shred

SHRED(1)                              FSF                             SHRED(1)



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

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  operat-
       ing 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  PARTICULAR
       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          October 2003                         SHRED(1)