Comment 3 for bug 1124803

Max (m-gorodok) wrote :

Please, issue an update for 12.10 quantal (network-manager 0.9.6.0-0ubuntu7)
Due to this bug root filesystem can not be cleanly unmounted on shutdown.

Upstart launch NetworkManager as a daemon.
If a system-wide network connection is established,
dhclient and dnsmasqd open files for writing in /var directory.
During shutdown upstart sends SIGTERM to NetworkManager,
but the signal is blocked. 5 seconds later NetworkManager
is killed (SIGKILL) by upstart, but dhclient and dnsmasq are alive.
Also the directory /var/run/sendsigs.omit.d/ contains the following files

network-manager.dhclient-eth0.pid network-manager.dnsmasq.pid

At the very end /etc/init.d/umountroot can not unmount / filesystem
due to files open for writing by dhclient in /var/lib/dhcp

mount: / is busy

Message appears before poweroff. To make it apparent use
sudo halt
command.

There are a bunch of bugs (e.g. #1061639, #1073433, etc)
sometimes with mistereous comments and workarounds.
They can be connected with this issue.

I suppose that filestem recovery on every boot is strong reason for
package update in quantal