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From Allen Wittenauer <awittena...@linkedin.com>
Subject Re: Changing hostnames of tasktracker/datanode nodes - any problems?
Date Tue, 10 Aug 2010 13:42:35 GMT

On Aug 10, 2010, at 3:51 AM, Erik Forsberg wrote:

> Hi!
> Due to network reconfigurations, I need to change the hostnames of some
> of my worker nodes, i.e. the nodes running tasktracker and datanode. I
> need to do this to make my hostname naming schema actually concur with
> the network setup.
> Are there any problems doing this? It seems HDFS identifies things
> using some kind of hostname-independent UID, so I guess it should
> recover from one machine going down and then appear again under another
> hostname?

The name node metadata only matches blocks #s to files.  The data node to block part is determined
at run time.  So it is perfectly safe and legal to:

a) bring grid down
b) rename everything
c) fix config files
d) bring grid up

Don't forget to change your network topology script, slaves, and dfs.hosts as necessary. 
If fsck complains about topology violations, use setrep to increase then setrep to decrease
the violated files. 
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