Re: Different config options for different X servers?

[Seb Wills <saw27 mrao cam ac uk>]

Brian,

Thanks for the response.

Perhaps I am missing the point, but I don't see how your message relates 
to my query.

My problem was wanting different *gdm2* configurations for different 
xservers. To make it concrete, let's say I want some of my displays to 
have one value for HaltCommand and others to have another value, although 
in fact there are many other configuration options, particularly in 
[greeter] and [gui], which I might want to be different on different 
displays.

Your message seemed to talk about different *xserver* configurations. I am 
already doing this: in my [servers] section I have things like:

 0=Standard
 10=VNC
 11=VNC
 12=VNC

and I define a [server-VNC] section later in the file. This all works 
fine. But as far as I can see it only allows me to specify xserver 
configuration separately, not general options such as HaltCommand, 
GtkTheme etc. Have I misunderstood you?

The solution I initially suggested, which is a bit of a hack, is to allow 
some xservers to be defined as 'remote' even if they are not via XDMCP, 
and then make use of the gdm2's existing capability to set different 
values for some setttings for "remote" servers (e.g. Welcome and 
RemoteWelcome). Basically this would mean not passing the GDM_IS_LOCAL 
environment variable to the greeter for some servers even though the gdm 
daemon does think of that server as local (rather than XMCP). This is a 
bit of hack, although perhaps a useful one given the existance of X 
servers like VNC which do to all intents and purposes provide "remote" 
access but which gdm considers local.

A better solution to the problem would be to allow gdm.conf to contain 
server-specific versions of each of its configuration sections. So as well 
as a global [security] section, there could optionally be a [security-foo]
section which can override default settings in [security] but which only 
applies to the particular server "foo" (i.e. the server defined in a 
[server-foo] section.

Having had a quick look through the source just now, I begin to get an 
idea how this could be implemented. A few options which the gdm daemon 
processes (and which it makes sense to have defined per server) would have 
be to read later than they are now, once the server definitions have been 
parsed. But most of the per-server options are in the parts of the config 
file which are used by the greeter. gdm (the daemon) could pass an 
environment variable to the greeter specifying the name of the server on 
which it is appearing (e.g. "Standard", "foo",...), and gdmlogin could 
check for <section>-<servername>/<key> for each key it reads from the 
config file before checking <section>/<key>. Does this sound reasonable? 
It would allow any configuration option which gdmgreeter reads to be 
configurable either globally (applying to all servers) or per server type.

In your message you talked about people wanting a menu to select the 
xserver config. This seems to me to be a different feature entirely.

Although it's unlikely I would get around to working on this any time 
soon, I'd be interested to what you would think, in priciple, about 
allowing per-server versions of each of the config file sections 
(e.g. [gui-Standard], [gui-foo], [gui-VNC], etc).

Cheers

Seb

Brian wrote:
> Seb wrote:
> > I use gdm to start several local, 'static' X servers. One is an ordinary 
> > X.Org server. The others are Xvnc servers. In reality these provide remote 
> > access (since a remote VNC client of some kind connects to them), although 
> > gdm thinks of them as local X servers because they are not via XDMCP.
> >
> > I'd like to be able to specify different settings for some gdm options for 
> > these two classes of server. For example, I want Reboot and Shutdown 
> > buttons enabled on the local X.Org display, but not on the VNC displays.
> >
> > Is there any way I can do this?
>
> The gdm.conf file does let you specify multiple server configurations,
> but each one is assigned a different DISPLAY value.  So, if you can set
> up your machine to use different displays (via virtual tty's), then this
> might work for you.
>
> > Since gdm already has sensible and/or separately configurable behaviour for 
> > what it thinks of as "remote" logins (i.e. XDMCP), the neatest solution 
> > would be to be able to specify in an X server definition that gdm should 
> > consider it to be a "remote" login even if it is not via XDMCP.
>
> There have been a number of users who have requested that gdm2 support a
> new feature that allows the user to pick the xserver configuration via a
> menu in the login program.  This way if you set up an alternative xserver
> config, it would simply appear in a new menu where you could select it.
> Aside from adding the code to add the menu, this would also require a minor
> change to make use of the selection when starting up the Xserver.
>
> If you wanted to work on patching the code to support this sort of feature,
> I'd be happy to help you understand the code.
>
> > Another option I pondered was running two instances of gdm. I'm guessing 
> > that would get a bit problematic though since gdm integrates so closely 
> > with the system.
>
> Never tried this.  Does sound hacky.  You might be able to get it to work
> if you install gdm2 to different locations.  Though you would probably
> have difficulty getting them to share the same DISPLAY's.
>
> > Any thoughts? I think the ability to define a seemingly-local server as 
> > remote would be a useful feature, and perfect for VNC servers.
>
> I think the best option would be to allow user's to pick the Xserver
> config in the menu.  This would need to be a non-default feature, but
> a flag could be added to the gdm.conf to turn on the menu for this.
>
> --
>
> Brian