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Ubuntu VNC


so, you have no graphics card, but you still want GUI management / X Windows……

Perhaps you do have a graphics card but want the convenience of using VNC to reach your Fedora / Ubuntu machine?

There are some great turotials on getting the basics of VNC set up, but it always logs you right into the machine as a specific user…I want to choose my user….VNC + GDM is the answer

VNC + GDM will allow you to fire a vnc viewr at you linux box and have the GDM appear. This information contained below is a collection of personal knowledge and information collected from other postings on some other boards (note: go back and reference some of the contributors).

This mini-tutorial will not cover off security…so if you are doing this..make sure it is on your own network, behind a firewall etc. etc. etc….I hope to come back and add the security pieces in later…just don’t have too much time today.

How it will work
GDM will be running in the background (with no X-Server in this config). When we start a VNC session, VNC will contact the GDM to display the “Greeter”…then we log in as we normally do with GDM locally.

Configure GDM

GDM presents the graphical greeter. To allow VNC to contact the GDM we must turn on XDMCP (Security concious peeps should set their firewall to only allow LOCAL connections for XDMCP – i.e. from the localhost – because VNC is running on the same linux device) – there is another option here to change the XServer that GDM can run to be VNC but I have not explored this option…perhaps later, but for now we’ll do it with XDMCP:
1. Turn on XDMCP

edit /etc/X11/gdm/gdm.conf
find the [xdmcp] section

2. (optional) Turn off XWindows (VNC runs it’s own XWindows)

edit /etc/X11/gdm/gdm.conf
find the [servers] section

Configure VNC
We will have VNC run from xinetd. We will create 2 “services”. One for 800×600 and the other for 1024×768…if you want others, you can extrapolate yourself….800×600 will be available via :0 and 1024×768 as :1 (don’t worry yet if you do not understand what I mean by :0 and :1)

1. Create /etc/services

edit /etc/services
add the following 2 liines:
vnc800 5900/tcp # VNC & GDM
vnc1024 5901/tcp # VNC & GDM

2. create xinetd services

create etc/xinetd.d/vnc800
service vnc800
disable = no
socket_type = stream
protocol = tcp
wait = no
user = nobody
server = /usr/bin/Xvnc
server_args = -inetd -broadcast -geometry 800×600 -depth 16 -once -fp unix/:7100 -securitytypes=none

3. -securitytypes=none means VNC will not ask you to authenticate…we want GDM to do that part…

4. create xinetd services

create etc/xinetd.d/vnc1024
service vnc1024 {
disable = no
socket_type = stream
protocol = tcp
wait = no
user = nobody
server = /usr/bin/Xvnc
server_args = -inetd -broadcast -geometry 800×600 -depth 16 -once -fp unix/:7100 -securitytypes=none


1. stop any X Windows
init 3

2. Log into console (text mode)
3. Turn off “vncserver”…we don’t want VNC to run except for xinetd
chkconfig –level 2345 vncserver off
4. start GDM
init 5
5. start vncviewer
I tested my connection from Win XP…
for 800×600 -> vncviewer localhost:0
for 1024×768 -> vncviewer localhost:1

You should now be able to run a headless (no kbd/mouse/video) linux box with a GUI and GDM greeter….

I know this mini-tutorial is a little thin at the moment, but I only had a few mins to type it up..I will clean it up I promise…if anyone likes it…I could try and write a mini-howto…..anyway…good luck..