manpages.info - online man pages   

Linux man pages : shred (1)
SHRED(1)			      FSF			      SHRED(1)

NAME

shred - delete a file securely, first overwriting it to hide its con- tents

SYNOPSIS

shred [OPTIONS] FILE [...]

DESCRIPTION

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 show progress -x, --exact do not round file sizes up to the next full block -z, --zero add a final overwrite with zeros to hide shredding - shred standard output --help display this help and exit --version 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 operat- ing 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 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.

AUTHOR

Written by Colin Plumb.

REPORTING BUGS

Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

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.

SEE ALSO

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 info shred should give you access to the complete manual. shred (coreutils) 4.5.3 February 2003 SHRED(1)