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LPrint Documentation

LPrint v1.3.1 - Month DD, YYYY Copyright 2019-2024 by Michael R Sweet

LPrint is licensed under the Apache License Version 2.0. See the files "LICENSE" and "NOTICE" for more information.

Table of Contents

Overview

LPrint is a label printer application for macOS® and Linux®. I wrote it in response to criticism that coming changes in CUPS will leave users of label printers in the cold - see Apple CUPS Github issue #5271.

Basically, LPrint is a print spooler optimized for label printing. It accepts "raw" print data as well as PNG images (like those used for shipping labels by most shippers' current web APIs) and has built-in "drivers" to send the print data to USB and network-connected label printers. The spooler also tries to keep the labels moving by merging jobs over a single connection to the printer rather than starting and stopping like CUPS does to support a wider variety of printers.

LPrint supports the full range of options and features supported by the embedded drivers - currently most DYMO, Seiko, TSPL, and Zebra EPL2/ZPL label printers. Whenever possible, LPrint will auto-detect the make and model of your printer and its installed capabilities. And you can configure the default values of all options as well as manually configure the media that is loaded in each printer.

LPrint also offers a simple network server mode that makes your label printers appear as IPP Everywhere™/AirPrint™/Mopria™ printers on your network. Thus, any Android™, Chrome OS™, iOS®, Linux®, macOS®, or Windows® 10/11 client can use any label printer supported by LPrint. And you can, of course, send jobs from LPrint to an LPrint server on the network.

Finally, LPrint offers command-line and web-based monitoring of printer and job status.

Installation

LPrint is published as a snap for Linux. Run the following commands to install it and start the server:

sudo snap install core         (if you haven't already done so)
sudo snap install avahi
sudo snap install lprint
sudo snap connect lprint:raw-usb
sudo snap connect lprint:avahi-control avahi:avahi-control
sudo snap start lprint.lprint-server

A package file is included with all source releases on Github for use on macOS 11 and higher for both Intel and Apple Silicon.

If you need to install LPrint from source, you'll need a "make" program, a C99 compiler (Clang and GCC work), the CUPS developer files, and the PAPPL developer files. Once the prerequisites are installed on your system, use the following commands to install LPrint to "/usr/local/bin":

./configure
make
sudo make install

The "configure" script supports the usual autoconf options - run:

./configure --help

to get a list of configuration options.

Basic Usage

LPrint uses a single executable to perform all functions. The normal syntax is:

lprint SUB-COMMAND [OPTIONS] [FILES]

where "SUB-COMMAND" is one of the following:

  • "add": Add a printer
  • "cancel": Cancel one or more jobs
  • "default": Get or set the default printer
  • "delete": Delete a printer
  • "devices": List available printers
  • "drivers": List available drivers
  • "jobs": List queued jobs
  • "modify": Modify a printer
  • "options": Lists the supported options and values
  • "printers": List added printer queues
  • "server": Run in server mode
  • "shutdown": Shutdown a running server
  • "status": Show server or printer status
  • "submit": Submit one or more files for printing

You can omit the sub-command if you just want to print something, for example:

lprint labels.zpl

The options vary based on the sub-command, but most commands support "-d" to specify a printer and "-o" to specify a named option with a value, for example:

  • lprint -d myprinter labels.zpl: Print a file to the printer named "myprinter".
  • lprint -o media=na_index-4x6_4x6in label.png: Print a shipping label image to a 4x6 label.
  • lprint default -d myprinter: Set "myprinter" as the default printer.

You can find our more about each sub-command by reading its included man page, for example the following command will explain all of the supported options for the "submit" sub-command:

man lprint-submit

Adding Printers

The "add" sub-command adds a new printer:

lprint add -d PRINTER -v DEVICE-URI -m DRIVER-NAME

"PRINTER" is the name you want to give the print queue. Printer names can contain spaces and special characters, but if you do any printing from scripts you probably want to limit yourself to ASCII letters, numbers, and punctuation.

