What's the difference between ddrescue, gddrescue, and dd_rescue?

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ddrescue, confusingly, can refer to two completely separate programs, dd_rescue by Kurt Garloff, and GNU ddrescue. Both have the same purpose and are actively developed.

Garloff's program dd_rescue is the first attempt to improve on dd; GNU ddrescue is newer and was created to address shortcomings in dd_rescue.

Several sources prefer GNU ddrescue over dd_rescue. For example,

http://lwn.net/Articles/430000/

ddrescue wins (in my book) because it is an efficient self-contained program written in C++ (not a shell script kludge), produces much cleaner output on the console/terminal, and (most importantly) handles unreadable blocks gracefully and intelligently.

http://www.toad.com/gnu/sysadmin/index.html#ddrescue

GNU ddrescue is your best friend.

It is modeled after the two preceding programs, dd_rescue (with an underbar), and dd_rhelp. But GNU ddrescue it's far better than both -- I've tried all three, on the same drive, as well as...

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GNU ddrescue is a program that copies data from one file or block device (hard disk, cd/dvd-rom, etc) to another, it is a tool to help you to save data from crashed partition i.e. it is a data recovery tool. It tries to read and if it fails it will go on with the next sectors, where tools like dd will fail. If the copying process is interrupted by the user it is possible to continue at any position later. It can copy backwards.

This program is useful to rescue data in case of I/O errors, because it does not necessarily abort or truncate the output. This is why you need to use this program and not the dd command. I have recovered much data from many disks (CD/hard disk/software raid) over the years using GNU ddrescue on Linux. I highly recommend this tool to Linux sysadmins.

Install ddrescue on a Debian/Ubuntu Linux

Type the following apt-get command to install ddrescue:
# apt-get install gddrescue
Sample outputs:

Reading package lists......

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ddrescue is a raw disk imaging tool that "copies data from one file or block device to another, trying hard to rescue data in case of read errors." The application is developed as part of the GNU project and has written with UNIX/Linux in mind.

ddrescue and dd_rescue are completely different programs which share no development between them. The two projects are not related in any way except that they both attempt to enhance the standard dd tool and coincidentally chose similar names for their new programs.

From the ddrescue info pages:

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...

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Somewhere on the internets I read that gddrescue is superior to dd at least in terms of being able to distinguish between the amount of disk reads performed on a troubled sector. Is this really the case?

time dd if=/dev/sda skip=900343967 of=a.bin count=4 iflag=direct conv=noerror,sync

dd: reading `/dev/sda': Input/output error
2+0 records in
2+0 records out
1024 bytes (1.0 kB) copied, 18.6057 s, 0.1 kB/s
3+1 records in
4+0 records out
2048 bytes (2.0 kB) copied, 18.6707 s, 0.1 kB/s

real 0m18.672s
user 0m0.000s
sys 0m0.004s

Btw, the direct flag really helps, w/o it I was only able to read 1 sector out of 4 (vs 3/4 with it). However, that noticeably slows the transfer speed down - it is at least about 5 times slower for me: 5MB/s vs 25MB/s without this flag. Anyhow, now for the gddrescue (ddrescue) part..

time ddrescue -b512 -c1 -s4b -dnvD -i900343967b -o0b /dev/sda b.bin

About to copy 2048...

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1- Before using dd, ddrescue, or dd_rescue, you need to know which disk is which, you can do that by simply using the command “fdisk -l” in my case, the old disk turned out to be /dev/sdb and the new un-partitioned disk is /dev/sdc.

So, i have been cloning a 2TB hard drive ( WD20EARS ) to a WD20EARX, same disk, but with a few differences

WD20EARS is sata 2 and the other is sata 3, another difference is that using “hdparm -I /dev/sdb” the older WD20EARS reports (And should not be true)

WD20EARS

Logical/Physical Sector size: 512 bytes

wile with “hdparm -I /dev/sdc” the newer WD20EARX reports

Logical Sector size: 512 bytes Physical Sector size: 4096 bytes Logical Sector-0 offset: 0 bytes

The first clone did not work for a reason unknown to me, i cloned my NTFS disk with ddrescue (gddrescue) on a linux (because i don’t know how to clone on windows) and then plugged it into windows, where it simply did not...

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Short Intro.

I learned how to use “dd” and clone to image from beginning of the disk up to a bit more than the point where the partition1 ends and to save the image on my internal SSD drive and it works:

I have 2 questions:

1) How do I use “ddrescue”, or better “ddrescue-GUI”, to achieve the same clone to image from beginning of the disk up to a bit more than the point where the partition1 ends, in the same way as “dd”?


Ideas.

2) From cloning point of view, without affecting integrity of the data source disk and the file image obtained, is it the same these 2 options a. and b.?:
a. Usage of “dd” or “ddrescue” as one image file from beginning of the disk up to a bit more than the point where the partition1 ends.
Then use this single image file to write later the destination disk.
b. Clone to image using “dd” or “ddrescue” only MBR as one image file + clone to image partition1, seen as...

