lpd(8)
NAME
lpd − line printer daemon
SYNTAX
/usr/lib/lpd
/etc/lpdrestart
DESCRIPTION
The lpd command is the daemon for the line printer. The lpd daemon uses the directory /usr/spool/lpd. The file lock in that directory is used to prevent two daemons from becoming active. After the program has successfully set the lock, it forks and the main path exits, thus spawning the daemon. The directory is scanned for files beginning with df. Each such file is submitted as a job. Each line of a job file must begin with a key character to specify what to do with the remainder of the line.
L Specifies that the remainder of the line is to be sent as a literal.
B Specifies that the rest of the line is a file name.
F Is the same as B except a form feed is prepended to the file.
U Specifies that the rest of the line is a file name. After the job has been transmitted, the file is unlinked.
M Is followed by a user ID; after the job is sent, a message is mailed to the user via the mail(1) command to verify the sending of the job.
Any error encountered will cause the daemon to wait and start over. This means that an improperly constructed df file may cause the same job to be submitted repeatedly.
The lpd command is automatically initiated by the line printer command, lpr.
To restart lpd in the case of hardware or software malfunction, it is necessary to first kill the old daemon, if still alive, and remove the lock file before initiating the new daemon. All of this is done with the /etc/lpdrestart command. This is done automatically when the system is brought up, by /etc/rc, in case there were any jobs left in the spooling directory when the system last went down.
FILES
/usr/spool/lpd/* spool area for line printer daemon
/etc/passwd to get the user’s name
/dev/lp line printer device
/etc/lpdrestart to restart the line printer daemon(s)