D-Bus

D-Bus (short for "Desktop Bus") is a message-oriented middleware mechanism that allows communication between multiple processes running concurrently on the same machine. D-Bus was developed as part of the freedesktop.org project, initiated by GNOME developer Havoc Pennington to standardize services provided by Linux desktop environments such as GNOME and KDE. The freedesktop.org project also developed a free and open-source software library called libdbus, as a reference implementation of the specification. This library should not be confused with D-Bus itself, as other implementations of the D-Bus specification also exist, such as GDBus (GNOME), QtDBus (Qt/KDE), dbus-java and sd-bus (part of systemd). D-Bus is an inter-process communication (IPC) mechanism initially designed to replace the software component communications systems used by the GNOME and KDE Linux desktop environments (CORBA and DCOP respectively). The components of these desktop environments are normally distributed in many processes, each one providing only a few—usually one—services. These services may be used by regular client applications or by other components of the desktop environment to perform their tasks. Due to the large number of processes involved—adding up processes providing the services and clients accessing them—establishing one-to-one IPC between all of them becomes an inefficient and quite unreliable approach. Instead, D-Bus provides a software-bus abstraction that gathers all the communications between a group of processes over a single shared virtual channel. Processes connected to a bus do not know how it is internally implemented, but D-Bus specification guarantees that all processes connected to the bus can communicate with each other through it. Linux desktop environments take advantage of the D-Bus facilities by instantiating multiple buses, notably: a single system bus, available to all users and processes of the system, that provides access to system services (i.e.