Linux man pages : shred (1)
SHRED(1) FSF 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
change permissions to allow writing if necessary
Overwrite N times instead of the default (25)
shred this many bytes (suffixes like K, M, G accepted)
truncate and remove file after overwriting
do not round file sizes up to the next full block
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 <email@example.com>.
Copyright (C) 2002 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
The full documentation for shred is maintained as a Texinfo manual. If
the info and shred programs are properly installed at your site, the
should give you access to the complete manual.
shred (coreutils) 4.5.3 February 2003 SHRED(1)