1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
|
SHRED(1) User Commands 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 shred-
ding
--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 (C) 2005 Free Software Foundation, Inc.
This is free software; see the source for copying condi-
tions. There is NO warranty; not even for MERCHANTABIL-
ITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO
The full documentation for shred is maintained as a Tex-
info manual. If the info and shred programs are prop-
erly installed at your site, the command
info shred
should give you access to the complete manual.
shred 5.3.0 January 2005 SHRED(1)
|
