Re: how to rescue this backup data

[Bill Davidsen]

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 <david...@tmr.com>
 "We can't solve today's problems by using the same thinking we
  used in creating them." - Einstein


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