Comments on: Display remote applications on my local X server in Linux

By: Benny Boy

Benny Boy — Mon, 19 Sep 2011 15:49:59 +0000

In natty, it’s /usr/share/gdm/gdm.schemas

I know this is an old post, but I found it searching around for why I could redirect windows back to me, and it was still in the top ten results. Thanks for the post, it put me in the right area, and a quick “find /usr/share/gdm -type f -exec grep -il disallowtcp {} \;” go the updated file name for me.
BennyBoy

By: .yankee

.yankee — Tue, 04 Aug 2009 03:30:48 +0000

@B!n@ry:
The difference, as Thrift already pointed out, is security – from the user’s viewpoint. If you modify the configuration file, as dectibed in this howto, you end up with an X server open to the network, meaning anyone can run an X aplication on it (hack your box even). That’s because there’s no need of authentication.
When using ssh, you both require authentication and make all the client-server communication encrypted, preventing a potential curious person sniffing your traffic.

By: B!n@ry

B!n@ry — Fri, 23 Mar 2007 08:40:05 +0000

nixCraft,

y don’t we just stick with the -X option that is passed to ssh while connecting to a host ?

What is the different between both ?

By: rajeesh

rajeesh — Tue, 27 Feb 2007 13:19:17 +0000

really a great help yaar.. thanks a lot..

By: nixcraft

nixcraft — Mon, 15 Jan 2007 11:54:58 +0000

drewp,

Thanks for posting ubuntu hints :)

By: drewp

drewp — Mon, 15 Jan 2007 03:51:42 +0000

Just to elaborate on the last comment (for newbies and search engines):

Check if your X server isn’t even listening like this:
% ps ax | grep X
6081 tty7 SLs+ 204:24 /usr/bin/X :0 -br -audit 0 -auth /var/lib/gdm/:0.Xauth -nolisten tcp vt7

To get the -nolisten out of there, edit the file /etc/gdm/gdm.conf which (on ubuntu) ships with line 230 like this:
DisallowTCP=false

Set that to ‘true’ and restart X.

By: Thrift

Thrift — Thu, 21 Dec 2006 01:11:03 +0000

Try to disallow TCP connections from within the GDM config and then ssh -X, it should work without having X listen for TCP connections.

By: nixcraft

nixcraft — Tue, 19 Dec 2006 23:00:46 +0000

Thrift,

In this specific case GDM was disabled for disallows TCP connections from remote hosts. So I had to edit the file and reload the config. BTW it was RHEL 5.0 beta that developer testing for software compatibility.

Appreciate your post.

By: Thrift

Thrift — Tue, 19 Dec 2006 22:52:28 +0000

You may already be aware of this, but a much simpler and more secure way is to just ssh in with the -X (-Y on some Linux distros) flag which will set up an ssh tunnel to allow the same functionally to occur as well as automagically set the DISPLAY variable correctly, so that you don’t have to add -display as a flag to the applications you launch or edit the GDM settings.

This method doesn’t require you to allow the xserver to listen on your ethernet interfaces and doesn’t rely on IP based security.

The only time where I would really think that the way you have mentioned would be a better solution is if you don’t have SSH available, such as for compatibility with VMS or something like that. At which point you’d just use telnet instead of SSH and do everything else just as you have mentioned. You could manually set the DISPLAY variable as opposed to using -display as a flag though, which can be convenient.