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einheitlix
Tux's lil' helper
Joined: 03 Aug 2004
Posts: 144
Location: Saarbrücken, Germany
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 Posted: Tue Sep 30, 2008 10:44 am Post subject: [SOLVED] SSH Tunnels and X Forwarding |
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Hi all,
I'm having a problem setting up an SSH connection with X Forwarding in a very special setup, and hope you will be able to help me.
The setup is as follows: I live in a student residence and have a computer there named ririu. This computer isn't reachable from the outside, as the university's computer center blocks all ingoing connections to the residence from the outside.
The only reachable computer from the outside is our server in the residence, hal, for which the computer center makes an exception.
I'm now at my parent's place and want to build up an SSH connection with X Forwarding from my computer here, freya, to ririu, my computer in the residence. As hal is in the same LAN as ririu, obviously I can connect from freya to hal, and then from hal to ririu.
So I can also log in to hal and do a
| Code: |
malte@hal $ ssh -g -L 2508:ririu:22 malte@ririu
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to build up an SSH tunnel. Then I can connect from freya to ririu using
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malte@freya $ ssh -p 2508 malte@hal
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This works like a charm. However, now I also want to have X Forwarding 
So I tried to specify -X as an additional parameter.
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malte@freya $ ssh -p 2508 -X malte@hal
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I do succeed in connecting to ririu. Except that the X forwarding doesn't work!
| Code: |
malte@ririu $ firefox
Error: no display specified
malte@ririu $ echo $DISPLAY
malte@ririu $
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An X Forwarding to hal works flawlessly:
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malte@freya:~$ ssh -X malte@hal
malte@hal $ echo $DISPLAY
localhost:11.0
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...I can start X applications on hal and they are displayed on freya. But as you see, when I try to this from freya through an SSH tunnel from hal to ririu, the DISPLAY variable somehow gets lost. It doesn't help to randomly set the DISPLAY variable on ririu to localhost:11.0 or localhost:10.0 either, which I tried in desperation.
I hope I made it clear what the problem is, otherwise just ask 
Do you have any idea why this isn't working? I would have assumed that ssh doesn't even notice it's running through an SSH tunnel and that this should hence work without problems. But it doesn't... so, is there any way for me to build up an ssh connection with X forwarding from freya to ririu at all?
Thanks for your help
_________________
Collecting data is only the first step toward wisdom. But sharing data is the first step toward community.
Last edited by einheitlix on Thu Oct 02, 2008 7:17 pm; edited 1 time in total |
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michael_
n00b
Joined: 12 Jun 2007
Posts: 73
Location: Trier
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| Posted: Tue Sep 30, 2008 11:28 am Post subject: |
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hi,
i have not really concerned with ssh, but did you tried -Y (trusted forwarding) instead of -X.
greetings from trier |
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einheitlix
Tux's lil' helper
Joined: 03 Aug 2004
Posts: 144
Location: Saarbrücken, Germany
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| Posted: Tue Sep 30, 2008 12:24 pm Post subject: |
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Thanks for your answer. I just tried it, but unfortunately, same effect with -Y instead of -X... although it seemed like a good idea
_________________
Collecting data is only the first step toward wisdom. But sharing data is the first step toward community. |
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meyerm
Veteran
Joined: 27 Jun 2002
Posts: 1307
Location: Munich / Germany
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| Posted: Tue Sep 30, 2008 4:25 pm Post subject: |
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BTW: You can get X-apps from ririu by sshing "manually":
| Code: | freya # ssh -Y hal
hal # ssh -Y ririu
ririu # xterm // displayed on freya |
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Hu
Watchman
Joined: 06 Mar 2007
Posts: 6348
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| Posted: Wed Oct 01, 2008 3:57 am Post subject: |
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| Does ririu ever allow X forwarding? The sshd configuration can prohibit it system-wide, so perhaps it is blocked there and would not work even in the simple case of a direct connection from freya to ririu. |
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einheitlix
Tux's lil' helper
Joined: 03 Aug 2004
Posts: 144
Location: Saarbrücken, Germany
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| Posted: Thu Oct 02, 2008 7:16 pm Post subject: |
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Hu, you were perfectly right. I just didn't configure the sshd on ririu to allow X11Forwarding. What a silly mistake... thanks a lot, now it works like a charm
All, thanks for all of your kind answers!
Cheers,
Malte
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