Comment 9 for bug 963106

The underlying problem is that, at system shutdown time, dhclient isn't
given the opportunity to gracefully exit, closing any files it has open.
This causes /etc/init.d/umountroot to fail. When umountroot fails, the
filesystem must be recovered.

There is, to the best of my knowledge, nothing particularly unusual with
the various installs of 12.04 that I've been testing, and the problem is
evident with all of them. One difference might be that I have the
splash screen turned off in grub and so can see the messages. Maybe
that explains why you're not seeing them.

At some point, possibly in oneiric, changes were made which put the
dhclient pid in /var/run/sendsigs.omit.d/ and I believe that's the basis
of the problem. And it IS a problem - the root filesystem should not
need recovery on every reboot. The "orphaned inodes" messages are just
icing on the cake. Do "sudo apt-get install --reinstall libc6" then
reboot, and run "dmesg | grep EXT" and you should see the messages.