shred.1

Linux下文件工具。

.\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.28.
.TH SHRED "1" "July 2002" "shred (fileutils) 4.1.10" "User Commands"
.SH NAME
shred \- delete a file securely, first overwriting it to hide its contents
.SH SYNOPSIS
.B shred
[\fIOPTIONS\fR] \fIFILE \fR[...]
.SH DESCRIPTION
.\" Add any additional description here
.PP
Overwrite the specified FILE(s) repeatedly, in order to make it harder
for even very expensive hardware probing to recover the data.
.PP
Mandatory arguments to long options are mandatory for short options too.
.TP
\fB\-f\fR, \fB\-\-force\fR
change permissions to allow writing if necessary
.TP
\fB\-n\fR, \fB\-\-iterations\fR=\fIN\fR
Overwrite N times instead of the default (25)
.TP
\fB\-s\fR, \fB\-\-size\fR=\fIN\fR
shred this many bytes (suffixes like K, M, G accepted)
.TP
\fB\-u\fR, \fB\-\-remove\fR
truncate and remove file after overwriting
.TP
\fB\-v\fR, \fB\-\-verbose\fR
show progress
.TP
\fB\-x\fR, \fB\-\-exact\fR
do not round file sizes up to the next full block
.TP
\fB\-z\fR, \fB\-\-zero\fR
add a final overwrite with zeros to hide shredding
.TP
-
shred standard output
.TP
\fB\-\-help\fR
display this help and exit
.TP
\fB\-\-version\fR
output version information and exit
.PP
Delete FILE(s) if \fB\-\-remove\fR (-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 \fB\-\-remove\fR option.
.PP
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:
.PP
* log-structured or journaled filesystems, such as those supplied with
.IP
AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)
.PP
* filesystems that write redundant data and carry on even if some writes
.IP
fail, such as RAID-based filesystems
.PP
* filesystems that make snapshots, such as Network Appliance's NFS server
.PP
* filesystems that cache in temporary locations, such as NFS
.IP
version 3 clients
.PP
* compressed filesystems
.PP
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.
.SH AUTHOR
Written by Colin Plumb.
.SH "REPORTING BUGS"
Report bugs to <[e-mail]>.
.SH COPYRIGHT
Copyright \(co 2002 Free Software Foundation, Inc.
.br
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH "SEE ALSO"
The full documentation for
.B shred
is maintained as a Texinfo manual.  If the
.B info
and
.B shred
programs are properly installed at your site, the command
.IP
.B info shred
.PP
should give you access to the complete manual.