New option for newfs(3) to make life with GEOM easier

Bernd Walter ticso at
Mon Sep 3 04:48:58 PDT 2007

On Mon, Sep 03, 2007 at 01:20:12PM +0200, Ivan Voras wrote:
> Bernd Walter wrote:
> >Don't get me wrong, I'm not against cutting a few sectors per default,
> >just want to have a fallback.
> Fallback would be to say "-r 0", presumably.
> >However, I would still prefer if users get a warning if they try to
> >use a filesystem, which overflows the media.
> >I guess the foot-shooting is quite common about this point.
> How would the file system overflow the media? The case discussed here is 
> shrinking the file system to be a few sectors smaller than the media 
> size (i.e. those few sectors would be unused by the fs).

In case the media shrinks due to adding gmirror and the fielsystem
wasn't reduced.
I've seen an unbelieveable amount of systems were this was simply
forgotten, fortunately almost all of them mirror the whole device
and fdisk leaves quite a few sectors untouched in many cases.
It is a different point, but about the same problem.
Changing newfs defaults will help about new installations, but not
updating older systems, and it even catches those that already use
gmirror in such a faulty confguration.

bernd at           info at            support at

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