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19.3. Unmounting a File System

To detach a previously mounted file system, use either of the following variants of the umount command:
$ umount directory
$ umount device
Note that unless this is performed while logged in as root, the correct permissions must be available to unmount the file system. For more information, see Section 19.2.2, “Specifying the Mount Options”. See Example 19.9, “Unmounting a CD” for an example usage.


When a file system is in use (for example, when a process is reading a file on this file system, or when it is used by the kernel), running the umount command fails with an error. To determine which processes are accessing the file system, use the fuser command in the following form:
$ fuser -m directory
For example, to list the processes that are accessing a file system mounted to the /media/cdrom/ directory:
$ fuser -m /media/cdrom
/media/cdrom:         1793  2013  2022  2435 10532c 10672c

Example 19.9. Unmounting a CD

To unmount a CD that was previously mounted to the /media/cdrom/ directory, use the following command:
$ umount /media/cdrom