umount
umount功能说明：卸除文件系统。
语 法：umount [-ahnrvV][-t <文件系统类型>][文件系统]
补充说明：umount可卸除目前挂在Linux目录中的文件系统。
参 数：
-a 卸除/etc/mtab中记录的所有文件系统。
-h 显示帮助。
-n 卸除时不要将信息存入/etc/mtab文件中。
-r 若无法成功卸除，则尝试以只读的方式重新挂入文件系统。
-t<文件系统类型> 仅卸除选项中所指定的文件系统。
-v 执行时显示详细的信息。
-V 显示版本信息。
[文件系统] 除了直接指定文件系统外，也可以用设备名称或挂入点来表示文件系统。
umount
umount [options] [directory]
System administration command. Unmount filesystem specified by directory. You may also specify the filesystem by device name. umount announces to the system that the removable file structure previously mounted on the specified directory is to be removed. Any pending I/O for the filesystem is completed, and the file structure is flagged as clean. A busy filesystem cannot be unmounted.
Options
Unmount all filesystems listed in /etc/mtab other than /proc.
If the unmounted device was a loop device, free the loop device too. See also the losetup command.
Force the unmount. This option requires kernel 2.1.116 or later.
Print help message and exit.
Lazy unmount. Detach the filesystem from the hierarchy immediately, but don't clean up references until it is no longer busy. Requires kernel 2.4.11 or later.
Unmount, but do not record changes in /etc/mtab.
Unmount only filesystems with the specified options in /etc/fstab. Specify multiple options as a comma-separated list. Add no as a prefix to an option to indicate filesystems that should not be unmounted.
If unmounting fails, try to remount read-only.
Unmount only filesystems of type type. Multiple types can be specified as a comma-separated list, and any type can be prefixed with no to specify that filesystems of that type should not be unmounted.
Verbose mode.
Print version information and exit.