From owner-freebsd-stable@freebsd.org Mon May 2 21:26:07 2016 Return-Path: Delivered-To: freebsd-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 39D7FB2A8EB for ; Mon, 2 May 2016 21:26:07 +0000 (UTC) (envelope-from jilles@stack.nl) Received: from mx1.stack.nl (relay04.stack.nl [IPv6:2001:610:1108:5010::107]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client CN "mailhost.stack.nl", Issuer "CA Cert Signing Authority" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 065561768; Mon, 2 May 2016 21:26:06 +0000 (UTC) (envelope-from jilles@stack.nl) Received: from toad2.stack.nl (toad2.stack.nl [IPv6:2001:610:1108:5010::161]) by mx1.stack.nl (Postfix) with ESMTP id 54DFEB8061; Mon, 2 May 2016 23:26:03 +0200 (CEST) Received: by toad2.stack.nl (Postfix, from userid 1677) id 19290892D2; Mon, 2 May 2016 23:26:04 +0200 (CEST) Date: Mon, 2 May 2016 23:26:04 +0200 From: Jilles Tjoelker To: Melissa Jenkins , Edward Tomasz =?utf-8?Q?Napiera=C5=82a?= , freebsd-stable@freebsd.org Subject: Re: 10.3 and reboot -r (reroot) Message-ID: <20160502212604.GA9127@stack.nl> References: <45B67BCE-540F-432A-9AA2-192B20312D27@littlebluecar.co.uk> <20160419104654.GC5543@brick.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160419104654.GC5543@brick.home> User-Agent: Mutt/1.5.23 (2014-03-12) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 May 2016 21:26:07 -0000 On Tue, Apr 19, 2016 at 12:46:54PM +0200, Edward Tomasz Napierała wrote: > On 0419T0906, Melissa Jenkins wrote: > > I've been trying to get reboot -r to work but get an error that > > kern.proc.pathname is undefined. It then drops to single user mode. > > Interestingly I've checked the value of kern.proc.pathname and it > > appears to be undefined on all the OS boxes we have from 9.3 up to > > current. In fact the kern.proc tree doesn't appear to contain > > anything though it does exist at least on some of the boxes. > The kern.proc.pathname is a weird sysctl. It's per-process, and it's > impossible to access it via name, only by numeric ID. So, this is > normal. > The fact that reroot doesn't work because of this is not normal, > though. I have no idea why this would fail; I'll investigate. I can make it fail this way easily by installing a new init(8) binary. This makes the kern.proc.pathname sysctl fail because /sbin/init has been moved away or deleted. The command procstat -b 1 uses the same vnode-to-pathname translation code and fails similarly. If only a single install has been done, a command ls -l /sbin/init* will make the kernel realize that /sbin/init.bak is in fact the pathname of process 1's executable, and both procstat -b 1 and reboot -r start working. However, the reroot will use the old init binary to perform reboot(RB_REROOT) and to find init in the new root file system, which may be undesirable. It may be better to use the original argv[0]. The kernel passes a full pathname here. While reading the code, I noticed another issue. The kill(-1, SIGKILL) may fail with [ESRCH] if there is no process to kill. In this case, the reroot should continue. This problem sometimes occurs for me when rerooting from single user mode. -- Jilles Tjoelker