CUPS Compatibility

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PPR version 2.0 (currently under development) has an IPP server which implements IPP 1.1 with CUPS extensions. IPP stands for the Internet Printing Protocol, a protocol for communication between a print client and a print server. CUPS stands for the Common Unix Printing System, a print spooler for Unix which has replaced Berkeley BSD in serveral Linux distributions. CUPS provides an IPP server, an IPP client library, and replacements for the BSD lpr and System V lp command line tools. These replacement tools use the IPP client library to communicate with the CUPS IPP server.

Both the GNOME and the KDE projects have support for CUPS. GNOME and KDE application programs and printer utilities link to the CUPS IPP client library. This has proved to work much more smoothly and reliably than previous approaches such as running the BSD lpr or System V lp command-line tools such as lpq or lpstat and attempting to parse the output.

Now it would be nice if all of these programs provided support for PPR as well as CUPS. The easiest way to achive this was to implement IPP and at least some of the CUPS extensions, such as the ones which allow clients to request a list of available printers. That is precisely what was done. PPR can now work as a drop-in replacement for the CUPS IPP server. The procedure is as follows:

Disabling the CUPS IPP Server

You can disable the CUPS IPP server by shutting down cupsd:

 /etc/init.d/cupsys stop

To prevent it from starting again, edit /etc/init.d/cupsys and add "exit 0" after the first line.

Switching the CUPS IPP Server to Another Port

You can switch the CUPS IPP server to another port by editing /etc/cups/cupsd.conf (/etc/cups.d/ports.conf on recent versions of Ubuntu) and changing the line which says:


to something such as:


If there is a line like:

  Listen /var/run/cups/cups.sock

comment it out.

Then restart cupsd:

  /etc/init.d/cupsys restart

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Last edited November 15, 2006 11:27 am by (diff)