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The dd command is commonly used to make image backups of a drive or partition. However, it performs poorly if the source drive is unreliable or failing. I read that ddrescue/dd_rescue is a good tool to use to recover an image from a bad drive, since it intelligently attempts to re-read sectors that it failed to read the first time.

But in the Ubuntu repositories, I see two different ddrescue programs, with 3 different but similar names showing up in different places: ddrescue, gddrescue, dd_rescue. What's the difference?

Answers

ddrescue, confusingly, can refer to two completely separate programs, dd_rescue by Kurt Garloff, and GNU ddrescue. Both have the same purpose and are actively developed.

Garloff's program dd_rescue is the first attempt to improve on dd; GNU ddrescue is newer and was created to address shortcomings in dd_rescue.

Several sources prefer GNU ddrescue over dd_rescue. For example,

http://lwn.net/Articles/430000/
...
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This guide was written by one of our forum members SilverLeaf and was originally written as a forum post. This guide is intended for people who are looking to do quality data recovery using free tools. This guide is fairly technical requiring you to deal with the Linux command line. Some paid software is more straight forward than the steps here, but this is a great way to get the job done for free. Use at you own risk. Technibble and SilverLeaf take no responsibility for the loss of any data, business, reputation etc..

It seems that a guide for using ddrescue might be of some benefit to many members who may be shy of the linux terminal. So, I’ve decided to document some real-world examples from in the shop. I plan on doing this in 3 parts to cover the most common scenarios.

Part 1: Creating an image from a failing disk
Part 2: Restoring an image to a new disk & cloning directly to a new disk
Part 3: Working with the image files

In will be using...

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GNU ddrescue Manual

GNU ddrescue Manual

This manual is for GNU ddrescue (version 1.23, 13 February 2018).

Copyright © 2004-2018 Antonio Diaz Diaz.

This manual is free documentation: you have unlimited permission to copy, distribute and modify it.

1 Introduction

GNU ddrescue is a data recovery tool. It copies data from one file or block device (hard disc, cdrom, etc) to another, trying to rescue the good parts first 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, restart it from a new position, etc.

If you use the mapfile feature of ddrescue, the data is rescued very efficiently, (only the needed blocks are read). Also you may interrupt the rescue at any time and resume it later at the same point. The mapfile is an essential part of ddrescue's effectiveness. Use it unless you know what you are doing.

Ddrescue does not write zeros to the...

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Regardless of whether there was any NIH mentality in the motivation, ddrescue came later and was at least in part a response to the technical shortcomings of dd_rescue. If you try both on a dying disk, you will quickly see why. I'm not the only person who has done this and come away with this conclusion:

http://ubuntu-rescue-remix.org/node/51

dd_rescue is so problematic that it necessitated the invention of dd_rhelp, a script to wrap dd_rescue and try to make it do the things that it arguably should be doing.

So, perhaps it would be more fair to compare ddrescue with dd_rhelp. But once again, ddrescue wins (in my book) because it is an efficient self-contained program written in C++ (not a shell script kludge), produces much cleaner output on the console/terminal, and (most importantly) **handles unreadable blocks gracefully and intelligently**.
...

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Like dd, dd_rescue does copy data from one file or block device to another.dd_rescue is a tool to help you to save data from crashed partition. It tries to read and if it fails, it will go on with the next sectors where tools like dd will fail. If the copying process is interrupted by the user it is possible to continue at any position later. It can copy backwards.


dd_rescue Advantages

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 lose 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....

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I don't know if this has been covered before, but knoppix includes the program dd_rescue which is really a brilliant program for copying/imaging hard drives with bad sectors.

dd will give you lots of trouble when it encounters bad sectors, usually truncating the output or exiting when it gets a read error.

dd_rescue is much more forgiving.

"dd_rescue" without parameters will give you a list of command line parameters. Note that the command line syntax is much different from dd.

For example, "dd_rescue /dev/hda /dev/null" will copy from /dev/hda to /dev/null . I like to use this as a read test to see if an entire hard drive can be read.

I had a failing hard drive whose LBA sector 0 was completely unreadable. dd wouldn't even want to look at it. With dd_rescue I was able to get most of the good data off of this drive. Interestingly, knoppix 5.1 wouldn't even give me a /dev/hda in the device directory as it couldn't read the partition table in LBA 0 and...

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NOTE

These instructions are relevant to the blue ring - two drive model of the My Book World II NAS device.

If you have the "white light" version, (or any newer version of the MBW), these instructions may not work for you as written; so you may wish to try to find relevant recovery steps for your version.

If you find articles relevant to the newer versions, please leave me a private message, and I will update this page to point to the relevant page(s) for the newer MBW editions.

UPDATE

After the original article was written, I have learned more about the recovery process. I am going to include the additional information I have found, as well as fix some glaring errors (make that read "STUPID errors"), that I noticed re-reading this article.

Acknowledgments:

I want to acknowledge the help given me by Gabriel (who sure earned his name this time!) along with everyone else on these fora who posted their own experiences with the MBWE....

