1 .\" You may copy, distribute and modify under the terms of the LDP General
2 .\" Public License as specified in the LICENSE file that comes with the
3 .\" gnumaniak distribution
5 .\" The author kindly requests that no comments regarding the "better"
6 .\" suitability or up-to-date notices of any info documentation alternative
7 .\" is added without contacting him first.
9 .\" (C) 2002 Ragnar Hojland Espinosa <ragnar@ragnar-hojland.com>
11 .\" GNU shred man page
12 .\" man pages are NOT obsolete!
13 .\" <ragnar@ragnar-hojland.com>
14 .TH SHRED 1 "18 June 2002" "GNU fileutils 4.1"
16 \fBshred\fR \- overwrite files repeatedly
18 .BR "shred " [ \-\fIITERS\fB "] [" \-fuvxz "] [" "\-n \fIITERS\fB "] [" "\-s \fISIZE\fR "] "
19 .RB [ \-\-force "] [" \-\-iterations=\fIITER\fB "] [" \-\-size=\fISIZE\fB "] "
20 .RB [ \-\-remove "] [" \-\-verbose "] [" \-\-exact "] [" \-\-zero "] "
23 .BR shred " [" \-\-help "] [" \-\-version ]
26 writes repeatedly on the specified \fIFILE\fRs with special patterns in
27 order to make it more difficult to recover the data . If
31 standard input is used as input for that file.
33 Note that \fBshred\fR operates on the assumption that write operations to
34 a file will happen in the same place, and it might not be so (as in
35 transactional, distributed or remote filesystems). Also, when employed on
36 devices (/dev/hda), RAID will affect operations in a similar way.
40 Ignore permissions when writing if possible.
42 .B "\-\fIITERS\fB, \-n \fIITERS\fB, \-\-iterations=\fIITERS\fB"
43 Overwrite \fIITERS\fB times. (Default: 25)
45 .B "\-s \fISIZE\fR, \-\-size=\fISIZE\fR"
46 Shred only \fISIZE\fR bytes. Size may use multiplier letters (See below)
49 Truncate and unlink file after \fBshred\fR is done.
52 Show progress messages.
55 Don't round file sizes up to the full block.
58 Overwrite with NULs after \fBshred\fR is done.
61 Print a usage message on standard output and exit successfully.
64 Print version information on standard output then exit successfully.
66 Size numbers may be followed by a size letter to specify a multiple of that
67 size, and a \fBB\fR to select normal bytes or a \fBD\fR to select
68 decimal "commercial" bytes. For example `1KB' is equal to `1024' and
69 `1KD' is equal to `1000'. Exceptions are \fBb\fR (512 bytes), \fBc\fR (1
70 byte), and \fBw\fR (which should never be used - it means 2 in System V and
71 4 in 4.2BSD), which can't be followed by a \fBB\fR or \fBD\fR.
74 kilo: 2^10 = 1024 for normal bytes, or 10^3 = 1000 for decimal bytes
77 Mega: 2^20 = 1,048,576 or 10^6 = 1,000,000
80 Giga: 2^30 = 1,073,741,824 or 10^9 = 1,000,000,000
83 Tera: 2^40 = 1,099,511,627,776 or 10^12 = 1,000,000,000,000
86 Peta: 2^50 = 1,125,899,906,842,624 or 10^15 = 1,000,000,000,000,000
89 Exa: 2^60 = 1,152,921,504,606,846,976 or 10^18 = 1,000,000,000,000,000,000
92 Zetta: 2^70 = 1,180,591,620,717,411,303,424 or 10^21 =
93 1,000,000,000,000,000,000,000
96 Yotta: 2^80 = 1,208,925,819,614,629,174,706,176 or 10^24 =
97 1,000,000,000,000,000,000,000,000
99 Peter Gutmann's paper `Secure Deletion of Data from Magnetic and Solid-State
100 Memory', from the proceedings of the Sixth USENIX Security Symposium (San
101 Jose, California, 22-25 July, 1996). The paper is available online at
102 http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html
105 Report bugs in the program to bug-fileutils@gnu.org.
107 Man page by Ragnar Hojland Espinosa <ragnar@ragnar-hojland.com>