Using shred to delete a file and nobody can recover

Using shred to delete a file and nobody can recover

  You have a file "secret".  The following makes it so no one
     can read it.  If the file was 12 bytes, it's now 4096 after it
     has been over written 100 times.  There's no way to recover this.

      $ shred -n 100 -z secret

    Want to remove the file? Use the "u" option.

      $ shred -n 100 -z -u test2

    It can be applied to a device

      $ shred -n 100 -z -u /dev/fd0


      CAUTION: Note that shred relies on a very important assumption: that the file system  overwrites  data
      in  place.   This is the traditional way to do things, but many modern file system designs do not sat-
      isfy this assumption.  The following are examples of file systems on which shred is not effective,  or
      is not guaranteed to be effective in all file system modes:

      * log-structured or journaled file systems, such as those supplied with

             AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)