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man : lpd(8)

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LPD(8)                  OpenBSD System Manager's Manual                 LPD(8)

NAME
     lpd - line printer spooler daemon

SYNOPSIS
     lpd [-dlrs] [-b bind-address] [-n maxchild] [-w maxwait] [port]

DESCRIPTION
     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 bind-address
             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 maxchild
             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 maxwait
             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 300 seconds.

     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 (which follows the same syntax as hosts.equiv(5)).
     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.

     lpd performs reverse DNS lookups on network clients.  If a client
     hostname cannot be determined from its IP address, the print request will
     be silently dropped.  This is important to note when debugging print
     problems in dynamic address environments.

     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 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).

FILES
     /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.

SEE ALSO
     lpq(1), lpr(1), lprm(1), syslog(3), hosts(5), hosts.equiv(5),
     printcap(5), resolv.conf(5), lpc(8), pac(8)

     4.3BSD Line Printer Spooler Manual.

HISTORY
     An lpd daemon appeared in Version 6 AT&T UNIX.

     lpd previously required that clients connected using a privileged port
     (below 1024).  This restriction was removed because it does not provide
     additional security and also because many modern clients connect using an
     unprivileged port.

OpenBSD 4.9                    October 28, 2010                    OpenBSD 4.9


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