Crash course: How do virtual PCs actually work?

Anyone who frequently installs and uninstalls new software, tests beta versions of programs, or tinkers with the registry in Windows, often reaches the point where they have to completely re-install their operating system. With the help of a virtual machine, you can save yourself the effort. But even if you want to use Linux as a second operating system as easily as possible, a virtual PC is just the thing for you.

What a virtual PC can do

A virtual PC, also called a virtual machine or VM for short, is a fully-fledged PC system that runs in a window on your PC but remains isolated from it. The virtualization software required for this, called a hypervisor, sets up a sandbox on your PC in the form of a virtual machine, where you can install an operating system that runs isolated (and thus protected) from your main OS installation. Hypervisor classics in the Windows area include Oracle Virtualbox, Vmware Workstation Player, and Workstation Pro, as well as Microsoft Hyper-V, which is baked directly into Windows Pro and Enterprise versions.

With this method, several virtual machines with different operating systems can be run simultaneously on a standard PC, as long as the systems are all based on the x86 processor architecture. The virtual system can be used like a conventional operating system and easily reset to earlier states without changing the configuration of your main computer.

The motto: try everything, there’s no risk. For example, with new programs, you do not have to worry about possible interactions with software already installed on your “real” PC, unless you have specified a common exchange folder for the virtual machine.

Emulate hardware

On your real PC, Virtualbox, Vmware, and Hyper-V support all important hardware components that the host operating system accesses by means of suitable drivers. Virtual machines, on the other hand, offer a standard PC with a standardized controller including hard disk(s), CD/DVD drive, graphics card, and network adapter – regardless of the components actually installed, such as the processor and graphics card.

USB devices docked on the host are provided to varying degrees within virtual PCs. The hypervisor recognizes flash drives, printers, external USB drives, and smartphones and can pass them on to virtual machines. To do this, the USB devices are temporarily disconnected from the host operating system and reconnected after the (virtual) guest computer is shut down. The prerequisite is appropriate driver support on the part of the guest operating system.

Changing PCs with a mouse click

Once set up, virtual machines can be reconfigured at any time – for example by increasing the main memory, adding an interface, or integrating a drive. It lets you easily create different application environments.

Virtualbox and other VM software save the hard drives of the virtual PCs in container files on the real hard disk of the host PC. You specify the maximum size and let it grow dynamically. The file only occupies about as much storage space on your real PC as the virtual machine actually uses. However, virtual machine containers are also possible with a fixed size.

Once you have created a virtual machine and installed the desired operating system on it, the virtual hard disk can then also be used on another host PC and, in the case of a free system such as Linux Mint, passed on. You may also transfer the virtual machine to your notebook or save it on another drive for backup purposes.

Resource requirements

The number of simultaneously running virtual operating systems is only limited by the memory and hard disk resources of the host PC. The more RAM your computer has, the more operating systems can be started in parallel as a virtual machine.

Depending on the allocated RAM size, the operating systems in a virtual machine work comparatively slower than with a classic full installation on identical hardware, but in practice this is usually of little consequence on fast PC hardware.

The maximum RAM size that can be set for a virtual machine always depends on the RAM size of the physical PC: RAM that is not actually available in the host PC cannot be provided by the hypervisor.

Comprehensive crash protection

Virtual machines run independently in separate areas and are mutually secured in such a way that one operating system cannot crash the others or even the host operating system.

Crashes within virtual machines, on the other hand, are quite possible, for example due to errors (bluescreens) in the guest operating system, in one of the installed drivers, or even in an application. You can simply restart a crashed virtual computer via the virtualisation software without affecting the host computer or reset it to a previous state before restarting.

This article was translated from German to English and originally appeared on pcwelt.de.