SU+J on 9.1-RC2 ISO

Mateusz Guzik mjguzik at
Fri Nov 2 18:31:34 UTC 2012

On Sat, Nov 03, 2012 at 12:27:18AM +0700, Adam Strohl wrote:
> On 11/3/2012 0:13, Mike Jakubik wrote:
> >You can disable SU+J after installing, though it would be nice if the
> >installer gave you a choice.
> This assumes that you know about this flaw, which most people do not.
> I didn't until I discovered it by panic-ing a perfectly fine running
> server.  Getting burned by a known bug like this shouldn't be "SOP"
> for users of FreeBSD.

Currently when you try to take a snapshot, the kernel checks whether SUJ
is enabled on specified mount-point, and if yes it returns EOPNOTSUPP.

See this commit (MFCed as r230725): 

So it's not that bad.

> If anything it should be turned off by default, and people can turn
> it on if they want given the landmine it plants.  If they know how
> to turn it on they're much more likely to be aware of the issue.

That being said, sure, you may run into another bugs, but if SUJ was
enabled by default I guess it was felt that it works well enough (and in
case of known bugs like problems with snapshots just bails out early).

Mateusz Guzik <mjguzik>

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