SHRED(1) FSF SHRED(1)
shred - delete a file securely, first overwriting it to hide its contents
shred [OPTIONS] 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.
change permissions to allow writing if necessary
Overwrite N times instead of the default (25)
shred this many bytes (suffixes like K, M, G accepted)
truncate and remove file after overwriting
do not round file sizes up to the next full block
add a final overwrite with zeros to hide shredding
- shred standard output
--help display this help and exit
output version information and exit
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
CAUTION: Note that shred relies on a very important assumption: that the filesystem over-
writes data in place. This is the traditional way to do things, but many modern filesys-
tem designs do not satisfy this assumption. The following are examples of filesystems on
which shred is not effective:
* log-structured or journaled filesystems, such as those supplied with
AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)
* filesystems that write redundant data and carry on even if some writes
fail, such as RAID-based filesystems
* filesystems that make snapshots, such as Network Appliance's NFS server
* filesystems that cache in temporary locations, such as NFS
version 3 clients
* compressed filesystems
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.
Written by Colin Plumb.
Report bugs to <email@example.com>.
Copyright (C) 2002 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO warranty; not
even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
The full documentation for shred is maintained as a Texinfo manual. If the info and shred
programs are properly installed at your site, the command
should give you access to the complete manual.
shred (coreutils) 4.5.3 February 2003 SHRED(1)