORENow switch back over to the insecure connection, and copy the
one-time password generated by key over to the
keyinit program:s/key access password:CURE MIKE BANE HIM RACY GORE
ID unfurl s/key is 100 to17759
CURE MIKE BANE HIM RACY GOREThe rest of the description from the previous section applies
here as well.Generating a single one-time passwordOnce you've initialized S/Key, when you login you will be
presented with a prompt like this:&prompt.user; telnet example.com
Trying 10.0.0.1...
Connected to example.com
Escape character is '^]'.
FreeBSD/i386 (example.com) (ttypa)
login: <username>
s/key 97 fw13894
Password: As a side note, the S/Key prompt has a useful feature
(not shown here): if you press return at the password prompt, the
login program will turn echo on, so you can see what you are
typing. This can be extremely useful if you are attempting to
type in an S/Key by hand, such as from a printout. Also, if this
machine were configured to disallow UNIX passwords over a
connection from the source machine, the prompt would have also included
the annotation (s/key required), indicating
that only S/Key one-time passwords will be accepted.
+ MS-DOS
+ Windows
+ MacOS
+
At this point you need to generate your one-time password to
answer this login prompt. This must be done on a trusted system
that you can run the key command on. (There
- are versions of the key program from DOS,
+ are versions of the key program for MS-DOS,
Windows and MacOS as well.) The key program
needs both the iteration count and the seed as command line
options. You can cut-and-paste these right from the login prompt
on the machine that you are logging in to.On the trusted system:&prompt.user; key 97 fw13894
Reminder - Do not use this program while logged in via telnet or rlogin.
Enter secret password:
WELD LIP ACTS ENDS ME HAAGNow that you have your one-time password you can continue
logging in:login: <username>
s/key 97 fw13894
Password: <return to enable echo>
s/key 97 fw13894
Password [echo on]: WELD LIP ACTS ENDS ME HAAG
Last login: Tue Mar 21 11:56:41 from 10.0.0.2 ... This is the easiest mechanism if you have
a trusted machine. There is a Java S/Key key
applet, The Java OTP
Calculator, that you can download and run locally on any
Java supporting browser.Generating multiple one-time passwordsSometimes you have to go places where you do not have
access to a trusted machine or secure connection. In this case,
it is possible to use the key command to
generate a number of one-time passwords before hand to be printed
out and taken with you. For example:&prompt.user; key -n 5 30 zz99999
Reminder - Do not use this program while logged in via telnet or rlogin.
Enter secret password: <secret password>
26: SODA RUDE LEA LIND BUDD SILT
27: JILT SPY DUTY GLOW COWL ROT
28: THEM OW COLA RUNT BONG SCOT
29: COT MASH BARR BRIM NAN FLAG
30: CAN KNEE CAST NAME FOLK BILKThe requests five keys in sequence, the
specifies what the last iteration number
should be. Note that these are printed out in
reverse order of eventual use. If you are
really paranoid, you might want to write the results down by hand;
otherwise you can cut-and-paste into lpr. Note
that each line shows both the iteration count and the one-time
password; you may still find it handy to scratch off passwords as
you use them.Restricting use of UNIX passwordsRestrictions can be placed on the use of UNIX passwords based
on the host name, user name, terminal port, or IP address of a
login session. These restrictions can be found in the
configuration file /etc/skey.access. The
&man.skey.access.5; manual page has more info on the complete
format of the file and also details some security cautions to be
aware of before depending on this file for security.If there is no /etc/skey.access file
(this is the FreeBSD default), then all users will be allowed to
use UNIX passwords. If the file exists, however, then all users
will be required to use S/Key unless explicitly permitted to do
otherwise by configuration statements in the
skey.access file. In all cases, UNIX
passwords are permitted on the console.Here is a sample configuration file which illustrates the
three most common sorts of configuration statements:permit internet 192.168.0.0 255.255.0.0
permit user fnord
permit port ttyd0The first line (permit internet) allows
users whose IP source address (which is vulnerable to spoofing)
matches the specified value and mask, to use UNIX passwords. This
should not be considered a security mechanism, but rather, a means
to remind authorized users that they are using an insecure network
and need to use S/Key for authentication.The second line (permit user) allows the
specified username, in this case fnord, to use
UNIX passwords at any time. Generally speaking, this should only
be used for people who are either unable to use the
key program, like those with dumb terminals, or
those who are uneducable.The third line (permit port) allows all
users logging in on the specified terminal line to use UNIX
passwords; this would be used for dial-ups.KerberosKerberosContributed by &a.markm; (based on contribution by
&a.md;).Kerberos is a network add-on system/protocol that allows users to
authenticate themselves through the services of a secure server.
Services such as remote login, remote copy, secure inter-system file
copying and other high-risk tasks are made considerably safer and more
controllable.The following instructions can be used as a guide on how to set up
Kerberos as distributed for FreeBSD. However, you should refer to the
relevant manual pages for a complete description.4.4BSD-LiteIn FreeBSD, the Kerberos is not that from the original 4.4BSD-Lite,
distribution, but eBones, which had been previously ported to FreeBSD
1.1.5.1, and was sourced from outside the USA/Canada, and was thus
available to system owners outside those countries during the era
of restrictive export controls on cryptographic code from the USA.Creating the initial databaseThis is done on the Kerberos server only. First make sure that
you do not have any old Kerberos databases around. You should change
to the directory /etc/kerberosIV and check that
only the following files are present:&prompt.root; cd /etc/kerberosIV
&prompt.root; ls
README krb.conf krb.realmsIf any additional files (such as principal.*
or master_key) exist, then use the
kdb_destroy command to destroy the old Kerberos
database, of if Kerberos is not running, simply delete the extra
files.You should now edit the krb.conf and
krb.realms files to define your Kerberos realm.
In this case the realm will be GRONDAR.ZA and the
server is grunt.grondar.za. We edit or create
the krb.conf file:&prompt.root; cat krb.conf
GRONDAR.ZA
GRONDAR.ZA grunt.grondar.za admin server
CS.BERKELEY.EDU okeeffe.berkeley.edu
ATHENA.MIT.EDU kerberos.mit.edu
ATHENA.MIT.EDU kerberos-1.mit.edu
ATHENA.MIT.EDU kerberos-2.mit.edu
ATHENA.MIT.EDU kerberos-3.mit.edu
LCS.MIT.EDU kerberos.lcs.mit.edu
TELECOM.MIT.EDU bitsy.mit.edu
ARC.NASA.GOV trident.arc.nasa.govIn this case, the other realms do not need to be there. They are
here as an example of how a machine may be made aware of multiple
realms. You may wish to not include them for simplicity.The first line names the realm in which this system works. The
other lines contain realm/host entries. The first item on a line is a
realm, and the second is a host in that realm that is acting as a
key distribution center. The words admin
server following a hosts name means that host also
provides an administrative database server. For further explanation
of these terms, please consult the Kerberos man pages.Now we have to add grunt.grondar.za
to the GRONDAR.ZA realm and also add an entry to
put all hosts in the .grondar.za
domain in the GRONDAR.ZA realm. The
krb.realms file would be updated as
follows:&prompt.root; cat krb.realms
grunt.grondar.za GRONDAR.ZA
.grondar.za GRONDAR.ZA
.berkeley.edu CS.BERKELEY.EDU
.MIT.EDU ATHENA.MIT.EDU
.mit.edu ATHENA.MIT.EDUAgain, the other realms do not need to be there. They are here as
an example of how a machine may be made aware of multiple realms. You
may wish to remove them to simplify things.The first line puts the specific system into
the named realm. The rest of the lines show how to default systems of
a particular subdomain to a named realm.Now we are ready to create the database. This only needs to run
on the Kerberos server (or Key Distribution Center). Issue the
kdb_init command to do this:&prompt.root; kdb_initRealm name [default ATHENA.MIT.EDU ]:GRONDAR.ZA
You will be prompted for the database Master Password.
It is important that you NOT FORGET this password.
Enter Kerberos master key:Now we have to save the key so that servers on the local machine
can pick it up. Use the kstash command to do
this.&prompt.root; kstashEnter Kerberos master key:
Current Kerberos master key version is 1.
Master key entered. BEWARE!This saves the encrypted master password in
/etc/kerberosIV/master_key.Making it all runTwo principals need to be added to the database for
each system that will be secured with Kerberos.
Their names are kpasswd and rcmd
These two principals are made for each system, with the instance being
the name of the individual system.These daemons, kpasswd and
rcmd allow other systems to change Kerberos
passwords and run commands like rcp,
rlogin and rsh.Now let's add these entries:&prompt.root; kdb_edit
Opening database...
Enter Kerberos master key:
Current Kerberos master key version is 1.
Master key entered. BEWARE!
Previous or default values are in [brackets] ,
enter return to leave the same, or new value.
Principal name:passwdInstance:grunt
<Not found>, Create [y] ?y
Principal: passwd, Instance: grunt, kdc_key_ver: 1
New Password: <---- enter RANDOM here
Verifying password
New Password: <---- enter RANDOM here
Random password [y] ?y
Principal's new key version = 1
Expiration date (enter yyyy-mm-dd) [ 2000-01-01 ] ?Max ticket lifetime (*5 minutes) [ 255 ] ?Attributes [ 0 ] ?
Edit O.K.
Principal name:rcmdInstance:grunt
<Not found>, Create [y] ?
Principal: rcmd, Instance: grunt, kdc_key_ver: 1
New Password: <---- enter RANDOM here
Verifying password
New Password: <---- enter RANDOM here
Random password [y] ?
Principal's new key version = 1
Expiration date (enter yyyy-mm-dd) [ 2000-01-01 ] ?Max ticket lifetime (*5 minutes) [ 255 ] ?Attributes [ 0 ] ?
Edit O.K.
Principal name: <---- null entry here will cause an exitCreating the server fileWe now have to extract all the instances which define the services
on each machine. For this we use the ext_srvtab
command. This will create a file which must be copied or moved
by secure means to each Kerberos client's
/etc/kerberosIV directory. This file must be present on each server
and client, and is crucial to the operation of Kerberos.&prompt.root; ext_srvtab gruntEnter Kerberos master key:
Current Kerberos master key version is 1.
Master key entered. BEWARE!
Generating 'grunt-new-srvtab'....Now, this command only generates a temporary file which must be
renamed to srvtab so that all the server can pick
it up. Use the mv command to move it into place on
the original system:&prompt.root; mv grunt-new-srvtab srvtabIf the file is for a client system, and the network is not deemed
safe, then copy the
client-new-srvtab to
removable media and transport it by secure physical means. Be sure to
rename it to srvtab in the client's
/etc/kerberosIV directory, and make sure it is
mode 600:&prompt.root; mv grumble-new-srvtab srvtab
&prompt.root; chmod 600 srvtabPopulating the databaseWe now have to add some user entries into the database. First
let's create an entry for the user jane. Use the
kdb_edit command to do this:&prompt.root; kdb_edit
Opening database...
Enter Kerberos master key:
Current Kerberos master key version is 1.
Master key entered. BEWARE!
Previous or default values are in [brackets] ,
enter return to leave the same, or new value.
Principal name:janeInstance:
<Not found>, Create [y] ?y
Principal: jane, Instance: , kdc_key_ver: 1
New Password: <---- enter a secure password here
Verifying password
New Password: <---- re-enter the password here
Principal's new key version = 1
Expiration date (enter yyyy-mm-dd) [ 2000-01-01 ] ?Max ticket lifetime (*5 minutes) [ 255 ] ?Attributes [ 0 ] ?
Edit O.K.
Principal name: <---- null entry here will cause an exitTesting it all outFirst we have to start the Kerberos daemons. NOTE that if you
have correctly edited your /etc/rc.conf then this
will happen automatically when you reboot. This is only necessary on
the Kerberos server. Kerberos clients will automagically get what
they need from the /etc/kerberosIV
directory.&prompt.root; kerberos &
Kerberos server starting
Sleep forever on error
Log file is /var/log/kerberos.log
Current Kerberos master key version is 1.
Master key entered. BEWARE!
Current Kerberos master key version is 1
Local realm: GRONDAR.ZA
&prompt.root; kadmind -n &
KADM Server KADM0.0A initializing
Please do not use 'kill -9' to kill this job, use a
regular kill instead
Current Kerberos master key version is 1.
Master key entered. BEWARE!Now we can try using the kinit command to get a
ticket for the id jane that we created
above:&prompt.user; kinit jane
MIT Project Athena (grunt.grondar.za)
Kerberos Initialization for "jane"
Password:Try listing the tokens using klist to see if we
really have them:&prompt.user; klist
Ticket file: /tmp/tkt245
Principal: jane@GRONDAR.ZA
Issued Expires Principal
Apr 30 11:23:22 Apr 30 19:23:22 krbtgt.GRONDAR.ZA@GRONDAR.ZANow try changing the password using passwd to
check if the kpasswd daemon can get authorization to the Kerberos
database:&prompt.user; passwd
realm GRONDAR.ZA
Old password for jane:New Password for jane:
Verifying password
New Password for jane:
Password changed.Adding su privilegesKerberos allows us to give each user who
needs root privileges their own separatesupassword. We could now add an id which is
authorized to su to root.
This is controlled by having an instance of root
associated with a principal. Using kdb_edit we can
create the entry jane.root in the Kerberos
database:&prompt.root; kdb_edit
Opening database...
Enter Kerberos master key:
Current Kerberos master key version is 1.
Master key entered. BEWARE!
Previous or default values are in [brackets] ,
enter return to leave the same, or new value.
Principal name:janeInstance:root
<Not found>, Create [y] ? y
Principal: jane, Instance: root, kdc_key_ver: 1
New Password: <---- enter a SECURE password here
Verifying password
New Password: <---- re-enter the password here
Principal's new key version = 1
Expiration date (enter yyyy-mm-dd) [ 2000-01-01 ] ?Max ticket lifetime (*5 minutes) [ 255 ] ?12 <--- Keep this short!
