hadoop版本是：

[hadoop@L-6140-BBS: ~/src/hadoop/conf]$ hadoop version
Hadoop 0.20.1+169.89

我运行了mradmin freshnodes，但是看起来没有这个命令

[hadoop@L-6140-BBS: ~/src/hadoop/conf]$ hadoop mradmin -refreshNodes
efreshNodes: Unknown command
Usage: java MRAdmin
       [-refreshServiceAcl]
       [-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 copied 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]