Remote X sessions or VNC (was:Re: Headless YellowDog)

[Geert Janssens]

Back to VNC with another series of questions:
 >> Next point: I would like to display the VNC session on my YDL box in
 >> a separate console (or virtual terminal?), like MOL can be run in a
 >> separate console. I haven't managed that just yet. I only can have a
 >> window in my existing X session on my YDL box. What magic should be
 >> performed here ?
 >
 > VNC sessions always run their own X session. But your question here
 > seems to me to ask, "How do you get access to the VNC server's X
 > session from the console?"

1. This goes a bit to fast for me. Apparently, I'm quite confused about 
"console" and "virtual terminal". Maybe you can give some clarification 
on this first ?

2. Then the part about VNC sessions and their own X session: my 
experience here seems to contradict this. Let me explain.
My setup is:
aragorn: server machine in the basement, with an active KDE session on 
vt7, in this session, I have started a program called x0rfbserver (which 
gets started by the mandrake's menu option "Virtual Network Connection).
On g3ydl, I have an active KDE session on vt7 in which I start YDL's 
Remote Desktop Connection. The window I get, is the exact screen of the 
system in the basement, and when I move the mouse, or type something, 
the exact same movements and keys strokes are seen on the screen in the 
basement. So it seems to me the same X session is shared in this case. 
My guess is we're talking about different vnc servers. Is x0rfbserver 
something particular ?

In any case, this setup is not what I want, since it forces me to first 
start a kde session sitting in front of my aragorn box in the basement, 
starting the Virtual Network Connection menu item, and when this one 
crashes (happens consistently if I dare to use the scroll wheel in the 
vnc client on g3ydl) I have to go to the basement again...

3. So my curiosity goes out to vncserver you are referring to. Is this 
TightVNCserver (the only one I found in my Mandrake setup) ?

 > Well, you can't if you're just using
 > "vncserver", but if you just start up another X session on the console
 > that uses the VNC module, you'll be able to do it. Then you'd just VNC
 > to foomachine:1 instead of foomachine:0.4.

4. "Another X session that uses the VNC module"... Do you mean then, as 
in your faq, that on the local machine, I type 'X :1' to get a new X 
session on VT8 ? And next, I don't understand about the VNC module part.

5. In the last sentence, how can I tell the vncviewer to use display 
foomachine:1, instead of foomachine:0.4? Is this by starting vncviewer 
on the command line,after having set the DISPLAY variable ?

Forgive me, if all of these questions seem hopelessly obvious to you. My 
experience with limited to the GUI wrappers that YDL and Mandrake 
provide. And those, of course, don't help at all in undertanding what 
goes on under the hood.

6. Finally, is there some good reference documentation available for VNC 
? That way once I got started, I don't have to overload the list here.

Thanks.

Geert Jan

Longman, Bill wrote:
> So here are some questions that could further improve my VNC experience:
> 
> What is meant exactly with 'servers' in the above quote ? Is this in the
> (for me confusing) context of X where the screen you are working on is 
> the server, and the machine being connected to the client ? If so, what 
> exactly is meant with the :1, :2 and so on ? Until now, I always used :0
> which I was told to do in a former employment in a unix environment.
> 
> = Geert, in the context of VNC servers, you're talking about both a VNC
> server which accepts requests from client VNC sessions *AND* which is
> running an instance of an X server, in the usual X sense. So, I would say
> that a VNC server is two servers for the price of one - a VNC server which
> runs an X server.
> 
> = You know that when an X client connects to an X server, it does so with
> regard to the DISPLAY variable. If your DISPLAY environment variable is
> doppelbock.ales.com:2, your X client will try to send its output to that
> machine on display :2. You therefore necessarily have to have unique server
> identifiers on a given system. The console is generally on :0, but you can
> also run several X sessions on your console. As long as you have enough
> virtual terminals, you can run several of them. I often bring up KDE on my
> :0 and test my apps under Gnome on :1. Same machine, same hardware, just
> different X sessions.
> 
> 
> I understand that I don't need to connect to the local X session on the 
> server in the basement, but VNC can start it's own X session. Great!
> 
> Next point: I would like to display the VNC session on my YDL box in a 
> separate console (or virtual terminal?), like MOL can be run in a 
> separate console. I haven't managed that just yet. I only can have a 
> window in my existing X session on my YDL box. What magic should be 
> performed here ?
> 
> = VNC sessions always run their own X session. But your question here seems
> to me to ask, "How do you get access to the VNC server's X session from the
> console?" Well, you can't if you're just using "vncserver", but if you just
> start up another X session on the console that uses the VNC module, you'll
> be able to do it. Then you'd just VNC to foomachine:1 instead of
> foomachine:0.
> 
> Also, as I am using the system now, when I open the Remote Desktop 
> Connection tool on my YDL box, it starts with the following error
> message:
> 
> "Browsing the network is not possible. You probably did not install SLP 
> support correctly"
> 
> I have no clue what SLP is all about, and even less of a clue how to 
> install it. Any ideas ?
> 
> = SLP is just a multicasting method of device discovery. More and more
> printers are using it, for instance, so unlike the
> broadcast-all-my-printers-on-the-network-every-60-seconds stupidity of CUPS,
> your printer would just subscribe to an SLP instance and anyone else on the
> network would then see its capabilities. WITHOUT BROADCASTING EVERY DAMNED
> MINUTE!
> 
>