SHRED(1) FSF SHRED(1)
NAME
shred - delete a file(1,n) securely, first overwriting it to hide its con-
tents
SYNOPSIS
shred [OPTIONS] FILE [...]
DESCRIPTION
Overwrite the specified FILE(s) repeatedly, in(1,8) order to make it harder
for even very expensive hardware probing to recover the data.
-f, --force
change permissions to allow writing if(3,n) 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(2,7) and remove file(1,n) after overwriting
-v, --verbose
show progress
-x, --exact
do not round file(1,n) sizes up to the next full block
-z, --zero
add a final overwrite with zeros to hide shredding
- shred standard output
--help display this help and exit(3,n,1 builtins)
--version
print version(1,3,5) information and exit(3,n,1 builtins)
Delete FILE(s) if(3,n) --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(1,8) 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, etc.)
* filesystems that write(1,2) redundant data and carry on even if(3,n) some
writes
fail, such as RAID-based filesystems
* filesystems that make snapshots, such as Network Appliance's NFS
server
* filesystems that cache in(1,8) temporary locations, such as NFS
version(1,3,5) 3 clients
* compressed filesystems
AUTHOR
Written by Colin Plumb.
REPORTING BUGS
Report bugs to <bug-fileutils@gnu.org>.
COPYRIGHT
Copyright 2001 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(1,5,n) and shred programs are properly installed at your site, the
command
info(1,5,n) shred
should give you access(2,5) to the complete manual.
shred (fileutils) 4.1 April 2001 SHRED(1)