qemu-img commit windows7_snapshot1.qcow2 Even experienced users face problems with Windows 7 on QCOW2. Here are the top fixes. Issue 1: "Bootmgr is missing" after conversion Cause: The boot sector doesn't recognize the virtual disk geometry. Fix: Boot from a Windows 7 installation ISO, enter Repair > Command Prompt, and run:
qemu-img create -f qcow2 -o preallocation=metadata windows7.qcow2 50G Create an encrypted QCOW2 (LUKS-based): windows 7 qcow2 file
-drive file=windows7.qcow2,format=qcow2,if=virtio,discard=unmap This allows the guest OS to tell the host which blocks are free, shrinking the QCOW2 file automatically. Over time, even after deleting files, the QCOW2 file may stay large. To shrink it: qemu-img commit windows7_snapshot1
sudo modprobe nbd sudo qemu-nbd -c /dev/nbd0 windows7.qcow2 sudo mount /dev/nbd0p1 /mnt/win7 The windows 7 qcow2 file represents the perfect marriage of legacy software and modern infrastructure. By encapsulating Windows 7 in a thin-provisioned, snapshot-capable, high-performance virtual disk, you retain the ability to run critical legacy applications without the security nightmare of bare-metal Windows 7. Fix: Boot from a Windows 7 installation ISO,
-drive file=windows7.qcow2,format=qcow2,if=virtio,cache=writeback The true power of the QCOW2 format is external snapshots. This is perfect for testing software on Windows 7 without damaging your base install. Creating a Snapshot First, ensure your VM is off. Then:
# Clone physical /dev/sda to raw file (requires booting from a live USB) sudo dd if=/dev/sda of=windows7.raw bs=4M status=progress qemu-img convert -f raw -O qcow2 windows7.raw windows7.qcow2 Converting from VMware VMDK or VirtualBox VDI QEMU-img supports dozens of formats: