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Date:      Sun, 16 Oct 2016 23:41:20 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-bugs@FreeBSD.org
Subject:   [Bug 213549] /etc/rc remounts root readonly if /firstboot exists
Message-ID:  <bug-213549-8@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D213549

            Bug ID: 213549
           Summary: /etc/rc remounts root readonly if /firstboot exists
           Product: Base System
           Version: 11.0-STABLE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: conf
          Assignee: freebsd-bugs@FreeBSD.org
          Reporter: mcdouga9@egr.msu.edu

I have some custom system setup scripts that leverage "firstboot" support b=
ut I
discovered problems when trying them on FreeBSD 11 -stable and -release. The
short version is /etc/rc attempts to remount the / partition as readonly (r=
o)
at the end after it deletes /firstboot. I think this issue originated with:
https://svnweb.freebsd.org/base?view=3Drevision&revision=3D293115

Abbreviated code:
if [ -e ${firstboot_sentinel} ]; then
        [ ${root_rw_mount} =3D "yes" ] || mount -uw /
        chflags -R 0 ${firstboot_sentinel}
        rm -rf ${firstboot_sentinel}
        [ ${root_rw_mount} =3D "yes" ] || mount -ur /
fi

On a stock FreeBSD 11 install, if you touch /firstboot and reboot, here are=
 the
results:
UFS: prints "mount: /dev/vtbd0s1a: Device busy" late during boot but no
apparent harm
ZFS: succeeds in remounting / as ro even if it was rw to start with

Depending on your system configuration you might notice the issue immediate=
ly
on the console, for example programs which need to write to / will start
complaining. You can login and run mount -v to verify. Other random things =
fail
such as recording your login in 'w' output. I do not use
${firstboot_sentinel}-reboot which might be why this was not discovered, as=
 a
reboot makes the problem go away but I do not want to reboot.

Quick hack of a fix for me: comment out the last line containing "mount -ur=
 /"
but this is not a proper fix.

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