After mucking around with all the Plymouth stuff in the earlier comments, I can also confirm that simply unchecking 'Available to all users' on my Ethernet connection in Network Manager fixed the problem of unclean mounts at shutdown and reboot.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1019347 Title: A message: "mount: / is busy" appears every time shutting down or rebooting. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/plymouth/+bug/1019347/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
