Re: [Dump-users] Help please - recovery of partial dump

[Stelian P. <st...@po...>]

On Mon, Jan 31, 2005 at 09:35:31AM +0000, Tim Booth wrote:

> Hi,
> 
> A colleague of mine was using dump to archive some important data, and
> it looks like he made an error in the dump.  He has a single file dumped
> off an ext3 partition but when he tries to restore it:
> 
> # /sbin/restore -id -f Mal_06.01.05dmp
> Volume header (old inode format) begins with record 7961470
> Volume header (old inode format) begins with record 7961470
> Dump tape is compressed.
> /sbin/restore: Tape is not volume 1 of the dump
> 
> And indeed the GNU file command reveals:
> 
> # file /media/FWdrive/Mal_06.01.05dmp
> /media/FWdrive/Mal_06.01.05dmp: new-fs dump file (little endian), This
> dump Thu Jan  6 16:46:09 2005, Previous dump Thu Jan  1 01:00:00 1970,
> Volume 2, Level zero, type: tape header, Label /home, Filesystem /home,
> Device /dev/hda6, Host censored.foo.ox.ac.uk, Flags 81

Indeed, this is the second volume of a dump.
> 
> My colleague claims he made the dump with the command:
> 
> /sbin/dump -0 -j -n -f /tmp/Mal_06.01.05dmp /home
> 
> and that only one file was produced.  Given that I am unfamiliar with
> dump/restore (my suggestion was to use tar for this backup) could anyone
> tell me:
> 
> 1) Under what circumstances would dump overwrite the first volume with
> the second?

A possible explanation would be a space related one: maybe there
wasn't enough free space on the destination drive, this made dump
stop and *query* the operator to start the next volume. *If* the
operator answered 'yes', then dump continued by overwritting the 
previous volume with the second one.

But it could be anything else...

> 2) If my colleague really does have just the second volume, can anything
> be salvaged from the file?

Unfortunately no. The first volume is special because it contains 
the list of all directories and files dumped. If the missing volume
was another one, you would lose only the data on that volume. But here
you're out of luck, you losed the entire tree structure.

That being said, there is still some data on this second volume which
could very well be salvaged. However, you will have to modify the
restore source to do this, because it won't let you do it otherwise
(hint: if you do that, try to make 'restore -x -m' work, it should be 
the easiest path to hack).

Stelian.
-- 
Stelian Pop <st...@po...>