oh thanks i didnt know this difference exits between ext2 and ext3
From: Kumaraguru <kums@xxxxxxx>
To: Antano Solar John <solar345@xxxxxxxxxxx>
CC: ilugc@xxxxxxxxxxxxx
Subject: Re: [Ilugc] Undelete: impossible on ext3!
Date: Mon, 21 Aug 2006 20:21:10 +0530
No..no..no! this is not a Linux Vs Windows thing at all. You have
misunderstood me.. I think you missed the quote from ext3 developer that I
had given in my very first mail. For your convenience..here it is again
(from http://lkml.org/lkml/2003/1/7/135)
<quote>
..in order to ensure that ext3 can safely resume an unlink after a
crash, it actually zeros out the block pointers in the inode, whereas
ext2 just marks these blocks as unused in the block bitmaps and marks
the inode as "deleted" and leaves the block pointers alone.
Your only hope is to "grep" for parts of your files that have been deleted
and hope for the best...
</quote>
As he clearly explains, ext2 will maintain pointers to deleted blocks while
ext3 will not. That means, we know where the deleted blocks are and there's
a way we can differentiate them from the unused blocks that never had any
data before. fat32 has a similar way. So there is a logical possibility to
undelete. As ext3 doesn't maintain such pointers to deleted blocks, there's
no reliable way we can know where the deleted blocks are. I hope you see
the difference now.
Another thing..if your ext3 partition is fragmented then you won't be able
to retrieve your file completely by reading the partition contiguously. One
part of your file may be in one place and another somewhere else.
Antano Solar John wrote:
i am not sure how it is done but i think you can analyse overheads and
know which is a mp3 which is a text file ......... or there is pattern and
i think you can recognize the end of a file by the EOF character .........
if its possible in windows its possible in linux also just that one of us
have to write a code and distribute it to the others :)
From: Kumaraguru <kums@xxxxxxx>
To: ilugc@xxxxxxxxxxxxx
Subject: Re: [Ilugc] Undelete: impossible on ext3!
Date: Mon, 21 Aug 2006 10:53:42 +0530
Yes, you are right - if they are not overwritten they are definitely
there.. but the problem is.. I won't exactly know where they are in my
80 GB hard disk. I can try to recover some text files if I know some
unique words I had used in those files by grepping but if my files are
binary how would i know if, say.. "0F FF DE 6B 6E 73 76...." is a unique
byte combination that occurs only in my lost mp3 file?
I am learning the hard way. Don't forget to make your backups!
Regards
Kumaraguru
--
Antano Solar John wrote:
technically when u accidentally delete files , the data is not deleted
only the link to it is deleted , so it must be possible to recover
accidentially deleted data as long as it is not over written.
From: "Binand Sethumadhavan" <binand@xxxxxxxxx>
To: "Prashanth Mohan" <prashmohan@xxxxxxxxx>
CC: Kumaraguru <kums@xxxxxxx>, ilugc@xxxxxxxxxxxxx
Subject: Re: [Ilugc] Undelete: impossible on ext3!
Date: Sun, 20 Aug 2006 13:22:37 +0200
On 20/08/06, Prashanth Mohan <prashmohan@xxxxxxxxx> wrote:
IIRC I read some article on the net saying that Microsoft was planning
on shipping ``undelete'' as an option in their FSs (as part of Vista),
but then rolled it back due to security implications...
It was privacy concerns primarily with some security thrown in. And it
was generally, FUD - since the Recycle Bin provides approximately
similar functionality (and there are several recycle bin
implementations for Linux too).
The System Restore feature is another "time-travel" feature in
Windows. I believe Redhat has a similar feature for its high-end RHN
subscribers (part of its provisioning module).
http://arstechnica.com/news.ars/post/20060730-7383.html
Binand
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