Virtualbox 4.0.12 in Lubuntu

Summary:
1. Modified a system file
2. Download, register a public key
3. Download virtualbox package for Ubuntu 11.04 (Natty)

Installing Virtualbox 4.0.12 on Lubuntu 11.04 (Natty)

1. Modified the sources.list file

sudo nano /etc/apt/sources.list

insert the following line

deb http://download.virtualbox.org/virtualbox/debian natty contrib

and save the modifications.
2. Download and register the Oracle public key

wget -q http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc -O- | sudo apt-key add -

3. Run these:

sudo apt-get update
sudo apt-get install virtualbox-4.0

4. Download and install the Virtualbox extension pack
5. Add user login to the vboxusers group (under System Tools > Users and Groups)