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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.

       If FILE is -, shred standard output.

       Mandatory arguments to long options are	mandatory  for	short  options

       -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     truncate and remove file after overwriting

	      like -u but give control on HOW to delete;  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

	      output version information and exit

       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

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

       * 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  op-
       tion  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.

       GNU coreutils online help: <>
       Report shred translation	bugs to	<>

       Copyright (C) 2016 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.

       Full documentation at: <>
       or available locally via: info '(coreutils) shred invocation'

GNU coreutils 8.25		 January 2016			      SHRED(1)


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