Sharing Printers via CUPS

Overview

CUPS is not applicable to Windows. Windows users see Printing via Network

CUPS now the default print sub-system in most Operating Systems - Android, ChromeOS, MacOS, Linux and BSD.

Its use can enable printing over a LAN to be achieved relatively simply, often requiring:

no additional installation of software or "drivers"
only simple configuration changes

Applicability

Android & iOS

Typically these require an App, specific to the printer, to be downloaded from the relevant Store and connect with WiFi enabled printers.

Linux & OSX

Both use CUPS and can be configured as below.

For General Users

Definitions

Those acquainted with client/server model can skip to sub-item "CUPS Inter-Version Issues"

"client computer" means the computer/device from which the print job will be generated
it must have CUPS client installed, which is the default condition for Max OSX and Linux
it need not have any printer drivers installed
- indeed, it is less confusing if it does not

"server computer" means the computer controlling the printer. It can be:
for network printers, which are connected directly to a network, any computer on the network, having the relevant CUPS print drivers installed
- network may be wired, WiFi or bluetooth
- it is perfectly acceptable to configure several computers to use a particular network printer
for USB/parallel attached printers, the computer to which the printer is attached
- it must have CUPS server installed, which is the default condition for Max OSX and Linux
- the relevant printer must appear in its "Printers" list, anAs a general rule, the print server should have a version not earlier than the clientd be working
- the computet must be posered on, to enable printing, although logon won't usually be required .

Prerequisites

This guide assumes that CUPS is installed and generally functioning on both computers. The screen shots are from CUPS version 1.4.x/1.5.x. Versions 1.6 et seq have similar menus, but fewer options, with some changes having to be effected via computer's Control Panel instead.

CUPS Inter-Version Issues

Firstly it is essential to ascertain which release of CUPS is in use, because versions 1.6 and later are largely incompatible with earlier releases. If uncertain, then on each machine involved in the network printing browse to: https://localhost:631/admin

the release number should be displayed in the title bar

CUPS <= 1.5.4 uses substantially different process from 1.6 and later
- printing between machines mixing these versions is complicated. see below for guidelines, if unavoidable
- as CUPS <= 1.5.4 is now used mainly in older OS, there is a case for upgrading the OS on such machines to a current release.
  - it is not feasible for General Users to upgrade the version of CUPS without upgrading the whole OS
CUPS 1.6 and later offer better long term solution
- currently no interoperability issues between various releases
Devices sold by Apple Inc can deploy proprietary extensions to CUPS. Consequently, some features may not work as expected, if the print job is sent to a printer that is controlled by another version of CUPS

CUPS mixed networks <= 1.5.4 plus 1.6 et seq

Network printing in this environment is complex. For a guide to procedures see: http://doc.opensuse.org/release-notes/x86_64/openSUSE/Leap/42.1/

CUPS 1.6 and later

Later releases of CUPS impose greater network security. Default settings vary with system. Several settings might need to be changed to print via network - in summary:

amend firewall settings, on both ends, if necessary
- firewall on router should not be altered
activate cups-browsed service via system services (systemd) on both ends
- in many installations this suffices to get printing working via network, because the following two items are already activated
set CUPS on server to share printers
set CUPS on client to use printers shared by others

In Detail

From the server computer, use "Control Panel" to set the following, if available (exact menus and terminology will vary):

firewall on server must have port 631 open
modify "system services" (exact terminology will vary)
- enable and activate "cups-browsed"

From the server computer, use any browser to https://localhost:631/admin

and activate radio buttons to:

Share printers connected to this system
- using protocols DNSSD & CUPS
restrict sharing to "Local Network"
- could also be set as IP address eg 192.168.0.0/24
Allow remote administration

It is inadvisable to enable

Allow printing from the Internet*print via network

then click "Change Settings" button to save any changes, if necessary

Then click on the "Manage Printers" button in the same tab, select the relevant printer and pull down the "Administration" menu

select "modify printer" then click the "continue" button to proceed to its second screen

22

ensure that "share this printer" is checked
it will be helpful to make the "Location" the name of the computer controlling this printer
click "continue" until the process completes

From the client computer, in the CUPS "administration" tab, ensure that "Show printers shared by other systems" 2is checked

then click "Change Settings" button to save any changes, if necessary

Quicktest

Both computers must be connecting to the local LAN via wired or wireless interface. A quick test is to start a web browser and check that the Internet is accessible. Provided that network access is working:

Start a text editor (kate, leafpad etc)
- if the application is already running then it may need to be shutdown and restarted to recognize newly available printers
Open a new document and type a few words
From the file menu, select "Print"
Select the relevant printer from the drop-down dialog
- which should list all shared printers on the LAN
click on the properties/settings button
ensure that the key settings are suitable eg A4 paper size, portrait orientation
click OK/print

Preliminary Troubleshooting

1. No printers listed in the print dialog

This problem frequently is the result of a firewall running on one or both computers. Network printing can work only if either:

firewalls on each computer allow port 631 through or
Ethernet zones are set as "trusted/internal" in the firewalls on each computer

Only printers powered up will appear in the list

confirm that the relevant printer is powered on
if it is attached to another PC via parallel or USB cable then that PC must also be powered on
- (it is not necessary to log in to the sharing PC)

2. Print Job accepted but no output on Printer

This can be a result of many possible causes. Some simple checks:

is CUPS known to be installed and working on the computer from which the text was created ?.
Can it print to some printer at its home base ?
does a similar print job created on the server computer give output on the printer ?

3. Print Job rejected by Server

possible permissions issue - check thehat:
- printer is set as "share this printer" on the server
  - follow "modify this printer" dialog
possibly incompatible CUPS verions
- most suitable arrangement is for all machines using CUPS #< 1.6
  - achievable only by upgrading the complete OS
  - a new version of the driver for each printer is required at the server end, to support PDF print jobs
  - if a binary driver, from the manufacturer, was previously used, check whether a driver is now included in CUPS or, failing that, whether an updated driver can be obtained from the manufacturer
  - following the upgrade, follow the "modify this printer" dialog for each printer and select the most recent PPD file.
- on older installations, it might be necessary to keep all machines at CUPS version #< 1.5.4

If all else fails, then the CUPS Administration page has a button "View Error Log". Text towards the end of that file may give some clues.

CUPS <= 1.5.4

With this version, a (different) CUPS browsing module is usually enabled by default. Simpler configuration changes usually suffice.

At the server end, browse to https://localhost:631/admin and activate radio buttons to:

Share printers connected to this system

At the workstation/client end, browse to https://localhost:631/admin and activate radio buttons to:

Use printers shared by others

The above troubleshooting tips apply

Getting Techhnical

The above changes can also be implemented via a combination of editing config files and commands via CLI.

At the server end:

ensure that /etc/cups/cups-browsed.conf includes the statements

BrowseRemoteProtocols DNSSD,CUPS
BrowseProtocols DNSSD CUPS
BrowseAllow 192.168.1.0/24 (or network address your LAN, if not this)

Log to a terminal as root and execute:

# systemctl cups-browsed.service enable

# systemctl cups-browsed.service start

At the client end:

ensure that /etc/cups/cups-browsed.conf includes the statements

BrowseRemoteProtocols DNSSD,CUPS2
BrowseProtocols DNSSD CUPS
BrowseAllow 192.168.1.0/24 (or network address your LAN, if not this)

Log to a terminal as root and execute: