Provided by: coreutils_8.21-1ubuntu5_amd64 bug


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

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

       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

       *  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.


       Written by Colin Plumb.


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


       Copyright  ©  2013  Free  Software  Foundation, Inc.  License GPLv3+: GNU GPL version 3 or
       later <>.
       This is free software: you are free to change and redistribute it.  There is NO  WARRANTY,
       to the extent permitted by law.


       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.