Data Center

You can run multiple Virtual OS instances from within a Host OS using Virtual Box

If you want to run an application in another operating system from your computer, you either need to reboot the system (provided the other operating system is installed in dual boot) (or) use another computer for the same. But with an open source based cross platform virtualization application called Virtual Box, its possible to run multiple operating systems/ applications from within the current operating system. Well, there is more. Read on to find out…

If you are working on Windows (for example), but want to play a game that is available only on Linux, you could just click and open a Linux Virtual Machine (which opens in a separate window, side by side without disturbing your existing operating system/ applications) and play the game. You could just close the window after you are finished playing it!

That’s the advantage of Virtualization. Its possible to open and work on Virtual Machines – each with its own operating system and applications, simultaneously without the need to re-boot the system. Of course, these virtual machines and applications need to have been installed previously from within your primary (or host) operating system.

Generally, Server Virtualization consists of a bare-metal hypervisor, which attaches itself directly to the machine hardware. And the various operating systems / applications are installed over it. But with Virtual Box, a host (primary) operating system needs to be installed first on the machine, and then the other operating systems/ applications are installed as Virtual Machines from the host (primary) operating system.

While installing Virtual Box, two things need to be manually selected for each VM (Virtual Machine). One, the amount of RAM (Random Access Memory) that needs to be designated for each Virtual Machine. This is an important setting because, when this VM is running, the designated amount of RAM is reserved for this VM, which is borrowed from the host (primary) system’s RAM. Two, the amount of hard disk space that needs to be designated for each VM. Again, this is also borrowed from the host (primary) system’s Hard disk when the VM is in use.

But designating the hard disk space can be done either by specifying a fixed capacity of hard disk space (or) by allowing it to occupy variable  (dynamically expanding) space – more space, as more data is loaded to the VM. The hard disk space is allocated to VM’s by creating an image file in the primary (host) system’s hard disk. This image file can be copied intact with all its settings, moved to another system and opened with Virtual Box installed there, if required.

Its even possible to share some folders located in the host (primary) operating system so that they can be accessed from within the Virtual Machines (VM). Virtual Box supports Snapshots. So, its possible to back up the current state (and configuration settings) of the system as a file, and the machine can be restored to that state whenever required later. And, when the Virtual Machine is closed (by closing the window), it can either save the current state (to be opened later), or shut down the Virtual Machine.

Its possible to export the Virtual Machines and their configurations/ settings etc, using a OVF Format File (Open Virtualization Format) so that they can even be opened with some other virtualization software in some other system as long as the Open Virtualization Format is supported.

One important application of OVF files, is the ability to develop and distribute ready to use software packages (example – email server package) with default configuration and settings pre-installed so that they can be imported to a Virtual Machine. This saves time, and makes the configuration of software applications easier.

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