>> Though I'm not sure where I am supposed to mount [the file desc file
>> system].

> You mount it on /dev/fd and "ln -s /dev/fd/0 /dev/stdin" etc.

> At least this is the way SysVR4 did it.  This was the first place I
> saw a file descriptor file system (it was a beta SysVR4 ~1990.)

No, ken you use the "-o union" to merge FDESC into /dev:

mount_fdesc -o union fdesc /dev

in /etc/fstab:

fdesc   /dev    fdesc   rw,union