lpd - line printer daemon
/usr/lbin/lpd [-l]
Causes the lpd daemon to log valid requests received from
the network. This option is useful for debugging.
The lpd line printer daemon (spool area handler) normally
is invoked at boot time. The daemon makes a single pass
through the printcap(4) file to determine the existing
printers and to print all files that were not printed
before the system shut down. The daemon uses system calls
listen(2) and accept(2) to receive requests to print files
in the queue, to transfer files to the spooling area, and
to display the queue or remove jobs from the queue. In
each case, the daemon forks a child process to handle the
request so that the parent process can continue to listen
for more requests. The Internet port number used to
interact with other processes is identified with the getservbyname(3) system call and is specified in the
/etc/services file by its printer service record entry.
Access control is provided by the following means:
All requests must originate from one of the machines
listed in the /etc/hosts.equiv or /etc/hosts.lpd file.
When an rs capability, which restricts remote users to
those with local accounts, is specified in the /etc/printcap
file for the printer being accessed, an lpr or lp
request is honored only for those users having accounts on
the same machine as the printer.
The minfree ASCII file in each spool directory contains
the number of disk blocks to leave free so that the line
printer queue will not completely fill the disk.
The lock file in each /usr/spool subdirectory is used to
prevent more than one active lpd daemon and to store
information about the daemon process for other printer
spooling commands.
After the lpd daemon has successfully set the lock in the
lock file, it scans the /usr/spool subdirectory for files
beginning with the characters cf. Records in each of the
cf files specify files to be printed or specify one or
more non-printing actions to be performed. Each such
record begins with a key character that specifies what to
do with the remainder of the line. In the following
table, the columns list the beginning key character, the
key-character name, and its purpose: Name of the machine
where the lpr daemon or the lp command was invoked. Login
name of the person who invoked the lpr or lp commands.
This record is used to verify ownership by the lprm or
cancel commands. String to be used for the job name on
the burst page. String to be used for the classification
line on the burst page. The record line provides
identification information from the etc/passwd file and
initiates banner page printing. The number of character
spaces to indent the output (spacing is from the ASCII
character set). Sends mail to the specified user when the
current print job completes. Name of another font file to
use in place of the default font file. Name of another
font file to use in place of the default font file. Name
of another font file to use in place of the default font
file. Name of another font file to use in place of the
default font file. Changes the page width (in characters)
used by the pr command and by text filters. Selects the
input tray that supplies paper for the print job. Selects
the output tray where the printed paper is deposited.
Specifies the orientation of the printed output on the
page. Note that for certain print filters, such as pcfof,
the O option is used to specify other options such as even
to print even-numbered pages. Specifies whether the job
should be printed on both sides of the physical sheet and
whether the pages should be rotated by 180 degrees.
String to be used as the title for the pr command. Name
of an already formatted file to print. Name of a file to
print using the pr command as a filter. Similar to f, but
passes control characters and does not make page breaks.
The file contains troff output (cat phototypesetter commands).
The file contains DVI (device-independent) troff
output. The file contains Tex(l) output (DVI format from
Stanford). The file contains a raster image. The file
contains data produced by the cifplot command. The file
contains text data with Fortran carriage control characters.
Do not interpret any control characters in the
file. Name of file to remove on completion of printing.
The name of the file undergoing printing, or when blank,
for the standard input (when the lpr or lp command is
invoked in a pipeline or when the command is invoked from
the standard input).
Whenever a file cannot be opened for printing, a message
is logged via the syslog(3) subroutine using theLOG_LPR
facility. In this case, the lpd daemon tries to reopen a
file, which it expects to be referenced by a correct pathname,
up to 20 times. If a file cannot be opened after 20
tries, lpd goes to the next file.
The
lpd daemon uses the flock(2) system call to provide exclusive
access to the lock file and to prevent multiple daemons
from being simultaneously activated. If the daemon
is killed or dies unexpectedly, the lock file does not
have to be removed.
The 2-line ASCII /usr/spool/lock file contains two lines.
The first line specifies the process ID of the daemon, and
the second line specifies the control file name of the job
currently undergoing printing. The second line is updated
to reflect the current status of the lpd daemon for commands
lpq, lprm, cancel, and lpstat.
NOTE - Printer Log Files [Toc] [Back]
The lpd does not automatically purge log files. You
should monitor logs regularly or set up a cleaning task
using the cron command. See similar commands for syslog.dated
in /usr/var/spool/cron/crontabs
Specifies the command path. Printer description file.
Spool directories. The location of spool directories is a
convention, but not necessary (see the /etc/printcap
file). The transient lock file which records print daemon
and job status. On clustered systems, this transient file
is created to contain the daemon status. Note that the
/usr/spool/lpd directory is a Context Dependent Symbolic
Link (CDSL) and should not be manually created or
destroyed. Minimum free disk space to leave. Line
printer devices. Socket for local requests. Lists
machine names allowed access to a printer. Lists machine
names allowed access to a printer, but which are not under
same administrative control.
Commands: cancel(1), lp(1), lpc(8), lpr(1), lpq(1),
lpstat(1), lprm(1), pac(8), pcfof(8)
Calls: syslog(3)
lpd(8)
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