unmount

Unmounting is the process of detaching a previously mounted filesystem or device from a computer’s directory tree. After unmounting, the files on that filesystem are no longer accessible through the mount point, and the system stops presenting the data via that path. Unmounting is performed to safely remove media, detach network shares, or to prepare a device for maintenance, while preserving data integrity and freeing system resources.

In Unix-like systems, the standard command is umount (spelled without the final “n”). The command attempts to flush pending writes and release the mount point. Common options include -l for a lazy unmount, which detaches the filesystem and cleans up references later; -f for a forced unmount when the device is busy; -n to avoid updating /etc/mtab. The -a option unmounts all mounted filesystems, typically with safeguards. If an unmount fails because the filesystem is busy, tools such as lsof or fuser can identify processes using the mount, which should be closed before retrying.

Across other platforms, the concept persists with different tools. On macOS, diskutil unmount or diskutil unmountDisk removes the association between the filesystem and its mount point. On Windows, users typically eject removable media or use Disk Management to dismount volumes or detach virtual disk images. The overarching goal remains the same: ensure all data is safely written, no active I/O remains, and the device can be removed or repurposed without risking corruption.

See also: mount, mount point, filesystem, data integrity, device removal.