>>> $ hdfs dfs -put 123.txt 123.txt
文件将会拷贝到/user/username/123.txt
>>> $ hdfs dfs -ls
>>> $ hdfs dfs -ls /
>>> $ hdfs dfs -cat /user/fred/456.txt
>>> hdfs dfs -get /user/fred/456.txt 789.txt
>>> $ hdfs dfs -mkdir data
>>> $ hdfs dfs -rm -r data_old