Problem with XDMCP at Centos 6.x x64 (6.3 included)

General support questions

Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby georgeb » 2012/07/11 07:33:02

I have problem connect to my Centos 6.x x64 machines using a x server. This was never an issue with 5.x. Please help.
I have disable firewall, and my /etc/gdm/custom.conf is like

[xdmcp]
Enable=true
DisplaysPerHost=10
HonorIndirect=false
MaxPending=4
MaxSessions=32
MaxWait=30
MaxWaitIndirect=30
Port=177

[daemon]
User=gdm
Group=gdm

[security]
DisallowTCP=false
AllowRemoteRoot=true

[chooser]
Multicast=false

[debug]
Enable=false
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Re: Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby pschaff » 2012/07/11 15:50:53

Welcome to the CentOS fora. Please see the recommended reading for new users linked in my signature.

You have not provided enough information. Are you attempting a remote connection or local? Exactly what problems are you having, including the environment on which the X server is running, and any error messages? Why did you change the default GDM configuration?
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Re: Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby georgeb » 2012/07/11 22:27:51

I am trying to connect from windows to Centos 6.3 x64. I have tried two x-servers for windows, x-ming and netsarang, so far with no success.
I also tried from an ubuntu box again with no success.
The default GDM configuration is just an empty template file , with xdmcp disabled.
The same config with centos 6 x86 works fine. At /var/log/greeter there are messages like

** (:2452): DEBUG: Client registered with session manager: /org/gnome/SessionManager/Client1
** (process:2468): DEBUG: Greeter session pid=2468 display=:0.0 xauthority=/var/run/gdm/auth-for-gdm-V7h04k/database

(polkit-gnome-authentication-agent-1:2464): GLib-GObject-WARNING **: cannot register existing type `_PolkitError'

(polkit-gnome-authentication-agent-1:2464): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
Failed to play sound: File or data not found
gdm-simple-greeter[2468]: Gtk-WARNING: gtkwidget.c:5460: widget not within a GtkWindow
Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x1e0002b (Login Wind)
Window manager warning: meta_window_activate called by a pager with a 0 timestamp; the pager needs to be fixed.
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Re: Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby pschaff » 2012/07/12 13:42:54

A forum search will turn up some similar problems, but I don't know a direct solution. Running a display manager remotely is generally not a good idea. If running an X server, then running a display manager locally on the X server system, and just starting X applications on the remote system is usually preferable for performance reasons. Another approach is to forget the local X server and use VNC or NX/FreeNX.
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Re: Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby draker » 2012/11/09 03:17:57

pschaff wrote:
A forum search will turn up some similar problems, but I don't know a direct solution. Running a display manager remotely is generally not a good idea. If running an X server, then running a display manager locally on the X server system, and just starting X applications on the remote system is usually preferable for performance reasons. Another approach is to forget the local X server and use VNC or NX/FreeNX.


I registered for this site just so I could scold you for your attitude. When I started using Linux the attitude was "Cool, how did you do that? Will you help me do that? Thanks!"
Now the attitude is "Why are you trying to do that? You shouldn't do that. You should do this instead". Terrible.

There are plenty of reasons to run XDMCP, the one I've been struggling with lately is for use with SunRay thinclients. Flatly saying that it's "not a good idea" is not helpful. A reminder of the pitfalls (e.g. in the clear authentication) would be better.

From my perspective, gdm is just the wrong tool for the job. I'm not sure what it is good for, but it seems like xdm with all the best features disabled and an intentionally obfuscated configuration syntax. If the SunRays didn't expect gdm explicity I would have given up on it ages ago.

Best of luck with the original project...

Edit:
Oh -- I found the answer here: http://www.se.cuhk.edu.hk/~hmleung/wordpress/?p=1278
In short, make sure you have:

[greeter]
IncludeAll=true

(or =false, it controls who shows up on the user list).
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Re: Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby draker » 2012/11/09 03:35:21

Now what I would really like to know is how to disable the console X server on CentOS 6?

On CentOS 5 I could put '--no-console at the end of the prefdm line in /etcinittab.

I can do the same in CentOS 6 by editing /etc/init/prefdm.conf, but alas, gdm has lost the ability to understand that option.
As a result, it starts Xorg on my server five times before it gives up.

I would RTFM but gdm doesn't even have a man page on CentOS 6 anymore. Is it just me, or does the contempt the gdm developers have for regular users know no bounds?
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Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby toracat » 2012/11/09 06:28:04

draker wrote:

I registered for this site just so I could scold you for your attitude. When I started using Linux the attitude was "Cool, how did you do that? Will you help me do that? Thanks!"
Now the attitude is "Why are you trying to do that? You shouldn't do that. You should do this instead". Terrible.

I am not certain what you are referring to by "attitude". If I got to the original question before pschaff did, I would have given the same suggestion. In his helpful response, he was not forcing the OP to do anything. His advice was quite appropriate and indeed provided possible solutions.
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Re: Problem with XDMCP at Centos 6.x x64 (6.3 included)

Postby toracat » 2012/11/09 06:31:09

draker wrote:
Now what I would really like to know is how to disable the console X server on CentOS 6?

Please do not hijack other's thread. Instead, start a new one. If necessary, you can quote this thread for reference.
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