如何解决WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform...

1、在启动和操作Hadoop过程中，总是会提示warning信息：

WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform… using builtin-java classes where applicable

搜索的结果大部分说是操作系统与hadoop的位数不一致造成的，然而事实并非如此。

由于上述warning并不能提供更多有效的信息，需要增加debug信息：

export HADOOP_ROOT_LOGGER=DEBUG,console

再次执行./stop-dfs.sh，这次debug到一些有用的信息：

16/07/05 15:33:54 DEBUG util.Shell: setsid exited with exit code 0
16/07/05 15:33:54 DEBUG lib.MutableMetricsFactory: field org.apache.hadoop.metrics2.lib.MutableRate org.apache.hadoop.security.UserGroupInformation$UgiMetrics.loginSuccess with annotation @org.apache.hadoop.metrics2.annotation.Metric(value=[Rate of successful kerberos logins and latency (milliseconds)], about=, valueName=Time, type=DEFAULT, always=false, sampleName=Ops)
16/07/05 15:33:54 DEBUG lib.MutableMetricsFactory: field org.apache.hadoop.metrics2.lib.MutableRate org.apache.hadoop.security.UserGroupInformation$UgiMetrics.loginFailure with annotation @org.apache.hadoop.metrics2.annotation.Metric(value=[Rate of failed kerberos logins and latency (milliseconds)], about=, valueName=Time, type=DEFAULT, always=false, sampleName=Ops)
16/07/05 15:33:54 DEBUG lib.MutableMetricsFactory: field org.apache.hadoop.metrics2.lib.MutableRate org.apache.hadoop.security.UserGroupInformation$UgiMetrics.getGroups with annotation @org.apache.hadoop.metrics2.annotation.Metric(value=[GetGroups], about=, valueName=Time, type=DEFAULT, always=false, sampleName=Ops)
16/07/05 15:33:54 DEBUG impl.MetricsSystemImpl: UgiMetrics, User and group related metrics
16/07/05 15:33:55 DEBUG security.Groups:  Creating new Groups object
16/07/05 15:33:55 DEBUG util.NativeCodeLoader: Trying to load the custom-built native-hadoop library...
<span style="color:#FF0000;">16/07/05 15:33:55 DEBUG util.NativeCodeLoader: Failed to load native-hadoop with error: java.lang.UnsatisfiedLinkError: no hadoop in java.library.path
16/07/05 15:33:55 DEBUG util.NativeCodeLoader: java.library.path=/usr/local/sinasrv2/hadoop/hadoop-2.6.4/lib
16/07/05 15:33:55 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable</span>
16/07/05 15:33:55 DEBUG util.PerformanceAdvisory: Falling back to shell based
16/07/05 15:33:55 DEBUG security.JniBasedUnixGroupsMappingWithFallback: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping
16/07/05 15:33:55 DEBUG security.Groups: Group mapping impl=org.apache.hadoop.security.JniBasedUnixGroupsMappingWithFallback; cacheTimeout=300000; warningDeltaMs=5000
16/07/05 15:33:55 DEBUG security.UserGroupInformation: hadoop login
16/07/05 15:33:55 DEBUG security.UserGroupInformation: hadoop login commit
16/07/05 15:33:55 DEBUG security.UserGroupInformation: using local user:UnixPrincipal: hadoop
16/07/05 15:33:55 DEBUG security.UserGroupInformation: Using user: "UnixPrincipal: hadoop" with name hadoop
16/07/05 15:33:55 DEBUG security.UserGroupInformation: User entry: "hadoop"
16/07/05 15:33:55 DEBUG security.UserGroupInformation: UGI loginUser:hadoop (auth:SIMPLE)
16/07/05 15:33:55 DEBUG security.UserGroupInformation: PrivilegedAction as:hadoop (auth:SIMPLE) from:org.apache.hadoop.hdfs.tools.GetConf.run(GetConf.java:314)

我们发现，libhadoop.so是存放在/usr/local/sinasrv2/hadoop/hadoop-2.6.4/lib/native下的
在hadoop包中搜索发现，java.library.path被定义为$JAVA_LIBRARY_PATH

$ grep -R 'java.library.path' *
bin/yarn:  YARN_OPTS="$YARN_OPTS -Djava.library.path=$JAVA_LIBRARY_PATH"
bin/yarn.cmd:    set YARN_OPTS=%YARN_OPTS% -Djava.library.path=%JAVA_LIBRARY_PATH%
etc/hadoop/yarn-env.sh:  YARN_OPTS="$YARN_OPTS -Djava.library.path=$JAVA_LIBRARY_PATH"
etc/hadoop/yarn-env.cmd:  set YARN_OPTS=%YARN_OPTS% -Djava.library.path=%JAVA_LIBRARY_PATH%
libexec/hadoop-config.sh:# setup 'java.library.path' for native-hadoop code if necessary
libexec/hadoop-config.sh:  HADOOP_OPTS="$HADOOP_OPTS -Djava.library.path=$JAVA_LIBRARY_PATH"
libexec/hadoop-config.cmd:@rem setup 'java.library.path' for native hadoop code if necessary
libexec/hadoop-config.cmd:  set HADOOP_OPTS=%HADOOP_OPTS% -Djava.library.path=%JAVA_LIBRARY_PATH%
share/doc/hadoop/common/CHANGES.txt:    HADOOP-8756. Fix SEGV when libsnappy is in java.library.path but
share/doc/hadoop/common/CHANGES.txt:    HADOOP-1660. Add the cwd of the map/reduce task to the java.library.path
share/doc/hadoop/common/CHANGES.txt: 50. HADOOP-1493.  Permit specification of "java.library.path" system
share/doc/hadoop/common/CHANGES.txt:10. HADOOP-873.      Pass java.library.path correctly to child processes.
share/doc/hadoop/common/CHANGES.txt:42. HADOOP-838.  Fix tasktracker to pass java.library.path to
share/doc/hadoop/mapreduce/CHANGES.txt:    MAPREDUCE-4458. Warn if java.library.path is used for AM or Task
share/doc/hadoop/mapreduce/CHANGES.txt:    MAPREDUCE-4072. User set java.library.path seems to overwrite default
share/doc/hadoop/mapreduce/CHANGES.txt:    MAPREDUCE-3259. Added java.library.path of NodeManager to

但是此时发现环境变量JAVALIBRARYPATH并未定义，那么问题到这里终于算是找到了，解决方法也很简单了，vim /.bashrc，添加$JAV{A}_{L}IBRAR{Y}_{P}ATH并未定义，那么问题到这里终于算是找到了，解决方法也很简单了，vim/.bashrc，添加$JAVA_LIBRARY_PATH环境变量

export JAVA_LIBRARY_PATH=’/usr/local/sinasrv2/hadoop/hadoop-2.6.4/lib/native’

这里还要特别说明的是，一定要注意自己的Hadoop以及JDK版本型号，配置环境变量的时候不能有丝毫差错！
还有一点就是有些人在/etc/profile文件中配置变量，那就要在该文件中进行修改，本人是在~/.bashrc文件中进行修改的。
source ~/.bashrc 使之生效。
再执行，则不会出现上述warning信息

希望对大家有所帮助，此文是本人在借鉴前人的经验上总结出来的，我们热爱开源，于是将此文放到网上，谢谢！