Date: Fri, 16 Jul 1999 16:00:08 +0300 From: "Andy V. Oleynik" <andyo@prime.net.ua> To: cjclark@home.com Cc: freebsd-questions@FreeBSD.ORG Subject: Re: SSH X Forwarding Message-ID: <378F2CD7.46A27DEE@prime.net.ua> References: <199907151536.LAA21293@cc942873-a.ewndsr1.nj.home.com>
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I beleave there 3 schemes exist:
1. U sitting at non X host and ssh'ed at remote *running* X.
U can remotly run xapp on Xhost (*if allowed*). Window will
appear at remote's display. (I did it just now from one of
my machines).
2. U sitting at host running X and ssh'ed to remote *running* X
from xterm for example. U run remotly xapp and window appear
locally. I did it month ago from my home PC.
I've had only troubles trying to run xapp on ssh'ed machine when
PC where I ssh'ing from was not allowed to connect to X server
or when there wasnt running X server on remote or when I didnt
give an "-display :0" option to my xapps.
Look:
now I have at remote X server:
volodya# xhost
access control enabled, only authorized clients can connect
INET:localhost
INET:ns1.prime.net.ua
volodya#
then I ssh'ing at remote (non X host):
volodya# ssh ns1
Warning: Remote host denied X11 forwarding, perhaps xauth program could
not be run on the server side.
[snip]
You may also use `/stand/sysinstall' to re-enter the installation and
configuration utility. Edit /etc/motd to change this login
announcement.
You have new mail.
ns1#
here I cannot to run xapps of course ;)
then I shh'ing back to volodya:
ns1# ssh volodya
[snip]
You have new mail.
volodya#
Now look:
volodya# xterm
Warning: This program is an suid-root program or is being run by the
root user.
The full text of the error or warning message cannot be safely
formatted
in this environment. You may get a more descriptive message by running
the
program as a non-root user or by removing the suid bit on the
executable.
xterm Xt error: Can't open display: %s
volodya#
There are no defined DISPLAY variable:
volodya# set|more
addsuffix
argv ()
cwd /usr/home/root
dirstack /usr/home/root
echo_style bsd
edit
filec
gid 0
group wheel
history 100
home /usr/home/root
loginsh
mail /var/mail/root
owd
path (/sbin /bin /usr/sbin /usr/bin /usr/games /usr/local/sbin
/usr/local/bin /usr/X11R6/bin /usr/
home/root/bin)
prompt volodya#
prompt2 %R?
prompt3 CORRECT>%R (y|n|e|a)?
savehist 100
shell /usr/local/bin/tcsh
shlvl 1
status 0
tcsh 6.08.00
term xterm-color
tty ttyp3
uid 0
user root
version tcsh 6.08.00 (Astron) 1998-10-02 (i386-intel-FreeBSD) options
8b,nls,dl,al,sm,rh,color
volodya#
Now look:
volodya# xterm -display :0
gives correct result - xterm window appears at remote display. In case if
I'd ssh'ing in the remote X
from another X console I have had window locally.
Now I define DISPLAY variable:
volodya# set DISPLAY=:0
volodya# setenv DISPLAY :0
volodya# xterm
gives correct result - xterm window appears at remote display.
Ok. I remove ns1 from allowed list:
volodya# xhost -ns1
ns1 being removed from access control list
volodya# xhost
access control enabled, only authorized clients can connect
INET:localhost
volodya#
Shh'ing from remote nonX console or ssh'ing back to volodya from
xterm'ed ssh session on ns1 I still able to run xapp. Again when I
log from non X console I have window appeared on remote's X console.
But when DISPLAY variable defined or -display command option given and
access to X allowed.
That's all.
3. Scheme XDMCP. But I beleave it's not relevant to 1st 2 scheme.
"Crist J. Clark" wrote:
> osAndy V. Oleynik wrote,
> [Charset koi8-r unsupported, filtering to ASCII...]
> > Hmm..U ssh'ed from local X host to remote X host?
> > Yes?
>
> In the sense that I am ssh'ing between two machines with X installed
> and X is running on the machine at which I am sitting, yes.
>
> However, I am fairly sure xhost has nothing to do with this. For
> example, I am sitting at a machine at work right now ssh'ed into my
> home PC. My home PC is where the emacs window in which I am writing to
> you is running, but it is (obviously) showing up here on my X machine
> at work. My local machine has only itself in its xhost list (despite
> the fact I am ssh'ed into 2 machines with working X connections). The
> remote machine contains my local machine in its xhosts list. If I try
> to remove it, the removal is successful, but it immediately pops back
> up.
>
> All of that tells me that ssh is doing all of this for me.
>
> Of course, on the machine giving me problems, I cannot verify that it
> is including me in xhosts since the xhost command fails.
> --
> Crist J. Clark cjclark@home.com
>
> To Unsubscribe: send mail to majordomo@FreeBSD.org
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--
WBW Andy V. Oleynik (When U work in virtual office
prime.net.ua's U have good chance to obtain
system administrator virtual money ö%-)
+380442448363
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