http://phk.freebsd.dk/misc/build_options_stable_8_210741/
The configuration file consists of configuration options, which override the default values. The most important directives are: NANO_NAME Name of build (used to construct the workdir names). NANO_SRC Path to the source tree used to build the image. NANO_KERNEL Name of kernel configuration file used to build kernel. CONF_BUILD Options passed to the buildworld stage of the build. CONF_INSTALL Options passed to the installworld stage of the build. CONF_WORLD Options passed to both the buildworld and the installworld stage of the build. FlashDevice Defines what type of media to use. Check the FlashDevice.sub file for more details.