• The previous lesson showed you how a hypervisor creates virtual machines on top of physical hardware.
    Now let's look at what a VM really is, and what makes it fundamentally different from a physical server.

    The short answer: a physical server is a box you can touch, a VM is a set of files on a disk.
    This single difference unlocks everything that makes virtualization so powerful.

    A VM Is Just Files

    A VM lives on disk as a folder containing a few files. Nothing more.

    Virtual machine anatomy: a VM stored on disk as a folder with vmdk virtual disk, vmx configuration file, and nvram firmware state

    Figure 1 – A VM is just files

    The VM folder contains three core files:

    • .vmdk holds the virtual disk: the operating system, applications, and data

    • .vmx holds the configuration: how many vCPUs, how much vRAM, which virtual network

    • .nvram holds the BIOS and firmware state

    These are the VMware extensions. KVM/QEMU uses QCOW2, Hyper-V uses VHDX, but the principle is identical: a VM is a set of files on disk.

    Answer the question below

    What type of object is a VM stored as on disk?

    When your hypervisor starts a VM, it reads these files, loads them into memory, and runs the guest OS against virtual hardware.
    When you stop the VM, the hypervisor writes the current state back to disk and stops the process.

    The Guest OS Thinks It Is Real Hardware

    Inside the VM, the operating system does not know it is virtual.
    Your guest OS sees a CPU, RAM, a disk, and a network interface, and it boots and runs exactly like a physical machine.

    The hypervisor handles every hardware request from the guest OS and passes it to the real hardware underneath.
    This illusion is what makes VMs useful: any OS runs inside a VM as if it owned a physical server.

    Answer the question below

    What do we call the operating system that runs inside a VM and thinks it is on real hardware?