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Free hypervisor adds virtual machine cloning

Jul 19, 2011 — by LinuxDevices Staff — from the LinuxDevices Archive — 2 views

Oracle released a new version of its free virtualization software, now offering an easy way to clone virtual machines (VMs). VirtualBox 4.1 also includes a memory limit increase to 1TB for 64-bit hosts, guest support for Windows Aero, a new UDP networking tunnel for interconnecting VMs, and support for SATA hard disk hotplugging, among other cited new features.

Oracle's VirtualBox 4.x is a type 2 ("hosted") hypervisor, which requires a host operating system and then allows virtual machines to run on top of that host. It's distinct from type 1 ("bare metal") hypervisors, which theoretically offer more robustness and require less physical memory to operate.

As such, VirtualBox is similar to hypervisors from companies such as Parallels and VMWare, with comparable ease of use. Unlike these, however, it is offered for free — a tradition that Sun began when it bought developer Innotek, and which is now being continued by Oracle.

VirtualBox supports several host operating systems, including Windows, Mac OS X, most flavors of Linux (including Oracle Linux) and Oracle Solaris. It gained an easier-to-user interface and other new capabilities (see later in this story) when it was updated to version 4.0 last December.

The VirtualBox user interface (below), called VirtualBox Manager, provides a graphical preview of suspended virtual machines. In addition, virtual machines — including snapshots, saved states, and disk images — could be deleted in a single step as of version 4.0.

VirtualBox Manager
(Click to enlarge)

However, in Virtual Box 4.0 users could also make snapshots of a virtual machine, preserving an operating system state they could fall back to in case of subsequent mishaps. But there was no way to copy these snapshots to servers or otherwise share them with others.

Version 4.1 now provides users with an easy way to create clones (below) of virtual machines. These become independent entities that have a life of their own, according to Oracle.

Cloning a virtual machine
(Click to enlarge)

Wim Coekaerts, senior vice president of Oracle Linux and Virtualization Engineering, was quoted by eWEEK as saying, "Right now, when you have a virtual machine running, you create a snapshot, which is a child of the current virtual machine. But that's not something that can independently grow afterwards. With a clone, you have a new entity that can then have its own life and, subsequently, its own snapshots."

A host of other new features and fixes noted in the VirtualBox 4.1 changelog include:

  • an enhanced wizard for creating new virtual disks
  • an memory limit increase to 1TB for 64-bit hosts
  • an experimental WDDM graphics driver that supports Windows Aero and provides Direct3D support using a "cleaner approach" (no need to install the guest drivers in Safe Mode any more
  • a new UDP networking tunnel that "allows interconnect VMs running on different hosts easily and transparently"
  • support for SATA hard disk hotplugging


As noted above, Oracle released a significant VirtualBox 4.0 upgrade at the end of last year. At the time, improvements in performance and functionality are said to include:

  • the ability for 32-bit hosts to offer more than 1.5GB or 2GB of RAM to guest operating systems
  • emulation of Intel's ICH9 chipset, with PCI, PCI Express, and MSI (message signaled interrupts)
  • Intel HD audio
  • support for limiting a virtual machine's CPU time and I/O bandwidth

Oracle said at the time that Virtual Box 4.0 could now resize disk images, as well as exporting virtual machines from one format to another more rapidly. It can also package disk image files and their associated XML descriptions into the OVA (open virtualization format archive) format, the company added.

VirtualBox 4.1 running Windows 8, Linux, and Android virtual machines (with Apple's OS X as the host OS)
(Click to enlarge)

The way Virtual Box 4.0 is distributed and its licensing details also changed somewhat. Previously, Oracle offered an Open Source Edition (OSE), whose source code was available and which needed to be complied before use, and a main release with a ready-to-go-installer: Only the latter had full USB functionality and RDP (remote desktop protocol) support.

Now, Virtual Box is available in both source code and installer formats (covered by the GNU GPL v2 license), but USB 2.0 and RDP support have been moved to a separate extension pack, which is released under the Personal Use and Evaluation License (PUEL). Users whose existing virtual machines have USB 2.0 drivers will have to download and install the extension pack, as we discovered in our testing.

While Virtual Box and the one available extension pack remain free, it's possible Oracle (or third parties) will be releasing paid packs with additional hardware support. Meanwhile, Coekaerts said in December, the continuing investment Oracle is making in its Sun Microsystems-related open source-based products such as VirtualBox and OpenOffice is quite apparent.

Further information

Comprehensive documentation and downloads may be found on Oracle's website or at

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