Hadoop3.0.3自帶的例項程式路徑在
/usr/local/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-examples-3.0.3.jar中

在HDFS目錄中建立input目錄

[[email protected]]# hdfs dfs -mkdir /input
[[email protected] hadoop]# hdfs dfs -rm -r /input  #刪除HDFS中的input目錄

1.把測試檔案上傳到HDFS目錄中

此處以/usr/local/hadoop/README.txt為例，把README.txt檔案上傳到HDFS的/input

[[email protected] hadoop]# hdfs dfs -put README.txt /input

上傳後可用如下命令看到。

[[email protected] hadoop]# hdfs dfs -ls /input
2018-11-26 20:05:11,067 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Found 1 items
-rw-
 
r--r--   3 root supergroup       1366 2018-11-26 20:02 /input/README.txt
[[email protected] hadoop]# 

也可在Web端看到。

2.把測試檔案上傳到HDFS目錄中

[[email protected] hadoop]# hadoop jar /usr/local/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-examples-3.0.3.jar wordcount /input /output

3.列出輸出目錄

[[email protected] ~
 
]# hadoop fs -ls /output
2018-11-27 14:44:13,654 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Found 2 items
-rw-r--r--   3 root supergroup          0 2018-11-27 14:27 /output/_SUCCESS
-rw-r--r--   3 root supergroup       1306 2018-11-27 14:27 /output/part-r-00000
[[email protected] ~]# hdfs dfs -ls /output   #或此命令

4.列出輸出結果

[[email protected] ~]# hdfs dfs -cat /output/part-r-00000
[[email protected] ~]# hadoop fs -cat /output/part-r-00000

5.Hadoop常用命令

hadoop fs -mkdir /tmp/input              在HDFS上新建資料夾
hadoop fs -put input1.txt /tmp/input  把本地檔案input1.txt傳到HDFS的/tmp/input目錄下
hadoop fs -get  input1.txt /tmp/input/input1.txt  把HDFS檔案拉到本地
hadoop fs -ls /tmp/output                  列出HDFS的某目錄
hadoop fs -cat /tmp/ouput/output1.txt  檢視HDFS上的檔案
hadoop fs -rmr /home/less/hadoop/tmp/output  刪除HDFS上的目錄
hadoop dfsadmin -report 檢視HDFS狀態，比如有哪些datanode，每個datanode的情況
hadoop dfsadmin -safemode leave  離開安全模式
hadoop dfsadmin -safemode enter  進入安全模式