进入 $HADOOP/bin
一.文件操作
文件操作 类似于正常的linux操作前面加上“hdfs dfs -”
前缀也可以写成hadoop而不用hdfs,但终端中显示
Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.
1.创建目录：(注意 文件夹需一级一级创建)
hdfs dfs -mkdir /user
hdfs dfs -mkdir /user/com
hdfs dfs -mkdir /user/com/evor
2.删除文件目录
hdfs dfs -rm -r /user/com/evor （-rmr也可以） 删除文件夹下所有东西 rm的递归版本
hdfs dfs -rm /user/com/evor/hadoop.txt 删除文件
3.上传文件
1）hdfs dfs -put /本/地/路/径/spark.jar /user/com/evor
2）hdfs dfs -copyFromLocal /本/地/路/径/spark.jar /user/com/evor
区别 copyFromLocal 限定源路径为本地的路径，其他与-put相同
4.下载文件
复制文件到本地
1) hdfs dfs -get /user/com/evor/spark.jar /本/地/路/径
2) hdfs dfs -copyToLocal /user/com/evor/spark.jar /本/地/路/径
区别 copyToLocal 限定目标路径为本地的路径，其他与-get相同
5.查看文件
我们可以直接在hdfs中直接查看文件，功能与cat类似
将路径指定文件的内容输出到stdout。
hdfs dfs -cat /user/com/evor/hadoop.txt
hadoop fs -cat hdfs://host1:port1/file1 hdfs://host2:port2/file2
hadoop fs -cat file:///file3 /user/hadoop/file4
6.修改权限
hdfs dfs -chmod 777 /user/com/evor/WordCount.sh
二.MapReduce Job操作
提交MapReduce Job
运行jar文件。用户可以把他们的Map Reduce代码捆绑到jar文件中，原则上说，Hadoop所有的MapReduce Job都是一个jar包。
运行一个/home/admin/hadoop/job.jar的MapReduce Job
执行：hadoop jar /home/admin/hadoop/job.jar [jobMainClass] [jobArgs] (注意 是hadoop 不是hdfs)
杀死某个正在运行的Job
假设Job_Id为：job_201005310937_0053
执行：hadoop job -kill job_201005310937_0053
相关链接 ->http://www.cnblogs.com/xd502djj/p/3625799.html
更多命令提示：
输入hdfs
[email protected]:/$ hdfs
Usage: hdfs [--config confdir] COMMAND
where COMMAND is one of:
dfs run a filesystem command on the file systems supported in Hadoop.
namenode -format format the DFS filesystem
secondarynamenode run the DFS secondary namenode
namenode run the DFS namenode
journalnode run the DFS journalnode
zkfc run the ZK Failover Controller daemon
datanode run a DFS datanode
dfsadmin run a DFS admin client
haadmin run a DFS HA admin client
fsck run a DFS filesystem checking utility
balancer run a cluster balancing utility
jmxget get JMX exported values from NameNode or DataNode.
oiv apply the offline fsimage viewer to an fsimage
oev apply the offline edits viewer to an edits file
fetchdt fetch a delegation token from the NameNode
getconf get config values from configuration
groups get the groups which users belong to
snapshotDiff diff two snapshots of a directory or diff the
current directory contents with a snapshot
lsSnapshottableDir list all snapshottable dirs owned by the current user
Use -help to see options
portmap run a portmap service
nfs3 run an NFS version 3 gateway
cacheadmin configure the HDFS cache
Most commands print help when invoked w/o parameters.
格式化hadoop之后重新启动平台，输入jps 有时会发现没有namenode进程
查namenode日志文件，/usr/local/hadoop/hadoop-2.4.1/logs 里的namenode相关文件，发现namenode clusterID与datenode的不同造成了错误
分别察看
/usr/local/hadoop/hadoop-2.4.1/hdfs/data/current/VERSION
/usr/local/hadoop/hadoop-2.4.1/hdfs/name/current/VERSION
将clusterID改成相同即可。