From owner-svn-src-head@freebsd.org Sat Sep 26 17:02:14 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 2C979423F61; Sat, 26 Sep 2020 17:02:14 +0000 (UTC) (envelope-from freebsd@gndrsh.dnsmgr.net) Received: from gndrsh.dnsmgr.net (br1.CN84in.dnsmgr.net [69.59.192.140]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4BzFSj3sdPz3ZSJ; Sat, 26 Sep 2020 17:02:13 +0000 (UTC) (envelope-from freebsd@gndrsh.dnsmgr.net) Received: from gndrsh.dnsmgr.net (localhost [127.0.0.1]) by gndrsh.dnsmgr.net (8.13.3/8.13.3) with ESMTP id 08QH2AsT055655; Sat, 26 Sep 2020 10:02:10 -0700 (PDT) (envelope-from freebsd@gndrsh.dnsmgr.net) Received: (from freebsd@localhost) by gndrsh.dnsmgr.net (8.13.3/8.13.3/Submit) id 08QH2AQ1055654; Sat, 26 Sep 2020 10:02:10 -0700 (PDT) (envelope-from freebsd) From: "Rodney W. Grimes" Message-Id: <202009261702.08QH2AQ1055654@gndrsh.dnsmgr.net> Subject: Re: svn commit: r365643 - head/bin/cp In-Reply-To: To: Ian Lepore Date: Sat, 26 Sep 2020 10:02:10 -0700 (PDT) CC: rgrimes@freebsd.org, src-committers , svn-src-all , svn-src-head Reply-To: rgrimes@freebsd.org X-Mailer: ELM [version 2.4ME+ PL121h (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 4BzFSj3sdPz3ZSJ X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; ASN(0.00)[asn:13868, ipnet:69.59.192.0/19, country:US]; REPLY(-4.00)[] X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 26 Sep 2020 17:02:14 -0000 > On Fri, 2020-09-25 at 10:55 -0700, Rodney W. Grimes wrote: > > > I was under the impression from previous reading and kib's response > > > that this is a complete non-issue, there's no way you can go > > > multi-user without a mounted /dev and we go to somewhat great > > > lengths to make sure we're good. > > > > Though kib can assert that, it does not change the fact that I > > frequently find /dev/null FILES on unmounted root file systems. > > > > But lets not mix the 2 separate things of boot time /dev dependency > > and build time /dev dependency. > > If you look in sys/kern/vfs_mountroot.c you can see that the code to > mount /dev is invoked unconditionally as the first step of mounting > root, and that all the calls it makes to get devfs mounted have their > results checked with KASSERTs. > > That's pretty strong evidence that devfs is mounted before rc scripts > run. That creates a situation where you are making an extraordinary > claim, so you need to provide extraordinary evidence to support it. A > sequence of actions that allows others to recreate the situation would > do the trick. I have provided ways one can look for this file in other messages of the threads. A dump of a UFS root can show it up, and iirc you can find it in a zfs send of a boot dataset. > > (A question that occurs to me: could it be that the files you've seen > got created at shutdown after devfs was unmounted, rather than at > startup? I don't know enough about the shutdown sequence to know > whether that's possible.) Its not "the files" it is "a file, /dev/null". And yes, it could be very possible that it is during shutdown. Sadly the files is usually of 0 length so leave little clue as to what is creating them. > -- Ian -- Rod Grimes rgrimes@freebsd.org