Attributes [ 0 ] ?
Edit O.K.
Principal name: <---- null entry here will cause an exitNow try getting tokens for it to make sure it works:&prompt.root; kinit jane.root
MIT Project Athena (grunt.grondar.za)
Kerberos Initialization for "jane.root"
Password:Now we need to add the user to root's .klogin
file:&prompt.root; cat /root/.klogin
jane.root@GRONDAR.ZANow try doing the su:&prompt.user; suPassword:and take a look at what tokens we have:&prompt.root; klist
Ticket file: /tmp/tkt_root_245
Principal: jane.root@GRONDAR.ZA
Issued Expires Principal
May 2 20:43:12 May 3 04:43:12 krbtgt.GRONDAR.ZA@GRONDAR.ZAUsing other commandsIn an earlier example, we created a principal called
jane with an instance root.
This was based on a user with the same name as the principal, and this
is a Kerberos default; that a
<principal>.<instance> of the form
<username>.root will allow
that <username> to su to
root if the necessary entries are in the .klogin
file in root's home directory:&prompt.root; cat /root/.klogin
jane.root@GRONDAR.ZALikewise, if a user has in their own home directory lines of the
form:&prompt.user; cat ~/.klogin
jane@GRONDAR.ZA
jack@GRONDAR.ZAThis allows anyone in the GRONDAR.ZA realm
who has authenticated themselves to jane or
jack (via kinit, see above)
access to rlogin to jane's
account or files on this system (grunt) via
rlogin, rsh or
rcp.For example, Jane now logs into another system, using
Kerberos:&prompt.user; kinit
MIT Project Athena (grunt.grondar.za)
Password:
&prompt.user; rlogin grunt
Last login: Mon May 1 21:14:47 from grumble
Copyright (c) 1980, 1983, 1986, 1988, 1990, 1991, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD BUILT-19950429 (GR386) #0: Sat Apr 29 17:50:09 SAT 1995Or Jack logs into Jane's account on the same machine (Jane having
set up the .klogin file as above, and the person
in charge of Kerberos having set up principal
jack with a null instance:&prompt.user; kinit
&prompt.user; rlogin grunt -l jane
MIT Project Athena (grunt.grondar.za)
Password:
Last login: Mon May 1 21:16:55 from grumble
Copyright (c) 1980, 1983, 1986, 1988, 1990, 1991, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD BUILT-19950429 (GR386) #0: Sat Apr 29 17:50:09 SAT 1995FirewallsfirewallssecurityfirewallsContributed by &a.gpalmer; and Alex Nash.Firewalls are an area of increasing interest for people who are
connected to the Internet, and are even finding applications on private
networks to provide enhanced security. This section will hopefully
explain what firewalls are, how to use them, and how to use the
facilities provided in the FreeBSD kernel to implement them.People often think that having a firewall between your
internal network and the Big Bad Internet will solve all
your security problems. It may help, but a poorly setup firewall
system is more of a security risk than not having one at all. A
firewall can add another layer of security to your systems, but it
cannot stop a really determined cracker from penetrating your internal
network. If you let internal security lapse because you believe your
firewall to be impenetrable, you have just made the crackers job that
much easier.What is a firewall?There are currently two distinct types of firewalls in common use
on the Internet today. The first type is more properly called a
packet filtering router, where the kernel on a
multi-homed machine chooses whether to forward or block packets based
on a set of rules. The second type, known as a proxy
server, relies on daemons to provide authentication and to
forward packets, possibly on a multi-homed machine which has kernel
packet forwarding disabled.Sometimes sites combine the two types of firewalls, so that only a
certain machine (known as a bastion host) is
allowed to send packets through a packet filtering router onto an
internal network. Proxy services are run on the bastion host, which
are generally more secure than normal authentication
mechanisms.FreeBSD comes with a kernel packet filter (known as
IPFW), which is what the rest of this
section will concentrate on. Proxy servers can be built on FreeBSD
from third party software, but there is such a variety of proxy
servers available that it would be impossible to cover them in this
document.Packet filtering routersA router is a machine which forwards packets between two or more
networks. A packet filtering router has an extra piece of code in
its kernel which compares each packet to a list of rules before
deciding if it should be forwarded or not. Most modern IP routing
software has packet filtering code within it that defaults to
forwarding all packets. To enable the filters, you need to define a
set of rules for the filtering code so it can decide if the
packet should be allowed to pass or not.To decide whether a packet should be passed on, the code looks
through its set of rules for a rule which matches the contents of
this packets headers. Once a match is found, the rule action is
obeyed. The rule action could be to drop the packet, to forward the
packet, or even to send an ICMP message back to the originator.
Only the first match counts, as the rules are searched in order.
Hence, the list of rules can be referred to as a rule
chain.The packet matching criteria varies depending on the software
used, but typically you can specify rules which depend on the source
IP address of the packet, the destination IP address, the source
port number, the destination port number (for protocols which
support ports), or even the packet type (UDP, TCP, ICMP,
etc).Proxy serversProxy servers are machines which have had the normal system
daemons (telnetd, ftpd, etc) replaced with special servers. These
servers are called proxy servers as they
normally only allow onward connections to be made. This enables you
to run (for example) a proxy telnet server on your firewall host,
and people can telnet in to your firewall from the outside, go
through some authentication mechanism, and then gain access to the
internal network (alternatively, proxy servers can be used for
signals coming from the internal network and heading out).Proxy servers are normally more secure than normal servers, and
often have a wider variety of authentication mechanisms available,
including one-shot password systems so that even if
someone manages to discover what password you used, they will not be
able to use it to gain access to your systems as the password
instantly expires. As they do not actually give users access to the
host machine, it becomes a lot more difficult for someone to install
backdoors around your security system.Proxy servers often have ways of restricting access further, so
that only certain hosts can gain access to the servers, and often
they can be set up so that you can limit which users can talk to
which destination machine. Again, what facilities are available
depends largely on what proxy software you choose.What does IPFW allow me to do?ipfwIPFW, the software supplied with
FreeBSD, is a packet filtering and accounting system which resides in
the kernel, and has a user-land control utility,
&man.ipfw.8;. Together, they allow you to define and query the
rules currently used by the kernel in its routing decisions.There are two related parts to IPFW.
The firewall section allows you to perform packet filtering. There is
also an IP accounting section which allows you to track usage of your
router, based on similar rules to the firewall section. This allows
you to see (for example) how much traffic your router is getting from
a certain machine, or how much WWW (World Wide Web) traffic it is
forwarding.As a result of the way that IPFW is
designed, you can use IPFW on non-router
machines to perform packet filtering on incoming and outgoing
connections. This is a special case of the more general use of
IPFW, and the same commands and techniques
should be used in this situation.Enabling IPFW on FreeBSDipfwenablingAs the main part of the IPFW system
lives in the kernel, you will need to add one or more options to your
kernel configuration file, depending on what facilities you want, and
recompile your kernel. See reconfiguring
the kernel for more details on how to recompile your
kernel.There are currently three kernel configuration options relevant to
IPFW:options IPFIREWALLCompiles into the kernel the code for packet
filtering.options IPFIREWALL_VERBOSEEnables code to allow logging of packets through
&man.syslogd.8;. Without this option, even if you specify
that packets should be logged in the filter rules, nothing will
happen.options IPFIREWALL_VERBOSE_LIMIT=10Limits the number of packets logged through
&man.syslogd.8; on a per entry basis. You may wish to use
this option in hostile environments in which you want to log
firewall activity, but do not want to be open to a denial of
service attack via syslog flooding.When a chain entry reaches the packet limit specified,
logging is turned off for that particular entry. To resume
logging, you will need to reset the associated counter using the
&man.ipfw.8; utility:&prompt.root; ipfw zero 4500Where 4500 is the chain entry you wish to continue
logging.Previous versions of FreeBSD contained an
IPFIREWALL_ACCT option. This is now obsolete as
the firewall code automatically includes accounting
facilities.Configuring IPFWipfwconfiguringThe configuration of the IPFW software
is done through the &man.ipfw.8; utility. The syntax for this
command looks quite complicated, but it is relatively simple once you
understand its structure.There are currently four different command categories used by the
utility: addition/deletion, listing, flushing, and clearing.
Addition/deletion is used to build the rules that control how packets
are accepted, rejected, and logged. Listing is used to examine the
contents of your rule set (otherwise known as the chain) and packet
counters (accounting). Flushing is used to remove all entries from
the chain. Clearing is used to zero out one or more accounting
entries.Altering the IPFW rulesThe syntax for this form of the command is:
ipfw-NcommandindexactionlogprotocoladdressesoptionsThere is one valid flag when using this form of the
command:-NResolve addresses and service names in output.The command given can be shortened to the
shortest unique form. The valid commands
are:addAdd an entry to the firewall/accounting rule listdeleteDelete an entry from the firewall/accounting rule
listPrevious versions of IPFW used
separate firewall and accounting entries. The present version
provides packet accounting with each firewall entry.If an index value is supplied, it used to
place the entry at a specific point in the chain. Otherwise, the
entry is placed at the end of the chain at an index 100 greater than
the last chain entry (this does not include the default policy, rule
65535, deny).The log option causes matching rules to be
output to the system console if the kernel was compiled with
IPFIREWALL_VERBOSE.Valid actions are:rejectDrop the packet, and send an ICMP host or port unreachable
(as appropriate) packet to the source.allowPass the packet on as normal. (aliases:
pass and
accept)denyDrop the packet. The source is not notified via an
ICMP message (thus it appears that the packet never
arrived at the destination).countUpdate packet counters but do not allow/deny the packet
based on this rule. The search continues with the next chain
entry.Each action will be recognized by the
shortest unambiguous prefix.The protocols which can be specified
are:allMatches any IP packeticmpMatches ICMP packetstcpMatches TCP packetsudpMatches UDP packetsThe address specification is:fromaddress/maskporttoaddress/maskportvia interfaceYou can only specify port in
conjunction with protocols which support ports
(UDP and TCP).The is optional and may specify the IP
address or domain name of a local IP interface, or an interface name
(e.g. ed0) to match only packets coming
through this interface. Interface unit numbers can be specified
with an optional wildcard. For example, ppp*
would match all kernel PPP interfaces.The syntax used to specify an
address/mask is:
address
or
address/mask-bits
or
address:mask-patternA valid hostname may be specified in place of the IP address.
is a decimal
number representing how many bits in the address mask should be set.
e.g. specifying 192.216.222.1/24 will create a
mask which will allow any address in a class C subnet (in this case,
192.216.222) to be matched.
is an IP
address which will be logically AND'ed with the address given. The
keyword any may be used to specify any IP
address.The port numbers to be blocked are specified as:
port,port,port…
to specify either a single port or a list of ports, or
port-port
to specify a range of ports. You may also combine a single range
with a list, but the range must always be specified first.The options available are:fragMatches if the packet is not the first fragment of the
datagram.inMatches if the packet is on the way in.outMatches if the packet is on the way out.ipoptions specMatches if the IP header contains the comma separated list
of options specified in spec. The
supported list of IP options are: ssrr
(strict source route), lsrr (loose source
route), rr (record packet route), and
ts (time stamp). The absence of a
particular option may be denoted with a leading
!.establishedMatches if the packet is part of an already established
TCP connection (i.e. it has the RST or ACK bits set). You can
optimize the performance of the firewall by placing
established rules early in the
chain.setupMatches if the packet is an attempt to establish a TCP
connection (the SYN bit set is set but the ACK bit is
not).tcpflags flagsMatches if the TCP header contains the comma separated
list of flags. The supported flags
are fin, syn,
rst, psh,
ack, and urg. The
absence of a particular flag may be indicated by a leading
!.icmptypes typesMatches if the ICMP type is present in the list
types. The list may be specified
as any combination of ranges and/or individual types separated
by commas. Commonly used ICMP types are: 0
echo reply (ping reply), 3 destination
unreachable, 5 redirect,
8 echo request (ping request), and
11 time exceeded (used to indicate TTL
expiration as with &man.traceroute.8;).Listing the IPFW rulesThe syntax for this form of the command is:
ipfw-a-t-NlThere are three valid flags when using this form of the
command:-aWhile listing, show counter values. This option is the
only way to see accounting counters.-tDisplay the last match times for each chain entry. The
time listing is incompatible with the input syntax used by the
&man.ipfw.8; utility.-NAttempt to resolve given addresses and service
names.Flushing the IPFW rulesThe syntax for flushing the chain is:
ipfwflushThis causes all entries in the firewall chain to be removed
except the fixed default policy enforced by the kernel (index
65535). Use caution when flushing rules, the default deny policy
will leave your system cut off from the network until allow entries
are added to the chain.Clearing the IPFW packet countersThe syntax for clearing one or more packet counters is:
ipfwzeroindexWhen used without an index argument,
all packet counters are cleared. If an
index is supplied, the clearing operation
only affects a specific chain entry.Example commands for ipfwThis command will deny all packets from the host evil.crackers.org to the telnet port of the
host nice.people.org:&prompt.root ipfw add deny tcp from evil.crackers.org to nice.people.org 23The next example denies and logs any TCP traffic from the entire
crackers.org network (a class C) to
the nice.people.org machine (any
port).&prompt.root; ipfw add deny log tcp from evil.crackers.org/24 to nice.people.orgIf you do not want people sending X sessions to your internal
network (a subnet of a class C), the following command will do the
necessary filtering:&prompt.root; ipfw add deny tcp from any to my.org/28 6000 setupTo see the accounting records:
&prompt.root; ipfw -a list
or in the short form
&prompt.root; ipfw -a lYou can also see the last time a chain entry was matched
with:&prompt.root; ipfw -at lBuilding a packet filtering firewallThe following suggestions are just that: suggestions. The
requirements of each firewall are different and we cannot tell you
how to build a firewall to meet your particular requirements.When initially setting up your firewall, unless you have a test
bench setup where you can configure your firewall host in a controlled
environment, it is strongly recommend you use the logging version of the
commands and enable logging in the kernel. This will allow you to
quickly identify problem areas and cure them without too much
disruption. Even after the initial setup phase is complete, I
recommend using the logging for `deny' as it allows tracing of
possible attacks and also modification of the firewall rules if your
requirements alter.If you use the logging versions of the accept
command, it can generate large amounts of log
data as one log line will be generated for every packet that passes
through the firewall, so large ftp/http transfers, etc, will really
slow the system down. It also increases the latencies on those
packets as it requires more work to be done by the kernel before the
packet can be passed on. syslogd with also start using up a lot
more processor time as it logs all the extra data to disk, and it
could quite easily fill the partition /var/log
is located on.You should enable your firewall from
/etc/rc.conf.local or
/etc/rc.conf. The associated man page explains
which knobs to fiddle and lists some preset firewall configurations.
