lpd(ADMN) 19 June 1992 lpd(ADMN) Name lpd - line printer daemon Syntax /usr/lib/lpd [ -l ] [ port # ] Description lpd is the line printer daemon (spool area handler) and is normally invoked at boot time from the rc2(ADM) file. It makes a single pass through the printcap(SFF) file to find out about the existing printers and prints any files left after a crash. It then uses the system calls listen(SSC) and accept(SSC) 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 Internet port number used to rendezvous with other processes is normally obtained with getservbyname(SLIB) but can be changed with the port # argument. The -l flag causes lpd to log valid requests received from the network. This can be useful for debugging purposes. 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 entry for the printer being accessed, lp 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 file lock in each spool directory prevents multiple daemons from becoming active simultaneously, and to store information about the daemon process for lp(C), lpstat(C), and cancel(C). After the daemon has suc- cessfully set the lock, it scans the 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(C). H Host Name. Name of the machine where lp was invoked. P Person. Login name of the person who invoked lp. This is used to verify ownership by cancel. M Mail. 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. r Request ID. The request ID is used by the cancel(C) command. U Unlink. Name of file to remove upon completion of printing. If a file can not be opened, a message will be logged via syslog(SLIB) using the LOGLPR 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 fcntl(S) to provide exclusive access to the lock file and to prevent multiple deamons 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 filename of the current job being printed. The second line is updated to reflect the current status of lpd for the programs lpstat(C) and cancel(C). Files /etc/printcap printer description file /usr/spool/* spool directories /usr/spool/*/minfree minimum free space to leave /dev/lp* line printer devices /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 lp(C), lpstat(C), cancel(C), syslog(SLIB), printcap(SFF)