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\"     @(#)lpd.8        8.3 (Berkeley) 4/19/94
\"
Dd January 20, 2006
Dt LPD 8
Os
Sh NAME
Nm lpd
Nd line printer spooler daemon
Sh SYNOPSIS
Nm
Op Fl dlsrW
Op Fl b Ar bind-address
Op Fl n Ar maxchild
Op Fl w Ar maxwait
Op port
Sh DESCRIPTION
Nm
is the line printer daemon (spool area handler) and is normally invoked
at boot time from the
Xr rc 8
file.
It makes a single pass through the
Xr printcap 5
file to find out about the existing printers and prints any files
left after a crash.
It then uses the system calls
Xr listen 2
and
Xr 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.
Pp
Available options:
Bl -tag -width Ds
It Fl b
Normally, if the
Fl s
option is not specified,
Nm
will listen on all network interfaces for incoming TCP connections.
The
Fl b
option, followed by a
Ar bind-address
specifies that
Nm
should listen on that address instead of INADDR_ANY.
Multiple
Fl b
options are permitted, allowing a list of addresses to be specified.
Use of this option silently overrides the
Fl s
option if it is also present on the command line.
Ar 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.
It Fl d
The
Fl d
option turns on the
Dv SO_DEBUG
Xr socket 2
option.
See
Xr setsockopt 2
for more details.
It Fl l
The
Fl l
flag causes
Nm
to log valid requests received from the network.
This can be useful for debugging purposes.
It Fl n
The
Fl n
flag sets
Ar maxchild
as the maximum number of child processes that
Nm
will spawn.
The default is 32.
It Fl r
The
Fl r
flag allows the
Dq of
and
Dq if
filters to be used if specified for a remote
printer.
Traditionally,
Nm
would not use filters for remote printers.
It Fl s
The
Fl s
flag selects
Dq secure
mode, in which
Nm
does not listen on a TCP socket but only takes commands from a
Ux
domain socket.
This is valuable when the machine on which
Nm
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.
It Fl w
The
Fl w
flag sets
Ar 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.
It Fl W
The
Fl W
option will instruct lpd not to verify a remote tcp connection
comes from a reserved port (<1024).
El
Pp
If the
Op port
parameter is passed,
Nm
listens on this port instead of the usual
Dq printer/tcp
port from
Pa /etc/services .
Pp
Access control is provided by three means.
First,
Pa /etc/hosts.allow
and
Pa /etc/hosts.deny
are consulted as described in
Xr hosts_access 5
with daemon name
Nm .
Second, all requests must come from one of the machines listed in
the file
Pa /etc/hosts.equiv
or
Pa /etc/hosts.lpd
unless there is a line consisting of
Sq + ,
in which case any host
will be accepted that passes the
Xr hosts_access 5
test and has reverse resolving set up.
Lastly, if the
Li rs
capability is specified in the
Xr printcap 5
entry for the printer being accessed,
Em lpr
requests will only be honored for those users with accounts on the
machine with the printer.
Requests must pass all three tests.
Pp
The file
Em 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
Em minfree
file can be edited with your favorite text editor.
Pp
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
Em cf .
Lines in each
Em 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.
Bl -tag -width Ds
It J
Job Name.
String to be used for the job name on the burst page.
It C
Classification.
String to be used for the classification line
on the burst page.
It L
Literal.
The line contains identification info from the password file and
causes the banner page to be printed.
It T
Title.
String to be used as the title for
Xr pr 1 .
It H
Host Name.
Name of the machine where
Xr lpr 1
was invoked.
It P
Person.
Login name of the person who invoked
Xr lpr 1 .
This is used to verify ownership by
Xr lprm 1 .
It M
Send mail to the specified user when the current print job completes.
It f
Formatted File.
Name of a file to print which is already formatted.
It l
Like
Dq f
but passes control characters and does not make page breaks.
It p
Name of a file to print using
Xr pr 1
as a filter.
It t
Troff File.
The file contains
Xr troff 1
output (cat phototypesetter commands).
It n
Ditroff File.
The file contains device independent troff
output.
It d
DVI File.
The file contains
Tn Tex l
output
DVI format from Stanford.
It g
Graph File.
The file contains data produced by
Ic plot .
It c
Cifplot File.
The file contains data produced by
Ic cifplot .
It v
The file contains a raster image.
It o
The file contains PostScript data.
It r
The file contains text data with
FORTRAN carriage control characters.
It \&1
Troff Font R.
Name of the font file to use instead of the default.
It \&2
Troff Font I.
Name of the font file to use instead of the default.
It \&3
Troff Font B.
Name of the font file to use instead of the default.
It \&4
Troff Font S.
Name of the font file to use instead of the default.
It W
Width.
Changes the page width (in characters) used by
Xr pr 1
and the text filters.
It I
Indent.
The number of characters to indent the output by (in ascii).
It U
Unlink.
Name of file to remove upon completion of printing.
It N
File name.
The name of the file which is being printed, or a blank for the
standard input (when
Xr lpr 1
is invoked in a pipeline).
El
Pp
If a file cannot be opened, a message will be logged via
Xr syslog 3
using the
Em LOG_LPR
facility.
Nm
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.
Pp
Nm
uses
Xr 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
Tn 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
Nm
for the programs
Xr lpq 1
and
Xr lprm 1 .
Sh FILES
Bl -tag -width "/var/spool/output/*/minfree" -compact
It Pa /etc/printcap
printer description file
It Pa /var/spool/output/*
spool directories
It Pa /var/spool/output/*/minfree
minimum free space to leave
It Pa /dev/lp*
line printer devices
It Pa /var/run/printer
socket for local requests
It Pa /etc/hosts.allow
explicit remote host access list.
It Pa /etc/hosts.deny
explicit remote host denial of service list.
It Pa /etc/hosts.equiv
lists machine names allowed printer access
It Pa /etc/hosts.lpd
lists machine names allowed printer access,
but not under same administrative control.
El
Sh SEE ALSO
Xr lpq 1 ,
Xr lpr 1 ,
Xr lprm 1 ,
Xr setsockopt 2 ,
Xr syslog 3 ,
Xr hosts.equiv 5 ,
Xr hosts_access 5 ,
Xr hosts_options 5 ,
Xr printcap 5 ,
Xr lpc 8 ,
Xr pac 8
Rs
%T "4.3 BSD Line Printer Spooler Manual"
Re
Sh HISTORY
An
Nm
daemon appeared in Version 6 AT&T UNIX.

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