Comment 21 for bug 1061639

Ok, I've experienced again the problem on a new machine on which quantal was installed from scratch.
This is everything I've done to solve all issues and get back to a fast 5 seconds shutdown with no filesystem corruption:

- rm /etc/init/modem-manager.conf (it's started by network manager via dbus, we don't need a separate conf...)
- edit /etc/init/modem-manager.conf and /etc/init/dbus.conf to stop also on "runlevel [06]" (i.e. add "or runlevel [06]" at the end of "stop on" line
- add a "cleanup" script (chmod 755) in /etc/network/if-down.d/ which does "killall dhclient" and "killall dnsmasq"

If the machine is upgraded from older ubuntu versions check that there are no more references to /etc/init.d/networking from /etc/rc*.d directories.

Probably at this point is not ifupdown that should be patched anymore, but I decided to post here since this is one of the bug that most users should land searching for the problem.
If the above changes work for other users then separate bugs against each involved package should be filed. I hope someone else can eventually take care of it.