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umount Command

       umount - unmount file systems
       umount [-hV]
       umount -a [-dflnrv] [-t vfstype] [-O options]
       umount [-dflnrv] {dir|device}...
       The umount command detaches the file system(s) mentioned from the file hierarchy.  A file system is specified by giving the directory where it has been mounted.  Giving the special device on which the file system lives may also work, but is obsolete, mainly because it will fail in case this device was mounted on more than one directory.

       Note  that  a  file  system cannot be unmounted when it is ‘busy’ – for example, when there are open files on it, or when some process has  its working  directory  there,  or  when  a swap file on it is in use.  The offending process could even be umount itself - it opens libc, and libc in its turn may open for example locale files.  A lazy unmount avoids this problem.
Options for the umount command:
       -V              Print version and exit.
       -h              Print help message and exit.
       -v              Verbose mode.
       -n              Unmount without writing in /etc/mtab.
       -r              In case unmounting fails, try to remount read-only.
       -d              In case the unmounted device was a loop device, also  free  this loop device.
       -i               Don’t  call  the  /sbin/umount.<filesystem>  helper  even  if it exists. By default sbin/umount.<filesystem> helper is called if one exists.
       -a              All of the file systems described in /etc/mtab are unmounted. (With umount version 2.7 and later: the proc filesystem is not unmounted.)
      -t vfstype  Indicate  that  the actions should only be taken on file systems of the specified type.  More than one type may be specified in a comma separated list.  The list of file system types can be prefixed with no to specify the  file  system  types  on  which  no action should be taken.
       -O options Indicate  that  the actions should only be taken on file systems with the specified options in /etc/fstab.  More than one option type  may  be  specified in a comma separated list.  Each option can be prefixed with no to specify options for which  no  action      should be taken.
       -f               Force unmount (in case of an unreachable NFS system).
       -l               Lazy unmount. Detach the filesystem from the filesystem  hierarchy now, and cleanup all references to the filesystem as soon as


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