GNU ddrescue is a data recovery tool for
disk drive
Disc or disk may refer to:
* Disk (mathematics), a two dimensional shape, the interior of a circle
* Disk storage
* Optical disc
* Floppy disk
Music
* Disc (band), an American experimental music band
* ''Disk'' (album), a 1995 EP by Moby
Other ...
s,
DVD
The DVD (common abbreviation for digital video disc or digital versatile disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any ki ...
s,
CDs, and other digital storage media. It copies raw blocks of storage, such as
disk sector
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. For most disks, each sector stores a fixed amount of user-accessible data, traditionally 512 bytes for hard disk drives (HDDs), and 2048 byt ...
s, from one device or file to another, while handling read errors in an intelligent manner to minimize data loss by ''scraping'' good sectors from partially read blocks.
GNU ddrescue is written in the
C++ programming language, and is available as
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
software that was originally released in 2004. It is also available in binary form as a component in most
Linux distribution
A Linux distribution, often abbreviated as distro, is an operating system that includes the Linux kernel for its kernel functionality. Although the name does not imply product distribution per se, a distro—if distributed on its own—is oft ...
s.
Description
ddrescue uses a sophisticated algorithm to copy data from disk drives, and other storage devices, causing as little additional damage, if they are failing, as possible. It is considered to have the most sophisticated implementation of a block-size-changing algorithm in
free and open source software
Free and open-source software (FOSS) is software available under a Software license, license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term ...
, and is considered an essential data recovery tool.
The status of the copy process is recorded in a ''map file'' (previously called ''logfile'') that aids in the progress of multiple stages of the recovery algorithm, and facilitates interrupting the recovery, and repeating it as needed to recover more data. The program does not write zeros to the output in place of bad blocks, so that additional errors not encountered previously do not destroy previously recovered blocks. This makes it possible to merge multiple defective copies of CDs or DVDs into one backup file. By virtue of the map file, only the needed blocks are read from the second and successive copies.
ddrescue also features a ''fill mode'', able to selectively overwrite parts of the output file, which has uses such as wiping data, marking bad areas or even, in some cases, repair damaged sectors.
Unrelated recovery tools
GNU ddrescue is not a derivative of
dd which also copies blocks of storage from disk storage, but does not operate in a strategic, algorithmic manner.
GNU ddrescue is also distinct from the similarly named program .
Kurt Garloff's dd_rescue
/ref>
See also
* Backup
In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "wikt:back ...
* Disk cloning
Disk cloning is the process of duplicating all data on a Digital Storage, digital storage drive, such as a Hard disk drive, hard disk or Solid-state drive, solid state drive, using hardware or software techniques. Unlike file copying, disk cloning ...
* GNU Project
The GNU Project ( ) is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and Computer hardware, computing dev ...
Notes
References
{{Reflist, 2
External links
GNU ddrescue Manual
Free data recovery software
Hard disk software
GNU Project software
C++ software
Free software programmed in C++
fr:Ddrescue