Flaky Bison Greasy Catfish some services do both. Older services do dbus only, newer services tend to do varlink only, simply since it is so much easier to add, since it doesnt require multiplexing and handling multiple connections by the same program instance. (Instead you just let systemd activate multiple instances of your program, which simplifies things unbelievably much.) Sooner or later we should try to cover everything via varlink and do dbus for the stuff that focusses on desktop stuff.