What two processes must you do if you are running a Hadoop cluster with a single NameNode and six DataNodes

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Question : What two processes must you do if you are running a Hadoop cluster with a single NameNode and six DataNodes, and you want to change a configuration parameter so that it affects all six DataNodes

A. You must restart the NameNode daemon to apply the changes to the cluster B. You must restart all six DataNode daemons to apply the changes to the cluster. C. You don't need to restart any daemon, as they will pick up changes automatically. D. You must modify the configuration files on each of the six DataNode machines. E. You must modify the configuration files on only one of the DataNode machine F. You must modify the configuration files on the NameNode only. DataNodes read their configuration from the master nodes

Lot of places shows answers A & F but I want to know example of such parameter change. It looks like Ans B & D also looks correct since most likely all data nodes needs to be restarted and also configuration should be done on all datanodes configuration file as well.

What are correct answers ?

Can you suggest name of one parameter that only affects datanodes so that I can test out on my cluster.

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hadoop

1 Answers

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Configuration changes (e.g, in core-site.xml) must be done on all nodes, that is, the namenode and all data nodes. Hadoop then needs to be restarted. Some hadoop vendors provide tools that wraps this all up for you to make it easier, but that's what the tool will do under the covers.

I'll leave it up to you to decide which letters in your list this corresponds to best :)