Virtualization allows you to run multiple operating systems (OS) on a single machine without rebooting the machine each time you want to use a different OS. You can use it for testing or for reducing the amount of physical machines that you have running at once.
VirtualBox is a free virtualization product from Oracle. The software is licensed under the GNU General Public License (GPL).
To get started, download and install the correct binaries for the operating system that is currently installed on your computer. This is called the host operating system. There are binaries available for the Windows, Linux, Mac OSX and OpenSolaris operating systems. There are some platform specific differences in the installation phase, so read the User Manual section for your host system before installing the software.
Once you have the VirtualBox software installed on the host system, you can add as many guest operating systems as you like. A guest OS is an operating system that runs on top of the host operating system. You should remember that each guest will take up system resources while it is running. So, in theory you could have 10 virtual servers running at the same time, but your hardware may not support it.
To install each guest OS, you will need the installation media. If you are installing a free OS, such as Linux or OpenSolaris, you can download the ISO image. Otherwise, you will have to purchase media. VirtualBox can install the guest OS directly from an ISO image, or it can install it from the computer’s CD or DVD drive.
Open the VirtualBox program and click the “New” button. Give the guest OS a name an choose the operating system and type that you are going to install. The name should be descriptive, if you are going to be installing more than one guest OS.
On the next screen, choose the base memory size for the guest OS. When the OS is running, the amount of RAM specified here will be dedicated to the OS. Make sure you allocate enough memory to run the guest, but not so much that the host is in a deficit.
Create the hard drive for the guest. This is space set aside on the physical hard drive for the guest. Normally, you will create a new drive for each OS.
Decide whether you want a fixed size hard drive, or a dynamically expanding drive. Creating a fixed size hard drive will cause VirtualBox to set aside exactly that amount of space on the physical drive. This space will not be usable by any other OS. Creating a dynamically expanding hard drive will cause VirtualBox to set aside a small amount of space on the physical drive. More space will be added to the virtual hard drive when it is needed. Choose an appropriate size for the guest hard drive. Whether dynamic or fixed, this number is the maximum size for the hard drive.
When the RAM and disk space for the guest OS has been allocated, right click on the name of the guest on the left side of the screen and choose settings. Click the CD/DVD-ROM option and mount the installation media, either the CD-ROM or an ISO image. Click the OK button to save the settings change.
Click on the Start button in the tool bar and VirtualBox will start the installation process for the guest OS. A new window will open for the guest. The installation process will be the same as if you are installing it directly on the hardware. Once the installation process is completed, the guest is ready to be used.
Install the guest addition software for the guest OS to integrate the guest with the host. Otherwise, the guest OS will capture the mouse and you will have to use special keystrokes to release it. Once the guest additions are installed, you will also be able to share data between the guest and the host.
For more details, do check out VirtualBox for all your virtualization needs.