Hello Theodore,
please excuse the late reply, I was on business travel.

On Sun, Nov 09, 2014 at 08:19:19PM -0500, Theodore Ts'o wrote:
> On Sun, Nov 09, 2014 at 10:30:25PM +0100, Helge Kreutzmann wrote:
> > 
> > Thanks for the explanation, but would there be a way to figure out
> > this second process? I tried fuser and lsopen, both to no avail (but
> > I've might have missed the right set of options, of course).
> 
> Is there any chance that you might be using mount namespaces or bind
> mounts?  Are you using LXC, or something like schroot which might be
> doing this on your behalf without knowing it?  If so, it might be that
> although you *think* you've unmounted the file system, but in fact
> it's still mounted.  Try checking /proc/fs/ext4 and see if you see the
> device-mapper node corresponding to /dev/system_vg/video_lv.  If it's
> there, then you probably have some mount namespace where the file
> system is mounted.

None that I know of. I use LVM, but neither namespace nor bind bounds,
LXC is not installed and schroot currently not configured on this
machine.

I don't have »/proc/fs/ext4«. (But then I don't use ext4, the
partition in question uses ext3).

> Unfortunately depending on which namespaces are in use, trying to
> figure out what still has the file system mounted can be a bit of a
> mess.  If you're not using pid namespaces, you coulld look at
> /proc/<pid>/mounts for every single pid in the system, and see if one
> or more processes has a /proc/<pid>/mounts file that has the file
> system mounted.

Ok, this seems to point to something:
find /proc/ -name mounts -exec cat "{}" ";" | grep video
finds two entries.

Ok, the first one is:
/sbin/cgmanager --daemon -m name=systemd

(However, I don't use systemd on this machine, it does not really work
on this machine, and having it installed partially (though not as PID
1) caused only trouble; unfortunately sometimes hard depencendcies
require it, but I disgress).

The other entry points to the same programm, (/proc/2721/mounts and
/proc/2721/task/2721/mounts).

Now I removed cgmanager:

And e2fsck works again!

First of all, thanks for helping, I did not know about the trick with
/proc. 

Secondly should this bug be assigned to cgmanager?

(And probably a wishlist bug for the kernel to offer a reliable means
to detect mounted partitions?).

Thanks again!

Greetings

           Helge
-- 
      Dr. Helge Kreutzmann                     deb...@helgefjell.de
           Dipl.-Phys.                   http://www.helgefjell.de/debian.php
        64bit GNU powered                     gpg signed mail preferred
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