[FreeNX-kNX] black screen after authentication

[Johnny Hughes]

Michael Oevermann wrote:
> Am 16.11.2007 um 18:10 schrieb Fabian Franz:
> 
>>> When I do now a
>>>
>>> $ su - user
>>> $ DISPLAY=:1000 xterm
>>>
>>> I get the error
>>>
>>> xterm Xt error: Can't open display: :1000
>> Hm, and nxagent is really listeing on that port? (See ps aux | grep  
>> nxagent)
>>
> 
> No its not, its listening on 1002 (ps aux | grep nxagnet gives
> 
> oeverman  9563  0.1  0.2 70672 22804 ?       S    18:49   0:00 /usr/ 
> lib/NX/nxagent -persistent -R -name NX - oeverman at m01.local:1002 -  
> test (GPL Edition) -option /Users/oeverman/mac/.nx/C- 
> m01.local-1002-0607BEF3DED9220AEDCD57DF09FA6CAF/options -keyboard  
> pc102/ :1002
> 
> With DISPLAY=:1002 xterm I get the xterm on the client machine
> again.
> 
> Its not so easy to give you acces as the machine as it is not  
> reachable from the outside  internet. You would need also access to
> the only machine at our institute which allows connections from  
> outside. I don't know IRC but I will have a look
> at it.
> 
> Michael
> 
>> Perhaps you can give me temporary ssh access via Mail or IRC  
>> (irc.freenode.net, #nx)?
>>
>> Then I could look into it for a moment. Because I am clueless now.
>>
>> cu
>>
>> Fabian

Just as a side note ... I had that same issue on a laptop recently
(black screen after authentication).

In order to troubleshoot this problem, I did new installs on 2 machines
and put EXACTLY the same CentOS packages and configuration on each (the
only difference being hardware ... one was a p3 laptop, the other a p4
server).

The laptop always had the issue of a black scree with nx/freenx, the
server did not.  As I said before, the entire client installs were
identical except hardware.  They were connecting to the exact same NX
server.

I also noticed that I could connect to the "BAD" session (the black
screen) of the laptop with the other (good) machine's NX client.  There
as nothing wrong with the session when it was on the GOOD machine even
though it was blank in the laptop I reconnected to it several times,
from each machine, to be sure, and the session was OK on the good
machine ... and it would be blank on the bad machine.

I then decided that there must be some hardware issue with the laptop
(blank nx screen) that was not present on the server (good machine).

What I tried next was to use system-configure-display to turn the laptop
display from "Millions of Colors (24bit)" to "Thousands of Colors (16 bit)".

This fixed the problem for me, the laptop now creates 16bit connections
on all its connections to the NX server and they work fine.

In this case, there was NO issue on any logs, as the server thought the
connection was fine.  I also had no errors in any of the laptop's logs.

I am not sure if there is a way to tell the NX client to use 16bit
connections instead of 24bit, but you can try setting your client
machine's Display settings to 16bit and see if that helps.

Thanks,
Johnny Hughes

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