QjackCtl is a simple Qt application to control the JACK sound server daemon, specifically for the Linux Audio Desktop infrastructure. It is written in C++ around the Qt4 toolkit for X11, most exclusively using Qt Designer. It provides a simple GUI dialog for setting several JACK daemon parameters, which are properly saved between sessions, and a way to control of the status of the audio server daemon. With time, this primordial interface has become richer by including an enhanced patchbay and connection control features.