Bill Studenmund <wrstuden@netbsd.org> writes:

> -o union does an aggregation of all the files in both the "upper" and 
> "lower" directories. It's a quick&simple feature to let you mount fdesc 
> (mount_fdesc) file systems over /dev and yet keep all your existing 
> devices.

It also does a passable job at being a unionfs-lite, when one doesn't
want to touch the actual unionfs with a 10-foot pole because it panics
all the time, and a single level of unioning is all that's needed (or
at least the requirements can be shoehorned into working with it).

-- 
(let ((C call-with-current-continuation)) (apply (lambda (x y) (x y)) (map
((lambda (r) ((C C) (lambda (s) (r (lambda l (apply (s s) l))))))  (lambda
(f) (lambda (l) (if (null? l) C (lambda (k) (display (car l)) ((f (cdr l))
(C k)))))))    '((#\J #\d #\D #\v #\s) (#\e #\space #\a #\i #\newline)))))