Re: ssh X11forwarding won't work, please help

From: Nils Gorges (noctamid_at_gmx.de)
Date: 08/02/04

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    Date: Mon, 02 Aug 2004 22:54:49 +0200

    Dances With Crows wrote:
    > On Mon, 02 Aug 2004 19:04:34 GMT, Wayne Throop staggered into the Black
    > Sun and said:
    >
    >>>Nils Gorges <noctamid@gmx.de>
    >>>
    >>>>But anyways, you mean you are setting DISPLAY to machine1:0 and
    >>>>launching an X app on machine3, right? And "nothing happens"? The
    >>>>X app doesn't say something like "can't open display" "not
    >>>>authorized" or somesuch? Are there any error indications at all?
    >>>
    >>>yes exactly, no error messages, nowhere.
    >
    >
    > Seems a little strange. But read on...
    >
    >
    >>Then it's probably not an access or networking problem. The bad news
    >>is, that's strange enough that I can't think of anything to suggest.
    >>
    >>>But now ssh -X sets the DISPLAY variable. There are now firewall
    >>>rules and the X Server at machine1 is listening for TCP connections.
    >>>But this isn't even necessary if you use ssh -X or am I wrong?
    >>
    >>Right, ssh -X will bypass both firewalls and even connect to X servers
    >>that are only listening for local processes with no tcp connections.
    >>It does this by the ssh server process operating as a local X process
    >>on the same machine as the X clients, and the ssh client process operating
    >>as a local X process on the same machine as the X server, and both
    >>the X server and the X client being unaware that any traffic is going
    >>to a remote location.
    >
    >
    > FWIW, I had similar problems on Gentoo machines running recent sshd and
    > X releases. Like so:
    > machine1:~$ ssh -X machine2
    > machine2:~$ xeyes &
    > (cannot open display localhost:10.0)
    >
    > ...however,
    > machine1:~$ ssh -Y machine2
    > machine2:~$ xeyes &
    > (works)
    >
    > The -Y option to ssh allows "trusted X11 forwarding", which apparently
    > does something -X doesn't. I don't really have time to research
    > specifics right now, maybe later on tonight, but maybe this'll help you
    > out.
    >

    Thank you very much for your suggestions to both of you.

    This is really a very strange problem. The -Y option is a good idea but
    at machine1 impossible, because the openssh-clients version is too old.

    But now i started a brandnew Knoppix at another machine and here is the
    same problem, doesn't matter if i do ssh -X or ssh -Y the shell freezes
    after starting an X process. So i'm sure this problem is coming from the
    SuSE 9.1 machine3, maybe from the openssh version openssh-3.8p1-33 or
    some SuSE specific issue, i really don't know....

    Nils

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