Date: Wed, 6 Nov 2013 11:43:50 +0100 From: Polytropon <freebsd@edvax.de> To: mexas@bris.ac.uk Cc: freebsd-questions@freebsd.org Subject: Re: ktrace help Message-ID: <20131106114350.2b6b8015.freebsd@edvax.de> In-Reply-To: <201311060915.rA69FvRp075387@mech-cluster241.men.bris.ac.uk> References: <201311060915.rA69FvRp075387@mech-cluster241.men.bris.ac.uk>
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On Wed, 06 Nov 2013 01:16:02 -0800 (PST), Anton Shterenlikht wrote: > I suspect that nginx causes my box to reboot. > I don't get a panic or anything in the logs, > just a reboot. So I wanted to see what nginx > is doing prior to reboot with ktrace. > > I launch ktrace as "ktrace nginx", > and I see that ktrace.out has some data. > However, after reboot, it's empty: > > -rw------- 1 root wheel 0 Nov 6 09:04 ktrace.out > > Is this expected? Not intended, but can maybe be explained: The ktrace.out file is continuously written to, but at the time the system crashes and reboots, the data is lost because the file system is terribly interrupted in an inconsistent state. When the system boots up again, the damaged file is restored, but the data isn't associated anymore (and therefore lost). I don't know in how far it would be possible to have ktrace's output rerouted to a different kind of storage (e. g. a slower NFS share or a pipe that a different host / machine is listening to over the network)... In that case, all output that is lucky of being transmitted can be captured and won't be lost when the accidental reboot appears. By the way, this is an excellent example of a use case for a sufficiently fast and buffered dotmatrix line printer. :-) -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...
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