CUPS/Printer sharing

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• Samba
• CUPS

This article contains instruction on sharing printers between systems, be it between two GNU/Linux systems or between a GNU/Linux system and Microsoft Windows.

Creating class for multiple printers

'Class' in CUPS have meaning of a group. When you have multiple printers connected to single CUPS server you may want them to be balanced (printing jobs are automatically queued to different printers). This is also give an advantage that users on remote machine dealing with single 'printer'. Which is especially useful when one printer from class must be taken for repair, you just exclude it from class, yet for end users nothing have changed, printing jobs queued to another printer by CUPS server. Creating and managing classes can be done from CUPS Web GUI

Between GNU/Linux systems

The server can be configured using either the web interface or by manually editing /etc/cups/cupsd.conf. To configure the client, see CUPS.

Using the web interface

Open up the web interface to the server, select the Administration tab, look under the Server heading, and enable the "Share printers connected to this system" option. Save your change by clicking on the Change Settings button. The server will automatically restart.

For more complex configurations, you can directly edit the /etc/cups/cupsd.conf file by selecting Edit Configuration File. See #Manual setup for more information.

Manual setup

On the server computer (the one directly connected to the printer), allow access to the server by modifying the location directive. For instance:

/etc/cups/cupsd.conf

<Location />
    Order allow,deny
    Allow localhost
    Allow 192.168.0.*
</Location>
...

Also make sure the server is listening on the IP address the client will use:

/etc/cups/cupsd.conf

...
Listen <hostname>:631
...

There are more configuration possibilities, including automatic methods, which are described in detail in Using Network Printers and cupsd.conf(5).

After making any modifications, restart the org.cups.cupsd service.

If CUPS is started using socket activation, create a drop-in snippet for org.cups.cupsd.socket so that socket activation also works for remote connections:

/etc/systemd/system/org.cups.cupsd.socket.d/override.conf

[Socket]
ListenStream=631

Enabling browsing

To enable browsing (shared printer discovery), Avahi must be installed and running on the server. If you do not need printer discovery, Avahi is not required on either the server or the client.

To enable browsing, either select Share printers connected to this system in the web interface, or manually turn on Browsing and set the BrowseAddress:

/etc/cups/cupsd.conf

...
Browsing On
BrowseAddress 192.168.0.*:631
...

and restart the org.cups.cupsd service.

Note that "browsing" at the print server is a different thing from "browsing" at a remote networked host. On the print server, cupsd provides the DNS-SD protocol support which the avahi-daemon broadcasts. The cups-browsed service is unnecessary on the print server, unless also broadcasting the old CUPS protocol, or the print server is also "browsing" for other networked printers. On the remote networked host, the cups-browsed service is required to "browse" for network broadcasts of print services, and running cups-browsed will also automatically start cupsd.

The org.cups.cupsd.service service will be automatically started when a USB printer is plugged in, however this may not be the case for other connection types. If cupsd is not running, avahi-daemon does not broadcast the print services, so in that case the systemd unit service file must be modified to start on boot, and then the service must again be "enabled/installed" with the new dependency. To do this, edit the service file [Install] section to add a WantedBy=default.target dependency, and then enable and start the org.cups.cupsd.service service.

Between GNU/Linux and Windows

Linux server - Windows client

Sharing to Windows clients can be achieved using #Sharing via Bonjour, #Sharing via IPP, or #Sharing via Samba.

After setting up the server, install the native printer drivers for your printer on the Windows computer. If the CUPS server's print queue is set up to use its own printer drivers instead of as a raw queue, you can just select a generic postscript printer driver for the Windows client (e.g. 'HP Color LaserJet 8500 PS' or 'Xerox DocuTech 135 PS2' or 'Microsoft PS Class driver').

Sharing via Bonjour

Bonjour Printing Services allows Windows to easily connect to Unix printers shared in the local network using Avahi.

Sharing via IPP

The Internet Printing Protocol is a widely supported standard among operating systems that is simple to configure. It features port forwarding, tunnelling, etc.

Note: You may have to add the Internet Printing Client to Windows (Control Panel > Programs > Turn Windows features on or off > Print and Document Services)

First, configure the server as described in the section #Between GNU/Linux systems.

On the Windows computer, go to Control Panel > Devices and Printers and choose 'Add a printer'. If on Windows 10, click "The printer that I want isn't listed". Next, choose 'Select a shared printer by name' and type in the location of the printer:

http://hostname:631/printers/printer_name

(where hostname is the GNU/Linux server's hostname or IP address and printer_name is the name of the print queue being connected to. You can also use the server's fully qualified domain name, if it has one, but you may need to set ServerAlias my_fully_qualified_domain_name in /etc/cups/cupsd.conf for this to work).

