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From: Aaron W. Hsu on 8 Feb 2010 19:16
On Sun, 07 Feb 2010 18:24:04 -0500, Mike Jones <Not(a)arizona.bay> wrote:

> Everything else works fine. All connections run and all non-X11
> applications poerate as normal. The fault is a Can't open display
> "localhost:10.0" one and its appearance is a mystery to me.

> What I'm looking for here is what folks would be looking for if this
> glitch suddenly occured on their LAN.

If absolutely nothing changed in the state of the machines, then there
shouldn't be any reason for this error, but the best I can guess is that
something did, in fact, change. Whether this was configuration, firewall
or something, something changed, and it would be good to figure out what.

On the other hand, there are a few errors that you should see depending on
the context. If the DISPLAY variable isn't set, then you shouldn't be
getting the localhost in your error message. If there was a problem with
the client X server, then you should get a connection refused error.
Beyond these two errors, I found the following blog post that might be of
some help to you. An excerpt follows:

[N]ot only do you need X11Forwarding yes in /etc/ssh/sshd_config on the
machine youre sshing into, you also need AllowTcpForwarding yes. (And
also ForwardX11 yes, or ForwardX11Trusted yes, depending on your
security preferences and access requirements, in /etc/ssh/ssh_config on
the machine youre sshing from, for the record.)
-- Problems Forwarding X over SSH
Juliet Kemp [1]

I hope this helps.

Aaron W. Hsu

[1]
http://www.oreillynet.com/linux/blog/2006/08/problems_forwarding_x_over_ssh.html


--
A professor is one who talks in someone else's sleep.
From: Aaron W. Hsu on 8 Feb 2010 19:49
On Mon, 08 Feb 2010 07:40:46 -0500, Mike Jones <Not(a)arizona.bay> wrote:

> Yup. Not that that should make a difference, but...

Could you give us some more information on the client and server machines,
the LAN layout, as well as the software running on the machines at the
time you try to do this. I'm not sure why you think that it wouldn't make
a difference whether X is running on the client machine or not, because it
does. Unless you meant that it shouldn't make a difference that a question
is silly. :-)

Anyways, I'm sure that you are running X on the client machines, because
the DISPLAY environment is set, and unless you set that environment
variable manually, the only way to get that environment variable to show
up automatically is with the X server running.

Anyways, you didn't post the output of the -vvv options, and that could
help.

Aaron W. Hsu

--
A professor is one who talks in someone else's sleep.
From: Aaron W. Hsu on 8 Feb 2010 20:04
Okay, I'm going to be a little sarcastic here, so please be prepared.

On Sun, 07 Feb 2010 20:00:18 -0500, Mike Jones <Not(a)arizona.bay> wrote:

> Everything /except/ X11 apps is still working fine.

Yes, we know, you've told us this plenty of times, and of course, that
doesn't surprise any of us. X11 forwarding is a very special, particular
part of SSH and so it's very easy and common for everything else to be
working fine, but to have X11 Forwarding not working. That's not strange
at all. X11 Forwarding requires more configuration, and obviously
something is wrong. You haven't been providing us with much information,
and you need to do that if you want us to solve the problem.

> The LAN uses static
> IP addresses. All current client machines have the same X11 apps problem
> (with the common server) at the same time.

You haven't given us, to my recollection, any information about the
clients and their machines. You said that they were all on the local LAN,
I believe, but we need more information than that. Are they all running
the same SSH configuration? Are they all running the same firewall and
other software? You have not posted any of this information for us. You
should post your configuration files.

> Something odd has happened on
> the server box, and its got something to do with the display @ 10.0
> thing, related to -X and -Y usage.

Why is localhost:10.0 freaking you out? That is nothing special. It's a
simple specification or content of the DISPLAY variable. It's natural and
normal. Assuming that your X Server on the client side is actually getting
that variable, then nothing should surprise you. Of course it is related
to -X, -Y usage (yes, I'm being rather blunt), no duh, man, I mean, come
on, those options are the ones that you *use* to get X11 Forwarding, so of
course, if you don't have X11 Forwarding, then it has to do with X11
Forwarding. On the other hand, I'm pretty sure that you didn't mess up ssh
badly enough that -X and -Y don't work. They work.

It's possible that something has happened with the server box, and if your
clients all have different configurations, then it is that much more
likely that the problem is on the server box. You haven't told us, either,
whether this problem occurs with multiple users or not. I assume that it
does, since you say that multiple clients (I'm assuming this means
multiple users with different machines and potentially different
configurations) are having this issue.

