Date: Sat, 26 Sep 2020 10:02:10 -0700 (PDT) From: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> To: Ian Lepore <ian@freebsd.org> Cc: rgrimes@freebsd.org, src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org> Subject: Re: svn commit: r365643 - head/bin/cp Message-ID: <202009261702.08QH2AQ1055654@gndrsh.dnsmgr.net> In-Reply-To: <a1302355a272f5790562551dfe7631c280107b55.camel@freebsd.org>
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> 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
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