Note:

• The 'Add Printer' dialog in Windows suggests the format http://computername/printers/printername/.printer, which it will not accept. Instead, use the syntax suggested above.
• If you are using a proxy carefully check any used proxy exclusions. A wrong setting here may result in you being unable to add a printer until the next reboot even if you disable the proxy afterwards (at least on Windows 7).

Sharing via Samba

Samba is an implementation of the Windows file and printer sharing protocols, even the most vintage ones.

Note that printer sharing using Samba is usually more difficult to configure and maintain.

To configure Samba on the Linux server, edit /etc/samba/smb.conf file to allow access to printers. File smb.conf can look something like this:

/etc/samba/smb.conf

[global]
workgroup=Heroes
server string=Arch Linux Print Server
security=user

[printers]
    comment=All Printers
    path=/var/spool/samba
    browseable=yes
    # to allow user 'guest account' to print.
    guest ok=no
    writable=no
    printable=yes
    create mode=0700
    write list=@adm root yourusername

That should be enough to share the printer, yet adding an individual printer entry may be desirable:

/etc/samba/smb.conf

[ML1250]
    comment=Samsung ML-1250 Laser Printer
    printer=ml1250
    path=/var/spool/samba
    printing=cups
    printable=yes
    printer admin=@admin root yourusername
    user client driver=yes
    # to allow user 'guest account' to print.
    guest ok=no
    writable=no
    write list=@adm root yourusername
    valid users=@adm root yourusername

Please note that this assumes configuration was made so that users must have a valid account to access the printer. To have a public printer, set guest ok to yes, and remove the valid users line. To add accounts, set up a regular GNU/Linux account and then set up a Samba password on the server. For instance:

# useradd yourusername
# smbpasswd -a yourusername

After this, restart the Samba daemon.

Obviously, there are a lot of tweaks and customizations that can be done with setting up a Samba print server, so it is advised to look at the Samba and CUPS documentation for more help. The smb.conf.example file also has some good samples that might warrant imitating.

Windows server - Linux client

Warning: Any special characters in the printer URIs need to be appropriately quoted, or, if your Windows printer name or user passwords have spaces, CUPS will throw a "lpadmin: Bad device-uri" error.

For example: smb://BEN-DESKTOP/HP Color LaserJet CP1510 series PCL6

becomes:

smb://BEN-DESKTOP/HP%20Color%20LaserJet%20CP1510%20series%20PCL6

This result string can be obtained by running the following command:

$ python -c 'from urllib.parse import quote; print("smb://" + quote("BEN-DESKTOP/HP Color LaserJet CP1510 series PCL6"))'

Sharing via LPD

Windows 7, 8 and 10 have a built-in LPD server - using it will probably be the easiest approach as it does neither require an installation of Samba on the client nor heavy configuration on the server. It can be activated in the Control Panel under Programs -> Activate Windows functions in the section Print services. The printer must have shared activated in its properties. Use a share name without any special characters like spaces, commas, etc.

Then the printer can be added in CUPS, choosing LPD protocol. The printer address will look like this:

# lpd://windowspc/printersharename

Before adding the printer, you will most likely have to install an appropriate printer driver depending on your printer model. Generic PostScript or RAW drivers might also work.

Sharing via IPP

As above, IPP is also the preferred protocol for printer sharing although it only works with Windows Server versions. Windows Server versions (e.g. Server 2016) include IPP support ("Print and Document Services" role, "Internet Printing" service). Client versions (e.g. Windows 10), only include the IPP client, and do not support sharing through IPP.

Sharing via Samba

A much simpler way is using Window's native printer sharing via Samba. There is almost no configuration needed, and all of it can be done from the CUPS Backend. As above noted, if there are any problems the reason is mostly related to authentication trouble and Windows access restrictions.

On the server side enable sharing for your desired printer and ensure that the user on the client machine has the right to access the printer.

The following section describes how to set up the client, assuming that both daemons (cupsd and smbd) are running.

Configuration using the web interface

The Samba CUPS back-end is enabled by default, if for any reason it is not activate it by entering the following command and restarting CUPS.

# ln -s $(which smbspool) /usr/lib/cups/backend/smb

Next, simply log in on the CUPS web interface and choose to add a new printer. As a device choose "Windows Printer via SAMBA".

