When I reformat the namenode, I also delete the data and name
directories to avoid this problem. Other times, I changed the version
number in the VERSION file to what it was expecting. I did the latter
only during development, though. I would not attempt this on the
production cluster.
Dave
On Jul 2, 2008, at 12:21 PM, Xuan Dzung Doan wrote:
I was following the quickstart guide to run pseudo-distributed
operations with Hadoop 0.16.4. I got it to work successfully the
first time. But I failed to repeat the steps (I tried to re-do
everything from re-formating the HDFS). Then by looking at the log
files of the daemons, I found out the datanode failed to start
because its namespaceID didn't match with the namenode's. I after
that found that the namespaceID is stored in the text file VERSION
under dfs/data/current and dfs/name/current for the datanode and
the namenode, respectively. The reformatting step does change
namespaceID of the namenode, but not for the datanode, and that's
the cause for the inconsistency. So after reformatting, if I
manually update namespaceID for the datanode, things will work
totally fine again.
I guess there are probably others who had this same experience. Is
it a bug in Hadoop 0.16.4? If so, has it been taken care of in
later versions?
Thanks,
David.
