Retaining undelete data on ext3

Theodore Tso tytso at mit.edu
Sun Sep 24 20:45:13 UTC 2006


On Sun, Sep 24, 2006 at 09:00:00PM +0200, Keld Jørn Simonsen wrote:
> I have a design to improve ext3 so that one could salvage all files,
> even if you accidently reformated the partition, Available at 
> http://std.dkuug.dk/keld/lazy3.txt
> This design has been reviewed by Ted.

To be fair, reviewed != to "approve of all aspects of the design".  We
exchanged e-mails for a while on the subject, yes.  Note that the
design has a number of holes in it --- for example, simply saying,
"don't blank the inode when deleting it" is not so trivial if you also
want to maintain ext3's consistency guarantees.  So when the design
says things like "My idea is to not clear the inodes, when they are
marked as free", that's roughly equivalent to saying, "My idea is to
purify Uranium by using some really big centrifuges".  It is both
simultaneously true and not useful.  The hard part is all in the
engineering.  :-)

> I also have some patches for debugfs to undelete files in ext3,
> available at http://std.dkuug.dk/keld/readme-salvage.html

This should probably be turned into its own standalone program, since
it's far more than the scope of debugfs is intended to be.  So I don't
intend to merge them into debugfs.

Regards,

						- Ted




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