umount [-dflnrv] dir | device […]
umount -a [-dflnrv] [-t vfstype] [-O options]
Detaches the file system(s) from the file hierarchy.
dir is the directory where the file system is mounted ( aka mount point).
Filesystems cannot be unmounted when 'busy' - ie. when any process's current working directory is there,
have files are open on it or when it contains an active swap file.
-l may be allow the filesystem to be eventually unmounted.
Loop device will be freed if associated with the mount, when
-d was given. Any pending loop devices can be freed using
losetup -d, see losetup
The syntax of external umount helpers is:
/sbin/umount.suffix [-nlfvr] dir | device
suffix is filesystem type or a value from "uhelper=" mtab option.
The uhelper (unprivileged umount request helper) may be used when non-root user wants to umount a mountpoint which is not defined in
/etc/fstab (e.g devices mounted by HAL).
/etc/mtabtable of mounted file systems