dbus-launch manual page.
Copyright (C) 2003 Red Hat, Inc.
dbus-launch [--version] [--sh-syntax] [--csh-syntax] [--auto-syntax] [--exit-with-session] [--autolaunch=MACHINEID] [--config-file=FILENAME] [PROGRAM] [ARGS...]
See http://www.freedesktop.org/software/dbus/ for more information about D-Bus. See also the man page for dbus-daemon.
"dbus-launch --exit-with-session gnome-session" "dbus-launch --exit-with-session openbox" "dbus-launch --exit-with-session ~/.xsession"
## test for an existing bus daemon, just to be safe if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then ## if not found, launch a new one eval `dbus-launch --sh-syntax` echo "D-Bus per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS" fiNote that in this case, dbus-launch will exit, and dbus-daemon will not be terminated automatically on logout.
If DBUS_SESSION_BUS_ADDRESS is not set for a process that tries to use D-Bus, by default the process will attempt to invoke dbus-launch with the --autolaunch option to start up a new session bus or find the existing bus address on the X display or in a file in ~/.dbus/session-bus/
Whenever an autolaunch occurs, the application that had to start a new bus will be in its own little world; it can effectively end up starting a whole new session if it tries to use a lot of bus services. This can be suboptimal or even totally broken, depending on the app and what it tries to do.
There are two common reasons for autolaunch. One is ssh to a remote machine. The ideal fix for that would be forwarding of DBUS_SESSION_BUS_ADDRESS in the same way that DISPLAY is forwarded. In the meantime, you can edit the session.conf config file to have your session bus listen on TCP, and manually set DBUS_SESSION_BUS_ADDRESS, if you like.
The second common reason for autolaunch is an su to another user, and display of X applications running as the second user on the display belonging to the first user. Perhaps the ideal fix in this case would be to allow the second user to connect to the session bus of the first user, just as they can connect to the first user's display. However, a mechanism for that has not been coded.
You can always avoid autolaunch by manually setting DBUS_SESSION_BUS_ADDRESS. Autolaunch happens because the default address if none is set is "autolaunch:", so if any other address is set there will be no autolaunch. You can however include autolaunch in an explicit session bus address as a fallback, for example DBUS_SESSION_BUS_ADDRESS="something:,autolaunch:" - in that case if the first address doesn't work, processes will autolaunch. (The bus address variable contains a comma-separated list of addresses to try.)
The --autolaunch option is considered an internal implementation detail of libdbus, and in fact there are plans to change it. There's no real reason to use it outside of the libdbus implementation anyhow.
"--auto-syntax" Choose --csh-syntax or --sh-syntax based on the SHELL environment variable. "--binary-syntax" Write to stdout a nul-terminated bus address, then the bus PID as a binary integer of size sizeof(pid_t), then the bus X window ID as a binary integer of size sizeof(long). Integers are in the machine's byte order, not network byte order or any other canonical byte order.
"--close-stderr" Close the standard error output stream before starting the D-Bus daemon. This is useful if you want to capture dbus-launch error messages but you don't want dbus-daemon to keep the stream open to your application.
"--config-file=FILENAME" Pass --config-file=FILENAME to the bus daemon, instead of passing it the --session argument. See the man page for dbus-daemon
"--csh-syntax" Emit csh compatible code to set up environment variables.
"--exit-with-session" If this option is provided, a persistent "babysitter" process will be created that watches stdin for HUP and tries to connect to the X server. If this process gets a HUP on stdin or loses its X connection, it kills the message bus daemon.
"--autolaunch=MACHINEID" This option implies that dbus-launch should scan for a previously-started session and reuse the values found there. If no session is found, it will start a new session. The --exit-with-session option is implied if --autolaunch is given. This option is for the exclusive use of libdbus, you do not want to use it manually. It may change in the future.
"--sh-syntax" Emit Bourne-shell compatible code to set up environment variables.
"--version" Print the version of dbus-launch