Restore deleted nodes of a hadoop Cluster

I encountered some problems in learning hadoop over the past two weeks.

Today's question is how to restore the deleted datanode

At that time, because refreshNodes was not executed, the datanode was not started successfully.

The following error is reported:

ERROR org. apache. hadoop. hdfs. server. datanode. DataNode: org. apache. hadoop. ipc. RemoteException: java. io. IOException: verifyNodeRegistration: unknown datanode X003: 50010

The recovery steps are as follows:

First, delete the deleted datanode ip address in the excludes file.

Second, upload the excludes file to each machine.

Third, execute hadoop dfsadmin-refreshNodes on the master machine

Fourth, execute the hadoop-daemon.sh start datanode on the machine to recover

Hadoop-daemon.sh start tasktracker commands

Final verification

Run hadoop dfsadmin-report on the master machine

Check if multiple nodes exist.