Cannot get X11 forwarding working (with startx)

[ewildgoose]

I have one gentoo machine with X started via xdm (and running KDE). I can easily open remote X windows back on (say) my windows machine via PuTTy.

However, on my other gentoo machine I start X using "startx", which then boots into KDE. This refuses to let me open remote X sessions. I think the second line of the error message is relevant:

tb root # konqueror
_X11TransSocketOpen: socket() failed for tcp
_X11TransSocketOpenCOTSClient: Unable to open socket for tcp
_X11TransOpen: transport open failed for tcp/localhost:10
konqueror: cannot connect to X server localhost:10.0

Any ideas on how to make this work. I don't really understand the X security stuff, but it looks like an X11 option somewhere controls whether you can make any remote connections at all?

Thanks

Ed W

[gareth]

On the server machine, enter 'xhost +<xxx>' where <xxx> is the IP address or hostname of the machine. See man xhost for more details.

[MacMasta]

DO NOT DO THAT.

That gets rid of any ssh encryption you might have otherwise have had.

The correct approach is this:

edit /etc/ssh/sshd_config and /etc/ssh/ssh_config to have EnableX11Forwarding (or something like that) say yes.

Connect to the remote machine with 'ssh -X user@host'.

Note the capital 'X'.

Try that, tell me what happens.


~Mac~


EDIT: I am assuming you just want to forward windows, not a whole X11 session at once; that's a completely different beast.

[ewildgoose]

Thanks for the thought. Yes, /etc/ssh/sshd_config already has the X forwarding stuff enabled, and putty has the X11 forwarding enabled.

I do have this all setup on one server, so I can compare the configs with the non-working one, and I'm pretty sure that ssh is setup OK. The difference I suspect is that the startx script is setting some different server flags to xdm? Does this sound about right?

Also, can anyone please explain why X forwarding stops working on the good machine if I "su" to a different user? I get an error about "authentication" failed.

Anyone got any good pointers to some docs on how X authentication and net security work? ("good" in this case meaning relevant and "understandable"!)

Thanks all

[MacMasta]

I'm a bit confused at to what you are trying to do; are you just forwarding windows, or a whole X11 Session?


~Mac~

[ewildgoose]

yeah, just individual windows (although I would like to know how to forward a whole session to windows...?)

So basically I log in via putty, and then decide I need an app open (kmail for example), just typing "kmail &" works fine on the machine where X is started with xdm, but not on the machine where X was started by logging into the console and then doing "startx".

The point is to remotely access the two gentoo desktop machines from my windows laptop (there are a few reasons why I need to keep the laptop on windows sadly)

Thanks for any pointers. I'm sure that the "startx" script is the problem, but not sure how to tweak the security

[MacMasta]

...and I'm equally sure it's not the problem, because I have successfully forwarded X sessions from servers that are not only not running X, but have /never/ run X (even though they have it installed).

Post the contents of /etc/ssh/sshd_config and /etc/ssh/ssh_config for the machine that isn't working, please.


~Mac~

[ewildgoose]

Hmm, I see what you mean. I had assumed that X had to be started in order to do remote x connections, but if not, then that can't be the problem...

See below for sshd config, but I compared it to my working machine config and it's almost identical. Client machine is running windows XP using cygwin.

tb root # cat /etc/ssh/sshd_config |grep -v -e '^#' -e '^$'
Protocol 2
UsePAM yes
X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost yes
Subsystem sftp /usr/lib/misc/sftp-server

Any ideas..?

[MacMasta]

I have the X11DisplayOffSet and X11UseLocalHost lines commented out...I would think that those are the defaults, so the commenting wouldn't matter, but try commenting them out...


~Mac~

[ewildgoose]

Yes, those are the defaults, and they were commented out until just before I posted that config. I only uncommented them to be explicit and just test.

Any other ideas..?? Please...?

[MacMasta]

Let's have a look at your error message: post a session, starting from login, up through launching the program and having it not work...


~Mac~

[ewildgoose]

Thanks for the interest. My first post actually has that info exactly. That is literally what I did

I think I have traced the problem though. I re-emerged xfree and it's now working. I think I may have had the ipv6 flag enabled when I first emerged xfree, but the kernel is not ipv6 enabled. Clearly the default in a lot of programs is ipv6 by default

Thanks so much for your help!

[MacMasta]

[CopterGuy85]

I know this is an old thread, but maybe someone will see and and can still help me...

Okay, I've got Cygwin installed on my Windows box (Stargate), and I'm able to get everything running nice and smooth connecting to my Linux box (Atlantis) without using SSH tunnelling (Xwin, xhost +atlantis, ssh me@atlantis, export DISPLAY=stargate:0, enlightenment&).

Now, I am trying to get it to work with tunnelling. I enabled X11Forwarding in my server's /etc/ssh/sshd_config, as well as my local ~/.ssh/config. So then I did Xwin, followed by ssh -X me@atlantis, and I saw right above the prompt that it had created an .Xauthority file. When I did echo $DISPLAY it said "localhost:10.0" (if I understand this right, that is the display being forwarded to Cygwin). Now I run xclock, and poof, there's an xclock in Cygwin.

However, when I try to run a window manager such as twm, I get this message:

[CopterGuy85]

Well I seem to have found a temporary workaround for this problem...

Apparently it seems that windowmanagers don't like to be tunnelled through ssh, so I gave up on that. Although through experimentation, I found that it *is* possible to tunnel Xnest through ssh So the solution to my problem is (from within my ssh terminal):

[MacMasta]

I think the "can't forward windowmanagers" is because the faux-X server that SSH creates for you considers itself managed by whatever WM is running on the machine ssh'd from...so you can't start a new one.

~Mac~

[paul138]

It's been my experiance that there is practically no speed difference when using VNC (I use TightVNC).

I've also found that It helps a lot if you don't use something like KDE or Gnome on the remote system. Simple and elegant, twm works just fine for me.

You may want to look at: x2vnc (you wont have to leave your current desktop behind).
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