Re: how to rescue this backup data

Zhang Weiwu wrote:
> Hello. We have a website backup that has to be recovered thanks to 
> webserver hard disk crash. However the person who burned the backup 
> seems to have done it wrong. This is what we investigated what most 
> likely have happened:
>
> a. he have a DVD+R that has a session on it.
> b. he created a backup iso image by merging that session:
>  $ genisoimage -C ... -M /dev/sr0 -o backup.iso website_backup/
> c. he burnt the backup to a /different/ DVD+R that also had a session:
>  $ wodim dev=/dev/sr1 backup.iso
>   (or, might also have been "$ growisofs -M /dev/sr1=backup.iso" )
> d. he happily labeled the DVD+R in /dev/sr1 as "website backup". no 
> double check. done.
>
>
> Now, we have the DVD+R that was there in /dve/sr1 when he do step c, 
> because it is correctly labeled as website backup. I can dump 
> backup.iso by using this:
>   $ dd if=/dev/sr1 of=backup.iso bs=2048 count=155440 skip=1256096
>   where value of count and skip are found here
>     $ dvd+rw-mediainfo /dev/sr1 | grep -A 4 '.\[#2\]'
>     READ TRACK INFORMATION[#2]:
>      Track State:           partial/complete
>      Track Start Address:   1256096*2KB
>      Free Blocks:           0*2KB
>      Track Size:            155440*2KB
>
> We do not know which DVD+R was in /dev/sr0 when he do step b. There 
> are a few hundreds in stock. We can locate a dozen that might be if 
> really have to. The dumped backup.iso has the right size, that makes 
> me believe nothing merged from the previous session in step b are 
> important to me. In other words, backup.iso should contain all data I 
> need to recover the website.
>
> However, reasonable to believe, I could not mount backup.iso:
> # mount -o loop backup.iso /mnt/
> mount: /dev/loop0: can't read superblock
>
> My question is, is there a way to recover hierarchical file backup 
> from backup.iso, except all files and directories that refer to the 
> previous session, which we could not easily find and should not need?

What actually happens when you try to mount the session? That is, using 
the session= option to the mount command. What error message do you get?

-- 
Bill Davidsen <[email protected]>
  "We can't solve today's problems by using the same thinking we
   used in creating them." - Einstein


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