lpd - line printer daemon
/usr/sbin/lpd [ -l ] [ 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 sys-
tem calls listen(2) and accept(2) to receive requests to print files in the queue, trans-
fer 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 flag
causes lpd to log valid requests received from the network. This can be useful for debug-
Access control is provided by two means. First, All requests must come from one of the
machines listed in the file /etc/hosts.equiv or /etc/hosts.lpd. 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 minfree in each spool directory contains the number of disk blocks to leave free
so that the line printer queue won't completely fill the disk. The minfree file can be
edited with your favorite text editor.
The file lock in each spool directory is used to prevent multiple daemons 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 direc-
tory 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 spec-
ify 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 password 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 owner-
ship by lprm.
M Send mail to the specified user when the current print job completes.
f Formatted File. Name of a file to print which is already formatted.
l Like ``f'' but passes control characters and does not make page breaks.
p Name of a file to print using pr(1) as a filter.
t Troff File. The file contains troff(1) output (cat phototypesetter commands).
n Ditroff File. The file contains device independent troff output.
d DVI File. The file contains Tex(l) output (DVI format from Standford).
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 characters.
1 Troff Font R. Name of the font file to use instead of the default.
2 Troff Font I. Name of the font file to use instead of the default.
3 Troff Font B. Name of the font file to use instead of the default.
4 Troff Font S. Name of the font file to use instead of the default.
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 ascii).
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 stan-
dard input (when lpr is invoked in a pipeline).
If a file can not be opened, a message will be logged via syslog(3) using the LOG_LPR
facility. 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 printed.
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 unex-
pectedly, 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
/usr/spool/*/minfree minimum free space to leave
/dev/lp* line printer devices
/dev/printer socket for local requests
/etc/hosts.equiv lists machine names allowed printer access
/etc/hosts.lpd lists machine names allowed printer access,
but not under same administrative control.
lpc(8), pac(1), lpr(1), lpq(1), lprm(1), syslog(3), printcap(5)
4.2BSD Line Printer Spooler Manual
4.2 Berkeley Distribution October 23, 1996 LPD(8)