Can't umount a formerly mounted drive

[Ryan Stone]

On Fri, Feb 3, 2012 at 9:34 AM, Derek Tattersall <dlt at mebtel.net> wrote:
> I have two drives in a x86-64 machine.  Drive ada2 has current on it, and
> drive ada1 has 9-stable on it.  At some point, while running current, I
> mounted the /home partition from stable to copy some files and re-ipled
> the system into stable.  every thing worked properly.  Some time later I
> ipled current again.  I then noticed that the stable /home was mounted
> on /mnt.  I tried to umount it but the operation failed as /dev/ada1p7
> was not considered mounted.  Yet with out mounting I could access all
> the files on stable's /home, I could create and delete files.
>
> The current system was cvsup'ed on Wednesday this week, while the stable
> system was cvsup'ed last Sunday.  Neither system has exhibited any
> hiccups.  Can somebody explain what has happened her on the current
> system and how it should be corrected?

Does "mount" list anything as being mounted on /mnt?  If not, are you
sure that /mnt isn't a symlink to somewhere else?  Or maybe the
contents of the home directory were copied to /mnt by accident?