Ddrescue - Data recovery tool
Introduction
GNU ddrescue is a data recovery tool. It copies data from one file or block device (hard disc, cdrom, etc) to another, trying hard to rescue data in case of read errors.The basic operation of ddrescue is fully automatic. That is, you don't have to wait for an error, stop the program, read the log, run it in reverse mode, etc.
If you use the logfile feature of ddrescue, the data is rescued very efficiently (only the needed blocks are read). Also you can interrupt the rescue at any time and resume it later at the same point.
Automatic merging of backups: If you have two or more damaged copies of a file, cdrom, etc, and run ddrescue on all of them, one at a time, with the same output file, you will probably obtain a complete and error-free file. This is so because the probability of having damaged areas at the same places on different input files is very low. Using the logfile, only the needed blocks are read from the second and successive copies.
Ddrescue recommends lzip for compression of backups, because of its reliability and data recovery capabilities.
Recordable CD and DVD media keep their data only for a finite time (typically for many years). After that time, data loss develops slowly with read errors growing from the outer media region towards the inside. Just make two (or more) copies of every important CD/DVD you burn so that you can later recover them with ddrescue.
The logfile is periodically saved to disc. So in case of a crash you can resume the rescue with little recopying.
Also, the same logfile can be used for multiple commands that copy different areas of the file, and for multiple recovery attempts over different subsets.
Ddrescue aligns its I/O buffer to the sector size so that it can be used to read from raw devices. For efficiency reasons, also aligns it to the memory page size if page size is a multiple of sector size.
Documentation
The manual is available in the info system of the GNU Operating System. Use info to access the top level info page. Use info ddrescue to access the ddrescue section directly.An online manual for ddrescue can be found here.
Download
The latest released version of GNU ddrescue can be found in the subdirectory/gnu/ddrescue/ on your favorite GNU mirror. For other ways to obtain ddrescue, please read How to get GNU Software. The latest released version will be the most recent version available at http://ftp.gnu.org/gnu/ddrescue/. Old versions and testing versions can be found at http://download.savannah.gnu.org/releases/ddrescue/.
How to Get Help
For general discussion of bugs in ddrescue the mailing list bug-ddrescue@gnu.org is the most appropriate forum. Please send messages as plain text. Please do not send messages encoded as HTML nor encoded as base64 MIME nor included as multiple formats. Please include a descriptive subject line. If all of the subject are "bug in ddrescue" it is impossible to differentiate them.An archive of the bug report mailing list is available at http://lists.gnu.org/mailman/listinfo/bug-ddrescue.
How to Help
To contact the author, either to report a bug or to contribute fixes or improvements, send mail to bug-ddrescue@gnu.org. Please send messages as plain text. If posting patches they should be in unified diff format against the latest version. They should include a text description.See also the ddrescue project page at Savannah.
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Updated: $Date: 2010/04/06 16:10:04 $ $Author: antonio $
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http://www.gnu.org/software/ddrescue/ddrescue.html
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