What Is a Virtual Machine (VM)?

virtual machine (VM) is a simulated computer that runs within an actual, physical computer, also referred to as the host. VMs can be used to emulate existing or hypothetical computer architecture (hardware).

Essential components of a virtual machine are virtual disks and config files, as well as log and NVRAM setting files. You can run several VMs on one host simultaneously.

Virtual Machine – Definition

In essence, a virtual machine is a virtual computer. It provides the same functionalities as a physical computer, but only exists as a simulation, i.e. a program that runs on your PC. Based on their scope, virtual machines are divided into two categories:

  • System virtual machines simulate an entire computer down to the operating system, making them a full-fledged substitute or test environment.
  • Process virtual machines, also known as Managed Runtime Environments (MRE), exist on a smaller scale and are designed to support a single process. They can be used to provide a platform- and OS-independent environment for a particular process.

A common scenario where a virtual machine would be employed, for instance, is if an organization wants to expand its on-premises AD to Azure AD by migrating the domain controller to a VM in Azure.

How Do Virtual Machines Work?

A system virtual machine is a fully simulated PC that runs in a window on your desktop, much like any other program you would run, but is separated from your PC’s other systems. Running the VM requires virtualization software such as Oracle Virtualbox or Microsoft Hyper-V. These programs, also known as a hypervisor, are used to set up a “sandbox” (isolated window) on your PC and the operating system for the virtual PC is then installed inside the sandbox.

The virtual system can be used and configured like a regular operating system, but does not interfere with the configuration of your host computer. The virtual machine is often employed as a test environment, e.g. to try out new programs without having to worry about it affecting your PC or other programs.

How Many Virtual Machines Can Run on One Server?

The answer to how many VMs you can run at once really comes down to performance: In theory, you can run as many virtual machines with different operating systems as you want (assuming they are based on x86 architecture), but you will run into limitations based on RAM and CPU usage as well as hard disk storage.

However, a powerful server can easily host several virtual machines at the same time, possibly even dozens of them. It really depends on your hardware and what your are using the VMs for.

VM Use Cases: What Are the Advantages of a Virtual Machine?

The greatest advantage of virtual machines is that they are sandboxed, i.e. isolated away from the operating system on your PC. This enables you to utilize the VM as a test environment for new applications or programs. This feature can even be used to access infected files safely (mostly).

Additionally, VMs allow organizations to use their existing hardware more efficiently: Since most businesses don’t utilize the full capacity of their physical servers, they can spin up virtual servers with the remaining capacity instead of having to invest in entirely new hardware. Virtualization can also be used to more easily move environments to different systems. It even offers easier backup and recovery options. Learn more about the advantages of using a virtual machine.

Are Virtual Machines Safe?

As we’ve established, virtual machines run in a contained environment called a sandbox that is separated from the host PC or server. This layer of separation not only allows VMs to simulate different conditions for the guest environment (like various operating systems or hardware configurations), it also means that software that is running out of control (whether by accident or by design) cannot damage the host system. In theory, at least.

When it comes to the safety of virtual machines, we have to differentiate between their specific use:

VMs that are used to handle known malware or infected files will generally contain the threat within the sandbox, assuming they are configured correctly and all network connections to the host are disabled. However, hackers and malware producers occasionally discover exploits that allow them to break out of VMs. These vulnerabilities, also known as virtual machine escape, are quickly patched out of hypervisors. Even so, it’s worth keeping in mind that VMs do not offer 100% security against malware.

VMs that are used in place of physical machines to perform typical computing jobs, such as virtual servers that extend your current server range, are just as vulnerable to digital threats as a physical machine. Consequently, you should apply the same security measures and the same level of caution to VMs on your network as you would a regular computer.

More information:

Best Practices for Access Management in Microsoft® Environments [WHITE PAPER DOWNLOAD]

Azure Active Directory: What Is Azure AD?

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About the Author: Nele Nikolaisen

Nele Nikolaisen is a content manager at tenfold. She is also a book lover, cineaste and passionate collector of curiosities.