Re: deprecating /usr as a standalone filesystem?

[Brett Parker <iDunno@sommitrealweird.co.uk>]

On 08 May 14:35, Peter Palfrader wrote:
> On Fri, 08 May 2009, David Weinehall wrote:
> 
> > On Thu, May 07, 2009 at 07:27:08PM -0500, Manoj Srivastava wrote:
> > >         No. But we do leave /usr read-only the rest of the time, which
> > >  is often 99.999% of the time. A separate /usr is required for this.
> > 
> > Uhm, no?
> > 
> > mount --bind /usr /usr
> > 
> > Should do the trick (the same mount -o remount,rw / remount,ro then
> > applies).  all thanks to the magic of subtrees :)
> 
> Yeah.  Right.
> 
> weasel@intrepid:~/tmp$ mkdir foo
> weasel@intrepid:~/tmp$ touch foo/bar
> weasel@intrepid:~/tmp$ sudo mount -o bind,ro foo foo
> weasel@intrepid:~/tmp$ touch foo/baz
> weasel@intrepid:~/tmp$ 
> 
> bind mounts don't do ro.

http://lwn.net/Articles/281157/

As of 2.6.26 it's possible, but still not right:
    fleur:/tmp# rmdir foo
    fleur:/tmp# mkdir foo
    fleur:/tmp# touch foo/blah
    fleur:/tmp# mount -o bind foo foo
    fleur:/tmp# mount -o remount,ro foo
    fleur:/tmp# touch foo/blah
    touch: cannot touch `foo/blah': Read-only file system
    fleur:/tmp# umount foo
    fleur:/tmp# touch foo/blah
    fleur:/tmp# 

So it works, just not quite as you'd expect :/

Cheers,
-- 
Brett Parker