lpd Command in Linux

Introduction to Linux Printing with lpd

In this lab, we will delve into the world of Linux printing using the lpd (Line Printer Daemon) command. This essential tool enables efficient management of print jobs within a Linux environment. Our exploration will cover configuring the lpd daemon, effectively managing print queues, and executing various printing-related tasks. This guide provides an introduction to the lpd command, detailed steps for configuring the lpd daemon, and practical techniques for managing print jobs using lpd. We will cover how to check the status of the lpd service, create and enable new print queues, and utilize commands such as lpstat and lprm to streamline the printing workflow.

Understanding the lpd Command

In this section, we'll focus on the lpd (Line Printer Daemon) command, a pivotal tool for managing print jobs in Linux environments. The lpd command plays a crucial role in overseeing the entire printing process, from accepting print requests and organizing print queues to facilitating communication with connected printers.

First, let's examine the current status of the lpd service on our Ubuntu 22.04 Docker container:

sudo systemctl status lpd

Example output:

● lpd.service - LPD Line Printer Daemon
     Loaded: loaded (/lib/systemd/system/lpd.service; enabled; vendor preset: enabled)
     Active: active (running) since Fri 2023-04-21 12:34:56 UTC; 1min 23s ago
   Main PID: 1234 (lpd)
     Tasks: 1 (limit: 4915)
    Memory: 1.1M
    CGroup: /system.slice/lpd.service
            └─1234 /usr/sbin/lpd

As demonstrated, the lpd service is currently active and running on our system. The lpd daemon is responsible for managing print processes, including receiving print requests, organizing print queues, and interfacing with printers.

Next, let's explore some fundamental commands for interacting with the lpd service:

## List available print queues
sudo lpstat -a

## View the status of the print queue
sudo lpstat -t

## Cancel a print job
sudo lprm job_id

These commands provide the capability to view existing print queues, monitor the status of the print queue, and cancel specific print jobs as needed.

Configuring the lpd Daemon for Optimal Printing

This section details the process of configuring the lpd (Line Printer Daemon) service within our Ubuntu 22.04 Docker container to customize your printing environment.

First, we will create a new print queue. The lpadmin command will be utilized to establish a print queue named "myprinter":

sudo lpadmin -p myprinter -v file:/dev/null -P /usr/share/ppd/cups-pdf.ppd -E

This command creates a new print queue identified as "myprinter" and associates it with the CUPS-PDF virtual printer driver for virtual printing.

Next, we will enable the newly created print queue:

sudo enable-printer myprinter

Now, let's confirm that the print queue has been successfully created and enabled:

sudo lpstat -a

Example output:

myprinter accepting requests since Mon 01 Jan 2001 12:00:00 AM UTC

The output confirms that the "myprinter" queue is now actively accepting print requests.

For advanced lpd service configuration, the /etc/printcap file can be modified. This file serves as the central configuration repository for the lpd service, holding information about available print queues, their respective settings, and various other configuration parameters.

Open the /etc/printcap file using the nano text editor:

sudo nano /etc/printcap

Within this file, you can add new entries for custom print queues or modify existing ones. For example, you can set the default printer, configure specific printer options, or define the physical location of a connected printer.

After making any necessary changes, save the updated file and restart the lpd service to apply the new configuration:

sudo systemctl restart lpd

This command ensures that the newly applied configuration changes take effect within the lpd service.

Efficient Print Job Management with lpd

In this concluding section, we will cover how to effectively manage print jobs using the lpd command-line utility.

First, create a sample text file that will be used for printing tests:

echo "This is a test print job." > ~/project/test_print.txt

Next, submit the file to the "myprinter" print queue for processing:

lpr ~/project/test_print.txt

This command sends the "test_print.txt" file to the designated "myprinter" print queue to initiate the printing process.

To view a list of current print jobs residing in the queue, utilize the lpq command:

sudo lpq myprinter

Example output:

myprinter is ready
Rank   Owner   Job     File(s)                         Total Size
active labex   123     test_print.txt                  24 bytes

The output indicates that the "test_print.txt" file is currently being processed as print job number 123.

In situations where you need to cancel a print job, use the lprm command:

sudo lprm 123

This command cancels the print job identified by the ID 123.

Finally, check the print queue again to verify that the cancelled print job has been successfully removed:

sudo lpq myprinter

Example output:

myprinter is ready
no entries

The output confirms that the print queue is now empty, signifying that the specified print job has been successfully cancelled and removed from the queue. Understanding these commands and concepts can help any systemadmin manage their Linux printing environment effectively.

Conclusion

This lab provided a comprehensive exploration of the lpd (Line Printer Daemon) command, an invaluable tool for managing printing tasks within Linux systems. We covered how to assess the status of the lpd service, list available print queues, check the print queue status, and cancel print jobs. We also walked through configuring the lpd daemon by creating a new print queue, associating it with the CUPS-PDF virtual printer driver, and enabling the newly created queue. These steps provide a robust foundation for managing printing processes within any Linux-based environment, giving the systemadmin the tools needed to effectively manage print services.

400+ Linux Commands