SHRED(1)                         User Commands
SHRED(1)



NNAAMMEE
       shred - overwrite a file to hide its contents, and
       optionally delete it

SSYYNNOOPPSSIISS
       sshhrreedd [_O_P_T_I_O_N_S] _F_I_L_E
       [...]

DDEESSCCRRIIPPTTIIOONN
       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f, ----ffoorrccee
              change permissions to allow writing if necessary

       --nn, ----iitteerraattiioonnss=_N
              Overwrite N times instead of the default (25)

       ----rraannddoomm--ssoouurrccee=_F_I_L_E
              get random bytes from FILE (default /dev/urandom)

       --ss, ----ssiizzee=_N
              shred this many bytes (suffixes like K, M,
              G accepted)

       --uu, ----rreemmoovvee
              truncate and remove file after overwriting

       --vv, ----vveerrbboossee
              show progress

       --xx, ----eexxaacctt
              do not round file sizes up to the next full
              block;

              this is the default for non-regular files

       --zz, ----zzeerroo
              add a final overwrite with zeros to hide
              shredding

       ----hheellpp display this help and exit

       ----vveerrssiioonn
              output version information and exit

       If FILE is -, shred standard output.

       Delete  FILE(s)  if  ----rreemmoovvee (--u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 ----rreemmoovvee 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 sys‐ tem 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.

AAUUTTHHOORR
       Written by Colin Plumb.

RREEPPOORRTTIINNGG BBUUGGSS
       Report bugs to <bug-coreutils@gnu.org>.

CCOOPPYYRRIIGGHHTT
       Copyright © 2006 Free Software Foundation, Inc.
       This  is  free  software.   You may redistribute
       copies of it under the terms      of      the
       GNU      General       Public       License
       <http://www.gnu.org/licenses/gpl.html>.   There  is
       NO WARRANTY, to the extent permitted by law.

SSEEEE AALLSSOO
       The full documentation for sshhrreedd is
       maintained as a Texinfo manual.  If the  iinnffoo
       and  sshhrreedd programs are properly installed
       at your site, the command

              iinnffoo sshhrreedd

       should give you access to the complete manual.



shred 6.7                        December 2006
SHRED(1)
