qemu-img \
create \
-f qcow2 \
-b /dev/null \
--object secret,id=OtherDemoLuks.img_encrypt0,file=/path/to/secretFile \
-o backing_fmt=raw,encrypt.format=luks,encrypt.key-secret=OtherDemoLuks.img_encrypt0,compat=0.10 \
/var/lib/libvirt/images/OtherDemoLuks.img \
5242880K