Comment 34 for bug 963106

Tuhu, your ps output shows quite a lot still running. Did you execute
the command from a terminal in the desktop environment? To be helpful,
the ps and lsof commands should be run from the /etc/init.d/umountroot
script. See message #5 above.

Before adding debug commands to umountroot, you might want to try
un-checking "Available to all users" for your active network connection.
If the "mount: / is busy" message is no longer present when you shut the
system down, then your problem might be related to this bug.

Either way, you'll probably want to proceed with getting some debug
print from umountroot. There was a typo in message #5, although I'm not
sure that it makes a difference in practice. The lsof command should
read:

/usr/bin/lsof >> /DEBUG

Be sure to make a backup copy of umountroot before editing it:

sudo cp -p /etc/init.d/umountroot ~