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.
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:
* log-structured or journaled file systems, such as those supplied with
* file systems that write redundant data and carry on even if some writes
* file systems that make snapshots, such as Network Appliance’s NFS server
* file systems that cache in temporary locations, such as NFS
* compressed file systems
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.
should give you access to the complete manual.