umount

umount
  -V      # print version
  -h      # help
  -v      # verbose
  -n      # unmount w/o writing in /etc/mtab
  -r      # if unmount failed, try to remount read-only
  -d      # if unmouned device is loop device, also free this loop device
  -i      # do not call the /sbin/umount.filesystem helper (called by default)
  -a      # unmount all devices listed in /etc/mtab
  -t      # actions for a file system of a specific type
  -O      # actions for fs with specified options in /etc/fstab
  -f      # force unmount (in case of unreachable)
  -l      # "lazy" unmount ( perform when filesystem is not busy)
  --fake  # used to remove entries from /etc/mtab that were unmounted earlier with -n