If you do not use a preset configuration, ipfw list
will output the current ruleset into a file that you can
pass to rc.conf. If you do not use
/etc/rc.conf.local or
/etc/rc.conf to enable your firewall,
it is important to make sure your firewall is enabled before
any IP interfaces are configured.
The next problem is what your firewall should actually
do! This is largely dependent on what access to
your network you want to allow from the outside, and how much access
to the outside world you want to allow from the inside. Some general
rules are:Block all incoming access to ports below 1024 for TCP. This is
where most of the security sensitive services are, like finger,
SMTP (mail) and telnet.Block all incoming UDP traffic. There
are very few useful services that travel over UDP, and what useful
traffic there is normally a security threat (e.g. Suns RPC and
NFS protocols). This has its disadvantages also, since UDP is a
connectionless protocol, denying incoming UDP traffic also blocks
the replies to outgoing UDP traffic. This can cause a problem for
people (on the inside) using external archie (prospero) servers.
If you want to allow access to archie, you'll have to allow
packets coming from ports 191 and 1525 to any internal UDP port
through the firewall. ntp is another service you may consider
allowing through, which comes from port 123.Block traffic to port 6000 from the outside. Port 6000 is the
port used for access to X11 servers, and can be a security threat
(especially if people are in the habit of doing xhost
+ on their workstations). X11 can actually use a
range of ports starting at 6000, the upper limit being how many X
displays you can run on the machine. The upper limit as defined
by RFC 1700 (Assigned Numbers) is 6063.Check what ports any internal servers use (e.g. SQL servers,
etc). It is probably a good idea to block those as well, as they
normally fall outside the 1-1024 range specified above.Another checklist for firewall configuration is available from
CERT at http://www.cert.org/tech_tips/packet_filtering.htmlAs stated above, these are only guidelines.
You will have to decide what filter rules you want to use on your
firewall yourself. We cannot accept ANY responsibility if someone
breaks into your network, even if you follow the advice given
above.OpenSSLsecurityOpenSSLOpenSSLAs of FreeBSD 4.0, the OpenSSL toolkit is a part of the base
system. OpenSSL
provides a general-purpose cryptography library, as well as the
Secure Sockets Layer v2/v3 (SSLv2/SSLv3) and Transport Layer
Security v1 (TLSv1) network security protocols.However, one of the algorithms (specifically IDEA)
included in OpenSSL is protected by patents in the USA and
elsewhere, and is not available for unrestricted use.
IDEA is included in the OpenSSL sources in FreeBSD, but it is not
built by default. If you wish to use it, and you comply with the
license terms, enable the MAKE_IDEA switch in /etc/make.conf and
rebuild your sources using 'make world'.Today, the RSA algorithm is free for use in USA and other
countries. In the past it was protected by a patent.OpenSSLinstallSource Code InstallationsOpenSSL is part of the src-crypto and
src-secure cvsup collections. See the Obtaining FreeBSD section for more
information about obtaining and updating FreeBSD source
code.IPsecIPsecsecurityIPsecContributed by &a.shin;, 5 March
2000.The IPsec mechanism provides secure communication either for IP
layer and socket layer communication. This section should
explain how to use them. For implementation details, please
refer to The
Developers' Handbook.The current IPsec implementation supports both transport mode
and tunnel mode. However, tunnel mode comes with some restrictions.
http://www.kame.net/newsletter/
has more comprehensive examples.Please be aware that in order to use this functionality, you
must have the following options compiled into your kernel:options IPSEC #IP security
options IPSEC_ESP #IP security (crypto; define w/IPSEC)Transport mode example with IPv4Let's setup security association to deploy a secure channel
between HOST A (10.2.3.4) and HOST B (10.6.7.8). Here we show a little
complicated example. From HOST A to HOST B, only old AH is used.
From HOST B to HOST A, new AH and new ESP are combined.Now we should choose algorithm to be used corresponding to
"AH"/"new AH"/"ESP"/"new ESP". Please refer to the &man.setkey.8; man
page to know algorithm names. Our choice is MD5 for AH, new-HMAC-SHA1
for new AH, and new-DES-expIV with 8 byte IV for new ESP.Key length highly depends on each algorithm. For example, key
length must be equal to 16 bytes for MD5, 20 for new-HMAC-SHA1,
and 8 for new-DES-expIV. Now we choose "MYSECRETMYSECRET",
"KAMEKAMEKAMEKAMEKAME", "PASSWORD", respectively.OK, let's assign SPI (Security Parameter Index) for each protocol.
Please note that we need 3 SPIs for this secure channel since three
security headers are produced (one for from HOST A to HOST B, two for
from HOST B to HOST A). Please also note that SPI MUST be greater
than or equal to 256. We choose, 1000, 2000, and 3000, respectively.
(1)
HOST A ------> HOST B
(1)PROTO=AH
ALG=MD5(RFC1826)
KEY=MYSECRETMYSECRET
SPI=1000
(2.1)
HOST A <------ HOST B
<------
(2.2)
(2.1)
PROTO=AH
ALG=new-HMAC-SHA1(new AH)
KEY=KAMEKAMEKAMEKAMEKAME
SPI=2000
(2.2)
PROTO=ESP
ALG=new-DES-expIV(new ESP)
IV length = 8
KEY=PASSWORD
SPI=3000
Now, let's setup security association. Execute &man.setkey.8;
on both HOST A and B:
&prompt.root; setkey -c
add 10.2.3.4 10.6.7.8 ah-old 1000 -m transport -A keyed-md5 "MYSECRETMYSECRET" ;
add 10.6.7.8 10.2.3.4 ah 2000 -m transport -A hmac-sha1 "KAMEKAMEKAMEKAMEKAME" ;
add 10.6.7.8 10.2.3.4 esp 3000 -m transport -E des-cbc "PASSWORD" ;
^D
Actually, IPsec communication doesn't process until security policy
entries will be defined. In this case, you must setup each host.
At A:
&prompt.root; setkey -c
spdadd 10.2.3.4 10.6.7.8 any -P out ipsec
ah/transport/10.2.3.4-10.6.7.8/require ;
^D
At B:
&prompt.root; setkey -c
spdadd 10.6.7.8 10.2.3.4 any -P out ipsec
esp/transport/10.6.7.8-10.2.3.4/require ;
spdadd 10.6.7.8 10.2.3.4 any -P out ipsec
ah/transport/10.6.7.8-10.2.3.4/require ;
^D
HOST A --------------------------------------> HOST E
10.2.3.4 10.6.7.8
| |
========== old AH keyed-md5 ==========>
<========= new AH hmac-sha1 ===========
<========= new ESP des-cbc ============
Transport mode example with IPv6Another example using IPv6.ESP transport mode is recommended for TCP port number 110 between
Host-A and Host-B.
============ ESP ============
| |
Host-A Host-B
fec0::10 -------------------- fec0::11
Encryption algorithm is blowfish-cbc whose key is "kamekame", and
authentication algorithm is hmac-sha1 whose key is "this is the test
key". Configuration at Host-A:
&prompt.root; setkey -c <<EOF
spdadd fec0::10[any] fec0::11[110] tcp -P out ipsec
esp/transport/fec0::10-fec0::11/use ;
spdadd fec0::11[110] fec0::10[any] tcp -P in ipsec
esp/transport/fec0::11-fec0::10/use ;
add fec0::10 fec0::11 esp 0x10001
-m transport
-E blowfish-cbc "kamekame"
-A hmac-sha1 "this is the test key" ;
add fec0::11 fec0::10 esp 0x10002
-m transport
-E blowfish-cbc "kamekame"
-A hmac-sha1 "this is the test key" ;
EOF
and at Host-B:&prompt.root; setkey -c <<EOF
spdadd fec0::11[110] fec0::10[any] tcp -P out ipsec
esp/transport/fec0::11-fec0::10/use ;
spdadd fec0::10[any] fec0::11[110] tcp -P in ipsec
esp/transport/fec0::10-fec0::11/use ;
add fec0::10 fec0::11 esp 0x10001 -m transport
-E blowfish-cbc "kamekame"
-A hmac-sha1 "this is the test key" ;
add fec0::11 fec0::10 esp 0x10002 -m transport
-E blowfish-cbc "kamekame"
-A hmac-sha1 "this is the test key" ;
EOF
Note the direction of SP.Tunnel mode example with IPv4Tunnel mode between two security gatewaysSecurity protocol is old AH tunnel mode, i.e. specified by
RFC1826, with keyed-md5 whose key is "this is the test" as
authentication algorithm.
======= AH =======
| |
Network-A Gateway-A Gateway-B Network-B
10.0.1.0/24 ---- 172.16.0.1 ----- 172.16.0.2 ---- 10.0.2.0/24
Configuration at Gateway-A:
&prompt.root; setkey -c <<EOF
spdadd 10.0.1.0/24 10.0.2.0/24 any -P out ipsec
ah/tunnel/172.16.0.1-172.16.0.2/require ;
spdadd 10.0.2.0/24 10.0.1.0/24 any -P in ipsec
ah/tunnel/172.16.0.2-172.16.0.1/require ;
add 172.16.0.1 172.16.0.2 ah-old 0x10003 -m any
-A keyed-md5 "this is the test" ;
add 172.16.0.2 172.16.0.1 ah-old 0x10004 -m any
-A keyed-md5 "this is the test" ;
EOF
If port number field is omitted such above then "[any]" is
employed. `-m' specifies the mode of SA to be used. "-m any" means
wild-card of mode of security protocol. You can use this SA for both
tunnel and transport mode.and at Gateway-B:
&prompt.root; setkey -c <<EOF
spdadd 10.0.2.0/24 10.0.1.0/24 any -P out ipsec
ah/tunnel/172.16.0.2-172.16.0.1/require ;
spdadd 10.0.1.0/24 10.0.2.0/24 any -P in ipsec
ah/tunnel/172.16.0.1-172.16.0.2/require ;
add 172.16.0.1 172.16.0.2 ah-old 0x10003 -m any
-A keyed-md5 "this is the test" ;
add 172.16.0.2 172.16.0.1 ah-old 0x10004 -m any
-A keyed-md5 "this is the test" ;
EOF
Making SA bundle between two security gatewaysAH transport mode and ESP tunnel mode is required between
Gateway-A and Gateway-B. In this case, ESP tunnel mode is applied first,
and AH transport mode is next.
========== AH =========
| ======= ESP ===== |
| | | |
Network-A Gateway-A Gateway-B Network-B
fec0:0:0:1::/64 --- fec0:0:0:1::1 ---- fec0:0:0:2::1 --- fec0:0:0:2::/64
Tunnel mode example with IPv6Encryption algorithm is 3des-cbc, and authentication algorithm
for ESP is hmac-sha1. Authentication algorithm for AH is hmac-md5.
Configuration at Gateway-A:
&prompt.root; setkey -c <<EOF
spdadd fec0:0:0:1::/64 fec0:0:0:2::/64 any -P out ipsec
esp/tunnel/fec0:0:0:1::1-fec0:0:0:2::1/require
ah/transport/fec0:0:0:1::1-fec0:0:0:2::1/require ;
spdadd fec0:0:0:2::/64 fec0:0:0:1::/64 any -P in ipsec
esp/tunnel/fec0:0:0:2::1-fec0:0:0:1::1/require
ah/transport/fec0:0:0:2::1-fec0:0:0:1::1/require ;
add fec0:0:0:1::1 fec0:0:0:2::1 esp 0x10001 -m tunnel
-E 3des-cbc "kamekame12341234kame1234"
-A hmac-sha1 "this is the test key" ;
add fec0:0:0:1::1 fec0:0:0:2::1 ah 0x10001 -m transport
-A hmac-md5 "this is the test" ;
add fec0:0:0:2::1 fec0:0:0:1::1 esp 0x10001 -m tunnel
-E 3des-cbc "kamekame12341234kame1234"
-A hmac-sha1 "this is the test key" ;
add fec0:0:0:2::1 fec0:0:0:1::1 ah 0x10001 -m transport
-A hmac-md5 "this is the test" ;
EOF
Making SAs with the different endESP tunnel mode is required between Host-A and Gateway-A. Encryption
algorithm is cast128-cbc, and authentication algorithm for ESP is
hmac-sha1. ESP transport mode is recommended between Host-A and Host-B.
Encryption algorithm is rc5-cbc, and authentication algorithm for ESP is
hmac-md5.
