[Ubuntu] setup VNC with GUI desktop

After install gnome-core and vnc4server, there is the script for xstartup


#!/bin/sh

# Uncomment the following two lines for normal desktop:
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
#. /etc/X11/xinit/xinitrc
/usr/bin/gnome-session --session=gnome-classic

[ -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 &


solution from: http://ubuntuforums.org/showthread.php?t=1480094