# umount
## Command Function
This command is used to unmount a specified file system.
## Syntax
umount \[_-a \[-t TYPE\]_\] \[_dir_\]
## Parameters
**Table 1** Parameter description
Parameter
Description
Value Range
--help
Displays the parameters supported by the umount command.
N/A
-a
Unmounts all file systems mounted.
N/A
-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
dir
Specifies the directory from which the file system is to be unmounted.
Directory mounted with the file system
## Usage
By specifying the **dir** parameter in the **unmount** command, you can unmount the specified file system from the directory.
## Example
Run the following commands:
- umount ./nfs
- umount -a -t nfs
## Output
**unmount** command output:
Example 1: unmounting the file system from **./nfs**
```
OHOS:/$ umount ./nfs/
umount ok
```
Example 2: unmounting all NFS directories
```
OHOS:/$ umount -a -t nfs
umount ok
```