Hadoop hdfs命令

1. Format the filesystem:

     $ bin/hdfs namenode -format
   

2. Start NameNode daemon and DataNode daemon:

     $ sbin/start-dfs.sh
   

   The hadoop daemon log output is written to the $HADOOP_LOG_DIR directory (defaults to $HADOOP_HOME/logs).

3. Browse the web interface for the NameNode; by default it is available at:

   • NameNode - http://localhost:50070/

4. Make the HDFS directories required to execute MapReduce jobs:

     $ bin/hdfs dfs -mkdir /user
     $ bin/hdfs dfs -mkdir /user/<username>
   

5. Copy the input files into the distributed filesystem:

     $ bin/hdfs dfs -put etc/hadoop input
   

6. Run some of the examples provided:

     $ bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.3.jar grep input output 'dfs[a-z.]+'
   

7. Examine the output files: Copy the output files from the distributed filesystem to the local filesystem and examine them:

     $ bin/hdfs dfs -get output output
     $ cat output/*
   

   or

   View the output files on the distributed filesystem:

     $ bin/hdfs dfs -cat output/*
   

8. When you’re done, stop the daemons with:

     $ sbin/stop-dfs.sh