Wednesday, 20 May 2015 00:00

"Bad" ISO image recovery by executing rsync

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This example illustrates the recovery of an image created from the defective FreeBSD 6.0 disk.

1. We do a Google search for a rsync-mirror with images being of interest to us. You can find a list of images for the problem from our example here.

We choose the nearest mirror marked rsync against the address: ftp2.ru.freebsd.org и ftp5.ru.freebsd.org.

2. Then we find out what "modules" are available on selected rsync-servers by executing the command:

     rsync -n -vv ftp2.ru.freebsd.org::

The two-word answer is "FreeBSD"; we gather that the name of the module we are looking for is FreeBSD. You can not find out the module name from ftp5.ru.freebsd.org server in such a way - the server responds only with information of an advertising nature. Notes to the command: the -n key does not allow rsync to download anything; the -vv key allows seeing more information on an event on the screen; two colons are mandatory to put after the server name (instead of them, you can use rsync:// before the server name, but it is longer).

3. Let us learn the location of directories and files on the server:

     rsync -n -vv ftp2.ru.freebsd.org::FreeBSD/

As you can see, the module name followed by a slash (/) is added to the previous command. The slash is needed to specify that you want a directory listing to be displayed, and not the directory itself. As a result of the command execution, you can see that the file structure (in this case) replicates the location of the files on the FTP server. After that we determine where the sought-for images are (by paging through the directories we are interested in) and continue. Unfortunately, I could not make the -list-only key from man rsync work and had to find the above method by using the SWAG method.

4. Let's suppose that the disk image has already been created, for example, as follows:

readcd dev=ATA:1,0,0 speed=8 -noerror f=/path/to/6.0-RELEASE-i386-disc1.iso

(The details are in man readcd). And the image hash total does not match the hash total of the official website image.

5. We recover the image by the command:

rsync --stats --progress -z -vv \ 
ftp5.ru.freebsd.org::FreeBSD/ISO-IMAGES-i386/6.0/6.0-RELEASE-i386-disc1.iso \
/path/to/freebsd/6.0-RELEASE-i386-disc1.iso \

Notes to the command: -z is desirable for compressing the information to be passed (I have not tested its efficacy); -stats displays on completing the detailed information about what was made; -progress shows the percent completion of the running task.

6. We make sure that the hash total of the recovered image matches the hash of the images from the official website.

By using this method, I recovered images from FreeBSD 6.0 disks, burned with Nero software by a good man with a thicknet. The readcd barfed at the end of either.disk. The incoming traffic, in my case, was less than 1Mb for both disks.

Last modified on Wednesday, 20 May 2015 13:06
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Viktor S., Ph.D. (Electrical/Computer Engineering), was hired by DataRecoup, the international data recovery corporation, in 2012. Promoted to Engineering Senior Manager in 2010 and then to his current position, as C.I.O. of DataRecoup, in 2014. Responsible for the management of critical, high-priority RAID data recovery cases and the application of his expert, comprehensive knowledge in database data retrieval. He is also responsible for planning and implementing SEO/SEM and other internet-based marketing strategies. Currently, Viktor S., Ph.D., is focusing on the further development and expansion of DataRecoup’s major internet marketing campaign for their already successful proprietary software application “Data Recovery for Windows” (an application which he developed).

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