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Updated: July 2014

shred (1)


shred - ally delete it


shred [OPTION]... FILE...


User Commands                                            SHRED(1)

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

     shred [OPTION]... FILE...

     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)

          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

          display this help and exit

          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,

     *  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  Appli-
     ance'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

     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.

     Written by Colin Plumb.

     Report shred bugs to
     GNU coreutils home page:  <
     General  help  using GNU software: <
     Report shred  translation  bugs  to  <http://translationpro->

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User Commands                                            SHRED(1)

     Copyright  (C)  2012 Free Software Foundation, Inc.  License
     GPLv3+:     GNU     GPL     version     3      or      later
     This  is  free  software:  you are free to change and redis-
     tribute it.  There is NO WARRANTY, to the  extent  permitted
     by law.

     See   attributes(5)   for   descriptions  of  the  following

     |Availability   | file/gnu-coreutils |
     |Stability      | Uncommitted        |
     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.

     This  software  was   built   from   source   available   at    The  original
     community       source       was       downloaded       from

     Further  information about this software can be found on the
     open source community  website  at

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