FreeBSD: Opening X applications after su to root?

Question

Using FreeBSD 8.2. I'm accessing my machine over vnc using tightvnc. I log in as my normal user. This is okay. I can open X applications and they display fine. Then I su to root and they won't open. I used to be able to do xhost +localhost but this doesn't work anymore. I read online about copying .Xauthority, so now in my .cshrc for root I do this:

if ($user != "root") then
  setenv XAUTHORITY /home/$user/.Xauthoriy
endif

This gets me further but now I get an error:

GLib-GIO:ERROR:gdbusconnection.c:2270:initable_init: assertion failed ..

I searched for this online and someone said to prefix the command with dbus-launch first:

dbus-launch emacs

I tried this and it works but it seems kludgy. How do I get this working so I can launch X based programs after su'ing to root seamlessly (like I could with FreeBSD 6.x)?

Answer 1

Ok I kinda have a fix for this. There is a nice explanation from this site https://bugs.launchpad.net/ubuntu/+source/gconf/+bug/336660 :

The explanation of the problem is the following:

When you su to root from a terminal where you are logged in as another user the new "su-ed" user gonna inherit the environment variables from the parent shell user.

Example: let's say that for the user jack the DBUS_SESSION_BUS_ADDRESS environment variable is set to: "unix:abstract=/tmp/dbus-l5SiTFzmR8,guid=1af28c9d83400a896ef6268d4a7af59f" Now if you open a terminal as jack and make a su to root the DBUS_SESSION_BUS_ADDRESS variable shall remain as for the user jack. And here is the problem, exactly this specific env. variable (DBUS_SESSION_BUS_ADDRESS) generates that problem. Gnome programs like gedit, nautilus . . . use the dbus protocol to communicate with gconf where application specific configurations are stored, and not just. A program executed as root uses a different D-Bus session bus address compared when you execute that program as the jack user for instance. So the problem is that you switch to root, but the DBUS_SESSION_BUS_ADDRESS variable still points the the jack's dbus session bus address.

Solution: The root user has a separate dbus session address too (located in /root/.dbus/session-bus/. . .) So to use the root's dbus address when you are in a terminal and "su-ed" to root just clear the DBUS_SESSION_BUS_ADDRESS variable. like: export DBUS_SESSION_BUS_ADDRESS="" A program that needs dbus communication with gconf for instance, checks that environment variable, and if it is empty it reads the dbus address from the users ~/.dbus/session-bus/ directory (the right place). To make this permanent add the following line to the root users .bashrc file: export DBUS_SESSION_BUS_ADDRESS="" This means that every time when you su to root and the terminal is not a login shell (the case when you are logged in as jack and opened a terminal and executed su) the DBUS_SESSION_BUS_ADDRESS variable is cleared, so the applications gonna read the dbus address from the right place.

by the way you do not need to start a new dbus session with dbus-launch. Even if you do so but the applications still read the dbus address from the wrong place, the problem will persist.

When I unsetenv DBUS_SESSION_BUS_ADDRESS, I can now start emacs in X after su'ing. However I still get warnings:

(emacs 1879): GLib-WARNING **: In call to g_spawn_sync()...