So You Want a Virtual Machine? Let’s Actually Build One

Why bother with a virtual machine at all?

Let’s be honest: most people only look into virtual machines after something has gone wrong. They installed a sketchy program, broke their system, or needed an older version of Windows for that one stubborn app from 2010.

But VMs are actually perfect for a bunch of everyday situations:

• You want to try Linux without wiping your Windows laptop.
• You need an isolated place to test software or scripts.
• You’re learning IT, cybersecurity, or programming and want a safe sandbox.
• You want a “mess around” environment that you can reset anytime.

Think of a VM as a spare apartment inside your existing house. It has its own furniture, its own mess, its own rules. If you trash it? You just rebuild it. Your main system stays clean.

Now let’s walk through some concrete setups, the way you’d actually use them in real life.

Getting your tools ready: what you need before you start

Before we dive into examples, there are a few basics you’ll need no matter what kind of VM you’re setting up.

Does your machine support virtualization?

Most modern CPUs do. But sometimes the feature is turned off.

On Windows, the easiest way to check is:

• Press Ctrl + Shift + Esc to open Task Manager.
• Go to the Performance tab.
• Click CPU on the left.
• Look for Virtualization in the details. If it says Enabled, you’re good. If it says Disabled, you may need to turn it on in your BIOS/UEFI settings.

Intel calls it Intel VT-x, AMD calls it AMD-V, but in your firmware settings it usually just shows up as Virtualization Technology or something similar.

How much memory and disk space do you actually have?

A VM shares your real hardware. So if your laptop only has 4 GB of RAM, giving a VM 4 GB is… not going to end well.

As a rule of thumb:

• 8 GB RAM on the host: you can run one light VM (like a small Linux) comfortably.
• 16 GB RAM: you can run a Windows VM or a couple of light Linux VMs.
• 256 GB SSD or more: gives you enough room for several VMs without constantly juggling space.

For disk space, a basic VM usually needs:

• Linux VM: 20–30 GB is often plenty for testing.
• Windows VM: 40–60 GB is more realistic, especially if you install apps.

Picking your hypervisor: which VM software should you use?

For personal and learning use, three names come up again and again:

• VirtualBox – Free, runs on Windows, macOS, and Linux. Great for beginners.
• VMware Workstation Player – Free for personal use on Windows and Linux.
• Hyper-V – Built into some versions of Windows (Pro, Enterprise, Education). Good if you’re already on Windows and want to stay in that ecosystem.

In the examples below, I’ll mostly describe things in VirtualBox terms, because it’s easy to get and runs on almost anything. But the ideas carry over to other tools.

If you want more background on virtualization concepts, the National Institute of Standards and Technology (NIST) has a clear overview of virtualization security considerations here: https://csrc.nist.gov

Example: a “throwaway” Windows test machine on your laptop

Imagine Alex, who works in marketing but loves trying new tools. Alex wants to test some automation software that looks a bit sketchy and doesn’t feel like risking the main Windows install. A VM is perfect for this.

Step 1 – Grab the Windows ISO

Alex goes to Microsoft’s official download page and gets the Windows installation ISO. No random sites, no mystery downloads.

For Windows 10 or 11, Microsoft provides media creation tools and ISO downloads here:

• Windows download page: https://www.microsoft.com/software-download

The result is a big .iso file – basically a virtual DVD.

Step 2 – Create a new VM in VirtualBox

In VirtualBox, Alex clicks New and fills in the basics:

• Name: Win11-Test-Box (give it a name that actually means something).
• Type: Microsoft Windows.
• Version: Windows 11 (64-bit).

VirtualBox suggests some defaults, but Alex tweaks a few things:

• Memory: with 16 GB on the host, giving the VM 4 GB (4096 MB) is comfortable.
• Processors: 2 virtual CPUs is usually fine for testing.
• Disk: Alex creates a 50 GB virtual disk, dynamically allocated (so it only grows as needed, up to 50 GB).

Step 3 – Attach the ISO and boot

With the VM created, Alex:

• Opens the VM’s Settings.
• Goes to Storage.
• Clicks the empty optical drive icon.
• Chooses Choose a disk file… and selects the Windows ISO.

Then Alex starts the VM. It boots from the ISO just like a real PC booting from a DVD or USB.

From here, it’s the familiar Windows installation process: language, edition, partition (the virtual disk), and so on. Once that’s done, Alex has a clean Windows desktop in a window.

Step 4 – Install Guest Additions and tidy up

In VirtualBox, there’s an extra step that makes life nicer:

• With the VM running, Alex goes to Devices → Insert Guest Additions CD image….
• Runs the installer inside the VM.

