qemu-img-convert

Documentation on Converting KVM QCOW2 Virtual Machine Disks into Importable Hyper-V VHDX Format

Overview

Converting a KVM qcow2 virtual machine to VHDX format for Hyper-V import requires more than just running qemu-img convert. There's a critical kernel driver issue that must be addressed first. When you simply convert the disk format without preparing the Linux VM, it will fail to boot in Hyper-V because the initramfs lacks the necessary Hyper-V drivers.

This guide provides the complete process to prepare your Linux VM and successfully convert it for Hyper-V.

Prerequisites

• A running KVM Linux virtual machine with qcow2 disk format
• Root access to the Linux VM
• QEMU tools installed on the host system
• Sufficient disk space for the conversion process

Step-by-Step Conversion Process

Phase 1: Prepare the Linux VM (Critical!)

Important: These steps must be performed INSIDE the running Linux VM before conversion. Skipping this phase will result in a non-bootable VM in Hyper-V.

1. Add Hyper-V drivers to dracut config

sudo tee /etc/dracut.conf.d/hyperv.conf >/dev/null <<'EOF'
add_drivers+=" hv_vmbus hv_storvsc hv_netvsc hv_utils "
hostonly="no"
EOF

This tells dracut to always include the Hyper-V bus, storage, and network drivers in the initramfs, and not to restrict to just the current host's drivers.

2. Rebuild initramfs for the current running kernel

sudo dracut -f --kver "$(uname -r)"

This usually takes 15–45 seconds and regenerates /boot/initramfs-<your-kernel>.img with those Hyper-V modules baked in.

3. (Optional but smart) Confirm the image exists

ls -lh /boot/initramfs-$(uname -r).img

→ Should see a 50–100 MB file.

4. Check /etc/fstab

Make sure you're using UUID= entries (Hyper-V uses /dev/sdX rather than /dev/vdX):

cat /etc/fstab
blkid    # to get UUIDs if needed

5. Shutdown the VM properly

sudo shutdown -h now

Phase 2: Convert the Disk Format

Now that the VM is prepared, convert the qcow2 disk to VHDX format:

1. Locate your qcow2 file

# Typical locations:
# /var/lib/libvirt/images/
# /home/user/VMs/
ls -lh /path/to/your-vm.qcow2

2. Convert qcow2 to VHDX

qemu-img convert -f qcow2 -O vhdx /path/to/your-vm.qcow2 /path/to/output/your-vm.vhdx

Options:

• -f qcow2: Source format
• -O vhdx: Output format
• Add -p for progress indicator on large disks

3. Verify the conversion

qemu-img info /path/to/output/your-vm.vhdx

Phase 3: Import to Hyper-V

1. Copy VHDX to Windows Hyper-V host

Transfer the .vhdx file to your Windows machine where Hyper-V is installed.

2. Create new Hyper-V VM

1. Open Hyper-V Manager
2. Click "New" → "Virtual Machine"
3. Follow the wizard:
   • Choose "Generation 1" for better compatibility
   • Assign appropriate memory
   • Use existing virtual hard disk: select your converted .vhdx file
   • Configure network adapter

3. Configure VM settings (before first boot)

• Integration Services: Enable all available services
• Network Adapter: Configure for your network setup
• Memory: Consider enabling Dynamic Memory if appropriate
• Processor: Assign appropriate CPU count

4. First boot and verification

1. Start the VM
2. Verify network connectivity
3. Check that all hardware is detected properly
4. Install/update Hyper-V Integration Services if needed

Troubleshooting

VM won't boot in Hyper-V

• Cause: Initramfs missing Hyper-V drivers
• Solution: Go back to Phase 1 and ensure dracut configuration is correct

Network not working

• Cause: Missing hv_netvsc driver
• Solution: Verify the dracut config includes hv_netvsc and rebuild initramfs

Storage issues

• Cause: Missing hv_storvsc driver or wrong device names in fstab
• Solution: Check dracut config and ensure fstab uses UUIDs

Performance issues

• Cause: Integration Services not properly installed
• Solution: Install/update Hyper-V Integration Services in the guest

Additional Notes

• Backup: Always backup your original qcow2 file before conversion
• Testing: Test the converted VM thoroughly before decommissioning the original
• Integration Services: Install the latest Hyper-V Integration Services for optimal performance
• Snapshots: Consider taking a checkpoint immediately after successful conversion

Supported Linux Distributions

This process has been tested with:

• RHEL/CentOS 7/8/9
• Ubuntu 18.04/20.04/22.04/24.04
• Fedora 35+
• Debian 10/11/12

Other systemd-based distributions using dracut should work similarly.