
I recently wrote about virtualization, and during my research, I was reminded of the concept of a Kernel-Based Virtual Machine (KVM). It was then that I decided to dedicate an entire article to it — KVM technology is intriguing.
A KVM, or Kernel-Based Virtual Machine, turns a Linux server into a hypervisor.
Before I plunge into its depths, let me explain regular virtualization: a “traditional” virtualization solution like VMware Workstation allows you to create, manage, and run multiple “mini-computers,” called virtual machines (VMs), on a single physical machine.
Each VM has its own operating system (OS) and you can allocate hardware resources like CPU power and storage space to these VMs through a program called a hypervisor, which is VMware Workstation in this instance.
The reason I termed the ultra-modern VMware Workstation as “traditional” is that it operates as a separate software layer. KVM, on the other hand, integrates directly into the Linux kernel, turning that into a hypervisor.
I’ve often called the central processing unit (CPU) the “brain” of the computer. The true brain of the computer is the operating system, and the colonel… er… kernel is its right hand. The kernel directly manages all hardware resources and system processes, which highlights how remarkable its integration with KVM is.
It’s like putting Cristiano Ronaldo and Lionel Messi on the same team in their prime. Now that you’ve wet your feet, please put on your swimsuit (or trunks) for the full dive!
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The Basics of KVM
I mentioned the Linux kernel in the introduction. If you can put two and two together, KVM is primarily designed for Linux environments but isn’t limited to them. You can run it on a Windows computer, for example, by first setting up a Linux environment (you can’t run it directly).

In my opinion, it’s the best option for cloud virtualization (ahead of VMware vSphere). Before we get into that, I’m going to introduce you to its basic components:
- Kernel module: The KVM kernel module is like a GTA V cheat code — it adds virtualization capabilities to the Linux kernel, enabling it to “spawn” virtual machines. In simple terms, KVM is the integration of the KVM kernel module with the Linux kernel.
- User-space tools: Unlike VMware Workstation, which includes its own built-in user interface, KVM relies on user-space tools such as QEMU (Quick Emulator) for hardware emulation (creating virtual versions of hardware), Virt-Manager for VM management through a graphical user interface (GUI), and Libvirt for live migration and snapshots.
You can think of KVM as Batman and QEMU as Robin. Together, they create a powerful and flexible team.
How KVM Works
You may think you already know how KVM works (I’m one hell of a guru, after all), but I don’t want you to breeze past this section. Trust me, you’ve only skimmed the surface. If you’re looking for a crystal-clear understanding of KVM, it’s time to slow down.
I know you’re eager to learn how to run KVM on non-native OSes like Windows and macOS as well. Well, today’s your lucky day!
Architecture
You can add virtual machines to the list of KVM components from the previous section to complete its architecture (it’s self-explanatory, really). When you want to create a VM, you must use the QEMU interface to set it up and specify the required resources.
You can access the QEMU interface directly through the command line interface (CLI) or through a GUI like Virt-Manager. QEMU communicates these requirements to the KVM kernel module.
The KVM kernel module checks whether the requested resources are available and hands the baton over to the Linux kernel to execute. Once the Linux kernel has allocated your requested resources to the VM, you can operate it just like a regular computer.
Guest Operating Systems
KVM supports various guest operating systems, including:
- Linux distros such as Ubuntu, Debian, CentOS, RHEL, and Fedora
- Unix-like OSes such as FreeBSD, OpenBSD, NetBSD, Oracle Solaris, and AIX
- Windows
- macOS
Don’t get your hopes up just yet: you can’t run KVM directly on Unix-like OSes, Windows, or macOS. You can install it on Windows, for example, by first running a full Linux environment using VMware Workstation.
Additionally, if your CPU doesn’t support virtualization, you can’t use KVM at all. You can check if your computer supports virtualization by running the command “egrep -c ‘(vmx|svm)’ /proc/cpuinfo” in the CLI.
If it returns a result greater than zero, you’re good to go.
Resource Allocation
The only detail I left out about resource allocation so far is the significant role the Linux kernel plays in the grand scheme of things.
Once the KVM kernel module has approved a request, the Linux kernel has the authority to deny it if:
- The requested resources are unavailable
- The request exceeds system configuration limits
- It compromises system stability or security
If an error message pops up on your screen, it means the Linux kernel has denied your request. Don’t worry — the message will also indicate what went wrong, so modify the contents of your request and resubmit it!
