'mount -u' stumper

[Robert Bonomi]

> From owner-freebsd-questions at freebsd.org  Wed Jun 22 07:11:09 2011
> Date: Wed, 22 Jun 2011 13:10:35 +0100
> From: RW <rwmaillists at googlemail.com>
> To: freebsd-questions at freebsd.org
> Subject: Re: 'mount -u' stumper
>
> On Wed, 22 Jun 2011 06:45:27 -0500 (CDT)
> Robert Bonomi wrote:
>
> > 
> > Environment is FreeBSD 7.2  i386
> > 
> > I have a Berkeley FFS filesystem that is mounted ro at boot time.
> > 
> > If I do a 'mount -u' to make it writable, it _is_ made writable, but
> > "soft-updates' is also set.   Incidentally, does anybody know _where_
> > the 'soft-updates' optioon is documented??  I've looked evereywhere I
> > can think of, brute-force grepped wholee sections of
> > the /usr/share/man directory tree, all without succeess.
> > 
> > If I use 'mount -u -r' to return it to the readonly state,
> > 'soft-updates' is *still* set.
> > 
> > _HOW_ do I make'soft-updates' go away on a mounted filesystem ??
>
>
> It's set because sysinstall uses  newfs -U by default for non-root
> filesystems. You can turn it off with tunefs, although I don't see what
> difference it makes if it's  mounted ro.

That's a large part of why I want to make it 'go away'.  It _is_ a "lie"
on a RO system.  Meaningless, and 'misleading' if you don't see the RO
option as well.

When the filesystem _does_ need to be RW, I _want_ softupdates enabled.
It's a 'good thing' then;.  When it's initially mounted RO softupdates
are _visibly_ off.  I just want to restore that precise situaion/presentation
when i 'update' mount thefilesystem to RO.

Looks like I'm going mount(8) and/or kernel hacking.   
a