You saved the day again.

The FSEditLogTool worked like a charm, without modifications (https://issues.apache.org/jira/browse/HADOOP-915).

Here is what I did to perform an undelete of the root directory on my HDFS (hadoop 0.12.2.)

- first, I ran a few tests on another dfs to make sure the FSEditLogTool worked (and I understood what is was doing). Then on the affected dfs: - kill the namenode (already did that asap, and to be sure, I stopped all other hadoop daemons)
- run FSEditLogTool -dump ${dfs.name.dir}/edits edits.txt
- remove the last line from edits.txt which contains the DELETE entry.
- run FSEditLogTool -restore edits.txt ${dfs.name.dir}/edits
- start the namenode and datanodes again
- I had to turn off save-mode manually:
   $ bin/hadoop dfsadmin -safemode leave

\o/

Andrzej Bialecki wrote:
Mathijs Homminga wrote:
Thanks,

I stopped the namenode. How can I remove an entry from the editlog?

I wrote a tool for specifically this purpose ;) but it's not up to date anymore - I'm not sure how much hacking is required to make it work again. See HADOOP-915.



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