LPD(8) System Manager's Manual LPD(8)
lpd - line printer daemon
/usr/lib/lpd [ -l ] [ -L logfile ] [ port # ]
Lpd is the line printer daemon (spool area handler) and is normally
invoked at boot time from the rc(8) file. It makes a single pass
through the printcap(5) file to find out about the existing printers
and prints any files left after a crash. It then uses the system calls
listen(2) and accept(2) to receive requests to print files in the
queue, transfer files to the spooling area, display the queue, or
remove jobs from the queue. In each case, it forks a child to handle
the request so the parent can continue to listen for more requests.
The Internet port number used to rendezvous with other processes is
normally obtained with getservbyname(3) but can be changed with the
port# argument. The -L option changes the file used for writing error
conditions from the system console to logfile. The -l flag causes lpd
to log valid requests received from the network. This can be useful for
Access control is provided by two means. First, All requests must come
from one of the machines listed in the file /etc/hosts.equiv. Second,
if the ``rs'' capability is specified in the printcap entry for the
printer being accessed, lpr requests will only be honored for those
users with accounts on the machine with the printer.
The file lock in each spool directory is used to prevent multiple dae-
mons from becoming active simultaneously, and to store information
about the daemon process for lpr(1), lpq(1), and lprm(1). After the
daemon has successfully set the lock, it scans the directory for files
beginning with cf. Lines in each cf file specify files to be printed
or non-printing actions to be performed. Each such line begins with a
key character to specify what to do with the remainder of the line.
J Job Name. String to be used for the job name on the burst page.
C Classification. String to be used for the classification line
on the burst page.
L Literal. The line contains identification info from the pass-
word file and causes the banner page to be printed.
T Title. String to be used as the title for pr(1).
H Host Name. Name of the machine where lpr was invoked.
P Person. Login name of the person who invoked lpr. This is used
to verify ownership by lprm.
M Send mail to the specified user when the current print job com-
f Formatted File. Name of a file to print which is already for-
l Like ``f'' but passes control characters and does not make page
p Name of a file to print using pr(1) as a filter.
t Troff File. The file contains troff(1) output (cat phototype-
d DVI File. The file contains Tex(l) output (DVI format from
g Graph File. The file contains data produced by plot(3X).
c Cifplot File. The file contains data produced by cifplot.
v The file contains a raster image.
r The file contains text data with FORTRAN carriage control char-
1 Troff Font R. Name of the font file to use instead of the
2 Troff Font I. Name of the font file to use instead of the
3 Troff Font B. Name of the font file to use instead of the
4 Troff Font S. Name of the font file to use instead of the
W Width. Changes the page width (in characters) used by pr(1) and
the text filters.
I Indent. The number of characters to indent the output by (in
U Unlink. Name of file to remove upon completion of printing.
N File name. The name of the file which is being printed, or a
blank for the standard input (when lpr is invoked in a pipe-
If a file can not be opened, a message will be placed in the log file
(normally the console). Lpd will try up to 20 times to reopen a file
it expects to be there, after which it will skip the file to be
Lpd uses flock(2) to provide exclusive access to the lock file and to
prevent multiple deamons from becoming active simultaneously. If the
daemon should be killed or die unexpectedly, the lock file need not be
removed. The lock file is kept in a readable ASCII form and contains
two lines. The first is the process id of the daemon and the second is
the control file name of the current job being printed. The second
line is updated to reflect the current status of lpd for the programs
lpq(1) and lprm(1).
/etc/printcap printer description file
/usr/spool/* spool directories
/dev/lp* line printer devices
/dev/printer socket for local requests
/etc/hosts.equiv lists machine names allowed printer access
lpc(8), pac(1), lpr(1), lpq(1), lprm(1), printcap(5)
4.2BSD Line Printer Spooler Manual
4th Berkeley Distribution 18 July 1983 LPD(8)