When trying to unmount (via umount) a file system, I get 2 infamous "device is busy" messages. I've used both the lsof and fuser commands but nothing gets returned that references the file system I'm trying to unmount.

I've even tried to force an unmount, but that didn't work either. What was even more weird was that (as a test) I created a file on that file system and had it open and then used the lsof / fuser command to see what response I would get. Basically the response from both commands was blank.

Short of removing the mount entry from /etc/fstab and rebooting, is there another method for determining what file/process is attached to the file system that would cause it to show up as device is busy? Is there another method for forcing an unmount?

It doesn't want to unmount even if you're in the mounted fs's directory, but I'm sure you knew that already.

If you were viewing the filesystem in a filemanager such as Konquerer, or if you had a console open into that filesystem (as in cd to the filesystem), then the filesystem is busy. You will have to cd out of the filesystem, or close the file manager to release the filesystem for umount.

What is the mount point for the device? You said you ran lsof. Hmm, that should show you if any programs are blocking it. Make sure you run lsof as root (or with sudo), and use fgrep, like this:
If that doesn't show anything I'm stumped.

Thanks for the reply...however...I've tried the lsof | fgrep command and as far as I know there are no known consoles that are open to this filesystem. There must be a hung process or file somewhere that's attached to the filesystem. I've also used who extensively but that didn't reveal any login in sessions either.

Oh well...looks like a reboot on Monday.

If a process is hung, it's files should still be listed in lsof. You're running it as root?

Yes...I was running it as root.