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Re: Remounting as read-only



On Fri, 14 May 2010, Steven Bellovin wrote:
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.

Yup, understood.  I just want it to work, and work properly; it's a useful 
feature for embedded systems:

        # uptime
        11:21AM up 593 days, 14:32, 0 users, load averages: 0.06, 0.08, 0.08

With, probably, half a dozen configuration changes during that time.

*nod* That's exactly how I use it too (in thousands of machines in production daily with no problems). I suppose it might be argued that you could use WAPBL now.

I think the relevant lines in the kernel should be protected by an #ifndef so that people using it aren't inconvenienced by having to maintain kernel patches.

--
Stephen


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