umount2: Device or resource busy

mount point busy
device is busy

not able to unmount unix

apt-amd-02:~ # umount -f /opt
umount2: Device or resource busy
umount: /opt: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
umount2: Device or resource busy

find the process through lsof

apt-amd-02:~ # lsof /opt <<<<<<<<<<<<-------
lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/anujs/.gvfs
Output information may be incomplete.
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
kdm 1828 root txt REG 253,1 156904 83982271 /opt/kde3/bin/kdm
kdm 2022 root txt REG 253,1 156904 83982271 /opt/kde3/bin/kdm
acroread 5322 root mem REG 253,1 11664616 117462946 /opt/kde3/share/icons/hicolor/icon-theme.cache
bash 6061 root cwd DIR 253,1 4096 94473498 /opt/app/oracle/product/10.2/db10g/agent10g
bash 24434 root cwd DIR 253,1 4096 33666700 /opt/app/oracle/oraInventory/logs
firefox 31691 anujs mem REG 253,1 11664616 117462946 /opt/kde3/share/icons/hicolor/icon-theme.cache


kill all the process


apt-amd-02:~ # kill -9 1828 2022 5322 6061 24434 31691

apt-amd-02:~ # umount -f /opt
apt-amd-02:~ # mount /opt
apt-amd-02:~ # df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 10G 8.7G 1.4G 87% /
devtmpfs 1003M 452K 1003M 1% /dev
tmpfs 1005M 16K 1005M 1% /dev/shm
/dev/sda1 69M 59M 5.9M 91% /boot
/dev/mapper/system-home
42G 24G 17G 59% /home
/dev/mapper/system-opt
20G 14G 7.0G 66% /opt