================== ESP =================
| ======= ESP ======= |
| | | |
Host-A Gateway-A Host-B
fec0:0:0:1::1 ---- fec0:0:0:2::1 ---- fec0:0:0:2::2
Configuration at Host-A:
&prompt.root; setkey -c <<EOF
spdadd fec0:0:0:1::1[any] fec0:0:0:2::2[80] tcp -P out ipsec
esp/transport/fec0:0:0:1::1-fec0:0:0:2::2/use
esp/tunnel/fec0:0:0:1::1-fec0:0:0:2::1/require ;
spdadd fec0:0:0:2::1[80] fec0:0:0:1::1[any] tcp -P in ipsec
esp/transport/fec0:0:0:2::2-fec0:0:0:l::1/use
esp/tunnel/fec0:0:0:2::1-fec0:0:0:1::1/require ;
add fec0:0:0:1::1 fec0:0:0:2::2 esp 0x10001
-m transport
-E cast128-cbc "12341234"
-A hmac-sha1 "this is the test key" ;
add fec0:0:0:1::1 fec0:0:0:2::1 esp 0x10002
-E rc5-cbc "kamekame"
-A hmac-md5 "this is the test" ;
add fec0:0:0:2::2 fec0:0:0:1::1 esp 0x10003
-m transport
-E cast128-cbc "12341234"
-A hmac-sha1 "this is the test key" ;
add fec0:0:0:2::1 fec0:0:0:1::1 esp 0x10004
-E rc5-cbc "kamekame"
-A hmac-md5 "this is the test" ;
EOF
OpenSSHOpenSSHsecurityOpenSSHContributed by &a.chern;, April 21,
2001.Secure shell is a set of network connectivity tools used to
access remote machines securely. It can be used as a direct
replacement for rlogin,
rsh, rcp, and
telnet. Additionally, any other TCP/IP
connections can be tunneled/forwarded securely through ssh.
ssh encrypts all traffic to effectively eliminate eavesdropping,
connection hijacking, and other network-level attacks.OpenSSH is maintained by the OpenBSD project, and is based
upon SSH v1.2.12 with all the recent bug fixes and updates. It
is compatible with both SSH protocols 1 and 2. OpenSSH has been
in the base system since FreeBSD 4.0.Advantages of using OpenSSHNormally, when using &man.telnet.1; or &man.rlogin.1;,
data is sent over the network in an clear, un-encrypted form.
Network sniffers anywhere in between the client and server can
steal your user/password information or data transferred in
your session. OpenSSH offers a variety of authentication and
encryption methods to prevent this from happening.Enabling sshdOpenSSHenablingBe sure to make the following additions to your
rc.conf file:
sshd_enable="YES"This will load the ssh daemon the next time your system
initializes. Alternatively, you can simply run the
sshd daemon.SSH clientOpenSSHclientThe &man.ssh.1; utility works similarly to
&man.rlogin.1;.
&prompt.root ssh user@foobardomain.com
Host key not found from the list of known hosts.
Are you sure you want to continue connecting (yes/no)? yes
Host 'foobardomain.com' added to the list of known hosts.
user@foobardomain.com's password: *******The login will continue just as it would have if a session was
created using rlogin or telnet. SSH utilizes a key fingerprint
system for verifying the authenticity of the server when the
client connects. The user is prompted to enter 'yes' only during
the first time connecting. Future attempts to login are all
verified against the saved fingerprint key. The SSH client
will alert you if the saved fingerprint differs from the
received fingerprint on future login attempts. The fingerprints
are saved in ~/.ssh/known_hostsSecure copyOpenSSHsecure copyscpThe scp command works similarly to rcp;
it copies a file to or from a remote machine, except in a
secure fashion.&prompt.root scp user@foobardomain.com:/COPYRIGHT COPYRIGHT
user@foobardomain.com's password:
COPYRIGHT 100% |*****************************| 4735
00:00
&prompt.rootSince the fingerprint was already saved for this host in the
previous example, it is verified when using scp
here.
ConfigurationOpenSSHconfigurationThe system-wide configuration files for both the OpenSSH
daemon and client reside within the /etc/ssh
directory.
ssh_config configures the client
settings, while sshd_config configures the
daemon.
ssh-keygenInstead of using passwords, &man.ssh-keygen.1; can
be used to generate RSA keys to authenticate a user.
&prompt.user ssh-keygen
Initializing random number generator...
Generating p: .++ (distance 66)
Generating q: ..............................++ (distance 498)
Computing the keys...
Key generation complete.
Enter file in which to save the key (/home/user/.ssh/identity):
Enter passphrase:
Enter the same passphrase again:
Your identification has been saved in /home/user/.ssh/identity.
...&man.ssh-keygen.1; will create a public and private
key pair for use in authentication. The private key is stored in
~/.ssh/identity, whereas the public key is
stored in ~/.ssh/identity.pub. The public
key must be placed in ~/.ssh/authorized_keys
of the remote machine in order for the setup to work.
This will allow connection to the remote machine based upon
RSA authentication instead of passwords.If a passphrase is used in &man.ssh-keygen.1;, the user
will be prompted for a password each time in order to use the private
key.&man.ssh-agent.1; and &man.ssh-add.1; are
utilities used in managing multiple passworded private keys.
SSH TunnelingOpenSSHtunnelingOpenSSH has the ability to create a tunnel to encapsulate
another protocol in an encrypted session.The following command tells &man.ssh.1; to create a tunnel
for telnet.&prompt.user; ssh -2 -N -f -L 5023:localhost:23 user@foo.bar.com
&prompt.user;-2 this forces &man.ssh.1 to use version
2 of the protocol. (Do not use if you are working with older ssh
servers)-N indicates no command, or tunnel only.
If omitted, &man.ssh.1; would initiate a normal session.-f forces &man.ssh.1; to run
in the background.-L indicates a local tunnel in
localport:localhost:remoteport fashion.
foo.bar.com is the remote/target
SSH server.
An SSH tunnel works by creating a listen socket on the specified
local host and port. It then forwards any connection to the local
host/port via the SSH connection to the remote machine on the
specified remote port.
In the example, port 5023 on localhost
is being forwarded to port 23 on the remote
machine. Since 23 is telnet, this would
create a secure telnet session through an SSH tunnel.
This can be used to wrap any number of insecure TCP protocols
such as smtp, pop3, ftp, etc.
A typical SSH Tunnel&prompt.user; ssh -2 -N -f -L 5025:localhost:25 user@mailserver.foobar.com
user@mailserver.foobar.com's password: *****
&prompt.user; telnet localhost 5025
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 mailserver.foobar.com ESMTPThis can be used in conjunction with an &man.ssh-keygen.1;
and additional user accounts to create a more seamless/hassle-free
SSH tunneling environment. Keys can be used in place of typing
a password, and the tunnels can be run as a separate user.
Further ReadingOpenSSH&man.ssh.1; &man.scp.1; &man.ssh-keygen.1;
&man.ssh-agent.1; &man.ssh-add.1;&man.sshd.8; &man.sftp-server.8;
diff --git a/en_US.ISO8859-1/books/handbook/serialcomms/chapter.sgml b/en_US.ISO8859-1/books/handbook/serialcomms/chapter.sgml
index c03355b486..992d7b7d66 100644
--- a/en_US.ISO8859-1/books/handbook/serialcomms/chapter.sgml
+++ b/en_US.ISO8859-1/books/handbook/serialcomms/chapter.sgml
@@ -1,2721 +1,2721 @@
Serial CommunicationsSynopsisUNIX has always had support for serial communications. In fact,
the very first UNIX machines relied on serial lines for user input
and output. Things have changed a lot from the days when the average
terminal consisted of a 10-character-per-second serial
printer and a keyboard. This chapter will cover some of the ways in
which FreeBSD uses serial communications.Serial BasicsAssembled from FAQ.This section should give you some general information about serial
ports. If you do not find what you want here, check into the Terminal
and Dial-up sections of the handbook.The ttydX (or
cuaaX) device is the
regular device you will want to open for your applications. When a
process opens the device, it will have a default set of terminal I/O
settings. You can see these settings with the command&prompt.root; stty -a -f /dev/ttyd1When you change the settings to this device, the settings are in
effect until the device is closed. When it is reopened, it goes back to
the default set. To make changes to the default set, you can open and
adjust the settings of the initial state device. For
example, to turn on CLOCAL mode, 8 bits, and
XON/XOFF flow control by default for ttyd5,
do:&prompt.root; stty -f /dev/ttyid5 clocal cs8 ixon ixoffA good place to do this is in /etc/rc.serial.
Now, an application will have these settings by default when it opens
ttyd5. It can still change these settings to its
liking, though.You can also prevent certain settings from being changed by an
application by making adjustments to the lock state
device. For example, to lock the speed of ttyd5 to
57600 bps, do&prompt.root; stty -f /dev/ttyld5 57600Now, an application that opens ttyd5 and tries
to change the speed of the port will be stuck with 57600 bps.Naturally, you should make the initial state and lock state devices
writable only by root. The
MAKEDEV script does not do
this when it creates the device entries.TerminalsContributed by &a.kelly; 28 July 1996Terminals provide a convenient and low-cost way to access the power
of your FreeBSD system when you are not at the computer's console or on
a connected network. This section describes how to use terminals with
FreeBSD.Uses and Types of TerminalsThe original Unix systems did not have consoles. Instead, people
logged in and ran programs through terminals that were connected to
the computer's serial ports. It is quite similar to using a modem and
some terminal software to dial into a remote system to do text-only
work.Today's PCs have consoles capable of high quality graphics, but
the ability to establish a login session on a serial port still exists
in nearly every Unix-style operating system today; FreeBSD is no
exception. By using a terminal attached to a unused serial port, you
can log in and run any text program that you would normally run on the
console or in an xterm window in the X Window
System.For the business user, you can attach many terminals to a FreeBSD
system and place them on your employees' desktops. For a home user, a
spare computer such as an older IBM PC or a Macintosh can be a
terminal wired into a more powerful computer running FreeBSD. You can
turn what might otherwise be a single-user computer into a powerful
multiple user system.For FreeBSD, there are three kinds of terminals:Dumb terminalsPCs acting as terminalsX terminalsThe remaining subsections describe each kind.Dumb TerminalsDumb terminals are specialized pieces of hardware that let you
connect to computers over serial lines. They are called
dumb because they have only enough computational power
to display, send, and receive text. You cannot run any programs on
them. It is the computer to which you connect them that has all the
power to run text editors, compilers, email, games, and so
forth.There are hundreds of kinds of dumb terminals made by many
manufacturers, including Digital Equipment Corporation's VT-100 and
Wyse's WY-75. Just about any kind will work with FreeBSD. Some
high-end terminals can even display graphics, but only certain
software packages can take advantage of these advanced
features.Dumb terminals are popular in work environments where workers do
not need access to graphic applications such as those provided by
the X Window System.PCs Acting As TerminalsIf a dumb terminal has just
enough ability to display, send, and receive text, then certainly
any spare personal computer can be a dumb terminal. All you need is
the proper cable and some terminal emulation
software to run on the computer.Such a configuration is popular in homes. For example, if your
spouse is busy working on your FreeBSD system's console, you can do
some text-only work at the same time from a less powerful personal
computer hooked up as a terminal to the FreeBSD system.X TerminalsX terminals are the most sophisticated kind of terminal
available. Instead of connecting to a serial port, they usually
connect to a network like Ethernet. Instead of being relegated to
text-only applications, they can display any X application.We introduce X terminals just for the sake of completeness.
However, this chapter does not cover setup,
configuration, or use of X terminals.Cables and PortsTo connect a terminal to your FreeBSD system, you need the right
kind of cable and a serial port to which to connect it. This section
tells you what to do. If you are already familiar with your terminal
and the cable it requires, skip to Configuration.CablesBecause terminals use serial ports, you need to use
serial—also known as RS-232C—cables to connect the
terminal to the FreeBSD system.There are a couple of kinds of serial cables. Which one
you'll use depends on the terminal you want to connect:If you are connecting a personal computer to act as a
terminal, use a null-modem
cable. A null-modem cable connects two computers or terminals
together.If you have an actual terminal, your best source of
information on what cable to use is the documentation that
accompanied the terminal. If you do not have the documentation,
then try a null-modem cable.
If that does not work, then try a standard cable.Also, the serial port on both the terminal
and your FreeBSD system must have connectors that will fit the cable
you are using.Null-modem cablesA null-modem cable passes some signals straight through, like
signal ground, but switches other signals. For
example, the send data pin on one end goes to the
receive data pin on the other end.If you like making your own cables, here is a table showing a
recommended way to construct a null-modem cable for use with
terminals. This table shows the RS-232C signal names and the pin
numbers on a DB-25 connector.SignalPin #Pin #SignalTxD2connects to3RxDRxD3connects to2TxDDTR20connects to6DSRDSR6connects to20DTRSG7connects to7SGDCD8connects to4RTSRTS45CTSCTS5connects to8DCDFor DCD to RTS, connect pins 4 to 5 internally in the
connector hood, and then to pin 8 in the remote
hood.Standard RS-232C CablesA standard serial cable passes all the RS-232C signals
straight-through. That is, the send data pin on one
end of the cable goes to the send data pin on the
other end. This is the type of cable to connect a modem to your
FreeBSD system, and the type of cable needed for some
terminals.PortsSerial ports are the devices through which data is transferred
between the FreeBSD host computer and the terminal. This section
describes the kinds of ports that exist and how they are addressed
in FreeBSD.Kinds of PortsSeveral kinds of serial ports exist. Before you purchase or
construct a cable, you need to make sure it will fit the ports on
your terminal and on the FreeBSD system.Most terminals will have DB25 ports. Personal computers,
including PCs running FreeBSD, will have DB25 or DB9 ports. If you
have a multiport serial card for your PC, you may have RJ-12 or
RJ-45 ports.See the documentation that accompanied the hardware for
specifications on the kind of port in use. A visual inspection of
the port often works, too.Port NamesIn FreeBSD, you access each serial port through an entry in
the /dev directory. There are two different
kinds of entries:Call-in ports are named
/dev/ttydX
where X is the port number,
starting from zero. Generally, you use the call-in port for
terminals. Call-in ports require that the serial line assert
the data carrier detect (DCD) signal to work.Call-out ports are named
/dev/cuaaX.
