Examples of how to use qemu-img and qemu-nbd for various disk image operations.

Mounting Raw Image via kpartx & Loop Device

Mounting Qcow2 via NBD

~ # modprobe nbd
~ # qemu-nbd --port 10999 --connect=/dev/nbd0 disk.qcow2
~ # nbd-client localhost 10999 /dev/nbd0

Converting VirtualBox Images for KVM

~ # VBoxManage clonehd --format RAW input.vdi output.img
~ # qemu-img convert -f raw output.img -O qcow2 output.qcow2

Converting KVM Qcow2 to VirtualBox VDI

Compacting qcow2 Image Files

You have to zerofill the data on the disk first.

root@guest # sfill -fllvz

Then clone the image file

root@host # qemu-img convert -p -O qcow2 ./source.img ./packed.img

See Also