* When testing whether the fdesc file system is mounted, parse the
  output from mount(8) rather than df(1), because mount is more likely
  to be available on install media.  mount is invoked in a way that
  always prints an error message, and the content of the error message
  tells us whether fdesc is mounted.
* Don't use negative variable names.  Instead of nofdesc=false, use
  fdesc_mounted=true.
* Add a comment explaining that MAKEDEV may be executed in an environment
  that is missing some common commands.

(apb)