Re: Remounting as read-only

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Fri, May 14, 2010 at 01:27:08PM +0000, Wouter Klouwen wrote:
> Emmanuel Dreyfus(manu%netbsd.org@localhost) said 2010.05.14 13:13:47 +0000:
> > On Fri, May 14, 2010 at 01:00:53PM +0000, Emmanuel Dreyfus wrote:
> > > Of course I acan umount and remount, but that invalidate file descriptors
> > > that had been open read-only on the filesystem. Isthere any trick to get
> > > it working as it worked on NetBSD 4?
> > 
> > Ok, I found it: mount -f -u /flash
> 
> That updates it to rw, which is not what you want. There was another person
> asking for this in NetBSD 5.0. Turns out it can't sync meta data upon
> remount read only: http://gnats.netbsd.org/30525

I'm not sure what you mean by "it", but I should point out that the bug
in question -- kernel doesn't sync metadata on read-only remount -- is
extremely old, and *did* cause disk corruption after r/o remount set
the filesystem "clean" flag, thus corruption fsck would never find and
which could potentially eat your disk over time.

It's *always* been broken.  Not just in NetBSD, probably in 4.4BSD
and prior kernels as well.  It is unquestionably broken at least in older
releases of the other BSDs as well. We have opted for safety over a false
sense of security.

Thor