You usually do not use the call-out port for terminals, just
for modems. You may use the call-out port if the serial cable
or the terminal does not support the carrier detect
signal.See the &man.sio.4; manual page for more information.If you have connected a terminal to the first serial port
(COM1 in DOS parlance), then you want to
use /dev/ttyd0 to refer to the terminal. If
it is on the second serial port (also known as
COM2), it is
/dev/ttyd1, and so forth.Note that you may have to configure your kernel to support
each serial port, especially if you have a multiport serial card.
See Configuring the FreeBSD
Kernel for more information.ConfigurationThis section describes what you need to configure on your FreeBSD
system to enable a login session on a terminal. It assumes you have
already configured your kernel to support the serial port to which the
terminal is connected—and that you have connected it.In a nutshell, you need to tell the init
process, which is responsible for process control and initialization,
to start a getty process, which is responsible for
reading a login name and starting the login
program.To do so, you have to edit the /etc/ttys
file. First, use the su command to become root.
Then, make the following changes to
/etc/ttys:Add an line to /etc/ttys for the entry in
the /dev directory for the serial port if it
is not already there.Specify that /usr/libexec/getty be run on
the port, and specify the appropriate
getty type from the
/etc/gettytab file.Specify the default terminal type.Set the port to on.Specify whether the port should be
secure.Force init to reread the
/etc/ttys file.As an optional step, you may wish to create a custom
getty type for use in step 2 by making an
entry in /etc/gettytab. This document does
not explain how to do so; you are encouraged to see the
&man.gettytab.5; and the &man.getty.8; manual pages for more
information.The remaining sections detail how to do these steps. We will use
a running example throughout these sections to illustrate what we need
to do. In our example, we will connect two terminals to the system: a
Wyse-50 and a old 286 IBM PC running Procomm terminal software
emulating a VT-100 terminal. We connect the Wyse to the second serial
port and the 286 to the sixth serial port (a port on a multiport
serial card).For more information on the /etc/ttys
file, see the &man.ttys.5; manual page.Adding an Entry to /etc/ttysFirst, you need to add an entry to the
/etc/ttys file, unless one is already
there.The /etc/ttys file lists all of the ports
on your FreeBSD system where you want to allow logins. For example,
the first virtual console ttyv0 has an entry in
this file. You can log in on the console using this entry. This
file contains entries for the other virtual consoles, serial ports,
and pseudo-ttys. For a hardwired terminal, just list the serial
port's /dev entry without the
/dev part.When you installed your FreeBSD system, the
/etc/ttys file included entries for the first
four serial ports: ttyd0 through
ttyd3. If you are attaching a terminal on one
of those ports, you do not need to add an entry.In our example, we attached a Wyse-50 to the second serial port,
ttyd1, which is already in the file. We need
to add an entry for the 286 PC connected to the sixth serial port.
Here is an excerpt of the /etc/ttys file after
we add the new entry:ttyd1 "/usr/libexec/getty std.9600" unknown off secure
ttyd5Specifying the getty TypeNext, we need to specify what program will be run to handle the
logins on a terminal. For FreeBSD, the standard program to do that
is /usr/libexec/getty. It is what provides the
login: prompt.The program getty takes one (optional)
parameter on its command line, the getty
type. A getty type tells about
characteristics on the terminal line, like bps rate and parity. The
getty program reads these characteristics from
the file /etc/gettytab.The file /etc/gettytab contains lots of
entries for terminal lines both old and new. In almost all cases,
the entries that start with the text std will
work for hardwired terminals. These entries ignore parity. There is
a std entry for each bps rate from 110 to 115200.
Of course, you can add your own entries to this file. The manual
page &man.gettytab.5; provides more
information.When setting the getty type in the
/etc/ttys file, make sure that the
communications settings on the terminal match.For our example, the Wyse-50 uses no parity and connects at
38400 bps. The 286 PC uses no parity and connects at 19200 bps.
Here is the /etc/ttys file so far (showing just
the two terminals in which we are interested):ttyd1 "/usr/libexec/getty std.38400" unknown off secure
ttyd5 "/usr/libexec/getty std.19200"Note that the second field—where we specify what program
to run—appears in quotes. This is important, otherwise the
type argument to getty might be interpreted as
the next field.Specifying the Default Terminal TypeThe third field in the /etc/ttys file lists
the default terminal type for the port. For dial-up ports, you
typically put unknown or
dialup in this field because users may dial up
with practically any kind of terminal or software. For hardwired
terminals, the terminal type does not change, so you can put a real
terminal type in this field.Users will usually use the tset program in
their .login or .profile
files to check the terminal type and prompt for one if necessary.
By setting a terminal type in the /etc/ttys
file, users can forego such prompting.To find out what terminal types FreeBSD supports, see the
file /usr/share/misc/termcap. It lists
about 600 terminal types. You can add more if you wish. See
the &man.termcap.5; manual page for information.In our example, the Wyse-50 is a Wyse-50 type of terminal
(although it can emulate others, we will leave it in Wyse-50 mode).
The 286 PC is running Procomm which will be set to emulate a VT-100.
Here are the pertinent yet unfinished entries from the
/etc/ttys file:ttyd1 "/usr/libexec/getty std.38400" wy50 off secure
ttyd5 "/usr/libexec/getty std.19200" vt100Enabling the PortThe next field in /etc/ttys, the fourth
field, tells whether to enable the port. Putting
on here will have the init
process start the program in the second field,
getty, which will prompt for a login. If you put
off in the fourth field, there will be no
getty, and hence no logins on the port.So, naturally, you want an on in this field.
Here again is the /etc/ttys file. We have
turned each port on.ttyd1 "/usr/libexec/getty std.38400" wy50 on secure
ttyd5 "/usr/libexec/getty std.19200" vt100 onSpecifying Secure PortsWe have arrived at the last field (well, almost: there is an
optional window specifier, but we will ignore
that). The last field tells whether the port is secure.What does secure mean?It means that the root account (or any account with a user ID of
0) may login on the port. Insecure ports do not allow root to
login.How do you use secure and insecure ports?By marking a port as insecure, the terminal to which it is
connected will not allow root to login. People who know the root
password to your FreeBSD system will first have to login using a
regular user account. To gain superuser privileges, they will then
have to use the su command.Because of this, you will have two records to help track down
possible compromises of root privileges: both the
login and the su command make
records in the system log (and logins are also recorded in the
wtmp file).By marking a port as secure, the terminal will allow root in.
People who know the root password will just login as root. You will
not have the potentially useful login and su
command records.Which should you use?Just use insecure. Use insecureeven for terminals not in
public user areas or behind locked doors. It is quite easy to login
and use su if you need superuser
privileges.Here finally are the completed entries in the
/etc/ttys file, with comments added to describe
where the terminals are:ttyd1 "/usr/libexec/getty std.38400" wy50 on insecure # Kitchen
ttyd5 "/usr/libexec/getty std.19200" vt100 on insecure # Guest bathroomForce init to Reread
/etc/ttysWhen you boot FreeBSD, the first process,
init, will read the
/etc/ttys file and start the programs listed
for each enabled port to prompt for logins.After you edit /etc/ttys, you do not want
to have to reboot your system to get init to see
the changes. So, init will reread
/etc/ttys if it receives a SIGHUP (hangup)
signal.So, after you have saved your changes to
/etc/ttys, send SIGHUP to
init by typing:&prompt.root; kill -HUP 1(The init process always
has process ID 1.)If everything is set up correctly, all cables are in place, and
the terminals are powered up, you should see login prompts. Your
terminals are ready for their first logins!Debugging your connectionEven with the most meticulous attention to detail, something could
still go wrong while setting up a terminal. Here is a list of
symptoms and some suggested fixes.No login prompt appearsMake sure the terminal is plugged in and powered up. If it
is a personal computer acting as a terminal, make sure it is
running terminal emulation software on the correct serial
port.Make sure the cable is connected firmly to both the terminal
and the FreeBSD computer. Make sure it is the right kind of
cable.Make sure the terminal and FreeBSD agree on the bps rate and
parity settings. If you have a video display terminal, make
sure the contrast and brightness controls are turned up. If it
is a printing terminal, make sure paper and ink are in good
supply.Make sure that a getty process is running
and serving the terminal. Type&prompt.root; ps -axww|grep gettyto get a
list of running getty processes. You should
see an entry for the terminal. For example, the display
22189 d1 Is+ 0:00.03 /usr/libexec/getty std.38400 ttyd1
shows that a getty is running on the second
serial port ttyd1 and is using the
std.38400 entry in
/etc/gettytab.If no getty process is running, make sure
you have enabled the port in /etc/ttys.
Make sure you have run kill -HUP 1.Garbage appears instead of a login promptMake sure the terminal and FreeBSD agree on the bps rate and
parity settings. Check the getty processes to make sure the
correct getty type is in use. If
not, edit /etc/ttys and run kill
-HUP 1.Characters appear doubled; the password appears when
typedSwitch the terminal (or the terminal emulation software)
from half duplex or local echo to
full duplex.Dial-in ServiceContributed by &a.ghelmer;.This document provides suggestions for configuring a FreeBSD system
to handle dial-up modems. This document is written based on the author's
experience with FreeBSD versions 1.0, 1.1, and 1.1.5.1 (and experience
with dial-up modems on other UNIX-like operating systems); however, this
document may not answer all of your questions or provide examples
specific enough to your environment. The author cannot be responsible if
you damage your system or lose data due to attempting to follow the
suggestions here.PrerequisitesTo begin with, the author assumes you have some basic knowledge of
FreeBSD. You need to have FreeBSD installed, know how to edit files
in a UNIX-like environment, and how to look up manual pages on the
system. As discussed below, you will need certain versions of
FreeBSD, and knowledge of some terminology & modem and
cabling.FreeBSD VersionFirst, it is assumed that you are using FreeBSD version 1.1 or
higher (including versions 2.x). FreeBSD version 1.0 included two
different serial drivers, which complicates the situation. Also,
the serial device driver (sio) has improved
in every release of FreeBSD, so more recent versions of FreeBSD are
assumed to have better and more efficient drivers than earlier
versions.TerminologyA quick rundown of terminology:bpsBits per Second — the rate at which data is
transmittedDTEData Terminal Equipment — for example, your
computerDCEData Communications Equipment — your modemRS-232EIA standard for serial communications via hardwareIf you need more information about these terms and data
communications in general, the author remembers reading that
The RS-232 Bible (anybody have an ISBN?) is a
good reference.When talking about communications data rates, the author does
not use the term baud. Baud refers to the number of
electrical state transitions that may be made in a period of time,
while bps (bits per second) is the
correct term to use (at least it does not seem to
bother the curmudgeons quite a much).External v.s. Internal ModemsExternal modems seem to be more convenient for dial-up, because
external modems often can be semi-permanently configured via
parameters stored in non-volatile RAM and they usually provide
lighted indicators that display the state of important RS-232
signals. Blinking lights impress visitors, but lights are also very
useful to see whether a modem is operating properly.Internal modems usually lack non-volatile RAM, so their
configuration may be limited only to setting DIP switches. If your
internal modem has any signal indicator lights, it is probably
difficult to view the lights when the system's cover is in
place.Modems and CablesA background knowledge of these items is assumedYou know how to connect your modem to your computer so that
the two can communicate (unless you have an internal modem,
which does not need such a cable)You are familiar with your modem's command set, or know
where to look up needed commandsYou know how to configure your modem (probably via a
terminal communications program) so you can set the non-volatile
RAM parametersThe first, connecting your modem, is usually simple — most
straight-through serial cables work without any problems. You need
to have a cable with appropriate connectors (DB-25 or DB-9, male or
female) on each end, and the cable must be a DCE-to-DTE cable with
these signals wired:Transmitted Data (SD)Received Data (RD)Request to Send (RTS)Clear to Send (CTS)Data Set Ready (DSR)Data Terminal Ready (DTR)Carrier Detect (CD)Signal Ground (SG)FreeBSD needs the RTS and
CTS signals for flow-control at speeds above
2400bps, the CD signal to detect when a call has
been answered or the line has been hung up, and the
DTR signal to reset the modem after a session is
complete. Some cables are wired without all of the needed signals,
so if you have problems, such as a login session not going away when
the line hangs up, you may have a problem with your cable.The second prerequisite depends on the modem(s) you use. If you
do not know your modem's command set by heart, you will need to have
the modem's reference book or user's guide handy. Sample commands
for USR Sportster 14,400 external modems will be given, which you
may be able to use as a reference for your own modem's
commands.Lastly, you will need to know how to setup your modem so that it
will work well with FreeBSD. Like other UNIX-like operating
systems, FreeBSD uses the hardware signals to find out when a call
has been answered or a line has been hung up and to hangup and reset
the modem after a call. FreeBSD avoids sending commands to the
modem or watching for status reports from the modem. If you are
familiar with connecting modems to PC-based bulletin board systems,
this may seem awkward.Serial Interface ConsiderationsFreeBSD supports NS8250-, NS16450-, NS16550-, and NS16550A-based
EIA RS-232C (CCITT V.24) communications interfaces. The 8250 and
16450 devices have single-character buffers. The 16550 device
provides a 16-character buffer, which allows for better system
performance. (Bugs in plain 16550's prevent the use of the
16-character buffer, so use 16550A's if possible). Because
single-character-buffer devices require more work by the operating
system than the 16-character-buffer devices, 16550A-based serial
interface cards are much preferred. If the system has many active
serial ports or will have a heavy load, 16550A-based cards are
better for low-error-rate communications.Quick OverviewHere is the process that FreeBSD follows to accept dial-up logins.
