From owner-freebsd-questions@FreeBSD.ORG Thu May 1 12:33:05 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 70D701065670 for ; Thu, 1 May 2008 12:33:05 +0000 (UTC) (envelope-from fbsd.questions@rachie.is-a-geek.net) Received: from snoogles.rachie.is-a-geek.net (rachie.is-a-geek.net [66.230.99.27]) by mx1.freebsd.org (Postfix) with ESMTP id 3D2AF8FC19 for ; Thu, 1 May 2008 12:33:05 +0000 (UTC) (envelope-from fbsd.questions@rachie.is-a-geek.net) Received: from localhost (localhost [127.0.0.1]) by snoogles.rachie.is-a-geek.net (Postfix) with ESMTP id 067FD1CC91; Thu, 1 May 2008 04:33:03 -0800 (AKDT) From: Mel To: freebsd-questions@freebsd.org Date: Thu, 1 May 2008 14:33:02 +0200 User-Agent: KMail/1.9.7 References: <200805011019.50895.fbsd.questions@rachie.is-a-geek.net> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200805011433.02733.fbsd.questions@rachie.is-a-geek.net> Cc: "A. Hamilton-Wright" Subject: Re: dmesg empty after shutdown -r X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 May 2008 12:33:05 -0000 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.