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SHRED(1)			 User Commands			      SHRED(1)

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

       shred [OPTIONS] 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

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

       -n, --iterations=N
	      Overwrite N times instead of the default (25)

	      get random bytes from FILE (default /dev/urandom)

       -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 operat‐
       ing on regular files, most people use the --remove option.

       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
       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 bugs to <>.

       Copyright © 2006 Free Software Foundation, Inc.
       This  is	 free  software.   You may redistribute copies of it under the
       terms	  of	  the	   GNU	    General	  Public       License
       <>.	 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

	      info shred

       should give you access to the complete manual.

shred 6.4			 October 2006			      SHRED(1)

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