The Udev / D-Bus system - the foundation of modern desktop Linuxes
Németh Tamás
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Nyugat-magyarországi Egyetem
The infrastructure — built of the udev and D-Bus systems and their accessories — has became the foundation of modern Linux systems, expecially the desktop ones, but despite this its operation is generally not well known and comprehensive literature can be hardly found. D-Bus interprocess-communication protocol and its reference imlementation is the center it this infrastructure. The transporting and routing of D-Bus messages is done by the dbus daemon through Unix Domain Sockets, while lower level functions are carried out via netlink packages by the udev daemon in tight cooperation with the kernel. For application developers, the D-Bus channel shows up as a component based system, which allows creating and sharing of objects by the processes attaching to it. The methods and data fileds of these objects are used by the processes to grant various services to each other. Clients of these services are mostly user applications, while the service providers are usually privileged system processes. Relaying between
processes with different privilege levels, the D-Bus system is becoming a cornerstone of the security modell of modern UNIX systems, especially as it possesses its own security modell and editable policy, making it possible for system administrators to customize, which users can access what privileged services under which conditions.
In my presentation I introduce the services working on different levels of the infrastructure build around D-Bus and udev services. I also demonstrate the security modell of this system as a whole, accompanied with some practical eamples.