Advantages of KVM
During my research, I prepared a list of the best virtualization solutions, and KVM ranked third after VMware vSphere and Microsoft Hyper-V (with Citrix Hypervisor and Oracle VM VirtualBox completing the top five). In terms of cloud virtualization, it fares even better — it’s my number one pick.

It’s clear KVM offers several compelling advantages that make it a crowd favorite, and being free of cost is the icing on the cake.
Scalability
KVM is a magnificent choice for large data centers and cloud environments, as it’s designed with scalability in mind. You can scale horizontally by adding physical servers, CPUs, or RAM modules to your existing infrastructure without disrupting operations.
Furthermore, the live migration feature ensures you can move virtual machines between hosts with zero downtime. It’s safe to say you can use KVM to leverage the full potential of modern hardware.
Flexibility
Some hypervisors are limited to specific guest operating systems. KVM is no ordinary hypervisor; I’ve already mentioned the wide array of operating systems and configurations it supports.
Since KVM is so versatile, you can deploy multiple workloads without the need for additional physical hardware. If you’re looking for a robust virtualization solution for development and testing, look no further. And you thought being open-source was its only cost benefit!
Performance
Traditional hypervisors are commonly associated with overhead.
Since KVM is tightly integrated with the Linux kernel (they’re practically best buddies), your virtual machines can run at near-native execution speeds.
Additionally, KVM is well-known for efficiently allocating resources, ensuring your VM instances will receive the necessary resources when needed while minimizing waste.
Open Source
Speaking of cost-effectiveness, it’s hard to beat the overall package KVM provides. Since it’s open-source, you can easily leverage native tools and utilities for management and monitoring.
Additionally, you can customize the platform to meet your specific needs. The community is another plus point; it actively develops plugins and extensions that enhance operational efficiency.
Use Cases for KVM
Alongside development and testing, you can do a lot of other things with KVM. As I explained earlier, KVM is a popular choice for cloud service providers.

You can also use it to consolidate multiple physical servers into virtual machines and run multiple operating system environments on a single desktop computer (preferably if you’re a Linux or Unix enthusiast).
Server Consolidation
If you want to maximize server resources, consider consolidating your server resources into virtual machines using KVM. KVM offers two key features in this aspect: support for numerous guest operating systems and a zero downtime guarantee while migrating VMs.
Server consolidation using KVM will also help you lower hardware costs, save energy, and simplify management.
Development and Testing
If you’re a developer or run a team of developers, you understand just how important it is to test software in multiple environments.
For example, your favorite mobile games run on multiple operating systems, and the developers likely spent countless hours ensuring compatibility across these platforms in isolated test environments.
Instead of juggling virtualization solutions due to limited guest OS support, why not choose a virtualization software like KVM?
Cloud Computing
There are three reasons why KVM is often the go-to choice for cloud service providers:
- It enables efficient resource management.
- It offers quick scalability and flexibility for customization and integration with other tools.
- It provides multi-tenancy.
If you don’t know what multi-tenancy is, KVM permits multiple tenants, or customers in this case, to run on the same physical server without interference.
Desktop Virtualization
If you’re a developer and want to bring work back home, a hobbyist eager to learn about different operating systems, or just a practical user looking to maximize the muscle under your desktop’s hood, desktop virtualization through KVM is exactly what you need.
It offers the flexibility and power to create multiple virtual environments on a single machine, making it an ideal solution for a variety of use cases. Enough said.
Setting Up KVM
You’re probably sold on KVM by now. Let’s assume you want to set it up on your desktop or laptop, which is running a Linux distro like Ubuntu. Before you can turn this “want” into reality, you need to ensure your computer system meets the minimum hardware prerequisites.
Prerequisites
You need to check your hardware settings in the BIOS to determine whether your system meets the minimum criteria to run KVM.
To access it:
- Restart your computer and click on the BIOS access key. It varies between manufacturers and is generally “F2,” “F10,” “Delete,” or “Escape.”
- Look for the tab or section that’s labeled “System Information” and check whether your CPU supports virtualization. For Intel processors, look for Intel VT-x support, and for AMD processors, look for AMD-V support.
- Also, confirm whether you have at least four gigabytes of RAM (I recommend eight gigabytes or more).
You can now start your system.
