SHRED(1)

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

SYNOPSIS
shred [OPTIONS] FILE [...]

DESCRIPTION

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 (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

--help
    display this help and exit

--version
    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 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:

* 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 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.

AUTHOR
Written by Colin Plumb.

REPORTING BUGS
Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT
Copyright © 2005 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 PARTICULAR PURPOSE.

SEE ALSO
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 shred

should give you access to the complete manual.