HDFS命令行操作

启动后可通过命令行使用hadoop。

(1)所有命令 （先将$HADOOP_HOME/bin加入到.bashrc的$PATH变量中）

[hadoop@node14 hadoop-0.21.0]$ ll $HADOOP_HOME/bin
total 88
-rwxr-xr-x 1 hadoop hadoop 4131 Aug 17  2010 hadoop
-rwxr-xr-x 1 hadoop hadoop 8658 Aug 17  2010 hadoop-config.sh
-rwxr-xr-x 1 hadoop hadoop 3841 Aug 17  2010 hadoop-daemon.sh
-rwxr-xr-x 1 hadoop hadoop 1242 Aug 17  2010 hadoop-daemons.sh
-rwxr-xr-x 1 hadoop hadoop 4130 Aug 17  2010 hdfs
-rwxr-xr-x 1 hadoop hadoop 1201 Aug 17  2010 hdfs-config.sh
-rwxr-xr-x 1 hadoop hadoop 3387 Aug 17  2010 mapred
-rwxr-xr-x 1 hadoop hadoop 1207 Aug 17  2010 mapred-config.sh
-rwxr-xr-x 1 hadoop hadoop 2720 Aug 17  2010 rcc
-rwxr-xr-x 1 hadoop hadoop 2058 Aug 17  2010 slaves.sh
-rwxr-xr-x 1 hadoop hadoop 1367 Aug 17  2010 start-all.sh
-rwxr-xr-x 1 hadoop hadoop 1018 Aug 17  2010 start-balancer.sh
-rwxr-xr-x 1 hadoop hadoop 1778 Aug 17  2010 start-dfs.sh
-rwxr-xr-x 1 hadoop hadoop 1255 Aug 17  2010 start-mapred.sh
-rwxr-xr-x 1 hadoop hadoop 1359 Aug 17  2010 stop-all.sh
-rwxr-xr-x 1 hadoop hadoop 1069 Aug 17  2010 stop-balancer.sh
-rwxr-xr-x 1 hadoop hadoop 1277 Aug 17  2010 stop-dfs.sh
-rwxr-xr-x 1 hadoop hadoop 1163 Aug 17  2010 stop-mapred.sh

(2) hadoop命令

[hadoop@node14 hadoop-0.21.0]$ 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
  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

Most commands print help when invoked w/o parameters.

(3) hadoop fs 

[hadoop@node14 hadoop-0.21.0]$ hadoop fs
Usage: java FsShell
           [-ls <path>]
           [-lsr <path>]
           [-df [<path>]]
           [-du [-s] [-h] <path>]
           [-dus <path>]
           [-count[-q] <path>]
           [-mv <src> <dst>]
           [-cp <src> <dst>]
           [-rm [-skipTrash] <path>]
           [-rmr [-skipTrash] <path>]
           [-expunge]
           [-put <localsrc> ... <dst>]
           [-copyFromLocal <localsrc> ... <dst>]
           [-moveFromLocal <localsrc> ... <dst>]
           [-get [-ignoreCrc] [-crc] <src> <localdst>]
           [-getmerge <src> <localdst> [addnl]]
           [-cat <src>]
           [-text <src>]
           [-copyToLocal [-ignoreCrc] [-crc] <src> <localdst>]
           [-moveToLocal [-crc] <src> <localdst>]
           [-mkdir <path>]
           [-setrep [-R] [-w] <rep> <path/file>]
           [-touchz <path>]
           [-test -[ezd] <path>]
           [-stat [format] <path>]
           [-tail [-f] <file>]
           [-chmod [-R] <MODE[,MODE]... | OCTALMODE> PATH...]
           [-chown [-R] [OWNER][:[GROUP]] PATH...]
           [-chgrp [-R] GROUP PATH...]
           [-help [cmd]]

Generic options supported are
-conf <configuration file>     specify an application configuration file
-D <property=value>            use value for given property
-fs <local|namenode:port>      specify a namenode
-jt <local|jobtracker:port>    specify a job tracker
-files <comma separated list of files>    specify comma separated files to be co                                                                                                                     pied to the map reduce cluster
-libjars <comma separated list of jars>    specify comma separated jar files to                                                                                                                      include in the classpath.
-archives <comma separated list of archives>    specify comma separated archives                                                                                                                      to be unarchived on the compute machines.

The general command line syntax is
bin/hadoop command [genericOptions] [commandOptions]

(4)HDFS操作

hadoop fs
hadoop fs -ls
hadoop fs -mkdir firstdir			//HDFS创建目录
hadoop fs -rmr firstdir				//HDFS删除目录
hadoop fs -put test.txt first.txt		//从本地目录中将文件放入HDFS
hadoop fs  -cat first.txt
hadoop fs  -df
hadoop fs -get first.txt FirstTXTfromHDFS.txt    //从HDFS取文件到本地

若文件写入遇到异常

(0)检查和机器名是否正确
node14配置了外部IP和内部IP，在/etc/hosts中加入两条IP与机器名的对应表，如果外部IP放在内部IP的前面，
则通过netstat -npl查看时，发现9000和9001是外部IP占据，故应在/etc/hosts中内部IP放在外部的IP的前面。
或者在conf中配置文件中，全部用IP，而不要用机器名。


(1)关闭防火墙
sudo /etc/init.d/iptables stop


(2)查看磁盘空间是否正常
df -hl


(3)检查目录是否正常
hadoop.tmp.dir默认：/tmp/hadoop-${user.name}
删除/tmp下面的文件，重新hadoop namenode -format,重启所有进程。


(4)单独启动各个进程
在namenode和datanode上分别启动节点
$hadoop-daemon.sh start namenode
$hadoop-daemon.sh start datanode