I have two i586 machines running RH6.0 Machine A has a
CD-ROM drive which it mounts (ro) on /mnt/cdrom, and
NFS-exports it (ro) to Machine B. If I mount /mnt/cdrom on
Machine A, then on machine B, unmount on machine B, and then
attempt to umount it on machine A, I'm told that the
filesystem is busy. Consequently I have to reboot the
machine to eject the CD-ROM, which is a real pain.
Yes, you are not going to need to un-export the cdrom before you are
going to be able to unmount the drive. NFS is "using" it and
therefore you are getting the message that you are seeing.