[LightDM] Setting default X session

[Didier Roche]

Le 11/08/2011 17:48, Robert Ancell a écrit :
> On 20 July 2011 12:52, Сергей<shnatsel at gmail.com>  wrote:
>> In the version from recent Oneiric dailies I've worked it around with
>> setting session=<session name>  under [seat-0] in /etc/lightdm/lightdm.conf,
>> but there are some distribution and dpkg-related issues that are not really
>> lightdm's fault (https://bugs.launchpad.net/bugs/799754), and I'm afraid I
>> can't edit /etc/lightdm/lightdm.conf at all until that bug is fixed (or use
>> very ugly hacks - GRRRR!). Ubuntu seems to use undocumented features of
>> greeter (?!) or something like that, without tweaking lightdm.conf they have
>> the session name passed to the wrapper script as a parameter but I have no
>> idea where do they set it... Oh well. I'm afraid I can only ask Ubuntu
>> engineers about it now.
> If you're using a LightDM 0.9.0+ then the correct config is:
> [SeatDefaults]
> user-session=<session name>
>
> In the current Ubuntu package the default is "gnome", but this is a
> temporary fix.  Didier Roche (cc'd) is working on the correct solution
> so that derivatives can work more easily (the installer (casper) will
> write lightdm.conf, it will be written when first installed, etc).

The default is now "ubuntu" in the Ubuntu package ;)
There is a tool in trunk (since the last 3 days) that we backported in 
Oneiric that I wrote called lightdm-set-defaults (you can find it in 
/usr/lib/lightdm/), which enables you to set the greeter and the default 
session you desire.

Package should in their postinst call this one to set themselves as 
default (using the --keep-old options) and remove them on 
install/removal. For instance:
http://launchpadlibrarian.net/76923334/gnome-session_3.1.3-0ubuntu9_3.1.3-0ubuntu10.diff.gz
to set the default session to "ubuntu" for the ubuntu desktop case.
and:
http://launchpadlibrarian.net/76923333/unity-greeter_0.0.2-0ubuntu1_0.0.2-0ubuntu2.diff.gz
for the greeter.

So basically, installing them will set the first installed one (we don't 
expect having multiple greeters in a CD spin for instance) as the 
default. Then, casper has now a fix for just adding the autologin part 
without hammering those things:
http://launchpadlibrarian.net/77000287/casper_1.277_1.278.diff.gz

Please note that this is very similar to the patches I made for gdm back 
in the lucid days (10.04) which seems to have fit the numerous flavors 
and derivatives we have.

Cheers,
Didier