LPD(8) BSD System Manager's Manual LPD(8)
lpd - line printer spooler daemon
lpd [-l] [port#]
Lpd is the line printer daemon (spool area handler) and is normally in-
voked 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.
-l The -l flag causes lpd to log valid requests received from the
network. This can be useful for debugging purposes.
port# The Internet port number used to rendezvous with other processes
is normally obtained with getservbyname(3) but can be changed
with the port# argument.
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 daemon begins processing files after it has successfully set the lock
for exclusive access (described a bit later), and scans the spool 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 be-
gins with a key character to specify what to do with the remainder of the
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 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 format-
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 phototypeset-
n Ditroff File. The file contains device independent troff output.
r DVI File. The file contains Tex l output DVI format from Stand-
g Graph File. The file contains data produced by plot(3).
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 charac-
1 Troff Font R. Name of the font file to use instead of the de-
2 Troff Font I. Name of the font file to use instead of the de-
3 Troff Font B. Name of the font file to use instead of the de-
4 Troff Font S. Name of the font file to use instead of the de-
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 pipeline).
If a file cannot 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 daemons 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
/etc/printcap printer description file
/var/spool/* spool directories
/var/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)
4.2 BSD Line Printer Spooler Manual.
An lpd daemon appeared in Version 6 AT&T UNIX.
4.2 Berkeley Distribution April 19, 1994 3