Provided by: coreutils_7.4-2ubuntu2_i386 bug

NAME

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

SYNOPSIS

       shred [OPTION]... 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 (3)

       --random-source=FILE
              get random bytes from FILE

       -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
       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,  or  is  not guaranteed to be effective in all file
       system 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
       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 shred bugs to bug-coreutils@gnu.org
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>

COPYRIGHT

       Copyright © 2009 Free Software Foundation, Inc.   License  GPLv3+:  GNU
       GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This  is  free  software:  you  are free to change and redistribute it.
       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 coreutils 'shred invocation'

       should give you access to the complete manual.