SHRED linux command manual

SHRED(1)                      User Commands                        SHRED(1)

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

       shred [OPTIONS] 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

       -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;

              this is the default for non-regular files

       -z, --zero
              add a final overwrite with zeros to hide shredding

       -      shred standard output

       --help display this help and exit

              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

              fail, such as RAID-based filesystems

       *  filesystems  that  make  snapshots, such as Network Appliance's NFS

       * 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.

       Written by Colin Plumb.

       Report bugs to .

       Copyright (C) 2004 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 PARTICU-

       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

       should give you access to the complete manual.

shred (coreutils) 5.2.1            May 2004                          SHRED(1)