System doesn't shutdown anymore

[Removed by request]

I'm using Ubuntu 15.10 dev and for a few days I'm noticing that my system doesn't fully shutdown anymore. If I'm shutdown the system from the desktop environment (LXDE desktop with LXDM as login manager) the graphical interface exits and it hangs then while showing the console output. The last line in this output is "Unmounting local filesystems...".

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1471284/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[Martin Pitt (pitti)]

Can you please follow /usr/share/doc/systemd/README.Debian to debug this shutdown hang? I. e. start the debug shell, shut down, Ctrl+Alt+F9 to switch to it, and do

  systemctl list-jobs > /root/jobs.txt
  journalctl -b > /root/journal.txt
  reboot -f

then attach /root/jobs.txt and /root/journal.txt here? Thanks!

If saving the files does not work any more because the root fs is already readonly, please do "mount -o remount,rw /" and re-do the systemctl/journalctl commands. Thanks!

[Removed by request (removed3425744)]

On my system upstart-sysv is installed so the steps for systemd will maybe not work.

[Removed by request (removed3425744)]

I'm wondering if this ( https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1491005 ) has something to do with it. Is /etc/mtab checked on shutdown? If yes maybe /proc/mounts should be directly used instead.

[Martin Pitt (pitti)]

I can't say for sure, but a wrong /etc/mtab surely wreaks some havoc. Try replacing it with a symlink to /proc/mounts and see if that helps things?

[Removed by request (removed3425744)]

I have tested this now but the system still hangs on shutdown.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Removed by request (removed3425744)]

Any idea how to debug this more? It is a bit annoying to always shutdown the PC physically by holding the power button for 5 seconds which causes also often that the fast filesystem check on booting claims about orphan inodes.