VNC on Ubuntu 22.04 - DBUS_SESSION_BUS_ADDRESS unset; can't run "dconf reset"

Question

I want to reset my Ubuntu 22.04 desktop settings over a vnc terminal (Uubntu 22.04 is running TigerVNC.) I followed instructions at https://linuxhint.com/ubuntu_dock_settings/ and backed up the current desktop settings using

$ dconf dump / > backup.txt

However, when I try to reset the desktop settings using

dconf reset -f /

I get the following error.

error: Error spawning command line “dbus-launch --autolaunch=c7014a22ae9647b69f20ea2bbc28bec4 --binary-syntax --close-stderr”: Child process exited with code 1

I noticed that my ~/.vnc/xstartup file included unset DBUS_SESSION_BUS_ADDRESS (I copied the xstartup file from https://bytexd.com/how-to-install-configure-vnc-server-on-ubuntu/). Here are the contents of the xstarup file.

#!/bin/sh 

unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS

[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources

gnome-session

I commented out the unset DBUS_SESSION_BUS_ADDRESS, restarted the vncserver, and reconnected from a vnc client. But DBUS_SESSION_BUS_ADDRESS is still unset / undefined. I still get the same error when running dconf reset-f / .

Next, I commented out the unset DBUS_SESSION_BUS_ADDRESS line and added the following to the xstartup file just before the gnome-shell invocation and restarted the vncserver.

if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
    eval `dbus-launch --sh-syntax --exit-with-session`
    echo "D-BUS per-session daemon address is: \
    $DBUS_SESSION_BUS_ADDRESS"
fi

However, DBUS_SESSION_BUS_ADDRESS is still unset. Still the same error from the dconf reset -f / command.

At this point, I entered the following command in a terminal over vnc.

dbus-launch --sh-syntax --exit-with-session

This command responded with the following.

DBUS_SESSION_BUS_ADDRESS='unix:abstract=/tmp/dbus-wSUKXx6r0W,guid=3d557317b8f0a468242814d8636956e6';
export DBUS_SESSION_BUS_ADDRESS;
DBUS_SESSION_BUS_PID=4709;

However, DBUS_SESSION_BUS_ADDRESS is still unset / undefined in the terminal. And I still can't reset Ubuntu desktop settings.

Any ideas?

Answer 1

The xstartup is wrong - all these web tutorials use an ancient version which messes up DBUS_SESSION_BUS_ADDRESS, snap, and so on. Just delete your xstartup: the default on 22.04 is fine (/etc/X11/Xtigervnc-session). When you've got a terminal:

 $ echo $DBUS_SESSION_BUS_ADDRESS
unix:path=/run/user/1000/bus

(assuming you're UID 1000). If it's not working, you'll get something more complicated.

Answer 2

I got around this issue with this.

su -l username -c "(export DISPLAY=:5; dbus-launch --exit-with-session; vncserver -geometry 1792x899 -depth 24 :5)"

The command "dbus-launch --exit-with-session" sets dbus variables to be specific to the user running vncserver, otherwise it might pick them up from somewhere else or not have them set at all. 



DBUS_SESSION_BUS_PID=31898 DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1003/bus

These need to be set correctly or you will get a blank screen or permission denied. For example DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1003/bus Where 1003 is the id of the user.

You also need dbus-x11 or dbus-user-session package installed