Use the qemu-img utility to create a thin-provisioned virtual disk. Thin provisioning ensures the file only consumes space on your host drive as data is written inside the guest OS. qemu-img create -f qcow2 windows10.qcow2 60G Use code with caution. -f qcow2 : Specifies the target format.
qemu-system-x86_64 \ -m 4G \ -enable-kvm \ -drive file=windows10.qcow2,if=virtio \ -net nic,model=virtio -net user \ -cpu host Use code with caution. Copied to clipboard 3. Essential Tuning
QCOW2 offers several key advantages:
Progress through the initial setup screens until you reach the screen. Select Custom: Install Windows only (advanced) . windows 10qcow2
Add -p to show progress. Add -c for compression ( -O qcow2 -c ), but note compressed images have a slight performance penalty.
qcow2 is a versatile format for Windows 10 virtualization with clear benefits in storage efficiency and management flexibility. However, its features introduce measurable performance and complexity trade-offs. By following targeted tuning and workflow recommendations, administrators can leverage qcow2 effectively for desktop virtualization, testing, and lab environments.
Windows 10 does not natively include drivers for the fast storage and networking interfaces. To achieve high disk I/O, you must install the Virtio-win drivers during or after installation. Managing QCOW2 Images via Command Line qemu-img is the primary tool for managing these images. Checking Image Information See the virtual size vs. actual size: qemu-img info windows10.qcow2 Use code with caution. Resizing a Windows 10 Disk Use the qemu-img utility to create a thin-provisioned
Then inside Windows 10, open Disk Management and extend the partition.
Set to none or writeback . none bypasses the host cache and writes directly to physical storage, which reduces CPU overhead and is highly recommended for enterprise or SSD-based environments. IO Mode: Set to native (if using cache=none) or threads . 2. Enable Storage Discard (TRIM Support)
Click and navigate to the secondary CD-ROM drive containing the VirtIO images. -f qcow2 : Specifies the target format
You can save the "state" of your Windows 10 VM before making risky registry changes or installing updates. If something breaks, you can revert in seconds.
To set up a image for QEMU/KVM, you need to create a virtual disk, mount the Windows ISO, and—crucially—include VirtIO drivers so Windows can recognize the QCOW2 disk during installation . 1. Create the QCOW2 Virtual Disk
Set to Enter System Out-of-Box Experience (OOBE) . Check the Generalize box. Set Shutdown Options to Shutdown . Click OK .
lsmod | grep kvm
This method is commonly used when migrating from Hyper‑V to a KVM environment.