This improves things like:

• Screen resizing
• Mouse integration
• Shared clipboard

Alex also installs antivirus or security tools inside the VM if testing sketchy software. It’s still a Windows machine, even if it’s pretend.

Step 5 – Use snapshots as a “time machine”

Here’s where VMs get fun. Before installing the suspicious app, Alex takes a snapshot:

• In VirtualBox, with the VM off or on, open the Snapshots tab.
• Create a snapshot called Clean install.

Now Alex installs the questionable software, pokes around, maybe even breaks things. If it all goes sideways, Alex just restores the snapshot and the VM jumps back to that clean state.

No reinstall. No drama. Just rewind.

Example: a lightweight Linux playground for learning and scripting

Now picture Maya, who’s learning Python and wants to get comfortable with Linux. She’s not ready to ditch Windows, but she wants a safe place to experiment with commands, servers, and tools.

A small Linux VM is perfect here.

Picking a Linux distro that won’t fight you

Maya doesn’t need anything fancy. Something like Ubuntu Desktop or Linux Mint is perfect for beginners. They have friendly installers, big communities, and loads of tutorials.

She downloads an ISO directly from the official site, for example:

• Ubuntu: https://ubuntu.com/download

Creating the VM with lighter settings

In VirtualBox, Maya creates a new VM:

• Name: Ubuntu-Playground.
• Type: Linux.
• Version: Ubuntu (64-bit).

Because Linux can be quite efficient, she can give it modest resources:

• Memory: 2 GB (2048 MB) if the host has 8 GB or more.
• Disk: 25–30 GB dynamically allocated.

She attaches the Ubuntu ISO in the same way Alex did for Windows and boots the VM.

The Ubuntu installer is mostly “next, next, next,” with a few choices about language, keyboard layout, and whether to install updates and third-party software.

Making it a real learning lab

Once Ubuntu is installed, Maya wants this VM to feel like a playground, not a chore.

She might:

• Install development tools using the terminal:

  sudo apt update
  sudo apt install build-essential git python3 python3-pip
  

• Create a folder on the host for shared files and configure a shared folder in VirtualBox so she can move files easily between Windows and the VM.

• Practice core Linux commands (ls, cd, grep, find, chmod, systemctl) knowing that if she messes up system files, the damage is contained.

Because this VM is for learning, snapshots become a safety net again. Before trying something risky (like changing system configuration files), she takes a snapshot named Before service changes or something equally obvious.

If you want structured Linux learning paths, many universities offer free material; for example, MIT’s OpenCourseWare has computing courses you can browse: https://ocw.mit.edu

Example: a mini home lab with multiple VMs

Now let’s go one level up. Sam works in IT support and wants to move into system administration. Reading about servers is one thing; actually configuring them is another. So Sam decides to build a tiny home lab on a decent desktop with 32 GB of RAM.

Instead of one VM, Sam wants several:

• One VM as a domain controller or central authentication server.
• One or two client machines to join to that domain.
• Maybe a Linux server for web or database experiments.

Planning the resources so things don’t crawl

Sam knows the host has 32 GB of RAM, so there’s room to breathe. A simple split might look like this (again, not as a rigid rule, just a starting point):

• Domain controller VM: 4 GB RAM, 2 CPUs.
• Windows client VM: 4 GB RAM each, 2 CPUs each.
• Linux server VM: 2–4 GB RAM, 2 CPUs.

That leaves enough memory for the host and whatever Sam is using there.

Disk space gets divided too:

• 60 GB for the domain controller (Windows Server can be hungry).
• 40–50 GB per Windows client.
• 30–40 GB for the Linux server.

All of these are virtual disks, so they grow as needed up to those limits.

Creating an isolated virtual network

Here’s where it gets interesting. Sam doesn’t want this little lab to interfere with the home network. So instead of using NAT or bridged networking for everything, Sam creates an internal network in VirtualBox.

The idea:

• All lab VMs talk to each other on a private virtual network.
• Only one VM (maybe the Linux server) has a second network adapter using NAT for internet access, if needed.

In VirtualBox, Sam:

• Opens each VM’s Settings → Network.
• Sets Adapter 1 to Internal Network and gives the network a name like LabNet.

Now the lab behaves like a tiny separate office network inside the machine.

Building the lab step by step

Sam starts with the core piece: the domain controller (or main server). Installs Windows Server, sets up Active Directory, DNS, maybe DHCP. Takes a snapshot.

