lpd - line printer spooler daemon
lpd [-dlsrW] [-b bind-address] [-n maxchild] [-w maxwait]
[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 options are as follows:
-b Normally, if the -s option is not specified, lpd
will listen on
all network interfaces for incoming TCP connections.
The -b option,
followed by a bind-address specifies that lpd
should listen
on that address instead of INADDR_ANY. Multiple -b
options are
permitted, allowing a list of addresses to be specified. Use of
this option silently overrides the -s option if it
is also present
on the command line. bind-address can be a numeric host
name in IPV4 or IPV6 notation, or a symbolic host
name which will
be looked up in the normal way.
-d The -d option turns on the SO_DEBUG socket(2) option. See
setsockopt(2) for more details.
-l The -l flag causes lpd to log valid requests received from the
network. This can be useful for debugging purposes.
-n The -n flag sets maxchild as the maximum number of
child processes
that lpd will spawn. The default is 32.
-r The -r flag allows the ``of'' filter to be used if
specified for
a remote printer. Traditionally, lpd would not use
the output
filter for remote printers.
-s The -s flag selects ``secure'' mode, in which lpd
does not listen
on a TCP socket but only takes commands from a UNIX
domain socket.
This is valuable when the machine on which lpd
runs is subject
to attack over the network and it is desired
that the machine
be protected from attempts to remotely fill
spools and similar
attacks.
-w The -w flag sets maxwait as the wait time (in seconds) for dead
remote server detection. If no response is returned
from a connected
server within this period, the connection is
closed and a
message logged. The default is 120 seconds.
-W The -W option will instruct lpd not to verify a remote tcp connection
comes from a reserved port (<1024).
If the [port] parameter is passed, lpd listens on this port
instead of
the usual ``printer/tcp'' port from /etc/services.
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(5) 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 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 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(1) was invoked.
P Person. Login name of the person who invoked
lpr(1). This is
used to verify ownership by lprm(1).
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.
r DVI File. The file contains Tex l output DVI format
from Stanford.
g Graph File. The file contains data produced by
plot.
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 standard input (when lpr(1) 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
lprm(1).
/etc/printcap printer description file
/var/run/lpd.pid lock file for lpd
/var/spool/output/* spool directories
/var/spool/output/*/minfree minimum free space to leave
/dev/lp* line printer devices
/var/run/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.
lpq(1), lpr(1), lprm(1), syslog(3), hosts.equiv(5), printcap(5), lpc(8),
pac(8)
4.3BSD Line Printer Spooler Manual.
An lpd daemon appeared in Version 6 AT&T UNIX.
OpenBSD 3.6 May 18, 2002
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