shred - delete a file securely, first overwriting it to hide its contents
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 (25)
- -s, --size=N
shred this many bytes (suffixes like K, M, G accepted)
- -u, --remove
truncate and remove file after overwriting
- -v, --verbose
- -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
shred standard output
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 option.
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
* 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 <firstname.lastname@example.org
Copyright © 2004 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
is maintained as a Texinfo manual. If the
programs are properly installed at your site, the command
info coreutils shred
should give you access to the complete manual.
- REPORTING BUGS
- SEE ALSO