1 hadoop 命令：
[root@chinadaas01 ~]# hadoop
Usage: hadoop [--config confdir] COMMAND
where COMMAND is one of:
fs run a generic filesystem user client
version print the version
jar <jar> run a jar file
checknative [-a|-h] check native hadoop and compression libraries availability
distcp <srcurl> <desturl> copy file or directories recursively
archive -archiveName NAME -p <parent path> <src>* <dest> create a hadoop archive
classpath prints the class path needed to get the
Hadoop jar and the required libraries
daemonlog get/set the log level for each daemon
or
CLASSNAME run the class named CLASSNAME
常见的有：
hadoop job : 查看hadoop 任务 eg---> hadoop job -list all
Usage: JobClient <command> <args>
[-submit <job-file>]
[-status <job-id>]
[-counter <job-id> <group-name> <counter-name>]
[-kill <job-id>]
[-set-priority <job-id> <priority>]. Valid values for priorities are: VERY_HIGH HIGH NORMAL LOW VERY_LOW
[-events <job-id> <from-event-#> <#-of-events>]
[-history <jobOutputDir>]
[-list [all]]
[-list-active-trackers]
[-list-blacklisted-trackers]
[-list-attempt-ids <job-id> <task-type> <task-state>]
[-kill-task <task-id>]
[-fail-task <task-id>]
hadoop version 查看安装的版本
[root@chinadaas01 ~]# hadoop version Hadoop 2.0.0-transwarp Subversion file:///root/wangb/hadoop/build/hadoop/rpm/BUILD/hadoop-2.0.0-transwarp/src/hadoop-common-project/hadoop-common -r Unknown Compiled by root on Fri Oct 25 14:38:23 CST 2013 From source with checksum ec693572f265ae4d8b8c1f52a22e37f5 This command was run using /usr/lib/hadoop/hadoop-common-2.0.0-transwarp.jar
hadoop jar 运行hadoop jar程序：
[root@chinadaas01 ~]# hadoop jar RunJar jarFile [mainClass] args...
hadoop dfsadmin -report -safemode(在重新启动并且等待datanode发送信息给namenode时 不接受客户端请求 只有在都弄好后才开启服务 这个不接客过程就是安全模式)
hadoop fsck -openforwrite-files 数据块越大 内存空间中映射表越小 查询起来就越快
hadoop fs : hadoop 操作文件系统的命令 等效于 hdfs dfs 命令
hdfs :
[root@chinadaas01 ~]# 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
Use -help to see options
能看到 hadoop命令和 hdfs命令是两套独立的体系，
一个是集群层面的，比如查看版本，查看mr的Job任务，执行hdfs集群的文件相关命令
一个是hdfs集群层面的，比如namenode格式化 datanode命令等
这两个的关联相同点就是 hadoop dfs = hdfs dfs