+@item output_base_image
+forces the output image to be created as a copy on write
+image of the specified base image; @code{output_base_image} should have the same
+content as the input's base image, however the path, image format, etc may
+differ
+@item base_fmt
+is the disk image format of @var{base_image}. for more information look at @var{fmt}