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On Tue, 2016-02-16 at 07:27 -0600, Linda wrote:

> My daughters windows lap top hard drive that had sudden

> failure. Am hoping to recover some recent photos of my

> grandson that had not been backed up yet. I stuck it in a

> external case and and ran PhotoRec I am now trying testdisk

> any other suggestions for what I should use.

Stop.

Use dd to take an image of the disk partition. You can do this
regardless of what OS created the partition.

Then work with the image, not the disk. Continuing to use the disk risks
causing further damage.

If the data is truly precious, send the disk to a professional recovery
firm. They have tools not at your disposal.

Regards, K.

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer ([hidden email])
http://www.biplane.com.au/kauer
http://twitter.com/kauer389

GPG fingerprint: E00D 64ED 9C6A...

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Posted by Hans-Henry Jakobsen

GNU ddrescue (gddrescue) is a linux data recovery tool. It copies data from one file or block device (harddisc, cdrom, etc) to another, trying hard to rescue data in case of read errors.
It can also be used as a forensic cloning tool.

Installing gddrescue in Ubuntu linux

# aptitude install gddrescue

The command to use for gddrescue is ddrescue, don’t ask me why it is not called gddrescue.

First you copy as much data as possible, without retrying or splitting sectors.
This example rescues data from one disk to another

# ddrescue --force /dev/sda /dev/sdb logfile.ddrescue

Warning! This overwrites content on /dev/sdb

When you use a log file you can stop ddrescue any time by pressing Ctrl+ C to interrupt the process.

You restart it again with the same parameters and ddrescue will resume from where it was before it was interrupted. This is good to know since this can be a time consuming...

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Greetings fellow hoaders. I'm cleaning out my house for an upcoming move and I found my wife's old (circa 2003) 250 meg iomega zip drive along with seven disks. On a lark, I decided to see what I could recover.

The data probably isn't anything great. Four of the disks appear to be unused, one of them is labeled "old stuff", another "Fall 2003", and a third was labeled for the solar house project she worked on for a college club.

The first thing I did was plug in the drive. (It's the USB version and thankfully not the 80 pin parallel cable version) It whirred loudly to life, and surely enough dmesg informed me that a diver had loaded. Wow. Another reason I love linux - old device drivers never ever die.

The disks had been stored for a decade in our storage room, which is attached to the house but not very well insulated. It probably spends most summer days in the 90s and gets down in the low 60s in the winter. Not the best conditions for fragile...

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ddrescue is a tool provided by GNU to retrieve data from failing (block) storage devices like disk drives, CDROMs, or memory sticks, etc. It uses a similar technique as dd and copies block by block, but has an intelligent algorithm to recover failed data.

Installation

Emerge

Install sys-fs/ddrescue using the following command:

root #emerge --ask sys-fs/ddrescue

Usage

The general purpose of ddrescue is to recover data from failing block devices. It can be also used as a general disk (or even file) copying tool with quite a good efficiency and a nice progress bar.

Copy data

ddrescue can use block devices or files as input and output. The main difference to other programs used to copy files, is that the destination needs to be specified:

user $ddrescue /etc/portage/make.conf ~/make.conf

Rescue data

The strategy is to read and copy as much data as possible in the first round, since every access to the...

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GNU ddrescue is a data recovery tool. It copies data from one file or block device (hard disk, CD-ROM, etc.) to another, trying hard to rescue data in case of read errors. GNU ddrescue is a program written in C++ that was initially released in 2004 and has since become available in most Linux distributions.

Description[edit]

GNU ddrescue is not a derivative of dd, nor is it related to dd in any way except in that both can be used for copying data from one device to another. The difference is that ddrescue uses a sophisticated algorithm to copy data from failing drives causing them as little additional damage as possible.[1] GNU ddrescue is considered to have the most sophisticated implementation of a block-size-changing algorithm in free and open source software,[2][3] and is considered an essential data recovery tool.[4][5]

If one uses the "mapfile" (previously called "logfile") feature of ddrescue, the data is rescued very efficiently (only the needed blocks...

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Thanks for taking the time to reply, with such clarity, the amount of information given by you is priceless.

You're welcome - unfortunately trying to help on problems remotely like this isn't easy, and I have limited time available to assist. A few more suggestions below, but as I said before and

pcrecovery

also mentioned, a software-only approach (like ddrescue) has limitations. This is why I previously mentioned that you needed to decide whether to use a pro recovery (e.g. someone with h/w assisted recovery equipment, like those mentioned by

pcrecovery

), or accept the consequence of DIY.

I did try limiting the read area of ddrescue using

ddrescue -i3400M -s1G but i get a 1GB error file

once im reading any data between 3.2GB and 10GB.

I expect that you needed to power-cycle the drive, before it would respond again - is that correct?

It's not clear to me - after power-cycling the drive (if necessary), did you try similar...

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Sponsored Link

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.Ddrescuelog is a tool that manipulates ddrescue logfiles, shows logfile contents, converts logfiles to/from other formats, compares logfiles, tests rescue status, and can delete a logfile if the rescue is done. Ddrescuelog operations can be restricted to one or several parts of the logfile if the domain setting options are used.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.

Ddrescue does not write zeros to the output when it finds bad sectors in the input, and does not...

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