GNU ddrescue is a data recovery utility. It copies data from one file or block device (hard disk, CD-ROM, and so on.) To another, trying to recover data in case of read errors. GNU ddrescue is written in C ++ and was first released in 2004 and has since become available on most Linux distributions .
| GNU ddrescue | |
|---|---|
 | |
| Type of | Data recovery |
| Author | Antonio Diaz Diaz |
| Written on | C ++ |
| operating system | Unix-like |
| First edition | August 12, 2004 |
| Latest version | 1.23 (February 16, 2018 ) |
| License | GPLv2 + |
| Site | gnu.org/software/ddrescue/ |
Content
Description
GNU ddrescue is not derived from dd and is in no way associated with dd, except that both can be used to copy data from one device to another. The difference is that ddrescue uses a sophisticated algorithm to copy data from failed disks, which causes them as little additional damage as possible. GNU ddrescue is considered the most complex implementation of the block resizing algorithm in free, open source software and is considered an important data recovery tool.
If someone uses the mapfile function (previously called the logfile) in ddrescue, the data is saved very efficiently (only the necessary blocks are read). You can also interrupt salvation at any time and resume it later at the same point.
ddrescue does not write zeros to the output when it detects bad sectors in the input, and does not truncate the output file if it is not requested. Thus, every time you run ddrescue for the same output file, it tries to fill in the blanks without destroying the data already recovered.
Usage
Cloning the / dev / sda drive to / dev / sdb on Linux with writing the recovery log to the rescue.log file
ddrescue --force / dev / sda / dev / sdb rescue.log
Other use cases
Automatically merge backups: if you have two or more corrupted copies of a file, a CD, etc., you must run ddrescue on all of them, one at a time, with the same output file. The result is one complete and error-free file. Using the log file, only the second and subsequent copies read only the necessary blocks.
ddrescue recommends lzip for compressing backups, because the lzip format is designed for long-term data archiving and provides data recovery capabilities that perfectly complement the capabilities of ddrescue. (ddrescue fills unreadable sectors with data from other copies, and lziprecover fixes bad sectors with data from other copies). If the cause of the file corruption is damaged media, the ddrescue + lziprecover combination is the best option to recover data from several damaged copies.
Ddrescue also has a “fill mode” that can selectively overwrite parts of the output file, which has a number of interesting applications, such as erasing data, marking damaged areas, or even, in some cases, “repairing” damaged sectors.
See also
- Backup
- Disk cloning
- GNU Project
References
External links
- gnu.org/software/ddrescue/ - official Ddrescue website
- GNU ddrescue Manual