A getty process, spawned by
init, patiently waits to open the assigned serial
port (/dev/ttyd0, for our example). The command
ps ax might show this: 4850 ?? I 0:00.09 /usr/libexec/getty V19200 ttyd0When a user dials the modem's line and the modems connect, the
CD line is asserted by the modem. The kernel
notices that carrier has been detected and completes
getty's open of the port. getty
sends a login: prompt at the specified initial line
speed. getty watches to see if legitimate
characters are received, and, in a typical configuration, if it finds
junk (probably due to the modem's connection speed being different
than getty's speed), getty tries
adjusting the line speeds until it receives reasonable
characters.We hope getty finds the correct speed and the
user sees a login: prompt. After the user enters
his/her login name, getty executes
/usr/bin/login, which completes the login by
asking for the user's password and then starting the user's
shell.Let's dive into the configuration...Kernel ConfigurationFreeBSD kernels typically come prepared to search for four serial
- ports, known in the PC-DOS world as COM1:,
+ ports, known in the MS-DOS world as COM1:,
COM2:, COM3:, and
COM4:. FreeBSD can presently also handle
dumb multiport serial interface cards, such as the Boca
Board 1008 and 2016 (please see the manual page &man.sio.4; for kernel
configuration information if you have a multiport serial card). The
default kernel only looks for the standard COM ports, though.To see if your kernel recognizes any of your serial ports, watch
for messages while the kernel is booting, or use the
/sbin/dmesg command to replay the kernel's boot
messages. In particular, look for messages that start with the
characters sio. Hint: to view just the messages
that have the word sio, use the command:&prompt.root; /sbin/dmesg | grep 'sio'For example, on a system with four serial ports, these are the
serial-port specific kernel boot messages:sio0 at 0x3f8-0x3ff irq 4 on isa
sio0: type 16550A
sio1 at 0x2f8-0x2ff irq 3 on isa
sio1: type 16550A
sio2 at 0x3e8-0x3ef irq 5 on isa
sio2: type 16550A
sio3 at 0x2e8-0x2ef irq 9 on isa
sio3: type 16550AIf your kernel does not recognize all of your serial ports, you
will probably need to configure a custom FreeBSD kernel for your
system.Please see the BSD System Manager's Manual chapter on
Building Berkeley Kernels with Config [the source for
which is in /usr/src/share/doc/smm] and
FreeBSD Configuration Options [in
/sys/conf/options and in
/sys/arch/conf/options.arch,
with arch for example being
i386] for more information on configuring and
building kernels. You may have to unpack the kernel source
distribution if have not installed the system sources already
(srcdist/srcsys.?? in FreeBSD 1.1,
srcdist/sys.?? in FreeBSD 1.1.5.1, or the entire
source distribution in FreeBSD 2.0) to be able to configure and build
kernels.Create a kernel configuration file for your system (if you have
not already) by cding to
/sys/i386/conf. Then, if you are creating a new
custom configuration file, copy the file
GENERICAH (or GENERICBT, if
you have a BusTek SCSI controller on FreeBSD 1.x) to
YOURSYS, where YOURSYS is
the name of your system, but in upper-case letters. Edit the file,
and change the device lines:device sio0 at isa? port "IO_COM1" tty irq 4 vector siointr
device sio1 at isa? port "IO_COM2" tty irq 3 vector siointr
device sio2 at isa? port "IO_COM3" tty irq 5 vector siointr
device sio3 at isa? port "IO_COM4" tty irq 9 vector siointrYou can comment-out or completely remove lines for devices you do
not have. If you have a multiport serial board, such as the Boca
Board BB2016, please see the &man.sio.4; man page for complete
information on how to write configuration lines for multiport boards.
Be careful if you are using a configuration file that was previously
used for a different version of FreeBSD because the device flags have
changed between versions.port "IO_COM1" is a substitution for
port 0x3f8, IO_COM2 is
0x2f8, IO_COM3 is
0x3e8, and IO_COM4 is
0x2e8, which are fairly common port addresses for
their respective serial ports; interrupts 4, 3, 5, and 9 are fairly
common interrupt request lines. Also note that regular serial ports
cannot share interrupts on ISA-bus PCs
(multiport boards have on-board electronics that allow all the
16550A's on the board to share one or two interrupt request
lines).When you are finished adjusting the kernel configuration file, use
the program config as documented in Building
Berkeley Kernels with Config and the
&man.config.8; manual page to prepare a kernel building directory,
then build, install, and test the new kernel.Device Special FilesMost devices in the kernel are accessed through device
special files, which are located in the
/dev directory. The sio
devices are accessed through the
/dev/ttyd? (dial-in)
and /dev/cuaa?
(call-out) devices. On FreeBSD version 1.1.5 and higher, there are
also initialization devices
(/dev/ttyid? and
/dev/cuai0?) and
locking devices
(/dev/ttyld? and
/dev/cual0?). The
initialization devices are used to initialize communications port
parameters each time a port is opened, such as
crtscts for modems which use
CTS/RTS signaling for flow control. The locking
devices are used to lock flags on ports to prevent users or programs
changing certain parameters; see the manual pages &man.termios.4;,
&man.sio.4;, and &man.stty.1; for
information on the terminal settings, locking & initializing
devices, and setting terminal options, respectively.Making Device Special FilesA shell script called MAKEDEV in the
/dev directory manages the device special
files. (The manual page for &man.MAKEDEV.8; on FreeBSD 1.1.5 is
fairly bogus in its discussion of COM ports, so
ignore it.) To use MAKEDEV to make dial-up device
special files for COM1: (port 0),
cd to /dev and issue the
command MAKEDEV ttyd0. Likewise, to make dial-up
device special files for COM2: (port 1),
use MAKEDEV ttyd1.MAKEDEV not only creates the
/dev/ttyd? device
special files, but also creates the
/dev/cuaa? (and all
of the initializing and locking special files under FreeBSD 1.1.5
and up) and removes the hardwired terminal special file
/dev/tty0?, if it
exists.After making new device special files, be sure to check the
permissions on the files (especially the
/dev/cua* files) to make sure that only users
who should have access to those device special files can read &
write on them — you probably do not want to allow your average
user to use your modems to dial-out. The default permissions on the
/dev/cua* files should be sufficient:crw-rw---- 1 uucp dialer 28, 129 Feb 15 14:38 /dev/cuaa1
crw-rw---- 1 uucp dialer 28, 161 Feb 15 14:38 /dev/cuaia1
crw-rw---- 1 uucp dialer 28, 193 Feb 15 14:38 /dev/cuala1These permissions allow the user uucp and
users in the group dialer to use the call-out
devices.Configuration FilesThere are three system configuration files in the
/etc directory that you will probably need to
edit to allow dial-up access to your FreeBSD system. The first,
/etc/gettytab, contains configuration information
for the /usr/libexec/getty daemon. Second,
/etc/ttys holds information that tells
/sbin/init what tty devices
should have getty processes running on them.
Lastly, you can place port initialization commands in the
/etc/rc.serial script if you have FreeBSD 1.1.5.1
or higher; otherwise, you can initialize ports in the
/etc/rc.local script.There are two schools of thought regarding dial-up modems on UNIX.
One group likes to configure their modems and system so that no matter
at what speed a remote user dials in, the local computer-to-modem
RS-232 interface runs at a locked speed. The benefit of this
configuration is that the remote user always sees a system login
prompt immediately. The downside is that the system does not know
what a user's true data rate is, so full-screen programs like Emacs
will not adjust their screen-painting methods to make their response
better for slower connections.The other school configures their modems' RS-232 interface to vary
its speed based on the remote user's connection speed. For example,
V.32bis (14.4 Kbps) connections to the modem might make the modem run
its RS-232 interface at 19.2 Kbps, while 2400 bps connections make the
modem's RS-232 interface run at 2400 bps. Because
getty does not understand any particular modem's
connection speed reporting, getty gives a
login: message at an initial speed and watches the
characters that come back in response. If the user sees junk, it is
assumed that they know they should press the
<Enter> key until they see a recognizable
prompt. If the data rates do not match, getty sees
anything the user types as junk, tries going to the next
speed and gives the login: prompt again. This
procedure can continue ad nauseam, but normally only takes a keystroke
or two before the user sees a good prompt. Obviously, this login
sequence does not look as clean as the former
locked-speed method, but a user on a low-speed
connection should receive better interactive response from full-screen
programs.The author will try to give balanced configuration information,
but is biased towards having the modem's data rate follow the
connection rate./etc/gettytab/etc/gettytab is a &man.termcap.5;-style
file of configuration information for &man.getty.8;. Please see the
&man.gettytab.5; manual page for complete information on the
format of the file and the list of capabilities.Locked-Speed ConfigIf you are locking your modem's data communications rate at a
particular speed, you probably will not need to make any changes
to /etc/gettytab.Matching-Speed ConfigYou will need to setup an entry in
/etc/gettytab to give
getty information about the speeds you wish to
use for your modem. If you have a 2400 bps modem, you can
probably use the existing D2400 entry. This
entry already exists in the FreeBSD 1.1.5.1
gettytab file, so you do not need to add it
unless it is missing under your version of FreeBSD:#
# Fast dialup terminals, 2400/1200/300 rotary (can start either way)
#
D2400|d2400|Fast-Dial-2400:\
:nx=D1200:tc=2400-baud:
3|D1200|Fast-Dial-1200:\
:nx=D300:tc=1200-baud:
5|D300|Fast-Dial-300:\
:nx=D2400:tc=300-baud:If you have a higher speed modem, you will probably need to
add an entry in /etc/gettytab; here is an
entry you could use for a 14.4 Kbps modem with a top interface
speed of 19.2 Kbps:#
# Additions for a V.32bis Modem
#
um|V300|High Speed Modem at 300,8-bit:\
:nx=V19200:tc=std.300:
un|V1200|High Speed Modem at 1200,8-bit:\
:nx=V300:tc=std.1200:
uo|V2400|High Speed Modem at 2400,8-bit:\
:nx=V1200:tc=std.2400:
up|V9600|High Speed Modem at 9600,8-bit:\
:nx=V2400:tc=std.9600:
uq|V19200|High Speed Modem at 19200,8-bit:\
:nx=V9600:tc=std.19200:On FreeBSD 1.1.5 and later, this will result in 8-bit, no
parity connections. Under FreeBSD 1.1, add
:np: parameters to the
std.xxx entries at
the top of the file for 8 bits, no parity; otherwise, the default
is 7 bits, even parity.The example above starts the communications rate at 19.2 Kbps
(for a V.32bis connection), then cycles through 9600 bps (for
V.32), 2400 bps, 1200 bps, 300 bps, and back to 19.2 Kbps.
Communications rate cycling is implemented with the
nx= (next table) capability.
Each of the lines uses a tc= (table
continuation) entry to pick up the rest of the
standard settings for a particular data rate.If you have a 28.8 Kbps modem and/or you want to take
advantage of compression on a 14.4 Kbps modem, you need to use a
higher communications rate than 19.2 Kbps. Here is an example of
a gettytab entry starting a 57.6 Kbps:#
# Additions for a V.32bis or V.34 Modem
# Starting at 57.6 Kbps
#
vm|VH300|Very High Speed Modem at 300,8-bit:\
:nx=VH57600:tc=std.300:
vn|VH1200|Very High Speed Modem at 1200,8-bit:\
:nx=VH300:tc=std.1200:
vo|VH2400|Very High Speed Modem at 2400,8-bit:\
:nx=VH1200:tc=std.2400:
vp|VH9600|Very High Speed Modem at 9600,8-bit:\
:nx=VH2400:tc=std.9600:
vq|VH57600|Very High Speed Modem at 57600,8-bit:\
:nx=VH9600:tc=std.57600:If you have a slow CPU or a heavily loaded system and you do
not have 16550A-based serial ports, you may receive sio
silo errors at 57.6 Kbps./etc/ttys/etc/ttys is the list of
ttys for init to monitor.
/etc/ttys also provides security information to
login (user root may only
login on ttys marked secure). See the manual
page for
&man.ttys.5; for more information.You will need to either modify existing lines in
/etc/ttys or add new lines to make
init run getty processes
automatically on your new dial-up ports. The general format of the
line will be the same, whether you are using a locked-speed or
matching-speed configuration:ttyd0 "/usr/libexec/getty xxx" dialup onThe first item in the above line is the device special file for
this entry — ttyd0 means
/dev/ttyd0 is the file that this
getty will be watching. The second item,
"/usr/libexec/getty
xxx"
(xxx will be replaced by the initial
gettytab capability) is the process
init will run on the device. The third item,
dialup, is the default terminal type. The fourth
parameter, on, indicates to
init that the line is operational. There can be
a fifth parameter, secure, but it should only be
used for terminals which are physically secure (such as the system
console).The default terminal type (dialup in the
example above) may depend on local preferences.
dialup is the traditional default terminal type
on dial-up lines so that users may customize their login scripts to
notice when the terminal is dialup and
automatically adjust their terminal type. However, the author finds
it easier at his site to specify vt102 as the
default terminal type, since the users just use VT102 emulation on
their remote systems.After you have made changes to /etc/ttys,
you may send the init process a
HUP signal to re-read the file. You can use the
command
&prompt.root; kill -HUP 1
to send the signal. If this is your first time setting up the
system, though, you may want to wait until your modem(s) are properly
configured and connected before signaling init.
