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.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.35.
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.TH SHRED "1" "October 2012" "GNU coreutils 8.20" "User Commands"
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shred \- overwrite a file to hide its contents, and optionally delete it
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[\fIOPTION\fR]... \fIFILE\fR...
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.\" Add any additional description here
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Overwrite the specified FILE(s) repeatedly, in order to make it harder
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for even very expensive hardware probing to recover the data.
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Mandatory arguments to long options are mandatory for short options too.
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\fB\-f\fR, \fB\-\-force\fR
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change permissions to allow writing if necessary
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\fB\-n\fR, \fB\-\-iterations\fR=\fIN\fR
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overwrite N times instead of the default (3)
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\fB\-\-random\-source\fR=\fIFILE\fR
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get random bytes from FILE
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\fB\-s\fR, \fB\-\-size\fR=\fIN\fR
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shred this many bytes (suffixes like K, M, G accepted)
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\fB\-u\fR, \fB\-\-remove\fR
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truncate and remove file after overwriting
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\fB\-v\fR, \fB\-\-verbose\fR
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\fB\-x\fR, \fB\-\-exact\fR
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do not round file sizes up to the next full block;
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this is the default for non\-regular files
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\fB\-z\fR, \fB\-\-zero\fR
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add a final overwrite with zeros to hide shredding
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display this help and exit
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output version information and exit
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If FILE is \-, shred standard output.
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Delete FILE(s) if \fB\-\-remove\fR (\fB\-u\fR) is specified. The default is not to remove
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the files because it is common to operate on device files like /dev/hda,
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and those files usually should not be removed. When operating on regular
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files, most people use the \fB\-\-remove\fR option.
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CAUTION: Note that shred relies on a very important assumption:
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that the file system overwrites data in place. This is the traditional
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way to do things, but many modern file system designs do not satisfy this
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assumption. The following are examples of file systems on which shred is
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not effective, or is not guaranteed to be effective in all file system modes:
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* log\-structured or journaled file systems, such as those supplied with
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AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)
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* file systems that write redundant data and carry on even if some writes
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fail, such as RAID\-based file systems
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* file systems that make snapshots, such as Network Appliance's NFS server
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* file systems that cache in temporary locations, such as NFS
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* compressed file systems
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In the case of ext3 file systems, the above disclaimer applies
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(and shred is thus of limited effectiveness) only in data=journal mode,
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which journals file data in addition to just metadata. In both the
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data=ordered (default) and data=writeback modes, shred works as usual.
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Ext3 journaling modes can be changed by adding the data=something option
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to the mount options for a particular file system in the /etc/fstab file,
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as documented in the mount man page (man mount).
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In addition, file system backups and remote mirrors may contain copies
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of the file that cannot be removed, and that will allow a shredded file
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to be recovered later.
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Written by Colin Plumb.
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Report shred bugs to bug\-coreutils@gnu.org
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GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
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General help using GNU software: <http://www.gnu.org/gethelp/>
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Report shred translation bugs to <http://translationproject.org/team/>
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Copyright \(co 2012 Free Software Foundation, Inc.
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
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This is free software: you are free to change and redistribute it.
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There is NO WARRANTY, to the extent permitted by law.
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The full documentation for
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is maintained as a Texinfo manual. If the
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programs are properly installed at your site, the command
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.B info coreutils \(aqshred invocation\(aq
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should give you access to the complete manual.
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man/shred.1
