YARN加载本地库抛出Unable to load native-hadoop library解决办法

用官方的Hadoop 2.1.0-beta安装后，每次hadoop命令进去都会抛出这样一个Warning

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

设置logger级别，看下具体原因

export HADOOP_ROOT_LOGGER=DEBUG,console

13/08/29 13:59:38 DEBUG util.NativeCodeLoader: Trying to load the custom-built native-hadoop library...

13/08/29 13:59:38 DEBUG util.NativeCodeLoader: Failed to load native-hadoop with error: java.lang.UnsatisfiedLinkError: /usr/local/hadoop/hadoop-2.1.0-beta/lib/native/libhadoop.so.1.0.0: /usr/local/hadoop/hadoop-2.1.0-beta/lib/native/libhadoop.so.1.0.0: wrong ELF class: ELFCLASS32 (Possible cause: architecture word width mismatch)

13/08/29 13:59:38 DEBUG util.NativeCodeLoader: java.library.path=/usr/local/hadoop/hadoop-2.1.0-beta/lib/native/linux-amd64-64:/usr/local/hadoop/hadoop-2.1.0-beta/lib/native

13/08/29 13:59:38 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicablewrong ELFCLASS32，难道是加载的so文件系统版本不对

执行命令file libhadoop.so.1.0.0

libhadoop.so.1.0.0: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked, not stripped

果然是80386，是32位的系统版本，而我的hadoop环境是64位OS

原来直接从apache镜像中下载的编译好的Hadoop版本native library都是32版本的，如果要支持64位版本，必须自己重新编译，这就有点坑爹了，要知道几乎所有的生产环境都是64位的OS

YARN官方对于native library的一段话验证了这一点

“The pre-built 32-bit i386-Linux native hadoop library is available as part of the hadoop distribution and is located in the lib/native directory”

重新checkout source code

svn checkout http://svn.apache.org/repos/asf/hadoop/common/tags/release-2.1.0-beta/

加上编译native的选项，编译时会根据当前的操作系统架构来生产相应的native库

mvn package -Pdist,native -DskipTests -Dtar

再去native文件下查看所有的file type，已经都是64位版的了，替换线上文件，WARNING消除

file *

libhadoop.a: current ar archive

libhadooppipes.a: current ar archive

libhadoop.so: symbolic link to `libhadoop.so.1.0.0'

libhadoop.so.1.0.0: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, not stripped

libhadooputils.a: current ar archive

libhdfs.a: current ar archive

libhdfs.so: symbolic link to `libhdfs.so.0.0.0'

libhdfs.so.0.0.0: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, not stripped

更多Hadoop相关信息见 Hadoop 专题页面 http://www.linuxidc.com/topicnews.aspx?tid=13

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