HOWTO: Setting up a VNC to GDM connection

[intangible]

This howto is to show how to setup VNC to show a GDM login screen when you connect to your Ubuntu box, effectively using XDMCP over VNC. A VNC client is easier to get going on Windows than a X server for most people, so here's how to use it to connect to your linux box.

I posted the instructions in another thread already, but decided to put them here as well so it's easier to find for everyone.

First thing you'll need to do is enable the universe repositories: https://wiki.ubuntu.com//AddingRepositoriesHowto

Then it's just five easy steps:

1. System->Administration->Login Screen Setup
   Tab XDMCP->Enable XDMCP You can disable "Honor Indirect Requests"
   For kdm or even xdm, just look through the settings and find XDMCP, make sure it's enabled.
2. sudo apt-get install vnc4server (comes from universe)
3. Put the following line at the end of /etc/inetd.conf:
   

   5900    stream  tcp     nowait  nobody  /usr/bin/Xvnc Xvnc -inetd -desktop=Server -query localhost -IdleTimeout 7200 -depth 16 -once securitytypes=none

   Replace "Server" with something you want the window title to be, usually the server name.
4. sudo /etc/init.d/inetd restart
5. Log out of your desktop (to restart gdm, xdm, or kdm)

That's it! Try connecting from another machine using and see how it goes.

If you need a VNC client for Windows, try out UltraVNC http://ultravnc.sf.net it's the one I prefer.

For connecting from Linux vnc4viewer with tsclient work well.

[dazzla]

Excellent, i'd gone about things slightly different and set up a different user for each WM. This is a much simpler method.

Although i did have a problem getting it to work initially, i changed the user from nobody to my usual user account in "/etc/inetd.conf" and it all worked fine. Will this present me any problems?

[intangible]

The problem I might be worried about is that if you're using "securitytypes=none" like I posted, and you are letting the Xvnc process run as yourself, you might have given people a way into your account without a password. But I haven't seen your configuration so you may be safe.

[spacemonkey]

I tried this with my server install of ubuntu that has XDM on it, and it didn't seem to work. I assume that I didn't set up XDMCP properly on it. In Xaccess I uncommented the '*' line so it would allow any host, then I commented out the "DisplayManager.requestPort: 0" line in xdm-config to allow connections. Then I followed your howto. When I try to connect using vncviewer I get this:

ReadFromRFBServer: rdr::EndOfStream

Any suggestions would be greatly appreciated...I would love to be able to manage my server from my desktop using more than just the terminal via SSH.

[slimsam1]

I just wanted to say thank you. It worked great for me. I am using this method to administer a headless/keyboardless/mouseless backup server.

[intangible]

Ok, sorry, there are two things to do if you use XDM:
I installed xdm just to get to the right settings for ya .

1. Put a # before the last line in /etc/X11/xdm/xdm-config so it looks like this:
#DisplayManager.requestPort: 0

2. Only localhost is connecting back to XDM through VNC, so you only have to do is add "localhost" to /etc/X11/xdm/Xaccess. Only the VNC client connects to the remote host.

Restart XDM and there ya go!

[intangible]

Glad I helped.

Since you are running it headless, you made sure to disable the local X server to save yourself some memory, right?
If not, just comment out the 0=Standard line in the [servers] section in /etc/X11/gdm/gdm.conf.

[Blackie_Chan]

I am using gdm which doesn't have Xaccess so how do I change who has access to VNC?

Thanks in advance.

BTW, at the moment I can 'vncviewer localhost' and the vnc window will open, but if I type 'vncviewer my WAN IP' the window doesn't open, seems like nothing happens.

[zaguar]

Is this secure? ie. is it possible for a hacker to enter the system with VNC enabled?

[oofnik]

I am using gdm which doesn't have Xaccess so how do I change who has access to VNC?

Thanks in advance.

BTW, at the moment I can 'vncviewer localhost' and the vnc window will open, but if I type 'vncviewer my WAN IP' the window doesn't open, seems like nothing happens.

You probably just need to forward port 5900 to your LAN IP in your router settings.