User Commands                                            SHRED(1)



NAME
     shred - overwrite a file to hide its contents,  and  option-
     ally 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)

     --random-source=FILE
          get random bytes from FILE (default /dev/urandom)

     -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



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User Commands                                            SHRED(1)



     should  not  be  removed.   When operating on regular files,
     most people use the --remove option.

     CAUTION: Note that shred relies on a very important  assump-
     tion:   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 follow-
     ing 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 con-
     tain  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 O 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  WAR-
     RANTY, to the extent permitted by law.



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User Commands                                            SHRED(1)



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.

ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:

     
       ATRIBUTE TYPE      ATRIBUTE VALUE  
    
     Availability         SUNWgnu-coreutils 
    
     Interface Stability  Uncommitted       
    

NOTES
     Source    for    GNU    coreutils    is     available     on
     http:/opensolaris.org.































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