- use new getvfsbyname() interface.
- new -A option, like -a except only mounted file systems are unmounted.
All non-cosmetic FreeBSD changes in umount.c, except ignoring of
realpath() failures, went away because they are done better in Lite2.
realpath() failures must be ignored so that non-pathnames like
"<above>:/foo" and "host:/bar" get as far as mount(2).
Reviewed by: dfr
/sbin/umount does not return the correct exit status due to incorrect
logic in its internals.
Further, because of the nature of the code, you *cannot* use it to
umount a directory from a union mountpoint. Well, you can sometimes,
it depends on if the directory is at the top of the union stack or not :)
Submitted by: njw@cs.city.ac.uk (Nick Williams)