So, why don't you post up all the information you can give us, including
logs, terminal sessions, configuration files, and the like?

> "ssh -t 192.168.1.1 nano" gets me nano.
>
> "ssh -X 192.168.1.1 dillo" doesn't get me an expected "bad atom" fault.

This is strange, in that I have been able to run dillo fine with the -X
option, and I havne't had this bad atom problem. I'd like to know more
about this problem once you have the other issue figured out.

> "ssh -Y 192.168.1.1 dillo" gets Can't open display "localhost:10.0"

This means, quite literally, that while you can, supposedly, connect to
the localhost, the X server running on the local host is not providing any
display 10.0, and I don't know if this is true or not. It does seem like
this could be a problem, unless you have a lot of clients connecting at a
time. Here are some things I wonder:

1) Why on earth would you have 10 X sessions running on your client
machine!? Now, I don't know, because I have seen high values like 10.0 on
single sessions, but usually, it is much more likely for the client to
have a DISPLAY environment variable like localhost:0.0.

2) What is the startup script for the user's login script? Is there
anything in there that manually sets the DISPLAY variable? The DISPLAY
variable needs to be handled automatically or you need to know ahead of
time the location. I don't like the 10.0, because it seems high, and this
is why I ask this question.

3) Have you done nay port sniffing on your client machines to ensure that
the right ports are open? Post your results.

> AFAICR I've done nothing that could cause a SNAFU here, and this has been
> a problem for up to the last week, based on client reports of failure to
> access X11 apps via ssh. I'm scratching for clues here.

You are basing this on client reports, so why don't you check out the logs
on your server machine? What's happening? Who are these clients of yours?
You tell me that they can't connect? Where are they located? Have you
tried this on other various machines and users and verified whether it
works or not? We are guessing blind here, because we have no idea how your
current network configuration looks.

MORE INFO!

Aaron W. Hsu

--
A professor is one who talks in someone else's sleep.
From: Aaron W. Hsu on 9 Feb 2010 04:38
On Tue, 09 Feb 2010 02:35:02 -0500, Henrik Carlqvist
<Henrik.Carlqvist(a)deadspam.com> wrote:

> His local display is probably set to something like localhost:0 but when
> doing ssh with X tunneling the display gets a uniqueue number on the
> remote machine.

Yes, that's right, I forgot about that.

Aaron W. Hsu

--
A professor is one who talks in someone else's sleep.
From: Mike Jones on 9 Feb 2010 08:05
Responding to Aaron W. Hsu:

> On Sun, 07 Feb 2010 18:24:04 -0500, Mike Jones <Not(a)arizona.bay> wrote:
>
>> Everything else works fine. All connections run and all non-X11
>> applications poerate as normal. The fault is a Can't open display
>> "localhost:10.0" one and its appearance is a mystery to me.
>
>> What I'm looking for here is what folks would be looking for if this
>> glitch suddenly occured on their LAN.
>
> If absolutely nothing changed in the state of the machines, then there
> shouldn't be any reason for this error, but the best I can guess is that
> something did, in fact, change. Whether this was configuration, firewall
> or something, something changed, and it would be good to figure out
> what.
>
> On the other hand, there are a few errors that you should see depending
> on the context. If the DISPLAY variable isn't set, then you shouldn't be
> getting the localhost in your error message. If there was a problem with
> the client X server, then you should get a connection refused error.
> Beyond these two errors, I found the following blog post that might be
> of some help to you. An excerpt follows:
>
> [N]ot only do you need X11Forwarding yes in /etc/ssh/sshd_config on
> the machine youre sshing into, you also need AllowTcpForwarding
> yes. (And also ForwardX11 yes, or ForwardX11Trusted yes, depending
> on your security preferences and access requirements, in
> /etc/ssh/ssh_config on the machine youre sshing from, for the
> record.)
> -- Problems Forwarding X over SSH
> Juliet Kemp [1]
>
> I hope this helps.
>
> Aaron W. Hsu
>
> [1]
> http://www.oreillynet.com/linux/blog/2006/08/
problems_forwarding_x_over_ssh.html


Interesting, but I've aready covered all that. Thats why everything has
worked fine up until this mystery glitch.

See posted logfile in reply to Hernrik.

--
*=( http://www.thedailymash.co.uk/
*=( For all your UK news needs.
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