Dear All,

I'm struggling to get a union mount working.  Taking two random
directories:

crowley:david# mount -t union web web_tool
mount_union: /usr/home/david/web on /usr/home/david/web_tool: Operation
not supported by device
crowley:david#


man mount_union tells me what to do about this:

BUGS
     Without whiteout support from the filesystem backing the upper layer,
     there is no way that delete and rename operations on lower layer
objects
     can be done.  An attempt to mount a union directory under one which
does
     not have whiteout support will return EOPNOTSUPP (``Operation not
sup-
     ported'').  Whiteout support can be added to an existing FFS
filesystem
     by using the -c option of fsck_ffs(8).



...sounds like the thing I need.  However, I have now run fsck_ffs with -c
1, 2 and 3 on the relevant parition to no avail (having booted
single-user).  Not only does fsck_ffs not tell me that it is increasing
the level, it yields no difference when trying the union mount.
Helpfully, man fsck_ffs tells me that I can use dumpfs to find out the
current level of the file-system...except that this is the /usr partition
that I'm interested and `which dumpfs` = /usr/sbin/dumpfs.


Clues greatly appreciated?  If it matters this is a /arm32 machine running
-current that is probably a couple of months old by now.

Thanks,

David.

PS - Are there any disadvantages to raising the ffs level using fsck_ffs?

PPS - Assuming I can get a basic ffs on ffs union mount going, is it
possible to use NFS as the top layer?  (i.e. can white-out be done over
NFS, assuming the mounted filesystem supports it?)