Re: launching a remote webbrowser with cygwin

[Andrew McRae <anm at pobox dot com>]

(Apologies; most of this message is really not very Cygwin-specific.)

Chris Bullock wrote:
> What I desire.  I wish to load a very small portion of Cygwin on each 
Windows
> box.  When the user clicks the icon it would then connect to the Linux
> Terminal Server and launch $browser of choice.  First off is this 
possible?
> and if so can someone point me on how to make this happen.  I do not 
want to
> have to run the entire terminal client.  Currently, what we have 
tested is
> from the cygwin prompt we run 'X --query $LTSP:1' but this gives us 
the
> entire terminal server and all I want the users to do is access a 
webbrowser.

That's a slightly odd command line: I would expect you to be saying
    X -query <hostname>

Anyway, the "-query" argument tells the X server that you are launching 
to talk to the display manager on the remote host. Usually, the display 
manager pops up some kind of authentication dialog, and when the user 
is authenticated, it starts up the user's session. In your case, it 
sounds like the user's session is a whole desktop environment (perhaps 
GNOME or KDE?), and that's what you don't want.

(For reference: the X server contacts the display manager using the 
XDMCP protocol; the display manager is also an X client, so once the 
connection is made it can display things back on the X server.)

So it's important to understand that you're already running just the 
part of Cygwin that you need -- the Cygwin X server -- and that all the 
other stuff that you see, and don't want, is running on the Linux 
machine.

There are a couple of different ways you might like to handle the 
problem.

----

1) One approach is to change things on the Linux box so that a user's X 
session just runs an instance of the web browser, not an entire desktop 
environment.

How to do this may depend on what display manager / desktop environment 
you're using. The "traditional" X display manager is "xdm". If you're 
running GNOME, you're probably using "gdm". If you're running KDE, 
you're probably using "kdm".

In each case, though, the display manager ends up running a shell 
script to start the user's session. Usually, the last thing the shell 
script does is to launch a "session manager", which handles starting up 
all the programs that make up the user's environment.

For example, xdm runs a script called "Xsession" to start the user's 
session. The "Xsession" script looks for an executable file named 
".xsession" in the user's home directory. If that's not present, it 
runs "xsm" (the "traditional" X session manager). So under xdm, to make 
a user's session contain just an instance of their web browser, you can 
set up a ".xsession" script in their home directory that just runs the 
web browser. (And to make that change for all users on a system, you 
could modify the "Xsession" script.)

Sorry, I don't have a GNOME or KDE system to hand to give an 
appropriate example; I'm pretty sure that gdm uses ".xsession" in the 
same way; I would guess that kdm does as well.

----

2) Alternatively, you could arrange for your users to specifically 
invoke the web browser. The obvious way to do this is with SSH. Once 
the X server is started, and the DISPLAY environment variable is set 
appropriately, they could run

    ssh -f -X <hostname> mozilla

to run the Mozilla browser, as an example. As long as X forwarding is 
allowed on the server (option "X11Forwarding") this will start an 
instance of the browser on the remote machine that thinks it's talking 
to an X server on the same remote machine, but SSH will forward the X 
traffic back to your local X server.

(The "-X" option may be unnecessary depending on your SSH client 
configuration. The "-f" option puts the SSH process into the 
background, which is probably what you want for interactive use but may 
not be what you want in a script.)

So the process that you need there is: start the X server, wait until 
it's running and ready to accept connections, and start a client. The 
"xinit" and "startx" programs (see their man pages) are designed to 
automate this kind of process.

----

Hope this helps,
Andrew.