A number of CUPS features have been adapted for openSUSE. Some of the most important changes are covered here.
After having performed a default installation of openSUSE, SuSEfirewall2 is active and the external network devices are configured to be in the External Zone which blocks incoming traffic. These default settings have to be adjusted when using CUPS. More information about the SUSEfirewall2 configuration is available in Section 35.4, SuSEfirewall2.
Normally a CUPS client runs on a regular workstation located in a network behind a firewall. In this case it is recommended to configure the external network devices to be in the Internal Zone, so the workstation is reachable from within the network.
If the CUPS server is part of network protected by a firewall, the external network device should be configured to be in the Internal Zone of the firewall. When being part of the external zone, the TCP and UDP port 631 needs to be opened in order to make the CUPS server available in the network.
The access permissions set for BrowseAllow and BrowseDeny apply to all kinds of packages sent to cupsd. The default settings in /etc/cups/cupsd.conf are as follows:
BrowseAllow @LOCAL BrowseDeny All
and
<Location /> Order Deny,Allow Deny From All Allow From 127.0.0.1 Allow From 127.0.0.2 Allow From @LOCAL </Location>
In this way, only LOCAL hosts can access cupsd on a CUPS server. LOCAL hosts are hosts whose IP addresses belong to a non-PPP interface (interfaces whose IFF_POINTOPOINT flags are not set) and whose IP addresses belong to the same network as the CUPS server. Packets from all other hosts are rejected immediately.
In a standard installation, cupsd is activated automatically, enabling comfortable access to the queues of CUPS network servers without any additional manual actions. The items in Generalized Functionality for BrowseAllow and BrowseDeny are vital preconditions for this feature, because otherwise the security would not be sufficient for an automatic activation of cupsd.
The YaST printer configuration sets up the queues for CUPS using only the PPD files installed in /usr/share/cups/model. To find the suitable PPD files for the printer model, YaST compares the vendor and model determined during hardware detection with the vendors and models in all PPD files available in /usr/share/cups/model on the system. For this purpose, the YaST printer configuration generates a database from the vendor and model information extracted from the PPD files. When you select a printer from the list of vendors and models, receive the PPD files matching the vendor and model.
The configuration using only PPD files and no other information sources has the advantage that the PPD files in /usr/share/cups/model can be modified freely. The YaST printer configuration recognizes changes and regenerates the vendor and model database. For example, if you only have PostScript printers, normally you do not need the Foomatic PPD files in the cups-drivers package or the Gimp-Print PPD files in the cups-drivers-stp package. Instead, the PPD files for your PostScript printers can be copied directly to /usr/share/cups/model (if they do not already exist in the manufacturer-PPDs package) to achieve an optimum configuration for your printers.
The generic PPD files in the cups package have been complemented with adapted Foomatic PPD files for PostScript level 1 and level 2 printers:
/usr/share/cups/model/Postscript-level1.ppd.gz
/usr/share/cups/model/Postscript-level2.ppd.gz
Normally, the Foomatic printer filter foomatic-rip is used together with Ghostscript for non-PostScript printers. Suitable Foomatic PPD files have the entries *NickName: ... Foomatic/Ghostscript driver and *cupsFilter: ... foomatic-rip. These PPD files are located in the cups-drivers package.
YaST prefers a Foomatic PPD file if a Foomatic PPD file with the entry *NickName: ... Foomatic ... (recommended) matches the printer model and the manufacturer-PPDs package does not contain a more suitable PPD file.
Instead of foomatic-rip, the CUPS filter rastertoprinter from Gimp-Print can be used for many non-PostScript printers. This filter and suitable Gimp-Print PPD files are available in the cups-drivers-stp package. The Gimp-Print PPD files are located in /usr/share/cups/model/stp/ and have the entries *NickName: ... CUPS+Gimp-Print and *cupsFilter: ... rastertoprinter.
The manufacturer-PPDs package contains PPD files from printer manufacturers that are released under a sufficiently liberal license. PostScript printers should be configured with the suitable PPD file of the printer manufacturer, because this file enables the use of all functions of the PostScript printer. YaST prefers a PPD file from the manufacturer-PPDs package if the following conditions are met:
The vendor and model determined during the hardware detection match the vendor and model in a PPD file from the manufacturer-PPDs package.
The PPD file from the manufacturer-PPDs package is the only suitable PPD file for the printer model or a there is a Foomatic PPD file with a *NickName: ... Foomatic/Postscript (recommended) entry that also matches the printer model.
Accordingly, YaST does not use any PPD file from the manufacturer-PPDs package in the following cases:
The PPD file from the the manufacturer-PPDs package does not match the vendor and model. This may happen if the manufacturer-PPDs package contains only one PPD file for similar models, for example, if there is no separate PPD file for the individual models of a model series, but the model name is specified in a form like Funprinter 1000 series in the PPD file.
The Foomatic PostScript PPD file is not recommended. This may be because the printer model does not operate efficiently enough in PostScript mode, for example, the printer may be unreliable in this mode because it has too little memory or the printer is too slow because its processor is too weak. Furthermore, the printer may not support PostScript by default, for example, because PostScript support is only available as an optional module.
If a PPD file from the manufacturer-PPDs package is suitable for a PostScript printer, but YaST cannot configure it for these reasons, select the respective printer model manually in YaST.