Hi

我的xstartup

#!/bin/sh

# Uncomment the following two lines for normal desktop:
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
#exec /etc/X11/xinit/xinitrc

[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
x-terminal-emulator -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &
#x-window-manager &

export DESKTOP_SESSION=Ubuntu
export GDMSESSION=Ubuntu
export STARTUP="/usr/bin/gnome-session --session=Ubuntu"

$STARTUP

我的ubuntu session
root@chao-HP-Z600-Workstation:~/.vnc# cat /usr/share/gnome-session/sessions/ubuntu.session
[GNOME Session]
Name=Ubuntu
RequiredComponents=unity-settings-daemon;compiz;
DesktopName=Unity

http://askubuntu.com/a/150488
How a desktop user GUI session gets started with Ubuntu 12.04-14.04