Remote Applications via X11 - Hard Way

Here I will show you how to interact with applications remotely. This is quite useful when you have for example an Ubuntu Server that doesn't have a graphical environment (Gnome or KDE) and a Desktop that has and you need to use some graphical applications on the Ubuntu Server but you cant because you don't have a graphical environment.

So whit this you can show and interact with the graphical applications on the Ubuntu Server, using your Desktop's, graphical environment. So in the X11 world you have the following:

Ubuntu Server - X11 Client --> Application is executed
Ubuntu Desktop - X11 Server --> Application is shown

It's a bit confusing at first, that your Ubuntu Server is you X11 Client, and you Desktop is the X11 Server.

Note: this was tested on Ubuntu 8.04 and 9.04.

X Server - 192.168.1.68 (Where the remote apps will be shown)
=======================================
## Allow that the remote applicatilõns to be show on the X11 Server #####
$ sudo gedit /etc/gdm/gdm.conf

DisallowTCP=true
change it to
DisallowTCP=false


## Reboot to load the new gdm.conf file #####
$ sudo reboot


## Check if the X Server TCP Connections ######
$ netstat -natp |grep :6000

(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 0.0.0.0:6000 0.0.0.0:* LISTEN -
tcp6 0 0 :::6000 :::* LISTEN -


## Add permission for the remote X Client applications #####
## to be shown locally this is temporary, when you #####
## reboot, you must do this again #####
$ sudo xhost 192.168.1.71

## Find the id of the display you are in currently, #####
## and were we see the remote apps, from the X Clinet #####
$ echo $DISPLAY
:0.0


X client - 192.168.1.71 (Where the remote apps will be executed)
========================================

In order to show an application remotely you should use one of the options bellow, where 192.168.1.68 is the IP of the remote computer were the applications will be shown and 0.0 is the id of the graphical terminal on that computer, found earlier, were the remote applications will be displayed.

In this example we execute the application "nautilus", you should change it to the application you want to see remotely.
$ sudo DISPLAY=192.168.1.68:0.0 nautilus
or
$ sudo export DISPLAY=192.168.1.68:0.0
$ nautilus

some applications will not work with the first option so try the second.

After executing one of the two options above, the applications
will be running locally on the X Client (192.168.1.71) but displayed remotely on X Server (192.168.1.68), the applications will not be able to see or use anything on the X Server, there you can only interact with it, and all the resources it may use are from the X Client (local machine).

For example if you replace "nautilus" with "gedit", write something on it and save it the file will be saved on the X Client and not on the X Server were you are interacting with it.


With this method all the data over the network will not be encrypted, if you want a method with encription and a lot easyer using X11 over ssh, you can check the post "Run Applications Remotely via X11 - Easy Way (over ssh)"


Inspired on:

http://ubuntuforums.org/showthread.php?t=162566
http://www.cisl.ucar.edu/docs/ssh/guide/node29.html
http://www.hackinglinuxexposed.com/articles/20040513.html
http://www.linuxquestions.org/questions/linux-newbie-8/how-do-i-restart-x-without-rebooting-418785/
http://www.linuxplanet.com/linuxplanet/tutorials/857/3/
http://www.codingdomain.com/linux/remote/x11/