I have mounted an ISO-file to do a network install of Red Hat. Afterwards, I removed the ISO and forgot about the mount.
Now, I am unable to unmount this mount, because the target no longer exists...
Here's the error I get when I try to unmount:
Even if I put all the files back and remount, I cannot unmount is, this is probably because it uses a different inode now.
How can I get rid of this listing in mount? I do not want to reboot this machine, since it has almost 1 year uptime...
You can edit /etc/fstab (and perhaps reboot).
I manually mounted it, so it was not listed in /etc/fstab... 
I had kind of hoped to resolve this without a reboot... Thanks anyway.
Try umount -f to force the unmount of the now dead ISO image or try to umount by the mounted sub-dir name:
umount /mnt/some_iso_image_of_redhat
Sigh.... It no longer matters, the problem is solved...
I had a power outage and it took a little longer than the UPS's could provide for... My entire home-network performed a shutdown... Most of these machines had been on for as long as one year...
Bye bye uptime...
What a waste...
Thanks to all who replied!
It was just Mr. Murphy trying to show you the way he wanted it done... 
Now thats got to hurt!! 