How LP Administers Files and Schedules Local Print Requests

The LP print service has a scheduler daemon called lpsched. The scheduler daemon updates the LP system files with information about printer setup and configuration.

The lpsched daemon schedules all local print requests on a print server, as shown in the figure below, whether users issue the requests from an application or from the command line. Also, the scheduler tracks the status of printers and filters on the print server. When a printer finishes a request, the scheduler schedules the next request, if there is one, in the queue on the print server.

Figure 8-1 The lpsched Daemon Schedules Local Print Requests

Each print server must have only one LP scheduler running. The scheduler is started when a system is booted (or enters run level 2) by the control script /etc/rc2.d/S80lp. Without rebooting the systems, you can stop the scheduler with the /usr/lib/lp/lpshut command and restart the scheduler with the lpsched command. The scheduler for each system manages requests issued to the system by the lp commands.