Date: Thu, 1 May 2008 14:33:02 +0200 From: Mel <fbsd.questions@rachie.is-a-geek.net> To: freebsd-questions@freebsd.org Cc: "A. Hamilton-Wright" <andrewhw@ieee.org> Subject: Re: dmesg empty after shutdown -r Message-ID: <200805011433.02733.fbsd.questions@rachie.is-a-geek.net> In-Reply-To: <alpine.BSF.1.10.0805010854030.1782@qemg.org> References: <alpine.BSF.1.10.0804302052580.1123@qemg.org> <200805011019.50895.fbsd.questions@rachie.is-a-geek.net> <alpine.BSF.1.10.0805010854030.1782@qemg.org>
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On Thursday 01 May 2008 13:58:45 A. Hamilton-Wright wrote:
> > On Thursday 01 May 2008 01:58:46 A Hamilton-Wright wrote:
> >> After "shutdown -r now" and the subsequent reboot, I have
>
> (... no dmesg)
>
> On Thu, 1 May 2008, Mel wrote:
> > dmesg -M doesn't show anything either?
>
> Wish I'd thought to try that last night. I eventually shut it
> down again (shutdown -p) until I could come in this morning and
> take a look at the console while booting -- and now everything
> is fine. I have now tried a few reboots (shutdown -r) and halts
> (shutdown -h), and I have a dmesg every time it recovers.
Just for the record, I asked because by default, dmesg uses kvm_read(3) to
read the kernel's message buffer. -M tries to read the sysctl kern.msgbuf, so
in the event kvm_read screwed up somewhere without noting an error,
the 'backdoor' might just work. Pure speculation without having looked in
detail at the kernel code, but I wanted to rule it out. What I did suspect,
is that kernel's message buffer didn't get filled to begin with and that's a
whole different ballgame.
FYI: unless you really need dmesg to work for normal operations, you could've
just let it up running and use scroll-lock+arrows/pgup|down to go all the way
back up to btx loader. If it was the kernel message buffer not getting
filled, I'd suspect some kind of message complaining about that.
I know that doesn't help now, but for next time and googlers ;)
--
Mel
Problem with today's modular software: they start with the modules
and never get to the software part.
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