Installation Steps
I bet you’re wondering how to install KVM and create your very first virtual machine. Consider this step-by-step guide your answer:
- Before you can install KVM on your system, you need to ensure the KVM kernel modules are loaded (the core and architecture-specific modules). Run the lsmod | grep kvm command in the CLI to check this.
- You need to install four packages: qemu-kvm, libvirt, bridge-utils (for network bridging), and virt-manager. You can do this by executing the following command: sudo apt install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils virt-manager.
- Add your user account to the libvirt and kvm groups to obtain necessary permissions to manage VMs using KVM. Run this command: sudo usermod -aG kvm $USER.
- Log out and log back in for the changes to take effect.
- Start and enable the Libvirt service by running: sudo systemctl start libvirtd.
- Lastly, verify your KVM installation by executing: virsh list –all. This command will list all your virtual machine instances, which will be empty initially.
You can now use QEMU (through the CLI) or Virt-Manager to create a virtual machine!
Creating and Managing Virtual Machines
The hard part is over, and it’s time to enjoy the perks of virtual machines.
If you’re comfortable with command-line syntax and might need advanced customizations, QEMU is the better option. On the other hand, if you’re new to virtualization or prefer a user-friendly interface, Virt-Manager is more suitable.
Using QEMU/KVM
Here’s the basic command to create a VM with QEMU: qemu-system-x86_64 -m 2048 -cdrom /path/to/your/iso -hda /path/to/your/disk.img -boot d -enable-kvm (you know what to replace and where).
Once you run this command, the VM will boot up, and you can follow the installation steps for Ubuntu (or any other compatible guest operating system). Virt-Manager makes things much easier. Simply launch it by running virt-manager.
Then click on the Create a new virtual machine button and enter the resource configurations you need for your VM instance.
Networking Configuration
Bridged networking is advantageous as it connects your VMs directly to the physical network, with each VM getting its own IP address. This allows you to communicate with other devices in the network; however, it does expose your VMs to security risks.
Network Address Translation (NAT) is a similar concept but is used for external network access. Unlike bridged networking, the VMs are isolated from the external network, as they share the host’s IP address.
Note: I saved this tidbit of knowledge for now: Virt-Manager also integrates the capabilities of Libvirt and offers networking options.
Challenges and Considerations
It’s fair to say setting up KVM isn’t a piece of cake. I mean, if you’re new to the CLI or virtualization, you might encounter some roadblocks while performing the six-step checklist I prepared for you.
There’s no shame in taking a step back and opting for a more user-friendly virtualization solution like VMware Workstation, especially if you need virtualization for personal use (or VMware vSphere for enterprise use).
Here are some challenges and considerations for you.
Complexity
KVM is powerful, but you might find it difficult to configure and manage compared to some other virtualization solutions. If you’re less familiar with CLI tools, KVM may not be the right fit for you, as much of its functionality relies on it.
And while Virt-Manager greatly simplifies many tasks, you’ll still need significant command line knowledge for advanced configurations and customizations.
Performance Tuning
Again, while performance tuning is somewhat possible through Virt-Manager, you may need to fine-tune KVM for specific workloads, including CPU pinning and advanced memory allocation strategies.
This is primarily achievable through command line access or manual editing of configuration files.
Security
If you don’t intend to use virtualization solely for development and testing, chances are you’ll want to connect your VM instances to your internal network (through bridged networking) or an external network (through NAT).
While NAT provides a greater level of isolation for your VMs, it can still expose them and your network to security risks.
Even if you maintain complete isolation between your virtual machines and the host, you need to be aware of potential security risks like hypervisor escape (look it up), misconfigurations, and resource contention.
KVM: Virtualization for Beginners and Advanced Professionals
To summarize, KVM is a standout virtualization option for beginners, largely thanks to the Virt-Manager user-space tool. To maximize its capabilities, you need to grasp the intricacies of the command-line interface, which might be a turn-off for you.
While knowledge of command line syntax may seem outdated, I suggest you begin learning it, as it’s a trivial reason to avoid KVM — always be open to learning new things.
Whether you’re a casual user or a professional, every ounce of knowledge could work in your favor. If you want to succeed in cloud computing, in particular, KVM knowledge can be helpful — it’s the clear winner in cloud virtualization, in my opinion.
Roles such as cloud architect, cloud engineer, systems administrator, DevOps engineer, infrastructure engineer, and cloud operations specialist come to mind.
Regardless, put your best foot forward and try to extract maximum value from KVM.