Use Microsoft’s official Command Line utility SDelete to overwrite all deleted disk space with blocks of zeros. This tells the QCOW2 compressor exactly which segments are blank. sdelete64.exe -z c: Use code with caution. On the Linux Host: Compress the QCOW2 File
Set the cache mode of your QCOW2 disk to writeback or none for the best balance of speed and safety. writeback uses the host cache to accelerate disk writes.
none bypasses the host cache entirely, which is ideal if your host utilizes fast enterprise NVMe storage. 3. Implement Disk Discard (TRIM)
After installation, you need to remove the ISO to prevent it from booting back into the installer. You can do this by ejecting it or simply omitting the -cdrom option when starting your VM: Windows 10.qcow2
qemu-img snapshot -l Windows10.qcow2 qemu-img snapshot -c -d snapshot_name Windows10.qcow2
: While convenient, always exercise caution when downloading pre-built qcow2 images from unverified sources. They could contain malware, unwanted software, or be missing critical security patches. The safest method is always to build your own from an official Microsoft ISO.
This command creates a 60GB .qcow2 image. Adjust the size as needed. Use Microsoft’s official Command Line utility SDelete to
: If you need to run Windows applications on a non-Windows host (Linux, Mac, or Android), a .qcow2 image is the gold standard for speed and ease of use, provided you stay cautious about its lack of new security patches.
Summary
qemu-img convert -c -O qcow2 windows_10.qcow2 windows_10_compressed.qcow2 Use code with caution. On the Linux Host: Compress the QCOW2 File
Windows 10 will not natively recognize KVM's virtio-net architecture. Open the Windows Device Manager, find the unrecognized Ethernet Controller, select , and point it to the NetKVM folder inside the mounted VirtIO ISO. 3. High CPU Usage on the Host
This creates a new Windows 10.clean-install.qcow2 overlay. The original becomes read-only.
. This process might take a while.
You've booted the Windows ISO, but when you get to the partition screen, no disk is present.
After optimization, trim the QCOW2 image from the host: