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Old 10-22-2012, 06:20 PM   #1
Aaron_A_Anderson
LQ Newbie
 
Registered: Oct 2012
Posts: 3

Rep: Reputation: Disabled
Question Debian 6 with Xinetd + XDMCP + tightVNC


Good Evening Ladies and Gentlemen,

first this is my first question here - so if i forgot anything important please let me know i will supply all necessary information asap. Second i already posted this question elsewhere in a different Linux forum - i hope this is in line with the general policy (the desperation level is high).

I am currently trying to set up a server for scientific calculations. The general idea is that all users can log onto the machine via VNC and upon connecting see a normal Gnome login interface where they can log in with their individual accounts having individual home folders etc. So far this already works well.

The problem is now that whenever the VNC session is closed the individual x-servers are also closed - including all the running software. The combination of multi day calculations and a forced windows update (from hell) on the client machines is just one scenario that underlines the absurdity of this situation.

Now the solution for this problem obviously lies in the configuration of the xinetd super server that needs to create XDMCP sessions that dont terminate upon loosing the tcp connection from the VNC session. Also this seems to be straight forward. Xinetd has a general config file /etc/xinetd.conf and individual configurations for the services that are stored in /etc/xinetd.d/

My xinetd.conf looks like this:

Code:
# Simple configuration file for xinetd
#
# Some defaults, and include /etc/xinetd.d/

defaults
{

log_type = SYSLOG daemon info
log_on_success  = HOST PID USERID
log_on_failure  = HOST USERID
cps             = 200 5

}

includedir /etc/xinetd.d

And my service configuration file called "vnc" looks like this
Code:
service vnc-1
{
   disable     = no
   socket_type = stream
   protocol    = tcp
   wait        = yes
   flags       = NOLIBWRAP
   user        = standarduser
   server      = /usr/bin/Xvnc
   server_args = -inetd -query localhost -geometry 1024x768 -depth 16 -rfbauth /home/standarduser/.vnc/passwd
   type        = UNLISTED
   port        = 5900
}
The curx of the bisquit is there the entry "wait = yes". Without this entry everything works just fine - the sessions are just not resumable. Anyhow with it the server is not connectable anymore - but if working it would be resumable - and i would be happy.

The content of my /var/log/demon.log for starting the xinetd daemon:
Code:
Oct 22 23:26:13 atto-calc xinetd[2913]: Reading included configuration file: /etc/xinetd.d/chargen [file=/etc/xinetd.conf] [line=20]
Oct 22 23:26:13 atto-calc xinetd[2913]: Reading included configuration file: /etc/xinetd.d/daytime [file=/etc/xinetd.d/daytime] [line=28]
Oct 22 23:26:13 atto-calc xinetd[2913]: Reading included configuration file: /etc/xinetd.d/discard [file=/etc/xinetd.d/discard] [line=26]
Oct 22 23:26:13 atto-calc xinetd[2913]: Reading included configuration file: /etc/xinetd.d/echo [file=/etc/xinetd.d/echo] [line=25]
Oct 22 23:26:13 atto-calc xinetd[2913]: Reading included configuration file: /etc/xinetd.d/time [file=/etc/xinetd.d/time] [line=26]
Oct 22 23:26:13 atto-calc xinetd[2913]: Reading included configuration file: /etc/xinetd.d/vnc [file=/etc/xinetd.d/vnc] [line=28]
Oct 22 23:26:13 atto-calc xinetd[2913]: added service swat [file=/etc/inetd.conf] [line=39]
Oct 22 23:26:13 atto-calc xinetd[2913]: removing chargen
Oct 22 23:26:13 atto-calc xinetd[2913]: removing chargen
Oct 22 23:26:13 atto-calc xinetd[2913]: removing daytime
Oct 22 23:26:13 atto-calc xinetd[2913]: removing daytime
Oct 22 23:26:13 atto-calc xinetd[2913]: removing discard
Oct 22 23:26:13 atto-calc xinetd[2913]: removing discard
Oct 22 23:26:13 atto-calc xinetd[2913]: removing echo
Oct 22 23:26:13 atto-calc xinetd[2913]: removing echo
Oct 22 23:26:13 atto-calc xinetd[2913]: removing time
Oct 22 23:26:13 atto-calc xinetd[2913]: removing time
Oct 22 23:26:13 atto-calc xinetd[2913]: xinetd Version 2.3.14 started with libwrap loadavg options compiled in.
Oct 22 23:26:13 atto-calc xinetd[2913]: Started working: 7 available services
and the content of the same log as soon as i try to connect to the server with "wait = yes" via "vncconnect localhost:5900"

