umount: device is busy
Sometimes after mounting some nfs devices, you cannot easily un-mount them. You get some error: “device is busy”. I often get this error when I want to un-mount some shared folders like ‘/home’ and ‘/usr’.The reason is simple: the devices you are un-mouting are busy;) That’s to say some files on the mouted devices are being used by some process.
On internet you can find a lot of posts talking this problem. The essential thing is to figure out what processes are using the device and kill them. You can try ‘fuser’, ‘lsof’, ‘ps|grep’ . But in my cases, those commands don’t always work. Then I suggest you try ‘umount -l the_device’. This command solved my problem and most probably it should work for you too.
The ‘-l’ option for umount means ‘lazy unmount’, which detaches the filesystem from the filesystem hierarchy and cleanups all references to the filesystem as soon as it is not busy anymore. It needs kenerl version higher than 2.4.11.
