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SHRED(1)                         User Commands                        SHRED(1)

       shred - overwrite a file to hide its contents, and optionally delete it

       shred [OPTION]... FILE...

       Overwrite  the  specified  FILE(s)  repeatedly, in order to make it harder for even
       very expensive hardware probing to recover the data.

       Mandatory arguments to long options are mandatory for short options too.

       -f, --force
              change permissions to allow writing if necessary

       -n, --iterations=N
              overwrite N times instead of the default (3)

              get random bytes from FILE

       -s, --size=N
              shred this many bytes (suffixes like K, M, G accepted)

       -u, --remove
              truncate and remove file after overwriting

       -v, --verbose
              show progress

       -x, --exact
              do not round file sizes up to the next full block;

              this is the default for non-regular files

       -z, --zero
              add a final overwrite with zeros to hide shredding

       --help display this help and exit

              output version information and exit

       If FILE is -, shred standard output.

       Delete FILE(s) if --remove (-u) is specified.  The default is  not  to  remove  the
       files  because  it  is  common  to operate on device files like /dev/hda, and those
       files usually should not be removed.  When operating on regular files, most  people
       use the --remove option.

       CAUTION:  Note that shred relies on a very important assumption: that the file sys-
       tem overwrites data in place.  This is the traditional way to do things,  but  many
       modern file system designs do not satisfy this assumption.  The following are exam-
       ples 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.)

       * file systems that write redundant data and carry on even  if  some  writes  fail,
       such as RAID-based file systems

       * file systems that make snapshots, such as Network Appliance's NFS server

       * file systems that cache in temporary locations, such as NFS version 3 clients

       * compressed file systems

       In  the  case of ext3 file systems, the above disclaimer applies (and shred is thus
       of limited effectiveness) only in data=journal mode, which journals  file  data  in
       addition  to  just metadata.  In both the data=ordered (default) and data=writeback
       modes, shred works as usual.  Ext3 journaling modes can be changed  by  adding  the
       data=something  option  to  the  mount  options for a particular file system in the
       /etc/fstab file, as documented in the mount man page (man mount).

       In addition, file system backups and remote mirrors may contain copies of the  file
       that  cannot be removed, and that will allow a shredded file to be recovered later.

       Written by Colin Plumb.

       Report shred bugs to bug-coreutils AT
       GNU coreutils home page: <>
       General help using GNU software: <>
       Report shred translation bugs to <>

       Copyright (C) 2010 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version  3
       or later <>.
       This  is  free  software:  you are free to change and redistribute it.  There is NO
       WARRANTY, to the extent permitted by law.

       The full documentation for shred is maintained as a Texinfo manual.   If  the  info
       and shred programs are properly installed at your site, the command

              info coreutils 'shred invocation'

       should give you access to the complete manual.

GNU coreutils 8.4                 March 2017                          SHRED(1)

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