Code:
Oct 22 23:27:08 atto-calc xinetd[2913]: START: vnc-1 pid=4352 from=<no address>
Oct 22 23:27:08 atto-calc xinetd[2913]: START: vnc-1 pid=4353 from=<no address>
Oct 22 23:27:08 atto-calc xinetd[2913]: START: vnc-1 pid=4354 from=<no address>

(...to infinity and beyond ...)

Some further information:



The relevant parts of my /etc/gdm3/daemon.conf looks like this

Code:
# GDM configuration storage

[security]
DisallowTCP = false

[xdmcp]
Enable = 1
MaxSessions = 30
MaxPending = 60
DisplaysPerHost = 4
MaxWaitIndirect = 40
MaxWait = 40

[greeter]

[chooser]
Further i have explicitly added vnc-1 with 5900/tcp to /etc/services and made corresponding entries in /etc/hosts and /etc/hosts.allow

I also tried several different VNC servers - like tightVNC, turboVNC, x11vnc and vnc4server but it workes with none of them (in combination with xinetd). As of now it seems like the complication lies somewhre with either Xinetd or XDMCP.

There might have been a few things i fixed on the way that i forgot to mention but. Thats the overall picture.

I have no idea anymore what to do. Hopefully you guys can help me out here ...

kind regards
Aaron

Last edited by Aaron_A_Anderson; 10-22-2012 at 06:32 PM. Reason: Adding some details.
 
Old 10-23-2012, 04:09 AM   #2
Aaron_A_Anderson
LQ Newbie
 
Registered: Oct 2012
Posts: 3

Original Poster
Rep: Reputation: Disabled
Update:

I think im getting closer to the issue. From nmap localhost i get:



Code:
Starting Nmap 6.00 ( http://nmap.org ) at 2012-10-23 10:50 CEST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.0000090s latency).
Not shown: 983 closed ports
PORT      STATE SERVICE
(...)
5900/tcp  open  vnc
5902/tcp  open  vnc-2
5903/tcp  open  vnc-3
(...)


However if i do netstat -a
Code:
root@atto-calc:/home/standarduser# netstat -a | grep tcp
(...)
tcp        0      0 *:5902                  *:*                     LISTEN     
tcp        0      0 *:5903                  *:*                     LISTEN        
(...)


Therefore nothing listening on 5900. Now what doesnt make any sense to me is this:
Code:
root@atto-calc:/home/standarduser# netstat -a | grep vnc*
tcp        0      0 *:vnc-1                 *:*                     LISTEN     
tcp        1      0 localhost:vnc-1         localhost:45520         CLOSE_WAIT 
tcp        1      0 localhost:vnc-1         localhost:45518         CLOSE_WAIT
Can anybody enlighten me what the above means?

EDIT: actually this means nothing. Apparently this is just due to the fact that i added vnc-1 with 5900 to /etc/services. Back to square 0.

regards
/Aaron

Last edited by Aaron_A_Anderson; 10-23-2012 at 04:27 AM.
 
Old 10-23-2012, 05:03 AM   #3
Aaron_A_Anderson
LQ Newbie
 
Registered: Oct 2012
Posts: 3

Original Poster
Rep: Reputation: Disabled
[RESOLVED] Well my bad. While trying all the other vnc servers yesterday in a 0-dark-30 manner i must have forgotten to relink Xvnc while doing the testing with vnc4server.

Baseline: with the Xvnc supplied by vnc4server it works. With Xvnc supplied by TurboVNC, TightVNC i couldnt get it working. (x11vnc is a different story but also didnt work properly)

/Cheers
 
  


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