SHRED(1)			 User Commands			      SHRED(1)



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

SYNOPSIS
       shred [OPTIONS] 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 (25)

       -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

       --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.  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  Appliances  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.

AUTHOR
       Written by Colin Plumb.

REPORTING BUGS
       Report bugs to .

COPYRIGHT
       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.

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 shred

       should give you access to the complete manual.



shred 5.97			 January 2007			      SHRED(1)