Mail Archives: cygwin/2007/05/29/15:21:07
The GNU ddrescue package is now part of the Cygwin distribution.
http://www.gnu.org/software/ddrescue/ddrescue.html
Important note for Cygwin (<= 1.5.24-2):
When reading from a raw device with sector size > 512 Bytes, it is
required to specify the exact sector size with the '-b' option.
(for CD/DVD e.g: ddrescue -b 2048 /dev/scd0 cd.iso cd.log)
Otherwise, ddrescue may crash due to a bug in Cygwin's raw device
lseek(). The bug is fixed in Cygwin snapshot 2007-05-23 or later.
Description of ddrescue from README:
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.
Ddrescue does not truncate the output file if not asked to. So, every
time you run it on the same output file, it tries to fill in the gaps.
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.
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. Read the
info file to learn how to use raw devices with ddrescue.
Christian Franke
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