umount

umount is a command used on Unix-like systems to detach a mounted filesystem from the directory tree. After unmounting, the filesystem is no longer accessible through the standard path and the resources it used are released for other uses. The command typically requires elevated privileges.

How it works

umount takes a single target argument and unmounts the filesystem that is attached at that mount point or associated with the given device. The target can be a directory that is a mount point or a device special file. In most environments, you must not be using the mount point or have open files on the filesystem when attempting to unmount it. If the filesystem is busy, unmount may fail unless supported options are used or processes are stopped.

Common options

Options and their availability vary by system, but some widely supported ones include:

- -a to unmount all filesystems listed in the system’s mount table

- -t to restrict unmounting to filesystems of a specific type

- -l to perform a lazy unmount, detaching the filesystem immediately and cleaning up references when it is no longer active

- -f to force unmount in situations where the filesystem is not responding, though support for this option varies

cautions

Unounting system-critical filesystems or those in active use can disrupt running programs and services. If unmounting fails due to being busy, tools such as fuser or lsof can identify processes using the filesystem, and administrators may choose to terminate those processes or use a lazy unmount where appropriate.

See also

Related commands include mount (to attach filesystems), fuser and lsof (to identify open files), and system-specific tools for managing storage.