hard linking

hard link
hard linking

   <file system> One of several directory entries which refer to
   the same {Unix} {file}.  A hard link is created with the "ln"
   (link) command:

   	ln <old name> <new name>

   where <old name> and <new name> are {pathnames} within the
   same {file system}.  Hard links to the same file are
   indistinguishable from each other except that they have
   different pathnames.  They all refer to the same {inode} and
   the inode contains all the information about a file.

   The standard ln command does not usually allow you to create a
   hard link to a directory, chiefly because the standard {rm}
   and {rmdir} commands do not allow you to delete such a link.
   Some systems provide link and {unlink} commands which give
   direct access to the {system calls} of the same name, for
   which no such restrictions apply.

   Normally all hard links to a file must be in the same {file
   system} because a directory entry just relates a pathname to
   an inode within the same file system.  The only exception is a
   {mount point}.

   The restrictions on hard links to directories and between
   file systems are very common but are not mandated by {POSIX}.
   {Symbolic links} are often used instead of hard links because
   they do not suffer from these restrictions.

   The space associated with a file is not freed until all the
   hard links to the file are deleted.  This explains why the
   system call to delete a file is called "unlink".

   {Microsoft Windows} {NTFS} supports hard links via the
   {fsutil} command.

   {Unix manual page}: ln(1).

   
(http://microsoft.com/windowsxp/home/using/productdoc/en/fsutil_hardlink.asp).

   (2004-02-24)