umount

Unmount filesystems. Remove a special device or the remote node (rhost:path) from the filesystem tree at the point node. If either special or node are not provided, the appropriate information is taken from the fstab(5) file.

Syntax
      umount [-fv] special | node

      umount -a | -A [-fv] [-h host] [-t type]

Options
     -a      All the filesystems described in fstab(5) are unmounted.

     -A      All the currently mounted filesystems except the root are
             unmounted.

     -f      The filesystem is forcibly unmounted.  Active special devices
      continue to work, but all other files return errors if further
      accesses are attempted.  The root filesystem cannot be forcibly
      unmounted.

     -h host
      Only filesystems mounted from the specified host will be
      unmounted.  This option is implies the -A option and, unless oth-
      erwise specified with the -t option, will only unmount NFS
      filesystems.

     -t type
      Is used to indicate the actions should only be taken on filesys-
      tems of the specified type.  More than one type may be specified
      in a comma separated list.  The list of filesystem types can be
      prefixed with ``no'' to specify the filesystem types for which
      action should not be taken.  For example, the umount command:

      umount -a -t nfs,hfs

      umounts all filesystems of the type NFS and HFS.

     -v
      Verbose, additional information is printed out as each filesystem
      is unmounted.

FILES
     /etc/fstab  filesystem table

“Be nice to people on the way up, because you'll meet them on your way down” ~ Wilson Mizner

Related macOS commands:

hdiutil - manipulate disk images
mount - Mount a file system
fstab(5) -