"DEVICE-URI" is a "usb:", "snmp:", or "socket:" URI for the printer. For USB-connected label printers, use the "devices" sub-command to discover the URI to use:

lprint devices

For network-connected printers, print the configuration summary on your label printer to discover its IP address. The device URI will then be "socket://" followed by the IP address. For example, a printer at address 192.168.0.42 will use the device URI "socket://192.168.0.42".

Many network-connected label printers also support discovery via SNMP - use the "devices" sub-command to discover these printers' device URIs.

Finally, the "DRIVER-NAME" is the name of the internal LPrint driver for the printer. Use the "drivers" sub-command to list the available drivers:

lprint drivers

For example, the common 4-inch Zebra printer uses the "zpl_4inch-203dpi-dt" driver:

lprint add -d myprinter -v socket://192.168.0.42 -m zpl_4inch-203dpi-dt

Printing Options

The following options are supported by the "submit" sub-command:

  • "-n NNN": Specifies the number of copies to produce.
  • "-o media=SIZE-NAME": Specifies the media size name using the PWG media size self-describing name (see below).
  • "-o media-source=ROLL-NAME": Specifies the roll to use such as 'main-roll' or 'alternate-roll'.
  • "-o media-top-offset=NNNin" or "-o media-top-offset=NNNmm": Specifies a printing offset from the top of the label.
  • "-o media-type=TYPE-NAME": Specifies a media type name such as 'labels', 'labels-continuous', or 'continuous'.
  • "-o orientation-requested=none": Prints in portrait or landscape orientation automatically.
  • "-o orientation-requested=portrait": Prints in portrait orientation.
  • "-o orientation-requested=landscape": Prints in landscape (90 degrees counter- clockwise) orientation.
  • "-o orientation-requested=reverse-portrait": Prints in reverse portrait (upside down) orientation.
  • "-o orientation-requested=reverse-landscape": Prints in reverse landscape (90 degrees clockwise) orientation.
  • "-o print-color-mode=bi-level": Prints black-and-white output with no shading.
  • "-o print-color-mode=monochrome": Prints grayscale output with shading as needed.
  • "-o print-content-optimize=auto": Automatically optimize printing based on content.
  • "-o print-content-optimize=graphic": Automatically optimize printing for graphics like lines and barcodes.
  • "-o print-content-optimize=photo": Automatically optimize printing for photos or other shaded images.
  • "-o print-content-optimize=text": Automatically optimize printing for text.
  • "-o print-content-optimize=text-and-graphic": Automatically optimize printing for text and graphics.
  • "-o print-darkness=NNN": Specifies a relative darkness from -100 (lightest) to 100 (darkest).
  • "-o print-quality=draft": Print using the lowest quality and fastest speed.
  • "-o print-quality=normal": Print using good quality and speed.
  • "-o print-quality=high": Print using the best quality and slowest speed.
  • "-o print-speed=NNNin" or "-o print-speed=NNNmm": Specifies the print speed in inches or millimeters per second.
  • "-o printer-resolution=NNNdpi": Specifies the print resolution in dots per inch.
  • "-t TITLE": Specifies the title of the job that appears in the list produced by the "jobs" sub-command.

Media sizes use the PWG self-describing name format which looks like this:

CLASS_NAME_WIDTHxLENGTHin
CLASS_NAME_WIDTHxLENGTHmm

"CLASS" is "na" for North American media sizes, "oe" for other cut label sizes in inches, "om" for other cut label sizes in millimeters, or "roll" for continuous roll sizes in inches or millimeters. "NAME" is a string of letters, numbers, dots ("."), and dashes ("-") describing the size. "WIDTH" and "LENGTH" are the width and length of the label or receipt you want to print. The trailing "in" or "mm" specifies the units in inches or millimeters, respectively. For example, a 4x6" shipping label uses the size name na_4x6-index_4x6in while a 1.25x3.5" address label uses oe_address-label_1.25x3.5in and a 50x200mm receipt uses roll_receipt_50x200mm.

2-up labels (where two labels are placed side-by-side) use the combined sizes of both labels. For example, a 2-up 0.5x1" multipurpose label uses the size name oe_square-multipurpose-label_1x1in.

