Quoted: http://seb.so/vnc-from-boot-without-logging-in-ubuntu-lubuntu-xubuntu-and-mint-lmde/

Instructions

LightDM apparently supports a VNC server out of the box; however, it’s designed to work with tightvncserver (or similar) which create separate X sessions (the 2nd lot of VNC servers I mentioned above) so not quite what we’re after1.
Ubuntu derivatives use Upstart (upstart.ubuntu.com) to manage startup processes - LightDM (and GDM!) creates a login-session-start event when the display manager is up (i.e. when X is all loaded, but before you’ve logged in) so we’ll create an upstart job that listens for that, and starts a VNC server on the existing X session, allowing connections before login.
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$ sudo apt-get install numlockx
$ sudo gedit /etc/lightdm/lightdm.conf
add this line at he end
greeter-setup-script=/usr/bin/numlockx on

Get exFat support for Ubuntu 10.04 LTS.

Get fuse-exfat
$ sudo add-apt-reprository ppa:relan/exfat
$ sudo apt-get update
$ sudo apt-get install fuse-exfat

Create mount point.
$ sudo mkdir /media/Data

Manually mount:
$ sudo mount -t exfat-fuse /dev/sda6 /media/Data
umount:
$ sudo umount /media/Data

Automatically mount (by edit fstab):
$ sudo gedit /etc/fstab
add new line
/dev/sda6 /media/Data exfat-fuse defaults 0 0
save and restart.

*1 '/dev/sda6' is Device ID, could be '/dev/sdXX', such as '/dev/sdb1', please check in Disk Utility.
*2 Someone says, update util-linux-ng 2.17 to 2.18, ubuntu will identify exfat automatically, but still need fuse-exfat. (actually not test)