For the device location, enter:

smb://username:password@hostname/printer_name

Or without a password:

smb://username@hostname/printer_name

Make sure that the user actually has access to the printer on the Windows computer and select the appropriate drivers. If the computer is located on a domain, make sure the URI includes the domain:

smb://username:password@domain/hostname/printer_name

Manual configuration

For manual configuration stop the CUPS daemon and add your printer to /etc/cups/printers.conf, which might for example look like this

/etc/cups/printers.conf

<DefaultPrinter MyPrinter>
AuthInfoRequired username,password
Info My printer via SAMBA
Location In my Office
MakeModel Samsung ML-1250 - CUPS+Gutenprint v5.2.7        # <= use 'lpinfo -m' to list available models
DeviceURI smb://username:password@hostname/printer_name   # <= server URI as described in previous section
State Idle
Type 4
Accepting Yes
Shared No
JobSheets none none
QuotaPeriod 0
PageLimit 0
KLimit 0
AllowUser yourusername                                    # <= do not forget to change this
OpPolicy default
ErrorPolicy stop-printer
</Printer>

Then restart the CUPS daemon and try to print a test page.

Finding URIs for Windows print servers

Sometimes Windows is a little less than forthcoming about exact device URIs (device locations). If having trouble specifying the correct device location in CUPS, run the following command to list all shares available to a certain windows username:

$ smbtree -U windowsusername

This will list every share available to a certain Windows username on the local area network subnet, as long as Samba is set up and running properly. It should return something like this:

 WORKGROUP
	\\REGULATOR-PC   		
		\\REGULATOR-PC\Z              	
		\\REGULATOR-PC\Public         	
		\\REGULATOR-PC\print$         	Printer Drivers
		\\REGULATOR-PC\G              	
		\\REGULATOR-PC\EPSON Stylus CX8400 Series	EPSON Stylus CX8400 Series

What is needed here is first part of the last line, the resource matching the printer description. So to print to the EPSON Stylus printer, one would enter:

smb://username.password@REGULATOR-PC/EPSON Stylus CX8400 Series

as the URI into CUPS.

Remote administration

Once the server is set up as described in #Between GNU/Linux systems, it can also be configured so that it can be remotely administered. Add the allowed hosts to the <Location /admin> block in /etc/cups/cupsd.conf, using the same syntax as described in #Manual setup. Note that three levels of access can be granted:

<Location />           #access to the server
<Location /admin>	#access to the admin pages
<Location /admin/conf>	#access to configuration files

To give remote hosts access to one of these levels, add an Allow statement to that level's section. An Allow statement can take one or more of the forms listed below:

Allow from all
Allow from host.domain.com
Allow from *.domain.com
Allow from ip-address
Allow from ip-address/netmask
Allow from @LOCAL

Deny statements can also be used. For example, to give full access to all hosts on your local network interfaces, edit /etc/cups/cupsd.conf to include this:

# Restrict access to the server...
# By default only localhost connections are possible
<Location />
   Order allow,deny
   Allow from @LOCAL
</Location>

# Restrict access to the admin pages...
<Location /admin>
   Order allow,deny
   Allow from @LOCAL
</Location>

# Restrict access to configuration files...
<Location /admin/conf>
   AuthType Basic
   Require user @SYSTEM
   Order allow,deny
   Allow from @LOCAL
</Location>

You might also need to add:

DefaultEncryption Never

This should avoid the error: 426 - Upgrade Required when using the CUPS web interface from a remote machine.

Kerberos

Kerberos can be used to authenticate users accessing a remote CUPS server. This assumes that your machine has a keytab and it will need a ticket for "HTTP". Instead of using http://localhost:631 you must use https://host.example.co.uk:631 - encryption is required for auth (hence https) and the full hostname is needed so that Kerberos/Negotiate can work. In addition, the server must be configured in /etc/cups/cupsd.conf to use a DefaultAuthType of Negotiate.

If you are using Samba's winbind NSS support, you can add an AD group name to /etc/cups/cups-files.conf - in the following example sysadmin might be an AD group:

SystemGroup sys root sysadmin

Troubleshooting

See CUPS/Troubleshooting for general troubleshooting tips.

Cannot print with GTK applications

If you get a getting printer information failed message when you try to print from GTK applications, add this line to your /etc/hosts:

 # serverip 	some.name.org 	ServersHostname

Permission errors on Windows

Some users fixed 'NT_STATUS_ACCESS_DENIED' (Windows clients) errors by using a slightly different syntax:

smb://workgroup/username:password@hostname/printer_name

Other operating systems

More information on interfacing CUPS with other printing systems can be found in the CUPS manual, e.g. on http://localhost:631/help/network.html