Start Hadoop. start-all.sh Missing Datanode Process

1) Modify the Namespaceid of each slave to make it consistent with the Namespaceid of the master.

Or

2) Modify the Namespaceid of master so that it is consistent with the Namespaceid of slave.

The "Namespaceid" is located in the "/usr/hadoop/tmp/dfs/data/current/version" file and the front Blue May vary according to the actual situation, but the red in the back is unchanged.

Example: View the "VERSION" file under "Master"

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Viewing error log Accesshttp://localhost:50070, in the page, clickNamenode LogsLinks, inlogsPage clickHadoop-hadoop-datanode-ubuntu.logLink

Find this prompt in the log:Invalid directory in Dfs.data.dir:Incorrect permission For/usr/local/hadoop/hdfs/data, Expected:rwxr-xr-x, while a CTUAL:RWXR-XRWX。 Reason isDataFolder permissions issue, execution:chmod g-w/usr/local/hadoop/hdfs/data, after you modify the folder permissions, start againHadoop, problem solving.

Start Hadoop. start-all.sh missing Datanode process