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 shred-
              ding

       --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 operating 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:

       *  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 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) 2005 Free Software Foundation, Inc.
       This is free software; see the source for copying condi-
       tions.  There is NO warranty; not even for MERCHANTABIL-
       ITY or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO
       The full documentation for shred is maintained as a Tex-
       info  manual.   If the info and shred programs are prop-
       erly installed at your site, the command

              info shred

       should give you access to the complete manual.



shred 5.3.0               January 2005                 SHRED(1)
