$> cat /usr/share/xsessions/compiz.desktop 

[Desktop Entry]

Encoding=UTF-8

Name=Compiz

Comment=This session logs you into GNONE with Compiz enabled

Exec=/usr/local/bin/compiz.sh

# no icon yet, only the top three are currently used

Icon=

Type=Application

X-Ubuntu-Gettext-Domain=gnome-session-2.0



$> cat /usr/local/bin/compiz.sh 

#!/bin/sh

# $Revision: 1.3 $

# Luis Mondesi < lemsx1@gmail.com >

#

# DESCRIPTION: A script to start a gnome session under gdm with Compiz+gnome-window-decorator

#EOF

# USAGE: compiz.sh

# LICENSE: GPL

# NOTES:

# * http://lems.kiskeyix.org/puntoyaparte/index.php?story_id=58

# * https://wiki.ubuntu.com/XglHowto

# * https://wiki.nurd.se/global:howto:xgl:session

# * Assumes that you are creating a file named:

##> cat > /usr/share/xsessions/compiz.desktop <<EOF

#[Desktop Entry]

#Encoding=UTF-8

#Name=Compiz

#Comment=This session logs you into GNONE with Compiz enabled

#Exec=/usr/local/bin/compiz.sh

## no icon yet, only the top three are currently used

#Icon=

#Type=Application

#X-Ubuntu-Gettext-Domain=gnome-session-2.0

#EOF

# 

# Now, in gdm.conf-custom you need:

##> cat /etc/gdm/gdm.conf-custom

# [server-Standard]

# name=Xgl server

# command=/usr/bin/Xgl -fullscreen -ac -accel xv -accel glx:pbuffer

# flexible=true

# 

# NOTE thatt :1 is not needed here as gdm will do that for you in the following

# line.

#

# And finally, in /etc/gdm/gdm.conf you need to change:

# 0=Standard to 1=Standard:

##0=Standard

#1=Standard

#

# Now when gdm start, make sure you select your new "compiz" session

#



MY_DISPLAY=:0



# assumes Xgl was launched as:

#Xgl $MY_DISPLAY -ac -accel xv -accel glx:pbuffer -fullscreen &



# and since that takes a little while to load, we sleep for 5 seconds...

#sleep 2



# ATI's drivers couldn't start Xgl on :0.0 because the driver wrongly attempts 

# to open :0.0 even if the display is set to :93.0 (as Xgl does by default)

# so, we force the whole thing to go to :1.0 as defined in MY_DISPLAY

if [ -z "$DISPLAY" -o "x$DISPLAY" = "x:0" -o "x$DISPLAY" = "x:0.0" ]; then

    DISPLAY=$MY_DISPLAY

    export DISPLAY

fi



gnome-window-decorator &

sleep 1

compiz --replace gconf # no need to background this. it will do it alone

sleep 1



# this is the proper way to start gnome-session. We need ssh-agent and dbus-launch first

#/usr/bin/ssh-agent /usr/bin/dbus-launch --exit-with-session 

exec /usr/bin/gnome-session