How to execute applications in existing X window from virtual console?

Question

I run Debian Wheezy and have Xfce as my X-Window Manager on virtual console 7, which starts up automatically.

Once I've logged on and I'm using the xfce interface, is it possible for me to press Ctrl+Alt+F2 and move to another virtual console (non-X, console 2), and start an application in my, already running, x-session on console 7?

Also, can I do this remotely: say I have a laptop running Linux with Xfce running at home. Can I start an application on that instance of Xfce over ssh from work?

Answer 1

Yes, you can. The program needs the $DISPLAY environment variable. In some more complex linux distributions you also need 2 other variables $XAUTHORITY and $DBUS_SESSION_BUS_ADDRESS.

For example type in the terminal:

DISPLAY=:0 xterm 

If it is still not working export the 2 varibales:

export DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-LoSJ0EDrKV,guid=d46a103f4e55832818aa23c80000219c
export XAUTHORITY=/var/run/gdm/auth-for-user-6jbaaz/database

To find out the values of those variables, type echo VARIABLE in the graphic session.

Answer 2

On Ubuntu, that is very similar to Debian, you can do

DISPLAY=:0 xterm &

Also, after connecting to the ssh server you can perform the same command.

Answer 3

Yes, but Xfce is red herring. It is all about X11.

Any X11 application needs two things to connect to a display server (which provides keyboard, video and mouse to the application), it needs to know which server and it needs permission.

In the common case of connecting to the local X server it has the name :0 which means local host first display. In most cases you can tell your application the name of the server to use either on the command line (commonly -display or --display, but it may vary) or by setting the DISPLAY environment variable.

Authorization is typically provided in the ~/.Xauthority file, but if it is somewhere else the XAUTHORITY variable will tell you where.