You have installed a cluster HDFS and MapReduce version 2 (MRv2) on YARN. You have no
dfs.hosts entry(ies) in your hdfs-site.xml configuration file. You configure a new worker node by
setting fs.default.name in its configuration files to point to the NameNode on your cluster, and you
start the DataNode daemon on that worker node. What do you have to do on the cluster to allow
the worker node to join, and start sorting HDFS blocks?
A.
Without creating a dfs.hosts file or making any entries, run the commands hadoop.dfsadminrefreshModes on the NameNode
B.
Restart the NameNode
C.
Creating a dfs.hosts file on the NameNode, add the worker Node’s name to it, then issue the
command hadoop dfsadmin –refresh Nodes = on the Namenode
D.
Nothing; the worker node will automatically join the cluster when NameNode daemon is started
Hi,
Can you please confirm if the answer is D ? dfs.hosts entry is blank so any node can join the cluster. Please let me know
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d is correct
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http://wiki.apache.org/hadoop/FAQ#I_have_a_new_node_I_want_to_add_to_a_running_Hadoop_cluster.3B_how_do_I_start_services_on_just_one_node.3F
If you are using the dfs.include/mapred.include functionality, you will need to additionally add the node to the dfs.include/mapred.include file, then issue hadoop dfsadmin -refreshNodes and hadoop mradmin -refreshNodes so that the NameNode and JobTracker know of the additional node that has been added.
A is correct
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Please note “If” on beginning of the sentence. Nodes refreshing is not required.
D is correct answer.
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c
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Than would required also NN restart.
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Answer : C
If you are using the dfs.include/mapred.include functionality, you will need to additionally add the node to the dfs.include/mapred.include file, then issue hadoop dfsadmin -refreshNodes and hadoop mradmin -refreshNodes so that the NameNode and JobTracker know of the additional node that has been added.
A is wrong , because its command does not exsists.
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C is wrong,D must right.
Because here is not using the dfs.include/mapred.include functionality.
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it might just be a typo, not Modes…but Nodes
hadoop dfsadmin [GENERIC_OPTIONS] [-report] [-safemode enter | leave | get | wait] [-refreshNodes]
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still I think D is right , coz datanode will send package to namenode , then namenode will aware the new datanode.
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real quetion now in exam change…to
You have dfs.hosts entry(ies) in your hdfs-site….
Anyway, this blog /discussion very helpful
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D
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https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.5.0/bk_administration/content/ref-4303e343-9aee-4e70-b38a-2837ae976e73.1.html
If no dfs.include file is specified, all DataNodes are considered to be included in the cluster (unless excluded in the dfs.exclude file). The dfs.hosts and dfs.hosts.exlude properties in hdfs-site.xml are used to specify the dfs.include and dfs.exclude files.
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D is right.
A is a good choice, but there’s no need to run the hadoop dfsadmin refreshNodes specificaly on the nameNode.
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-refreshNodes command used for Re-read the hosts and exclude files to update the set of Datanodes that are allowed to connect to the Namenode and those that should be decommissioned or recommissioned.
So A not the correct answer. D is right answer.
https://hadoop.apache.org/docs/r2.6.0/hadoop-project-dist/hadoop-hdfs/HDFSCommands.html#dfsadmin
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I have the same idea. A
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