相关工具：
[grid@h1 conf]$ hadoop daemonlog -h
USAGES:
java -getlevel <host:port> <name>
java -setlevel <host:port> <name> <level>
例如：
[grid@h1 conf]$ hadoop daemonlog -getlevel h1:50070 NameNode
Connecting to http://h1:50070/logLevel?log=NameNode
Submitted Log Name: NameNode
Log Class: .Log4JLogger
Effective level: INFO
[grid@h1 conf]$ hadoop daemonlog -setlevel h1:50070 NameNode debug
Connecting to http://h1:50070/logLevel?log=NameNode&level=debug
Submitted Log Name: NameNode
Log Class: .Log4JLogger
Submitted Level: debug
Setting Level to debug ...
Effective level: DEBUG