redhat man page for shred

SHRED(1)								FSF								  SHRED(1)

NAME
       shred - delete a file securely, first overwriting it to hide its contents

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

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

       -      shred standard output

       --help display this help and exit

       --version
	      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.  When operating on regular files, most people use the --remove option.

       CAUTION: Note that shred relies on a very important assumption: that the filesystem overwrites data in place.  This is the traditional  way
       to  do things, but many modern filesystem designs do not satisfy this assumption.  The following are examples of filesystems on which shred
       is not effective:

       * log-structured or journaled filesystems, such as those supplied with

	      AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)

       * filesystems that write redundant data and carry on even if some writes

	      fail, such as RAID-based filesystems

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

       * filesystems that cache in temporary locations, such as NFS

	      version 3 clients

       * compressed filesystems

       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 <bug-coreutils@gnu.org>.

COPYRIGHT
       Copyright (C) 2002 Free Software Foundation, Inc.
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

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 (coreutils) 4.5.3 					   February 2003							  SHRED(1)