Windows 10qcow2 | 2025-2026 |

Cause: The boot sector (MBR or GPT) was not preserved correctly. Solution: Use qemu-img convert with no additional flags. If the issue persists, boot a Windows recovery ISO and run bootrec /fixmbr and bootrec /rebuildbcd.

The qemu-img command handles all major formats.

From VMDK to qcow2:

qemu-img convert -f vmdk -O qcow2 windows10.vmdk windows10.qcow2

From VHDX to qcow2:

qemu-img convert -f vhdx -O qcow2 windows10.vhdx windows10.qcow2

From raw .img to qcow2:

qemu-img convert -f raw -O qcow2 windows10.raw windows10.qcow2

Add compression on the fly:

qemu-img convert -f vmdk -O qcow2 -c windows10.vmdk windows10-compressed.qcow2

qemu-img create -f qcow2 windows10.qcow2 80G

Why 80G? Windows 10 needs at least 64 GB for comfort (updates require significant space). The -f qcow2 flag specifies the format. windows 10qcow2

<disk type='file' device='disk'>
  <driver name='qemu' type='qcow2' cache='writeback' discard='unmap' io='native'/>
  <source file='/var/lib/libvirt/images/win10.qcow2'/>
  <target dev='vda' bus='virtio'/>
</disk>

Running Windows 10 on qcow2 can be nearly bare-metal fast with proper tuning.

Before diving into the "how," let’s understand the "why." Virtual machine disk formats are not one-size-fits-all. Here is why the qcow2 format is superior for running Windows 10 on Linux-based hypervisors: Cause: The boot sector (MBR or GPT) was