D-Bus

D-Bus is a message bus system that provides a mechanism for inter-process communication. System D-Bus service needs to be installed before launching a D-Bus session instance.

Some services like Pipewire rely on a D-Bus session instance or expect it by default. Other processes will only be able to communicate with these services if D-Bus is running.

Installation

Tip: Check if system D-Bus service is already installed and running:$ rc-service dbus status, before proceeding futher.

Install the dbus package:

# apk add dbus

If you are using x11 you might also want to install the X11 add-ons which provide the dbus-launch command:

# apk add dbus-x11

If you want dbus to be started at system startup enable the OpenRC service:

# rc-update add dbus

To start the service immediately, use service start|stop|restart commands as follows:

# rc-service dbus start

D-Bus session

Tip: If D-Bus session bus is properly configured, the command:$ echo $DBUS_SESSION_BUS_ADDRESS must provide a output.

You can start a dbus session using the command like this: dbus-run-session -- sh, by replacing sh with your shell or a window manager.

If you are running a X11 based window manager using .xinitrc, use : exec dbus-launch --exit-with-session your_favourite_wm so that D-Bus passes the environment variable $DBUS_SESSION_BUS_ADDRESS to its children. Running dbus-launch in a terminal means that other running process won't find this D-Bus's socket without a export $(dbus-launch).

If $DBUS_SESSION_BUS_ADDRESS is undefined, many applications will attempt to use the standard path:$XDG_RUNTIME_DIR/bus

Running D-Bus like so should work for many applications:

dbus-daemon --nofork --address unix:path=$XDG_RUNTIME_DIR/bus --session

For applications that dont work without $DBUS_SESSION_BUS_ADDRESS you can prepend your program with the follow workaround script which avoid launching multiple user dbus sessions:

#!/bin/sh
if [ ! -e "/tmp/dbus-$USER-env" ]; then
       echo "Creating new dbus session on /tmp/dbus-$USER-env"
       export $(dbus-launch)
       echo "${DBUS_SESSION_BUS_ADDRESS}" > /tmp/dbus-$USER-env
       echo "Dbus session address is: ${DBUS_SESSION_BUS_ADDRESS}"
else
       echo "Using dbus session address from /tmp/dbus-$USER-env"
       export DBUS_SESSION_BUS_ADDRESS="$(cat /tmp/dbus-$USER-env)"
       echo "Dbus session address is: ${DBUS_SESSION_BUS_ADDRESS}"
fi
if [ -n "$1" ]; then
       $@
fi

See also

• Pipewire and D-Bus
• Archwiki
• Gentoo Wiki