Unmounting a device that is currently “busy”.
Often times working on servers when using external hard drives or some other sort of drive that needs unmounted, you'll sometimes encounter "Device is busy" when trying to unmount it:
[root@p97650 934627]# umount /external/ umount: /external: device is busy umount: /external: device is busy
In this example, I currently have /dev/sdb1 (external drive) mounted to /external :
[root@p97650 934627]# fuser -m /dev/sdb1 /dev/sdb1: 11686
Now you want to find what process is running that is keeping it busy:
[root@p97650 934627]# ps aux | grep 11686 root 11686 28.1 0.0 5428 1820 ? Ss 02:20 35:28 /sbin/mount.ntfs /dev/sdb1 /external/ -o rw root 17934 0.0 0.0 4020 700 pts/0 S+ 04:26 0:00 grep 11686
Great, now lets kill that process and unmount the drive:
[root@p97650 934627]# kill -9 11686 [root@p97650 934627]# umount /external [root@p97650 934627]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup-lv_root 225G 59G 155G 28% / /dev/sda1 244M 15M 216M 7% /boot tmpfs 1013M 0 1013M 0% /dev/shm /usr/tmpDSK 2.1G 68M 1.9G 4% /tmp