xenial: Watch out for boot failures due to /etc/mtab file

[Dale Trombley]

Should we wait a couple days to do our next update or is this just for new
installs of xenial?
On Oct 29, 2015 9:43 AM, "Martin Pitt" <martin.pitt at ubuntu.com> wrote:

> Hello all,
>
> /etc/mtab is supposed to be a symlink to /proc/self/mounts (or
> /proc/mounts) for stuff to work. We've also shipped
> "debian-fixup.service" since vivid to turn a file into a symlink on
> boot.
>
> However, if you have /etc/mtab as a file (e. g. right after
> installation), current xenial's systemd will fail hard to boot with
> something like
>
> | systemd [1]: /etc/mtab is not a symlink or not pointing to
> /proc/self/mounts. This is not supported anymore. Please replace /etc/mtab
> with a symlink to /proc/self/mounts.
> | systemd [1]: Freezing execution.
>
> This is of course a really harsh failure mode, and it will be changed
> again in a few weeks or so to merely warn about that. But as these
> warnings have existed for a long time already, and nobody notices
> them, having this hard failure mode will actually tell us which places
> we need to fix. E. g. a week ago debian-installer was fixed [1], and I
> just heared on IRC that a Xubuntu desktop install fails as well; bug
> was just filed [2].
>
> We really must stop writing /etc/mtab files. It breaks libmount's
> monitoring and all kinds of old school software which still reads
> /etc/mtab directly; ideally they should of course be fixed to look
> into /proc, and /etc/mtab should just die, but there's still some way
> to go (e. g. [3]).
>
> So for now, if you see a boot failure like this, please report it and
> ping me, so that we can fix our installers, images etc. to not produce
> a broken /etc/mtab any more. After that, just remove /etc/mtab (e. g.
> temporarily boot with upstart) to resume.
>
> After we fixed our installers (ubiquity, d-i, cloud-init, etc.), we'll
> go back to warning (IOW: ignore) mode.
>
> Thanks,
>
> Martin
>
> [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=802187
> [2] https://launchpad.net/bugs/1511376
> [3] https://sourceware.org/bugzilla/show_bug.cgi?id=19108
>
> --
> Martin Pitt                        | http://www.piware.de
> Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)
>
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