Recently I talked about a new print spooler under development, printerd. In that post I mentioned briefly how printerd is structured, but did not go very deeply into why or what the project is for.

Firstly, printerd is experimental and is very far from being a functional print spooler. It doesn’t yet run any filters, for instance, and has no backends of its own to transport jobs to devices. So far it is just a test of what a Linux print spooler would look like if it were written today.

There are several problems printerd aims to solve. Some of the solutions come automatically from implementing it as a polkit-enabled D-Bus system service.  I mentioned one of them in the original post about printer: the fact of having an asynchronous client API. All D-Bus services can be used asynchronously thanks to the D-Bus client library. This approach means the print dialog will be able to use printerd without blocking (and without having to start another thread to use it).

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For the last few weeks I’ve been working on an experimental new print spooler called printerd. It was designed in collaboration with Richard Hughes and it aims to be a modern print spooler for Linux.

It is a polkit-enabled D-Bus system service, written using the GLib object system. Although modelled on concepts from IPP (Internet Printing Protocol), printerd is not in itself an IPP server. Its only interface is D-Bus, although the aim is to be able to implement an IPP server on top of the D-Bus API as a separate process. Having a D-Bus interface means that applications wanting to print automatically get to use printerd asynchronously.

As a design decision, the range of input formats accepted by printerd will be very limited: essentially only PDF. The existing CUPS drivers and backends will be compatible with printerd.

There isn’t much written yet aside from the basic framework and a very simple command line tool.

Feel free to take a look around: http://gitorious.org/printerd

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