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HDFS >> mail # dev >> Recovering fsImage from Namenode Logs


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Re: Recovering fsImage from Namenode Logs
Your NameNode directory, if it still exists, should have a
previous.checkpoint/ directory under it where you can extract its
previous checkpoint's files and replace the original with that? Ensure
its not too old and that things are fine before you eject NN out of
safemode finally.

What you say is possible; if you can reconstruct files and their
allocated block IDs (along with generation stamps) and thereby form
proper INode entries of them to append/recreate your fsimage. They are
merely serialized operation entries, understandable if you go over its
format in depth. Provided you have all of the exact data required and
the skills to browse, understand and modify the code and reconstruct
the entries and store them in proper order, this is certainly doable.
It is usually simpler to just roll back to the previous checkpoint to
save some of the blocks.

On Thu, Dec 20, 2012 at 11:56 AM, ishan chhabra <[EMAIL PROTECTED]> wrote:
> Hi all,
> I accidentally issued a rmr on my home directory, but killed the NameNode
> as soon as i realized it. Currently I am in a situation where my DataNodes
> have a good percentage of blocks on them, but the NameNode fsImage and
> editlog don't have a mention of any file or file to block to mappings in
> that directory. I also don't have any previous checkpoints of fsImage.
>
> Fortunately, what I do have is namenode logs for the past few days that
> have NameSystem changes recorded. Is there a way to reconstruct my old
> fsImage from the logs so that it recognizes the blocks that are there on
> the datanodes? Has anybody tried something like this before?
>
> --
> Thanks.
>
> Regards,
> Ishan Chhabra

--
Harsh J