Enable VNC on virtualbox-ose >=4.2

If you have:

$ VBoxManage  list extpacks
Extension Packs: 1
Pack no. 0: VNC
Version: 4.2.6_OSE
Revision: 82870
Description: VNC plugin module
VRDE Module: VBoxVNC
Usable: true
Why unusable:

Then you most likely don’t need:

$ VBoxManage setproperty vrdeextpack VNC

Just set per virtual machine settings:

% VBoxManage modifyvm test --vrdeproperty VNCPassword=somepass
% VBoxManage modifyvm test --vrdeauthlibrary null
% VBoxManage modifyvm test --vrdeport 1501
% VBoxHeadless -s test &`

Set vrdeextpack to VNC only if you have other extention packs installed.