Locked-Speed ConfigFor a locked-speed configuration, your
ttys entry needs to have a fixed-speed entry
provided to getty. For a modem whose port
speed is locked at 19.2 Kbps, the ttys entry
might look like this:ttyd0 "/usr/libexec/getty std.19200" dialup onIf your modem is locked at a different data rate, substitute
the appropriate name for the
std.speed entry for
std.19200 from
/etc/gettytab for your modem's data
rate.Matching-Speed ConfigIn a matching-speed configuration, your
ttys entry needs to reference the appropriate
beginning auto-baud (sic) entry in
/etc/gettytab. For example, if you added the
above suggested entry for a matching-speed modem that starts at
19.2 Kbps (the gettytab entry containing the
V19200 starting point), your
ttys entry might look like this:ttyd0 "/usr/libexec/getty V19200" dialup on/etc/rc.serial or
/etc/rc.localHigh-speed modems, like V.32, V.32bis, and V.34 modems, need to
use hardware (RTS/CTS) flow control. You can
add stty commands to
/etc/rc.serial on FreeBSD 1.1.5.1 and up, or
/etc/rc.local on FreeBSD 1.1, to set the
hardware flow control flag in the FreeBSD kernel for the modem
ports.For example, on a sample FreeBSD 1.1.5.1 system,
/etc/rc.serial reads:#!/bin/sh
#
# Serial port initial configuration
stty -f /dev/ttyid1 crtscts
stty -f /dev/cuai01 crtsctsThis sets the termios flag
crtscts on serial port #1's
(COM2:) dial-in and dial-out initialization
devices.On an old FreeBSD 1.1 system, these entries were added to
/etc/rc.local to set the
crtscts flag on the devices:# Set serial ports to use RTS/CTS flow control
stty -f /dev/ttyd0 crtscts
stty -f /dev/ttyd1 crtscts
stty -f /dev/ttyd2 crtscts
stty -f /dev/ttyd3 crtsctsSince there is no initialization device special file on FreeBSD
1.1, one has to just set the flags on the sole device special file
and hope the flags are not cleared by a miscreant.Modem SettingsIf you have a modem whose parameters may be permanently set in
non-volatile RAM, you will need to use a terminal program (such as
- Telix under PC-DOS or tip under FreeBSD) to set the
+ Telix under MS-DOS or tip under FreeBSD) to set the
parameters. Connect to the modem using the same communications speed
as the initial speed getty will use and configure
the modem's non-volatile RAM to match these requirements:CD asserted when connectedDTR asserted for operation; dropping DTR
hangs up line & resets modemCTS transmitted data flow controlDisable XON/XOFF flow controlRTS received data flow controlQuiet mode (no result codes)No command echoPlease read the documentation for your modem to find out what
commands and/or DIP switch settings you need to give it.For example, to set the above parameters on a USRobotics
Sportster 14,400 external modem, one could give these commands to
the modem:ATZ
AT&C1&D2&H1&I0&R2&WYou might also want to take this opportunity to adjust other
settings in the modem, such as whether it will use V.42bis and/or MNP5
compression.The USR Sportster 14,400 external modem also has some DIP switches
that need to be set; for other modems, perhaps you can use these
settings as an example:Switch 1: UP — DTR NormalSwitch 2: Do not care (Verbal Result Codes/Numeric Result
Codes)Switch 3: UP — Suppress Result CodesSwitch 4: DOWN — No echo, offline commandsSwitch 5: UP — Auto AnswerSwitch 6: UP — Carrier Detect NormalSwitch 7: UP — Load NVRAM DefaultsSwitch 8: Do not care (Smart Mode/Dumb Mode)Result codes should be disabled/suppressed for dial-up modems to
avoid problems that can occur if getty mistakenly
gives a login: prompt to a modem that is in command
mode and the modem echoes the command or returns a result code. I
have heard this sequence can result in a extended, silly conversation
between getty and the modem.Locked-speed ConfigFor a locked-speed configuration, you will need to configure the
modem to maintain a constant modem-to-computer data rate independent
of the communications rate. On a USR Sportster 14,400 external
modem, these commands will lock the modem-to-computer data rate at
the speed used to issue the commands:ATZ
AT&B1&WMatching-speed ConfigFor a variable-speed configuration, you will need to configure
your modem to adjust its serial port data rate to match the incoming
call rate. On a USR Sportster 14,400 external modem, these commands
will lock the modem's error-corrected data rate to the speed used to
issue the commands, but allow the serial port rate to vary for
non-error-corrected connections:ATZ
AT&B2&WChecking the Modem's ConfigurationMost high-speed modems provide commands to view the modem's
current operating parameters in a somewhat human-readable fashion.
On the USR Sportster 14,400 external modems, the command
ATI5 displays the settings that are stored in the
non-volatile RAM. To see the true operating parameters of the modem
(as influenced by the USR's DIP switch settings), use the commands
ATZ and then ATI4.If you have a different brand of modem, check your modem's
manual to see how to double-check your modem's configuration
parameters.TroubleshootingHere are a few steps you can follow to check out the dial-up modem
on your system.Checking out the FreeBSD systemHook up your modem to your FreeBSD system, boot the system, and,
if your modem has status indication lights, watch to see whether the
modem's DTR indicator lights when the
login: prompt appears on the system's console
— if it lights up, that should mean that FreeBSD has started a
getty process on the appropriate communications
port and is waiting for the modem to accept a call.If the DTR indicator doesn't light, login to
the FreeBSD system through the console and issue a ps
ax to see if FreeBSD is trying to run a
getty process on the correct port. You should see
a lines like this among the processes displayed: 114 ?? I 0:00.10 /usr/libexec/getty V19200 ttyd0
115 ?? I 0:00.10 /usr/libexec/getty V19200 ttyd1If you see something different, like this: 114 d0 I 0:00.10 /usr/libexec/getty V19200 ttyd0and the modem has not accepted a call yet, this means that
getty has completed its open on the
communications port. This could indicate a problem with the cabling
or a mis-configured modem, because getty should
not be able to open the communications port until
CD (carrier detect) has been asserted by the
modem.If you do not see any getty processes waiting
to open the desired
ttyd? port,
double-check your entries in /etc/ttys to see
if there are any mistakes there. Also, check the log file
/var/log/messages to see if there are any log
messages from init or getty
regarding any problems. If there are any messages, triple-check the
configuration files /etc/ttys and
/etc/gettytab, as well as the appropriate
device special files /dev/ttyd?, for any
mistakes, missing entries, or missing device special files.Try Dialing InTry dialing into the system; be sure to use 8 bits, no parity, 1
stop bit on the remote system. If you do not get a prompt right
away, or get garbage, try pressing <Enter>
about once per second. If you still do not see a
login: prompt after a while, try sending a
BREAK. If you are using a high-speed modem to do
the dialing, try dialing again after locking the dialing modem's
interface speed (via AT&B1 on a USR
Sportster, for example).If you still cannot get a login: prompt, check
/etc/gettytab again and double-check
thatThe initial capability name specified in
/etc/ttys for the line matches a name of a
capability in /etc/gettytabEach nx= entry matches another
gettytab capability nameEach tc= entry matches another
gettytab capability nameIf you dial but the modem on the FreeBSD system will not answer,
make sure that the modem is configured to answer the phone when
DTR is asserted. If the modem seems to be
configured correctly, verify that the DTR line is
asserted by checking the modem's indicator lights (if it has
any).If you have gone over everything several times and it still does
not work, take a break and come back to it later. If it still does
not work, perhaps you can send an electronic mail message to the
&a.questions;describing your modem and your problem, and the good
folks on the list will try to help.AcknowledgmentsThanks to these people for comments and advice:&a.kelly;for a number of good suggestionsDial-out ServiceInformation integrated from FAQ.The following are tips to getting your host to be able to connect
over the modem to another computer. This is appropriate for
establishing a terminal session with a remote host.This is useful to log onto a BBS.This kind of connection can be extremely helpful to get a file on
the Internet if you have problems with PPP. If you need to FTP
something and PPP is broken, use the terminal session to FTP it. Then
use zmodem to transfer it to your machine.Why cannot I run tip or
cu?On your system, the programs tip and
cu are probably executable only by
uucp and group dialer. You
can use the group dialer to control who has
access to your modem or remote systems. Just add yourself to group
dialer.Alternatively, you can let everyone on your system run
tip and cu by typing:&prompt.root; chmod 4511 /usr/bin/tipYou do not have to run this command for cu,
since cu is just a hard link to
tip.My stock Hayes modem is not supported, what can I do?Actually, the man page for tip is out of date.
There is a generic Hayes dialer already built in. Just use
at=hayes in your /etc/remote
file.The Hayes driver is not smart enough to recognize some of the
advanced features of newer modems—messages like
BUSY, NO DIALTONE, or
CONNECT 115200 will just confuse it. You should
turn those messages off when you use tip (using
ATX0&W).Also, the dial timeout for tip is 60 seconds.
Your modem should use something less, or else tip will think there is
a communication problem. Try ATS7=45&W.Actually, as shipped tip does not yet support
it fully. The solution is to edit the file
tipconf.h in the directory
/usr/src/usr.bin/tip/tip Obviously you need the
source distribution to do this.Edit the line #define HAYES 0 to
#define HAYES 1. Then make and
make install. Everything works nicely after
that.How am I expected to enter these AT commands?Make what is called a direct entry in your
/etc/remote file. For example, if your modem is
hooked up to the first serial port, /dev/cuaa0,
then put in the following line:cuaa0:dv=/dev/cuaa0:br#19200:pa=noneUse the highest bps rate your modem supports in the br capability.
Then, type tip cuaa0 and you will be connected to
your modem.If there is no /dev/cuaa0 on your system, do
this:&prompt.root; cd /dev
&prompt.root; MAKEDEV cuaa0Or use cu as root with the following command:&prompt.root; cu -lline -sspeedline is the serial port
(e.g./dev/cuaa0) and
speed is the speed
(e.g.57600). When you are done entering the AT
commands hit ~. to exit.The @ sign for the pn capability does not
work!The @ sign in the phone number capability tells
tip to look in /etc/phones for a phone number.
But the @ sign is also a special character in
capability files like /etc/remote. Escape it
with a backslash:pn=\@How can I dial a phone number on the command line?Put what is called a generic entry in your
/etc/remote file. For example:tip115200|Dial any phone number at 115200 bps:\
:dv=/dev/cuaa0:br#115200:at=hayes:pa=none:du:
tip57600|Dial any phone number at 57600 bps:\
:dv=/dev/cuaa0:br#57600:at=hayes:pa=none:du:Then you can things like:&prompt.root; tip -115200 5551234If you prefer cu over tip,
use a generic cu entry:cu115200|Use cu to dial any number at 115200bps:\
:dv=/dev/cuaa1:br#57600:at=hayes:pa=none:du:and type:&prompt.root; cu 5551234 -s 115200Do I have to type in the bps rate every time I do that?Put in an entry for tip1200 or
cu1200, but go ahead and use whatever bps rate is
appropriate with the br capability. tip thinks a
good default is 1200 bps which is why it looks for a
tip1200 entry. You do not have to use 1200 bps,
though.I access a number of hosts through a terminal server.Rather than waiting until you are connected and typing
CONNECT <host> each time, use tip's
cm capability. For example, these entries in
/etc/remote:pain|pain.deep13.com|Forrester's machine:\
:cm=CONNECT pain\n:tc=deep13:
muffin|muffin.deep13.com|Frank's machine:\
:cm=CONNECT muffin\n:tc=deep13:
deep13:Gizmonics Institute terminal server:\
:dv=/dev/cuaa2:br#38400:at=hayes:du:pa=none:pn=5551234:will let you type tip pain or tip
muffin to connect to the hosts pain or muffin; and
tip deep13 to get to the terminal server.Can tip try more than one line for each site?This is often a problem where a university has several modem lines
and several thousand students trying to use them...Make an entry for your university in
/etc/remote and use @ for the
pn capability:big-university:\
:pn=\@:tc=dialout
dialout:\
:dv=/dev/cuaa3:br#9600:at=courier:du:pa=none:Then, list the phone numbers for the university in
/etc/phones:big-university 5551111
big-university 5551112
big-university 5551113
big-university 5551114tip will try each one in the listed order, then
give up. If you want to keep retrying, run tip in
a while loop.Why do I have to hit CTRL+P twice to send CTRL+P once?CTRL+P is the default force character, used to tell
tip that the next character is literal data. You
can set the force character to any other character with the
~s escape, which means set a
variable.Type
~sforce=single-char
followed by a newline. single-char is any
single character. If you leave out
single-char, then the force character is
the nul character, which you can get by typing CTRL+2 or CTRL+SPACE.
A pretty good value for single-char is
SHIFT+CTRL+6, which is only used on some terminal
servers.You can have the force character be whatever you want by
specifying the following in your $HOME/.tiprc
file:force=<single-char>Suddenly everything I type is in UPPER CASE??You must have pressed CTRL+A, tip's
raise character, specially designed for people with
broken caps-lock keys. Use ~s as above and set the
variable raisechar to something reasonable. In
fact, you can set it to the same as the force character, if you never
expect to use either of these features.Here is a sample .tiprc file perfect for Emacs users who need to
type CTRL+2 and CTRL+A a lot:force=^^
raisechar=^^The ^^ is SHIFT+CTRL+6.How can I do file transfers with tip?If you are talking to another UNIX system, you can send and
receive files with ~p (put) and
~t (take). These commands run
cat and echo on the remote
system to accept and send files. The syntax is:~plocal-fileremote-file~tremote-filelocal-fileThere is no error checking, so you probably should use another
protocol, like zmodem.How can I run zmodem with tip?To receive files, start the sending program on the remote end.
Then, type ~C rz to begin receiving them
locally.To send files, start the receiving program on the remote end.
