Convert Ubuntu Physical machine to Virtual machine

You can run Ubuntu in VirtualBox, via raw disk access. It will use a real disk as if it were a virtual disk.

To convert the disk into an image, see this answer.

You can use VMware vCenter Converter.

From VMWare:

VMware vCenter Converter can run on a wide variety of hardware, and supports most commonly used versions of the Microsoft Windows and Linux operating systems.

Automate and simplify physical to virtual machine conversions as well as conversions between virtual machine formats with VMware vCenter Converter. Use the intuitive wizard-driven interface of VMware vCenter Converter to transform your physical machines to virtual machines.

• Convert Microsoft Windows and Linux-based physical machines and third-party image formats to VMware virtual machines.
• Complete multiple conversions simultaneously with a centralized management console.
• Minimize the number of steps to conversion with easy-to-use wizards.

For more info, and to download it visit VMWare