Usage: shred [OPTION]... FILE...
指定されたファイルに対して上書きを繰り返し、非常に高価な機械でさえも
データ復元の為の調査を行う事が非常に困難となるようにします。
長いオプションに必須の引数は短いオプションにも必須です.
-f, --force change permissions to allow writing if necessary
-n, --iterations=N overwrite N times instead of the default (3)
--random-source=FILE get random bytes from FILE
-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 この使い方を表示して終了
--version バージョン情報を表示して終了
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, or is not guaranteed to be effective in all file system modes:
* 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 the case of ext3 file systems, the above disclaimer applies
(and shred is thus of limited effectiveness) only in data=journal mode,
which journals file data in addition to just metadata. In both the
data=ordered (default) and data=writeback modes, shred works as usual.
Ext3 journaling modes can be changed by adding the data=something option
to the mount options for a particular file system in the /etc/fstab file,
as documented in the mount man page (man mount).
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.
Report shred bugs to bug-coreutils@gnu.org
GNU coreutils home page:
Usage: shred [OPTION]... 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 too.
-f, --force change permissions to allow writing if necessary
-n, --iterations=N overwrite N times instead of the default (3)
--random-source=FILE get random bytes from FILE
-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, or is not guaranteed to be effective in all file system modes:
* 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 the case of ext3 file systems, the above disclaimer applies
(and shred is thus of limited effectiveness) only in data=journal mode,
which journals file data in addition to just metadata. In both the
data=ordered (default) and data=writeback modes, shred works as usual.
Ext3 journaling modes can be changed by adding the data=something option
to the mount options for a particular file system in the /etc/fstab file,
as documented in the mount man page (man mount).
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.
Report shred bugs to bug-coreutils@gnu.org
GNU coreutils home page:
SHRED(1) SHRED(1)
名前
shred - ファイルを繰り返し上書きする
書式
shred [-ITERS] [-fuvxz] [-n ITERS ]["-s SIZE ] [--force] [--itera-
tions=ITER] [--size=SIZE] [--remove] [--verbose] [--exact] [--zero]
FILE[...]
shred [--help] [--version]
説明
shred は指定されたファイル FILE を特別なパターンで繰り返し上書きし、デ
ータの復旧がより困難になるようにする。 FILE が ‘-’ の場合、入力ファイル
として標準入力が使われる。
shred はファイルへの実際の書き込み操作が (訳註: 書き込み操作を行ったデ
バイスと) 同じ場所で起ることを仮定して動作するが、 (トランザクション 管
理ファイルシステム・分散ファイルシステム・リモートファイルシステムでは)
書き込みが同じ場所で起らない可能性もあるので注意すること。また (RAID が
使 用されている場合) あるデバイス (/dev/hda など) で shred が使用される
と、 RAID はこの操作を他のデバイスに対しても同じように行う。
オプション
-f, --force
可能であれば、パーミッションを無視する。
-ITERS, -n ITERS, --iterations=ITERS
ITERS 回繰り返し上書きする。(デフォルト: 25)
-s SIZE, --size=SIZE
SIZE バイトのみを切れ切れにする。サイズには乗数の文字を使うこ と
ができる (下記参照)。
-u, --remove
shred を実行した後、切り詰めて (truncate) アンリンクする。
-v, --verbose
進捗状況のメッセージを表示する。
-x, --exact
全ブロック数以上にファイルサイズを大きくしない。
-z, --zero
shred を実行した後、NUL で上書きする。
--help 標準出力に使用方法のメッセージを出力して正常終了する。
--version
標準出力にバージョン情報を出力して正常終了する。
乗数
サ イズ数値の後には乗数を指定するサイズ文字と、通常のバイトを選択する B
または 10 進の「商業用」バイトを選択する D を続けてもよい。例えば ‘1KB’
は ‘1024’ で ‘1KD’ は ‘1000’ である。 b (512 バイト), c (1 バイト), w (
これは使用すべきでない - System V では 2、 4.2BSD では 4 を意味する) は
例外であり、 B や D を続けることはできない。
k キ ロ: 通常のバイトなら 2^10 = 1024、 10 進のバイトなら 10^3 =
1000
M メガ: 2^20 = 1,048,576 または 10^6 = 1,000,000
G ギガ: 2^30 = 1,073,741,824 または 10^9 = 1,000,000,000
T テラ: 2^40 = 1,099,511,627,776 または 10^12 = 1,000,000,000,000
P ペ タ: 2^50 = 1,125,899,906,842,624 ま た は 10^15 =
1,000,000,000,000,000
E エ ク サ: 2^60 = 1,152,921,504,606,846,976 ま たは 10^18 =
1,000,000,000,000,000,000
Z ゼタ: 2^70 = 1,180,591,620,717,411,303,424 ま た は 10^21 =
1,000,000,000,000,000,000,000
Y ヨ タ: 2^80 = 1,208,925,819,614,629,174,706,176 または 10^24 =
1,000,000,000,000,000,000,000,000
関連項目
Peter Gutmann の論文 ‘Secure Deletion of Data from Magnetic and Solid-
State Memory’, 出典 the proceedings of the Sixth USENIX Security Sympo-
sium (San Jose, California, 22-25 July, 1996) 。 こ の 論 文 は
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html からオンライ
ンで入手できる。
注意
プログラムのバグは bug-fileutils@gnu.org へ報告してください。
この man ページは Ragnar Hojland Espinosa
SHRED(1) User Commands SHRED(1)
NAME
shred - overwrite a file to hide its contents, and optionally delete it
SYNOPSIS
shred [OPTION]... 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 (3)
--random-source=FILE
get random bytes from FILE
-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 operat-
ing 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, or is not guaranteed to be effective in all file sys-
tem modes:
* 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 the case of ext3 file systems, the above disclaimer applies (and
shred is thus of limited effectiveness) only in data=journal mode,
which journals file data in addition to just metadata. In both the
data=ordered (default) and data=writeback modes, shred works as usual.
Ext3 journaling modes can be changed by adding the data=something
option to the mount options for a particular file system in the
/etc/fstab file, as documented in the mount man page (man mount).
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 shred bugs to bug-coreutils@gnu.org
GNU coreutils home page:
Copyright(C) linux-cmd.com All Rights Reserved. Author Takayuki Yukawa