Bug#189249: ITP: ddrescue -- Like dd, dd_rescue does copy data from one file or block device to another
Version: unavailable; reported 2003-04-16
* Package name : dd_rescue
Version : 1.0.2
Upstream Author : Kurt Garloff <email@example.com>
* URL : http://www.garloff.de/kurt/linux/ddrescue/
* License : GPL
Description : dd_rescue does copy data from one file or block device to another
The latter three features make it suitable for rescuing data from a
medium with errors, i.e. a hard disk with some bad sectors.
* Imagine, one of your partitions is crashed, and as there are some
hard errors, you don't want to write to this hard disk any more. Just
getting all the data off it and retiring it seems to be suitable.
However, you can't access the files, as the file system is damaged.
* Now, you want to copy the whole partition into a file. You burn it on
CD-Rom, just to never loose it again. You can setup a loop device, and
repair (fsck) it and hopefully are able to mount it.
* Copying this partition with normal Un*x tools like cat or dd will
fail, as those tools abort on error. dd_rescue instead will try to read
and if it fails, it will go on with the next sectors. The output file
naturally will have holes in it, of course. You can write a log file,
to see, where all these errors are located.
* The data rate drops very low, when errors are encountered. If you
interrupt the process of copying, you don't loose anything. You can
just continue at any position later. The output file will just be
filled in further and not truncated as with other Un*x tools.
* If you have one spot of bad sectors within the partition, it might be
a good idea, to approach this spot from both sides. Reverse direction
copy is your friend.
* The two block sizes are a performance optimization. Large block sizes
result in superior performance, but in case of errors, you want to try
to salvage every single sector. So hardbs is best be set to the
hardware sector size (most often 512 bytes) and softbs to a large
value, such as the default 16k.
It will be uploaded soon by my sponsor Gerfried Fuchs<alfie!debian.org>.
-- System Information:
Debian Release: testing/unstable
Kernel: Linux matrix 2.4.18-bf2.4 #1 Son Apr 14 09:53:28 CEST 2002 i686
Locale: LANG=de_DE@euro, LC_CTYPE=de_DE@euro
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