You can get a list of supported values for these options using the "options" sub-command:

lprint options
lprint options -d PRINTER

Setting Default Options

You can set the default values for each option with the "add" or "modify" sub-commands:

lprint add -d PRINTER -v DEVICE-URI -m DRIVER-NAME -o OPTION=VALUE ...
lprint modify -d PRINTER -o OPTION=VALUE ...

In addition, you can configure the installed media and other printer settings using other "-o" options. For example, the following command configures the labels that are installed in a Dymo LabelWriter 450 Twin Turbo printer:

lprint modify -d Dymo450TT \
  -o media-ready=oe_address-label_1.25x3.5in,oe_shipping-label_2.125x4in

Use the "options" sub-command to see which settings are supported for a particular printer.

Running a Server

The "server" sub-command runs a standalone spooler. The following options control the server operation:

  • "-o admin-group=GROUP": Specifies a group to use for remote authentication.
  • "-o auth-service=SERVICE": Specifies a PAM service for remote authentication.
  • "-o listen-hostname=HOSTNAME": Sets the network hostname to resolve for listen addresses - "*" for the wildcard addresses, "localhost" to only listen for local print requests.
  • "-o log-file=FILENAME": Specifies a log file.
  • "-o log-file=-": Specifies that log entries are written to the standard error.
  • "-o log-file=syslog": Specifies that log entries are sent to the system log.
  • "-o log-level=LEVEL": Specifies the log level - "debug", "info", "warn", "error", or "fatal".
  • "-o server-hostname=HOSTNAME": Sets the network hostname to advertise.
  • "-o server-name=DNS-SD-NAME": Sets the DNS-SD name to advertise.
  • "-o server-options=OPTION[,...,OPTION]": Sets server options:
    • 'none': No options
    • 'dnssd-host': Use the hostname in printer DNS-SD names
    • 'no-multi-queue': Don't allow multiple queues
    • 'raw-socket': Enable raw socket (JetDirect) support for all printers
    • 'usb-printer': Enable the IPP-USB gadget for the default printer (Raspberry Pi)
    • 'no-web-interface': Disable the web interface
    • 'web-log': Enable web access of the log
    • 'web-network': Enable web-based network configuration
    • 'web-remote': Enable remote access for the web interface
    • 'web-security': Enable web-based security configuration
    • 'no-tls': Disable TLS (encryption) support
  • "-o server-port=NNN": Sets the network port number; the default is randomly assigned starting at 8000.
  • "-o spool-directory=DIRECTORY": Specifies the directory to store print files.

When using the LPrint snap you can set these options using the snap set command, for example:

sudo snap set lprint auth-service=other

When using the LPrint package for macOS, you can set these options by creating the "/Library/Application Support/lprint.conf" file and listing the options one per line, for example:

sudo vi "/Library/Application Support/lprint.conf"
i
auth-service=other
listen-hostname=localhost
:wq

Other operating systems will look for the "lprint.conf" file in the "/etc" and "/usr/local/etc" directories.

After changing these options you'll need to restart the server. On macOS the launchctl command is used:

sudo launchctl stop org.msweet.lprint
sudo launchctl start org.msweet.lprint

Similarly, on Linux the systemctl command is used:

sudo systemctl restart lprint.service

If you've run the server by hand, just use the "shutdown" sub-command and then run the server again:

sudo lprint shutdown
sudo lprint server

Note: When you install the LPrint snap on Linux or the package on macOS, the server is automatically run as root. When you install from source, a launchd (macOS) or systemd (all others) service file is installed but not activated - they can be used to automatically start LPrint when the system boots.

Server Web Interface

When you run a standalone spooler on a network hostname, a web interface can be enabled that allows you to add, modify, and delete printers, as well as setting the default printer. To require authentication for the various web interface operations, you set the PAM authentication service with the -o auth-service=SERVICE option. For example, to use the "cups" PAM service with LPrint, run:

lprint server -o server-name=HOSTNAME -o server-port=NNN -o auth-service=cups

By default, any user can authenticate web interface operations. To restrict access to a particular UNIX group, use the -o admin-group=GROUP option as well.

Resources

The following additional resources are available: