SHRED(1)			 User Commands			      SHRED(1)



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

SYNOPSIS
       shred [OPTION]... FILE...

DESCRIPTION
       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)

       --random-source=FILE
	      get random bytes from FILE

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

       -u, --remove[=HOW]
	      truncate and remove file after overwriting; See below

       -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

       --version
	      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.  The optional
       HOW parameter indicates how to remove a directory  entry:  'unlink'  =>
       use  a  standard	 unlink call.  'wipe' => also first obfuscate bytes in
       the name.  'wipesync' => also sync each obfuscated byte to  disk.   The
       default mode is 'wipesync', but note it can be expensive.

       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 satisfy 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 sys-
       tem 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.

       GNU  coreutils  online  help:  <http://www.gnu.org/software/coreutils/>
       Report shred translation bugs to <http://translationproject.org/team/>

AUTHOR
       Written by Colin Plumb.

COPYRIGHT
       Copyright  (C) 2013 Free Software Foundation, Inc.  License GPLv3+: GNU
       GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free  to	change	and  redistribute  it.
       There is NO WARRANTY, to the extent permitted by law.

SEE ALSO
       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 8.22		 February 2016			      SHRED(1)