I've searched around here on SX and other places but have not found an approach that gives me any traction on my issue. I've a volume (used by Time Machine as it happens) on an external Firewire drive. When the drive is connected, it has 3 volumes. Two out of three eject with no problems but the last one (LaCie) can never be unmounted unless by force (e.g.
$ umount -f LaCie). I can see the drive being accessed almost continuously but I have no idea which process is doing this; and
lsof is of limited help. Mostly it returns no results as below but occasionally it reports that Finder has a directory open on the volume. But I don't see why that would be a problem as Finder should close any open files or directories when a volume is unmounted. This problem only arose after I upgraded to Mountain Lion. I use a cloning tool (SuperDuper!) but have made sure that is not running; and
lsof appears to confirm this. How else can I find out what is locking up the volume? I'm not keen on forcibly ejecting the volume every time I want to disconnect the drive as I surely risk data loss on my main backup disk.
~ $ sudo diskutil unmount /Volumes/LaCie/ Volume LaCie on disk1s1 failed to unmount ~ $ lsof | grep LaCie ~ $ lsof | grep /Volumes/LaCie ~ $