Re: Problem starting a remote session...
Re: Problem starting a remote session...
- Subject: Re: Problem starting a remote session...
- From: "Roch M. Comeau" <email@hidden>
- Date: Mon, 10 Oct 2005 21:27:14 -0400
Hello,
While I have used X Windows off and on for years, I never had to get
into the details of remote login security and how secure shell and X
work together other than knowing to use ssh -X to forward the X11
display via secure shell. I (and my girlfriend on another Mac) had
been using ssh -X to log into her lab (and my old lab) fod some time,
however when I upgraded to Tiger, ssh -X stopped working (her Panther
Mac continued to work). To make things a bit more complicated, we
have to go through a gateway computer (an old SGI) and then log into
one of the Linux boxes from there. When I logged in using ssh -X I
got errors when trying to launch an application that needed X. The
solution was to log into the SGI using ssh -Y, however when I try to
log into the Linux box from the SGI, the ssh command would not
recognize -Y. I brought it up to the sys admin, but being overworked
he solved the problem for himself by not upgrading to Tiger.
More recently (maybe after updating to 10.4.2) I can manage to log
into the SGI with ssh - and then onto the Linux box with ssh -Y and
it seems to work so far. Can someone explain (it is not too big a
story), what is the difference between -X and -Y (X11 forwarding vs.
trusted X11 forwarding) and why this has been flaky on Tiger (what
changed).
Thanks,
Roch Comeau
On 10-Oct-05, at 10:55 AM, Don MacQueen wrote:
At 5:05 PM -0600 10/7/05, Steven Hamblin wrote:
Hello,
I'm trying to use X11 so that I can run a remote session from my
lab's Linux
boxes - i.e., I'm trying to use my Powerbook to login to the Linux
machine
in the lab and start a session, which if I recall correctly would
make my
powerbook the 'server' and the Linux machine the 'client'. (I'm
sorry, I've
just starting really getting into the *nix side of things, so
forgive my
lack of detailed knowledge).
In the X Windows world, the terms server and client refer to
software, not hardware. The machines are local and remote; the
software is server and client.
In other words, and for what you're trying to do, the powerbook is
*running* the "X server" or "X windows server" (not just plain
"server"), and that the "X client" or "X windows client" software
is running on the Linux machine.
You can have both the X server software and the X client software
running on the same machine. As a matter of fact, you *do* have
both running on the same machine: when you started up X11.app and
an xterm window came up, that xterm window was an X client running
on the powerbook.
I'm using OS X 10.4.2, and the Linux machine is running Fedora.
Apparently,
it's also using GNOME (which I used Fink to install on my
machine). Having
said that, I cobbled together a few instructions that I was
following,
without really understanding what half of them did, and it went
like this:
After starting X11.app on my machine, I did an ssh into the other
machine:
ssh -X myname@labcomputer, which worked fine. Then, I typed:
gnome-session[enter], and got the following pile of blah in the xterm
window,
I'd suggest starting more simply, just to establish that certain
basics are working.
As Itai suggested, use ssh -Y, not ssh -X. Prior to OS X 10.4, ssh -
X was correct, but a new version of ssh now requires -Y instead.
After having connected using ssh -Y, try running a simple X client,
such as xclock. At a command-line prompt on the Linux box, type
xclock
and you should get a little clock come up. If it does, you now have
an X client, namely xclock, running on the remote machine, and
displaying on the local machine (notice I don't say client and
server machines; that wouldn't be accurate). You also still have an
X client running on your local machine, namely, xterm (even though
you're logged in to the remote linux box, xterm is still running on
the local powerbook).
If that works, then try running whatever application you're really
interested in (presuming that's the purpose of the whole thing).
There is one other piece of software that is crucial to the X
windows system, besides the X windows server (always running
locally) and X windows clients (running on either or both the
remote and local machines). That is the "window manager". It's kind
of a middle-man between the X win server and the X win client.
Normally, the window manager runs on the local host. Also, and
especially with how Apple set things up, it is very easy to be
unaware that the X win server and the window manager are actually
separate things.
I don't use gnome, so I don't have a very good concept of what it
is -- but a quick look tells me that while it includes a window
manager, it does a whole lot more than that. In fact, it looks like
it's an entire desktop GUI system, kind of analogous to Apple's
Aqua. So attempting to run gnome on the Linux box, but have it
display on your powerbook (which may be what you were attempting,
with that "gnome-session" command), is a whole lot more complicated
than just running some remote application. If you can manage with
the latter, do it. It'll be a whole lot easier to configure and
maintain everything that way.
-Don
SESSION_MANAGER=local/labcomputer:/tmp/.ICE-unix/22385
Window manager warning: Log level 32: could not find XKB extension.
Window manager warning: Screen 0 on display "localhost:10.0"
already has a
window manager
Window manager warning: Log level 32: could not find XKB extension.
Window manager warning: Screen 0 on display "localhost:10.0"
already has a
window manager
The program 'nautilus' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadAtom (invalid Atom parameter)'.
(Details: serial 257 error_code 5 request_code 18 minor_code 0)
(Note to programmers: normally, X errors are reported
asynchronously;
that is, you will receive the error a while after causing it.
To debug your program, run it with the --sync command line
option to change this behavior. You can then get a meaningful
backtrace from your debugger if you break on the gdk_x_error()
function.)
On my end, the Fedora splash screen shows up, gets halfway through
loading,
and then does nothing and I have to click on it to make it go away.
Could someone with more experience in these matters point in the
right
direction to untangle this? I definitely appreciate any
assistance that
might be offered.
Cheers,
Steven Hamblin
--
Master of Arts student
Department of Psychology, University of Alberta.
Office: P-319F, Biological Sciences
Phone: 492-6681 e-mail: email@hidden
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--
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
--------------------------------------
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