Provided by: scrub_2.4-2build1_amd64 bug


       scrub - write patterns on disk/file


       scrub [OPTIONS] special-file
       scrub [OPTIONS] file
       scrub -X [OPTIONS] directory


       Scrub  iteratively  writes  patterns  on files or disk devices to make retrieving the data
       more difficult.  Scrub operates in one of three modes:

       1) The special file corresponding to an entire disk is scrubbed and  all  data  on  it  is
       destroyed.   This  mode is selected if file is a character or block special file.  This is
       the most effective method.

       2) A regular file is scrubbed and only the data in the file (and optionally  its  name  in
       the  directory entry) is destroyed.  The file size is rounded up to fill out the last file
       system block.  This mode is selected if file is a regular file.  See CAVEATS below.

       3) directory is created and filled with files until the file  system  is  full,  then  the
       files are scrubbed as in 2). This mode is selected with the -X option.  See CAVEATS below.

       Scrub accepts the following options:

       -v, --version
              Print scrub version and exit.

       -r, --remove
              Remove the file after scrubbing.

       -p, --pattern PATTERN
              Select  the  patterns  to  write.  nnsa selects patterns compliant with NNSA Policy
              Letter NAP-14.1-C; dod selects patterns compliant with DoD 5220.22-M;  bsi  selects
              patterns  recommended  by the German Center of Security in Information Technologies
              (; old selects pre-version 1.7 scrub patterns;  and  fastold
              is  old  without  the  random  pass.   gutmann  is  a 35-pass sequence described in
              Gutmann's paper cited below.  See STANDARDS below for more  detail.   random  is  a
              single  random  pass.   random2  is  two  random  passes.   schneier  is the method
              described by Bruce Schneier in ''Applied Cryptography'' (1996)  consisting  of  one
              0x00  pass,  one  0xff  pass,  and five random passes.  pfitzner7 is Roy Pfitzner's
              7-random-pass method.  pfitzner33 is Roy Pfitzner's 33-random-pass method.   usarmy
              is  the  US  Army AR380-19 method consisting of one 0x00 pass, one 0xff pass, and a
              random pass.  Default: nnsa.

       -b, --blocksize blocksize
              Perform read(2) and write(2) calls using the specified blocksize (in bytes).  K, M,
              or  G  may  be  appended  to the number to change the units to KiBytes, MiBytes, or
              GiBytes, respectively.  Default: 1M.

       -f, --force
              Scrub even if target contains signature indicating it has already been scrubbed.

       -S, --no-signature
              Do not write scrub signature.  Scrub will not be able to ascertain if the disk  has
              already been scrubbed.

       -X, --freespace
              Create  specified directory and fill it with files until write returns ENOSPC (file
              system full), then scrub the files as usual.  The size of each file can be set with
              -s, otherwise it will be the maximum file size creatable given the user's file size
              limit or 1g if umlimited.

       -D, --dirent newname
              After scrubbing the file, scrub its name in the directory entry, then rename it  to
              the  new  name.   The scrub patterns used on the directory entry are constrained by
              the operating system and thus are not compliant with cited standards.

       -s, --device-size size
              Override the device size (in bytes). Without this option,  scrub  determines  media
              capacity  using  OS-specific  ioctl(2)  calls.   K,  M, or G may be appended to the
              number to change the units to KiBytes, MiBytes, or GiBytes, respectively.

       -L, --no-link
              If file is a symbolic link, do not scrub the link target.  Do remove  it,  however,
              if --remove is specified.


       Scrub  may  be  insufficient  to thwart heroic efforts to recover data in an appropriately
       equipped lab.

       Scrub nnsa patterns are reasonable for sanitizing modern PRML/EPRML encoded disk devices.

       The effectiveness of scrubbing regular files through a file system will be limited by  the
       OS  and  file  system.   File  systems that are known to be problematic are journaled, log
       structured, copy-on-write, versioned, and network file systems.  If in  doubt,  scrub  the
       raw disk device.

       Scrubbing  free  blocks in a file system with the -X method is subject to the same caveats
       as scrubbing regular files, and in addition, is only useful to the extent the file  system
       allows  you  to  reallocate  the target blocks as data blocks in a new file.  If in doubt,
       scrub the raw disk device.

       [MacOS X HFS file system] Scrub attempts to overwrite a file's resource fork if it exists.
       Although MacOS X will support additional named forks in the future, scrub is only aware of
       the traditional data and resource forks.


       The dod scrub sequence is compliant  with  the  DoD  5220.22-M  procedure  for  sanitizing
       removable  and  non-removable  rigid  disks  which  requires  overwriting  all addressable
       locations with a character, its complement, then a random character, and  verify.   Please
       refer to the DoD document for additional constraints.

       The  nnsa  (default)  scrub  sequence  is  compliant with a Dec. 2005 draft of NNSA Policy
       Letter NAP-14.1-C (see reference below) for sanitizing removable  and  non-removable  hard
       disks, which requires overwriting all locations with a pseudorandom pattern twice and then
       with a known pattern.  Please refer to the NNSA document for additional constraints.

       Please consult local authorities regarding your site policy for disk sanitization.


       Jim Garlick <>

       This work was produced at  the  University  of  California,  Lawrence  Livermore  National
       Laboratory  under Contract No. W-7405-ENG-48 with the DOE.  Designated UCRL-CODE-2003-006,
       scrub is licensed under terms of the GNU General Public License.


       DoD 5220.22-M,  "National  Industrial  Security  Program  Operating  Manual",  Chapter  8,

       NNSA  Policy  Letter: NAP-14.1-C, "Clearing, Sanitizing, and Destroying Information System
       Storage Media, Memory Devices, and other Related Hardware", 05-02-08, page XVI-8.

       "Secure Deletion of Data from Magnetic and Solid-State Memory", by  Peter  Gutmann,  Sixth
       USENIX Security Symposium, San Jose, CA, July 22-25, 1996.

       "Gutmann Method", Wikipedia,

       Darik's boot and Nuke FAQ: