KVMs & Hypervisors

What Is a Hypervisor?

Imagine you have one powerful computer, but you want to run five different computers inside it. A hypervisor is the software that makes that possible. It creates and manages virtual machines, which are essentially isolated computers running inside your real physical machine.

Each virtual machine gets its own virtual CPU, memory, disk, network adapter, and operating system. One VM could run Windows Server, another could run Linux, another could run a firewall, and another could be a test client machine.

Type 1 Hypervisor: The Landlord Who Lives in the Building

A Type 1 hypervisor runs directly on the physical hardware. There is no normal operating system underneath it. The hypervisor boots up, takes control of the hardware, and then creates virtual machines on top of it.

This makes Type 1 hypervisors fast and efficient because there is no extra operating system sitting between the virtual machines and the hardware.

Common examples include VMware ESXi, Microsoft Hyper-V, Proxmox, and KVM.

Think of it like this: the landlord has the master key, lives in the building full time, controls everything directly, and is deeply embedded in how the building operates. Nobody gets in or out without going through them first.

Type 1 hypervisors are what you usually find in enterprise data centres and serious homelabs. They are built for performance, stability, and running workloads 24/7.

Type 2 Hypervisor: The Landlord Who Commutes

A Type 2 hypervisor runs on top of a regular operating system. You install Windows, macOS, or Linux first, and then install the hypervisor as an application.

This makes Type 2 hypervisors easier to install and use, especially on a laptop or desktop. The tradeoff is that every VM request has to go through the host operating system before reaching the hardware, which adds overhead.

Common examples include VMware Workstation, VirtualBox, and Parallels Desktop for Mac.

Think of it like this: the landlord works somewhere else, drives in when needed, and has to go through the building manager before doing anything. It works, but there is an extra step involved every time.

So Where Does KVM Fit In?

KVM stands for Kernel-based Virtual Machine. This is where virtualization gets interesting, and it is also where many people get confused.

KVM is built directly into the Linux kernel. When KVM is enabled on a Linux machine, the Linux kernel itself gains the ability to act as a hypervisor. You are not adding a separate virtualization layer on top. Linux itself becomes capable of running virtual machines with direct access to hardware virtualization features.

This technically makes KVM behave like a Type 1 hypervisor because it operates at the kernel level with direct hardware access. But it can feel like Type 2 virtualization because you are still interacting with a normal Linux system.

Think of it like this: the landlord still lives in the building, but now also has legal authority over the entire property. They did not move somewhere else or add another manager above them. They simply gained more control over how the building is divided and managed.

Why KVM Matters for Homelabs

KVM gives you near bare-metal performance while still letting Linux remain flexible and manageable. This is one reason Proxmox is so popular in homelabs. Proxmox uses KVM underneath, but gives you a clean web interface, VM management, storage options, clustering features, and backup tools.

In simple terms, KVM is the engine. Proxmox is the dashboard and management layer built around that engine.