[autofs] problems with "dirty" UFS2 partitions

[Cy Schubert]

In message <20170808132621.1f14cc1d at freyja.zeit4.iv.bundesimmobilien.de>, 
"O. H
artmann" writes:
> On Mon, 07 Aug 2017 23:48:15 -0700
> Cy Schubert <Cy.Schubert at komquats.com> wrote:
> 
> 
> Just for convenience, I 'glued" Warner Losh's messages below and reply inline
> as usual.
> 
> > In message <20170808071758.6a815d59 at freyja.zeit4.iv.bundesimmobilien.de>, 
> > "O. H
> > artmann" writes:
> > > Hello,
> > > 
> > > we're running a NanoBSD based appliance which resides on a small SoC and
> > > utilises a mSATA SSD for logging, database storage and mail folder. The
> > > operating system is recent CURRENT as it is still under development.
> > > 
> > > The problem ist, that from time to time, without knowing or seeing the
> > > reason ,
> > > the automounted partitions become "dirty (UFS2 partitions, no ZFS dur to
> > > memory and performance limitations). Journaling is enbaled.
> > > 
> > > When the partitions on the SSD become "dirty", logging or accessing them
> > > isn' t
> > > possible anymore and for some reason I do not see any log entries reporti
> ng
> > > this (maybe due to the fact all logs are going also to that disk since th
> e
> > > lo gs
> > > would pollute the serial console/console and the console is used for
> > > maintenance purposes/ssh terminal).
> > > 
> > > Is it possible to - automated! - check the filesystem on bootup? As on
> > > ordina ry
> > > FreeBSD systems with fstab-based filesystems, this happens due to the
> > > rc-init-infrastructure but autofs filesystems seem to be somehow standing
> > > asi de
> > > from this procedure.  
> > 
> > I'd be interested in finding out if your system either panicked or simply 
> > failed to unmount the filesystems in question during a boot or shutdown. Is
>  
> > the SSD being removed prior to FreeBSD having the chance to unmount it? I 
> > think if we answer These questions we're more than half way there.
> 
> The system in question is logging onto this mSATA SSD and the filesystem is
> mounted/unmounted via autofs. I do not see any syystem/core faults when doing
>  a
> reboot and the cases, where the filesystem is unclean after a reboot are rare
> .
> But it is even deadly if the system is required to log (it is a
> routing/PBX/DNS/firewalling system with FAX and answering machine/recording
> facilities). 
> 
> The only clue I have is that due to the unmount attempt of autounmountd while
> still writing logging data the filesystem remains in an unclean condition. Bu
> t
> the question is then what is causing this condition.

It's not unmounting for this very reason. It can't. (Try umount of a 
filesystem which has files still open.)

> 
> > 
> > Warner has a good suggestion worth considering.
> > 
> > Another option might be to use amd program maps. The program map being a 
> > program or script that would run fsck prior to issuing a mount. Having said
>  
> > that, this treats the symptom rather than addressing the cause. It's 
> > preferred to discover the cause so that autofs (or amd) can mount a clean 
> > filesystem.
> 
> Is this also possible with the in-kernel autofs facility? I replaced the amd
> daemon by the more modern autofs feature and - sorry - I didn't look into the
> man page while writing the mail. I'll check that out.
> 
> The main question is, if the above described condition of writing log data an
> d
> unmount at the same time results in an unresolvable race condition, to simply
> mount the SSD filesystem via /etc/fstab. The box is booting off a SD card, th
> e
> mSATA SSD is for loggin/data only and I wanted it to make it as robust as
> possible with the main on having the firewall/router online to let traffic
> traverse instead of being blocked when the system fails mounting a filesystem
> ,
> which is not necessary for survival. To have log or to have traffic passing i
> s
> the essential question to answere here ...

You could mount late or issue an fsck in rc.local. In rc.local, if it fails 
simply spit out an error message (or email).

> 
> 
> > 
> > 
> 
> [from Warner Losh]
> > Can't you just list them in /etc/fstab with the noauto option, but with a
> > non-zero number listed in the 'pass' number column? I know nanobsd doesn't
> > generate things this way, but maybe it should....
> >
> > Warner
> 
> I haven't though of this ever - will it force a check of a dirty filesystem
> even when it is mounted via autofs? I considered /etc/fstab and autofs as
> mutual exclusive - in my naive view ...
> 
> Thank you very much,
> 
> Oliver 


-- 
Cheers,
Cy Schubert <Cy.Schubert at cschubert.com>
FreeBSD UNIX:  <cy at FreeBSD.org>   Web:  http://www.FreeBSD.org

	The need of the many outweighs the greed of the few.