Then, type ~C sz files
to send them to the remote system.Setting Up the Serial Console&a.yokota; and &a.wpaul;:The text is heavily based on
/sys/i386/boot/biosboot/README.serial written by
&a.wpaul;.IntroductionThe FreeBSD/i386 operating system can boot on a system with only
a dumb terminal on a serial port as a console. Such a configuration
should be useful for two classes of people: system administrators who
wish to install FreeBSD on machines that have no keyboard or monitor
attached, and developers who want to debug the kernel or device
drivers.Starting from version 3.1, FreeBSD/i386 employs a three stage
bootstrap. The first two stages are in the boot block code which is
stored at the beginning of the FreeBSD slice on the boot disk. The
boot block will then load and run the boot loader
(/boot/loader) as the third stage code. (See
&man.boot.8; and &man.loader.8; for more details on the boot
process.)In order to set up the serial console you must configure the boot
block code, the boot loader code and the kernel.In FreeBSD version 3.0, the boot loader does not exist and there
are only two stages in the bootstrap; the boot blocks directly load
the kernel into memory. If you are using FreeBSD 3.0, then you should
disregard any reference to the boot loader in this section. You can
still use the serial port as a console.FreeBSD versions 2.X are quite different from 3.X, in that the
serial port driver, &man.sio.4;, must be configured in a different
way. This chapter will not describe the settings for version 2.X
systems. If you are using these older versions of FreeBSD, please
consult /sys/i386/boot/biosboot/README.serial
instead.6 Steps to Set up the Serial ConsolePrepare a serial cable.You will need either a null-modem cable or a standard serial
cable and a null-modem adapter. See for
a discussion on serial cables.Unplug your keyboard.Most PC systems probe for the keyboard during the Power-On
Self-Test (POST) and will generate an error if the keyboard is not
detected. Some machines complain loudly about the lack of a
keyboard and will not continue to boot until it is plugged
in.If your computer complains about the error, but boots anyway,
then you do not have to do anything special. (Some machines with
Phoenix BIOS installed merely say Keyboard
failed and continue to boot normally.)If your computer refuses to boot without a keyboard attached
then you will have to configure the BIOS so that it ignores this
error (if it can). Consult your motherboard's manual for details
on how to do this.Setting the keyboard to Not installed in the
BIOS setup does not mean that you will not
be able to use your keyboard. All this does is tell the BIOS
not to probe for a keyboard at power-on so that it will not
complain if the keyboard is not plugged in. You can leave the
keyboard plugged in even with this flag set to Not
installed and the keyboard will still work.If your system has a PS/2 mouse, chances are very good that
you may have to unplug your mouse as well as your keyboard.
This is because PS/2 mice share some hardware with the keyboard,
and leaving the mouse plugged in can fool the keyboard probe
into thinking the keyboard is still there. It is said that a
Gateway 2000 Pentium 90Mhz system with an AMI BIOS that behaves
this way. In general this is not a problem since the mouse is
not much good without the keyboard anyway.Plug a dumb terminal into COM1:
(sio0).If you do not have a dumb terminal, you can use an old PC/XT
with a modem program, or the serial port on another UNIX box. If
you do not have a COM1:
(sio0), get one. At this time, there is
no way to select a port other than COM1:
for the boot blocks without recompiling the boot blocks. If you
are already using COM1: for another
device, you will have to temporarily remove that device and
install a new boot block and kernel once you get FreeBSD up and
running. (It is assumed that COM1: will
be available on a file/compute/terminal server anyway; if you
really need COM1: for something else
(and you can not switch that something else to
COM2: (sio1)),
then you probably should not even be bothering with all this in
the first place.)Make sure the configuration file of your kernel has
appropriate flags set for COM1:
(sio0).Relevant flags are:0x10Enables console support for this unit. The other
console flags are ignored unless this is set. Currently, at
most one unit can have console support; the first one (in
config file order) with this flag set is preferred. This
option alone will not make the serial port the console. Set
the following flag or use the option
described below, together with this flag.0x20Forces this unit to be the console (unless there is
another higher priority console), regardless of the
option discussed below. This flag
replaces the COMCONSOLE option in FreeBSD
versions 2.X. The flag 0x20 must be used
together with the flag.0x40Reserves this unit (in conjunction with
0x10) and makes the unit unavailable for
normal access. You should not set this flag to the serial
port unit which you want to use as the serial console. The
only use of this flag is to designate the unit for kernel
remote debugging. See for more
information on remote debugging.In FreeBSD 4.0-CURRENT or later the semantics of the
flag 0x40 are slightly different and
there is another flag to specify a serial port for remote
debugging.Example:device sio0 at isa? port "IO_COM1" tty flags 0x10 irq 4See &man.sio.4; for more details.If the flags were not set, you need to run UserConfig (on a
different console) or recompile the kernel.Create boot.config in the root directory
of the a partition on the boot drive.This file will instruct the boot block code how you would like
to boot the system. In order to activate the serial console, you
need one or more of the following options—if you want
multiple options, include them all on the same line:Toggles internal and serial consoles. You can use this
to switch console devices. For instance, if you boot from
the internal (video) console, you can use
to direct the boot loader and the kernel
to use the serial port as its console device. Alternatively,
if you boot from the serial port, you can use the
to tell the boot loader and the kernel
to use the video display as the console instead.Toggles single and dual console configurations. In the
single configuration the console will be either the internal
console (video display) or the serial port, depending on the
state of the option above. In the dual
console configuration, both the video display and the
serial port will become the console at the same time,
regardless of the state of the option.
However, that the dual console configuration takes effect
only during the boot block is running. Once the boot loader
gets control, the console specified by the
option becomes the only console.Makes the boot block probe the keyboard. If no keyboard
is found, the and
options are automatically set.Due to space constraints in the current version of the
boot blocks, the option is capable of
detecting extended keyboards only. Keyboards with less
than 101 keys (and without F11 and F12 keys) may not be
detected. Keyboards on some laptop computers may not be
properly found because of this limitation. If this is to
be the case with your system, you have to abandon using
the option. Unfortunately there is no
workaround for this problem.Use either the option to select the
console automatically, or the option to
activate the serial console.You may include other options described in &man.boot.8; as
well.The options, except for , will be passed to
the boot loader (/boot/loader). The boot
loader will determine which of the internal video or the serial
port should become the console by examining the state of the
option alone. This means that if you specify
the option but not the
option in /boot.config, you can use the
serial port as the console only during the boot block; the boot
loader will use the internal video display as the console.Boot the machine.When you start your FreeBSD box, the boot blocks will echo the
contents of /boot.config to the console. For
example;/boot.config: -P
Keyboard: noThe second line appears only if you put in
/boot.config and indicates presence/absence
of the keyboard. These messages go to either serial or internal
console, or both, depending on the option in
/boot.config.OptionsMessage goes tononeinternal consoleserial consoleserial and internal consolesserial and internal consoles, keyboard presentinternal console, keyboard absentserial consoleAfter the above messages, there will be a small pause before
the boot blocks continue loading the boot loader and before any
further messages printed to the console. Under normal
circumstances, you do not need to interrupt the boot blocks, but
you may want to do so in order to make sure things are set up
correctly.Hit any key, other than Enter/Return, at the console to
interrupt the boot process. The boot blocks will then prompt you
for further action. You should now see something like:>> FreeBSD/i386 BOOT
Default: 0:wd(0,a)/boot/loader
boot:Verify the above message appears on either the serial or
internal console or both, according to the options you put in
/boot.config. If the message appears in the
correct console, hit Enter/Return to continue the boot
process.If you want the serial console but you do not see the prompt
on the serial terminal, something is wrong with your settings. In
the meantime, you enter and hit Enter/Return
(if possible) to tell the boot block (and then the boot loader and
the kernel) to choose the serial port for the console. Once the
system is up, go back and check what went wrong.After the boot loader is loaded and you are in the third stage of
the boot process you can still switch between the internal console and
the serial console by setting appropriate environment variables in the
boot loader. See .SummaryHere is the summary of various settings discussed in this section
and the console eventually selected.Case 1: You set the flags to 0x10 for sio0device sio0 at isa? port "IO_COM1" tty flags 0x10 irq 4Options in /boot.configConsole during boot blocksConsole during boot loaderConsole in kernelnothinginternalinternalinternalserialserialserialserial and internalinternalinternalserial and internalserialserial, keyboard presentinternalinternalinternal, keyboard absentserial and internalserialserialCase 2: You set the flags to 0x30 for sio0device sio0 at isa? port "IO_COM1" tty flags 0x30 irq 4Options in /boot.configConsole during boot blocksConsole during boot loaderConsole in kernelnothinginternalinternalserialserialserialserialserial and internalinternalserialserial and internalserialserial, keyboard presentinternalinternalserial, keyboard absentserial and internalserialserialTips for the Serial ConsoleSetting A Faster Serial Port SpeedBy default the serial port settings are set to 9600 baud, 8
bits, no parity, 1 stop bit. If you wish to change the speed, you
need to recompile at least the boot blocks. Add the following line
to /etc/make.conf and compile new boot
blocks:BOOT_COMCONSOLE_SPEED=19200If the serial console is configured in some other way than by
booting with , or if the serial console used by
the kernel is different from the one used by the boot blocks, then
you must also add the following option to the kernel configuration
file and compile a new kernel:options CONSPEED=19200Using Serial Port Other Than sio0 For
The ConsoleUsing a port other than sio0 as the
console requires some recompiling. If you want to use another
serial port for whatever reasons, recompile the boot blocks, the
boot loader and the kernel as follows.Get the kernel source.Edit /etc/make.conf and set
BOOT_COMCONSOLE_PORT to the address of the
port you want to use (0x3F8, 0x2F8, 0x3E8 or 0x2E8). Only
sio0 through
sio3 (COM1:
through COM4:) can be used; multiport
serial cards will not work. No interrupt setting is
needed.Create a custom kernel configuration file and add
appropriate flags for the serial port you want to use. For
example, if you want to make sio1
(COM2:) the console:device sio1 at isa? port "IO_COM2" tty flags 0x10 irq 3ordevice sio1 at isa? port "IO_COM2" tty flags 0x30 irq 3The console flags for the other serial ports should not be
set.Recompile and install the boot blocks:&prompt.root; cd /sys/boot/i386/boot2
&prompt.root; make
&prompt.root; make installRecompile and install the boot loader:&prompt.root; cd /sys/boot/i386/loader
&prompt.root; make
&prompt.root; make installRebuild and install the kernel.Write the boot blocks to the boot disk with
&man.disklabel.8; and boot from the new kernel.Entering the DDB Debugger from the Serial LineIf you wish to drop into the kernel debugger from the serial
console (useful for remote diagnostics, but also dangerous if you
generate a spurious BREAK on the serial port!) then you should
compile your kernel with the following options:options BREAK_TO_DEBUGGER
options DDBGetting a Login Prompt on the Serial ConsoleWhile this is not required, you may wish to get a
login prompt over the serial line, now that you
can see boot messages and can enter the kernel debugging session
through the serial console. Here is how to do it.Open the file /etc/ttys with an editor
and locate the lines:ttyd0 "/usr/libexec/getty std.9600" unknown off secure
ttyd1 "/usr/libexec/getty std.9600" unknown off secure
ttyd2 "/usr/libexec/getty std.9600" unknown off secure
ttyd3 "/usr/libexec/getty std.9600" unknown off securettyd0 through ttyd3
corresponds to COM1 through
COM4. Change off to
on for the desired port. If you have changed the
speed of the serial port, you need to change
std.9600 to match the current setting, e.g.
std.19200.You may also want to change the terminal type from
unknown to the actual type of your serial
terminal.After editing the file, you must kill -HUP 1
to make this change take effect.Changing Console from the Boot LoaderPrevious sections described how to set up the serial console by
tweaking the boot block. This section shows that you can specify the
console by entering some commands and environment variables in the
boot loader. As the boot loader is invoked as the third stage of the
boot process, after the boot block, the settings in the boot loader
will override the settings in the boot block.Setting Up the Serial ConsoleYou can easily specify the boot loader and the kernel to use the
serial console by writing just one line in
/boot/loader.rc:set console=comconsoleThis will take effect regardless of the settings in the boot
block discussed in the previous section.You had better put the above line as the first line of
/boot/loader.rc so as to see boot messages on
the serial console as early as possible.Likewise, you can specify the internal console as:set console=vidconsoleIf you do not set the boot loader environment variable
console, the boot loader, and subsequently the
kernel, will use whichever console indicated by the
option in the boot block.In versions 3.2 or later, you may specify the console in
/boot/loader.conf.local or
/boot/loader.conf, rather than in
/boot/loader.rc. In this method your
/boot/loader.rc should look like:include /boot/loader.4th
startThen, create /boot/loader.conf.local and
put the following line there.console=comconsoleorconsole=vidconsoleSee &man.loader.conf.5; for more information.At the moment, the boot loader has no option equivalent to the
option in the boot block, and there is no
provision to automatically select the internal console and the
serial console based on the presence of the keyboard.Using Serial Port Other than sio0 for
the ConsoleYou need to recompile the boot loader to use a serial port other
than sio0 for the serial console. Follow the
procedure described in .CaveatsThe idea here is to allow people to set up dedicated servers that
require no graphics hardware or attached keyboards. Unfortunately,
while (most?) every system will let you boot without a keyboard, there
are quite a few that will not let you boot without a graphics adapter.
Machines with AMI BIOSes can be configured to boot with no graphics
adapter installed simply by changing the `graphics adapter' setting in
the CMOS configuration to `Not installed.'However, many machines do not support this option and will refuse
to boot if you have no display hardware in the system. With these
machines, you'll have to leave some kind of graphics card plugged in,
(even if it's just a junky mono board) although you will not have to
attach a monitor into it. You might also try installing an AMI
BIOS.