| LPD(8) | System Manager's Manual | LPD(8) | 
lpd —
| lpd | [ -dlsrW] [-bbind-address] [-nmaxchild] [-wmaxwait] [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.
Available options:
-b-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-d option turns on the
      SO_DEBUG
      socket(2) option. See
      setsockopt(2) for more
      details.-l-l flag causes lpd to
      log valid requests received from the network. This can be useful for
      debugging purposes.-n-n flag sets maxchild as
      the maximum number of child processes that lpd
      will spawn. The default is 32.-r-r flag allows the “of” and
      “if” filters to be used if specified for a remote printer.
      Traditionally, lpd would not use filters for
      remote printers.-s-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-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-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 three means. First,
    /etc/hosts.allow and
    /etc/hosts.deny are consulted as described in
    hosts_access(5) with
    daemon name lpd. Second, all requests must come from
    one of the machines listed in the file
    /etc/hosts.equiv or
    /etc/hosts.lpd unless there is a line consisting of
    ‘+’, in which case any host will be accepted that passes the
    hosts_access(5) test and
    has reverse resolving set up. Lastly, 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. Requests must
    pass all three tests.
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.
plot.cifplot.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).
4.3 BSD Line Printer Spooler Manual.
lpd daemon appeared in Version 6 AT&T UNIX.
| January 20, 2006 | NetBSD 9.4 |