RFC: GDM in Karmic

Cody A.W. Somerville cody-somerville at ubuntu.com
Sat Jul 25 15:14:57 UTC 2009

Hello Folks,

 As you may or may not be aware, the developers of the gnome display manager
(GDM) began a major rewrite with version 2.21. Now at 2.27.x, the Ubuntu
development team has determined the new GDM ready for inclusion in Ubuntu
and as such uploaded this new version a few weeks ago. Unfortunately, the
new GDM heavily relies on a number of gnome desktop components currently
such as gnome-session, metacity, gnome-settings-daemon, etc. The reason for
this is because the new gdm effectively logs in as the gdm user, start a
minimal gnome environment, and launches a GTK application to provide a login

 Luckily I've been able to patch the gdm package to actually start and to
not pull in most of gnome like it was but the experience is still horrible.
Because gnome-settings-daemon is not running, nothing is themed and there is
no background. Because metacity is not running, you don't have any window
decorations. Because gnome-session is waiting for said applications (this is
just a hypothesis) to register with it, the cursor is always the busy
cursor. Other problems include but are not limited to the inability to set
the default session (except by adding a .dmrc file to /etc/skel - eww), and
no more gdm-cdd config (it now uses gconfd).

 One possible solution is to try and use xfce4 applications/components where
possible (gdm is hard coded to start gnome-session
--autostart=/usr/share/gdm/autostart/LoginWindow/ - as you might have
guessed, /usr/share/gdm/autostart/LoginWindow/ contains desktop files to be
used by gnome-session to launch our friends like gnome-settings-daemon,
metacity, gdm-simple-greeter or whatever). From initial investigations, the
effort could possibly involve patching gdm, gdm-simple-greeter,
xfce4-session, xfwm4, and more... which would be a lot of work for no
guarantee that we'll be able to end up with something we're happy with in
time for karmic.

 Another solution that quickly comes to mind is the use of another desktop
manager. Thus far I've evaluated slim and xdm and found them unsuitable.
Luckily, there appears there might be some other solutions still to be
investigated. If you know of anything, please send me a private e-mail with

 A third solution would be to reupload the 2.20.x series of GDM (the gdm we
know and for the most part love) under a new name (such as gdm-2.20,
gdm-legacy, or something) and use that. Its the least amount of work and its
been doing the job. The biggest drawback to this is that the 2.20.x series
is no longer supported/maintained by upstream so we'll not be able to run to
gdm's developers for bug fixes and we certainly can't expect any new
features. However, I'm personally starting to feel that this would be the
best option for Karmic as all this option requires is a decision (which I'd
like to make with consensus of the team and involved folks from the
community) and we can continue to work on integrating the new gdm and then
ship it when *we're ready* to do so.


Cody A.W. Somerville
Software Systems Release Engineer
Foundations Team
Custom Engineering Solutions Group
Canonical OEM Services
Phone: +1-781-850-2087
Cell: +1-506-471-8402
Email: cody.somerville at canonical.com
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