Recover Data from a Damaged hard disk using dd_rhelp

dd_rhelp is a bash script that handles a very usefull program written in C which is called dd_rescue, it roughly act as the dd linux command with the caracteristic to NOT stop when it falls on read/write errors.

This makes dd_rescue the best tool for recovering hard drive having bad sectors.In short, it’ll use dd_rescue on your entire disc, but will try to gather the maximum valid data before trying for ages on badsectors. So if you leave dd_rhelp work for infinite time, it’ll have the same effect as a simple dd_rescue. But because you might not have this infinite time , dd_rhelp will jump over bad sectors and rescue valid data. In the long run, it’ll parse all your device with dd_rescue.

You can Ctrl-C it whenever you want, and rerun-it at will, it’ll resume it’s job as it depends on the log files dd_rescue creates.In addition, progress will be shown in a ASCII picture of your device beeing rescued.

Why use dd_rhelp and not dd_rescue ?

dd_rhelp uses dd_rescue to compute a recovery path through the device that will focus on valid data recovering. This recovery path will go through all the device, exactly as dd_rescue could do it on its own without any path. This means that dd_rhelp will save you time ONLY IF YOU INTEND TO CANCEL ITS JOB BEFORE THE END of a full recovery.

Because a considerable amount of time is taken to try to rescue badsectors. This amount of time can be mesured in days,month, years, depending on your device capacity and its defectiveness. You might not want to spend this time knowing that 99 percent of this time will be taken to look at badsector and won’t lead to any more data recovering.

dd_rhelp shifts this useless waiting time to the end. Using dd_rescue strait throughout your device make your waiting time dependent on the badsector distribution.

Install dd_rhelp

First you need to download latest version from here

Preparing your system

sudo apt-get install make gcc g++ ddrescue

Download dd_rhelp using the follwoing command

wget http://www.kalysto.org/pkg/dd_rhelp-0.0.6.tar.gz

Now you have dd_rhelp-0.0.6.tar.gz file

Extract this file using the following command

tar xzvf dd_rhelp-0.0.6.tar.gz

cd dd_rhelp-0.0.6

Run the following commands

sudo ./configure

sudo make

sudo make install

This will complete the installation and this will install program under /usr/local/bin/dd_rhelp

dd_rhelp Syntax

dd_rhelp {filenamedevice} {output-file} [{info}]
or dd_rhelp --help
or dd_rhelp --version

Now we will see how to use ddrescue under damaged disk

If you have a damaged hard disk /dev/sda1 and you have an empty space hard disk /dev/sda2 Now if you want to copy data from /dev/sda1 to /dev/sda2 use the following command

sudo dd_rhelp /dev/sda1 /dev/sda2/backup.img

Output looks like below

/usr/bin/tail: Warning: “+number” syntax is deprecated, please use “-n +number”
=== launched via ‘dd_rhelp’ at 0k, 0 >>> ===
dd_rescue: (info): ipos: 104384.0k, opos: 104384.0k, xferd: 104384.0k
errs: 0, errxfer: 0.0k, succxfer: 104384.0k
+curr.rate: 10178kB/s, avg.rate: 8532kB/s, avg.load: 31.3%
dd_rescue: (info): /dev/sda2 (104391.0k): EOF
Summary for /dev/sda2 -> backup.img:
dd_rescue: (info): ipos: 104391.0k, opos: 104391.0k, xferd: 104391.0k
errs: 0, errxfer: 0.0k, succxfer: 104391.0k
+curr.rate: 355kB/s, avg.rate: 8519kB/s, avg.load: 31.3%
/usr/bin/tail: Warning: “+number” syntax is deprecated, please use “-n +number”

This copies an image of /dev/sda1 to sda2

Now you need to check the backup image consistency this will check for is there any problems with this image.

sudo fsck -y /dev/sda2/backup.img

After finishing this checking you need to mount your disk image in to your other hard disk

sudo mount /dev/sda2/backup.img /mnt/recoverydata

This will mount all the data from the backup.img under /mnt/recoverydata now you can try to access the data it should work without any problem.

Restore image

If you want to restore this image use the following command

sudo dd_rhelp /dev/sda2/backup.img /dev/sda1

Copy Disk Image to remote machine using SSH

If you want to copy your disk image to remote machine over ssh you need to use the following command

sudo dd_rhelp /dev/sda1 – ssh username@machineip ‘cat /datarecovery/backup.img’

This will be prompetd for password of the username you have menctioned in the above command after entering the password

dd_rhelp strats copying obviously it will take some time to copy over the network.

Source:
http://onlyubuntu.blogspot.com/2007/05/recover-data-from-damaged-hard-disk.html

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