[Bug 471726] Re: x2x sharing problem i karmic

[RCJ]

I found a way to make x2x work, I wouldn't call it a solution but it
points to what is missing when you get this error.  The xauth authority
file used when tunneling X through ssh does not have the cookie for the
X server.

Setup:
 - 2 machines, called 'desktop' and 'laptop' where x2x is run on the laptop.
 - Run 'ssh -XC laptop x2x -east -to :0.0' from desktop
 - Error seen: 'x2x - error: can not open display :0'

>From the desktop:
# ssh -X laptop 'xauth info'
Authority file:       /home/user/.Xauthority
File new:             no
File locked:          no
Number of entries:    2
Changes honored:      yes
Changes made:         no
Current input:        (argv):1

# ssh -X laptop 'xauth list'
laptop/unix:10  MIT-MAGIC-COOKIE-1  84924c4306f8234702fe1cec2c821c8f

>From the laptop:
# xauth info
Authority file:       /var/run/gdm/auth-for-user-w9KmhU/database
File new:             no
File locked:          no
Number of entries:    1
Changes honored:      yes
Changes made:         no
Current input:        (argv):1

# xauth list
laptop/unix:0  MIT-MAGIC-COOKIE-1  007d71f327f9cf279ff3c5fb9d21b5a7

At this point the ssh session from the desktop to the laptop has a
cookie for display :10 only.  So the message regarding a failure to open
:0 isn't a big surprise.  I resolved this by running the following from
the desktop:

# ssh -X laptop 'xauth merge /var/run/gdm/auth-for-user-w9KmhU/database'

After this is run, you can check that the cookie has been added for :0
by running:

# ssh -X laptop 'xauth list'
laptop/unix:0  MIT-MAGIC-COOKIE-1  007d71f327f9cf279ff3c5fb9d21b5a7
laptop/unix:10  MIT-MAGIC-COOKIE-1  84924c4306f8234702fe1cec2c821c8f

>From there I can run:

# ssh -X laptop 'x2x -east -to :0.0'

Here's the caveat, the cookie (and the file it's stored in) for :0
changes each time you log in on the remote machine (in this case,
'laptop').  Here's the output on the laptop after logging out and back
into X.

# xauth info
Authority file:       /var/run/gdm/auth-for-user-u4JpYD/database
File new:             no
File locked:          no
Number of entries:    1
Changes honored:      yes
Changes made:         no
Current input:        (argv):1

# xauth list
laptop/unix:0  MIT-MAGIC-COOKIE-1  149afc922a496cae086650e10f113bf5

At this point, the command 'ssh -X laptop x2x -east -to :0.0' will again
fail.  I cleaned up by running 'ssh -X laptop xauth remove
laptop/unix:0' so that I only had a cookie entry for :10 at this point.

I don't have a real solution, but I hope this helps improve the
understanding of the problem.

-- 
x2x sharing problem i karmic
https://bugs.launchpad.net/bugs/471726
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