1# umount 2 3 4## Command Function 5 6This command is used to unmount a file system. 7 8 9## Syntax 10 11umount [_-a [-t TYPE]_] [_dir_] 12 13 14## Parameters 15 16**Table 1** Parameter description 17 18| Parameter | Description | Value Range | 19| ------ | ------------------------------------------------------------ | -------------------------- | 20| --help | Displays the parameters supported by the **umount** command. | N/A | 21| -a | Unmounts all file systems mounted. | N/A | 22| -t | Used together with the **-a** option to restrict the file systems specified by **-a**, allowing only the file system specified by **-t** to be unmounted.| N/A | 23| dir | Specifies the directory from which the file system is to be unmounted. | Directory mounted with the file system| 24 25 26## Usage Guidelines 27 28By specifying the **dir** parameter in the **unmount** command, you can unmount the specified file system. 29 30## Note 31 32The shell does not support this command. mksh supports it. To switch to mksh, run **cd bin** and **./mksh**. 33 34## Example 35 36Run the following commands: 37 38- umount ./nfs 39 40- umount -a -t nfs 41 42 43## Output 44 45 46 47Example 1: Unmount the file system from **./nfs**. 48 49 50``` 51OHOS:/$ umount ./nfs/ 52umount ok 53``` 54 55Example 2: Unmount all NFS directories. 56 57 58``` 59OHOS:/$ umount -a -t nfs 60umount ok 61``` 62