Then the client VMs get installed and joined to the domain. More snapshots.

Finally, the Linux server is installed and configured to talk to the domain or host services like a simple web page or database.

This kind of setup lets Sam practice:

• User and group management.
• Group Policy.
• Service configuration.
• Backups and restores.

All without touching any real company systems or risking anyone’s data.

For general IT and cybersecurity lab ideas, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) has learning resources and guidance here: https://www.cisa.gov

Common settings that confuse people (and what to pick)

If you’ve ever stared at a VM settings window wondering what half the options mean, you’re not alone. Let’s clear up a few that trip people up all the time.

How much memory should you assign?

You might be tempted to give the VM as much RAM as possible. But remember: your host still needs to function.

A practical approach:

• Never give more than half of your physical RAM to a single VM, unless you really know what you’re doing.
• For simple testing:
  • 2 GB for light Linux.
  • 4 GB for Windows 10/11.

If you start the VM and everything feels painfully slow, shut it down and adjust. You’re allowed to experiment here.

How many CPUs should you give it?

More CPUs doesn’t always mean faster. If your host has 4 cores, giving a VM all 4 can make both the host and the VM sluggish.

Most personal setups do fine with:

• 1–2 virtual CPUs for light use.
• 2–4 for heavier tasks if your host has 8+ cores.

Should you use NAT, bridged, or something else for networking?

This one sounds more intimidating than it is:

• NAT: VM uses your host as a middleman to reach the internet. Simple, safe, usually the default. Good for most single-VM setups.
• Bridged: VM appears on your network like a separate physical machine. Good if you want other devices on your network to reach the VM directly.
• Internal or Host-only: Used for labs or isolated test networks, like Sam’s setup.

If you’re just testing software or learning Linux, NAT is usually fine. You can always change it later.

Keeping your VMs healthy and under control

It’s easy to go wild and suddenly have ten half-broken VMs eating your disk space. A little discipline helps.

Name things clearly

New Virtual Machine 1 means nothing three months from now. Use names like:

• Win11-Office-Tests
• Ubuntu-Python-Lab
• HomeLab-DC01

Future you will be grateful.

Use snapshots, but don’t hoard them forever

Snapshots are great, but each one takes space and can slow things down if you keep stacking them.

A simple habit:

• Keep a snapshot right after a clean install.
• Maybe another one before major changes.
• Delete old ones once you’re sure you won’t need to go back.

Watch your disk space

Every VM is a big file (or a set of files). If your disk starts filling up, check your VM folder. You might find old experiments you forgot about.

If you’re on Windows, you can use built-in tools like Storage settings to see which folders are growing, and third-party tools to visualize disk usage.

FAQ: questions people quietly Google while setting up VMs

Can a virtual machine damage my real computer?
Not in the usual sense. A VM is isolated in software. If you install malware inside the VM, it normally stays there. However, if you share folders, copy files back and forth, or run very advanced attacks, there are ways things could escape. For normal testing and learning, it’s considered a safe way to experiment, but basic security habits still apply.

Is running a VM going to slow my computer to a crawl?
It can, if you give the VM too many resources or your hardware is already limited. As long as you leave enough RAM and CPU for the host, you’ll be fine. On a modest laptop with 8 GB of RAM, stick to one light VM at a time and don’t assign more than 2–3 GB to it.

Do I need a Windows license for a Windows VM?
Yes, Microsoft’s licensing rules still apply inside a VM. You can install Windows without a key for a trial period, but long-term use requires proper licensing. For details, it’s best to check Microsoft’s official documentation or licensing pages.

Can I run a VM inside another VM?
This is called nested virtualization. It’s possible on some platforms and CPUs, but it’s more of an advanced scenario and can be quite slow. For everyday use, you’re better off running VMs directly on your physical machine.

Is this how “the cloud” works behind the scenes?
In many cases, yes. Cloud providers rely heavily on virtualization (and related technologies like containers) to run lots of separate environments on shared hardware. Your little VirtualBox VM is a small cousin of what big data centers are doing at scale.

If you want to go further into virtualization concepts and security best practices, NIST and other public institutions maintain helpful guides, for example:

• NIST virtualization security overview: https://csrc.nist.gov
• General cybersecurity learning resources: https://www.cisa.gov
• Open computer science and IT courses: https://ocw.mit.edu

Start with one VM. Give it a purpose: a Windows test box, a Linux playground, a tiny home lab. Once you see how forgiving and flexible this setup is, you’ll probably find yourself spinning up a second one “just to try something” before long.