[Natty] Unity will start from GDM, not from KDM

Bug Description

Binary package hint: unity

Unity won't start,

Finally found the reason ;-)

On 5 machines I upgraded from Maverick to Natty, Unity doesn't start on any of them.

However all my machines have both kubuntu-desktop and ubuntu-desktop installed, and use KDM as graphical login manager.

Starting the "Ubuntu" session from KDM will open a session where Unity doesn't start (only desktop background comes up)

Stopping KDM (sudo stop kdm), then starting GDM (sudo start gdm), logging into the "Ubuntu" session from GDM, and then unity works.

This being perfectly reproductible on all machines I tested it on (all upgraded from Maverick to Natty).

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: unity 3.8.10-0ubuntu2
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
Architecture: i386
CheckboxSubmission: 1ea6109db29b53f721a523a77b7f3abf
CheckboxSystem: d00f84de8a555815fa1c4660280da308
CompizPlugins: [core,bailer,detection,composite,opengl,decor,mousepoll,vpswitch,regex,animation,snap,expo,move,compiztoolbox,place,grid,imgpng,gnomecompat,wall,ezoom,workarounds,staticswitcher,resize,fade,unitymtgrabhandles,scale,session,unityshell]
Date: Thu Apr 28 17:49:31 2011
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
ProcEnviron:
LANGUAGE=fr_FR:en
PATH=(custom, user)
LANG=fr_FR.UTF-8
SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: Upgraded to natty on 2011年04月03日 (25 days ago)

Thanks for your bug report and help to make ubuntu better.

We base all our session switching on the GDMSESSION variable, this has to be switche to something else in oneiric generic between all DM (even lightdm?).

This is how I managed to start unity from KDM:

1) aptitude install unity compiz-gnome

apparently unity needs compiz-core to run, but it does not require it on its dependencies and it is not installed by default on a kubuntu-desktop machine.

2) add 'export GDMSESSION="$DESKTOP_SESSION" ' on top of /etc/kde4/kdm/Xsession
this is executed by kdm at user's login and fixes the environment variable issue.

This worked perfectly for me and I hope can help all KDE fans to enjoy the brand new, and much discussed, user interface.

By the way can "$DESKTOP_SESSION" be a candidate for a DM independent variable?

Setting 'export GDMSESSION="$DESKTOP_SESSION' at the top of /etc/kde4/kdm/Xsession didn't work for me. It appeared I already had compiz-gnome, unity, and compiz-core installed, so I didn't bother with that step.

Setting 'export GDMSESSION="$DESKTOP_SESSION' help me. Thank you.

I did some more playing around with this and I found my GDMSESSION variable is set to "default". If I add:

export GDMSESSION="$DESKTOP_SESSION"

if [ "$GDMSESSION" = "default" ] ; then
export GDMSESSION=gnome
fi

then Unity will start correctly. It doesn't seem to cause any problems if the session type is changed prior to login either.
I'm not sure why just 'export GDMSESSION="$DESKTOP_SESSION"' doesn't work for me, but I've tested this over several 11.04 x86_64 installs now using a clean (no data/config in the $HOME directory) account.

Could this line be added to the file by default in the package? I have the option to log in automatically set in KDM and I tried to log in to Unity just to find that I couldn't get the unity interface at all. I couldn't even log out and the only possibility was to kill kdm and start again but as it tries to resume the last session I get stuck and I can't use KDM. I don't think I'm the only one that could be affected by this problem.

UP !

This bug has been reported 2 months 1/2 ago. It prevents starting Ubuntu's main "Unity" environment from KDM. So it should be rated "CRITICAL".

A 4-lines script fix has been proposed in comment #6. This fix works and would be trivial to package.

So WTF ?

KDM 4.7 should export DESKTOP_SESSION=foo, where foo is the name of the desktop file foo.desktop. Thus it should work just fine in Oneiric.

Thank you for reporting this bug to Ubuntu. 11.04 reached EOL.
See this document for currently supported Ubuntu releases: https://wiki.ubuntu.com/Releases

Please upgrade to the latest version and re-test. If the bug is still reproducible, increase the verbosity of the steps to recreate it so we can try again.

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