I used to setup my xstartup like this in Ubuntu 12.04 as below and it worked fine.
#!/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-2d
export GDMSESSION=ubuntu-2d
export STARTUP="/usr/bin/gnome-session --session=ubuntu-2d"
$STARTUP
But now I transfered to Ubuntu 14.10, but what I've got is only a dark desktop with only a gnome-terminal. Under /usr/share/gnome-session/sessions/, there are no longer ubuntu-2d.session, but only ubuntu.session now. So I changed the 3 ubuntu-2d to ubuntu, but still the same situation. Anyone got any idea how to fix this?
PS: I don't want to use gnome-desktop, I just want to use unity... That's the problem.