xsysroot.conf

{

  "vbox-debian" : {
     "description" : "VirtualBox Debian",
     "nbdev" : "/dev/nbd1",
     "nbdev_part" : "p1",
     "sysroot" : "/tmp/vbox-debian",
     "tmp" : "~/systmp",
     "backing_image": "~/osimages/vbox-debian.img",
     "qcow_image": "~/osimages/vbox-debian.qcow",
     "qcow_size": "1G"
  }

}