下载了Hadoop预编译好的二进制包，hadoop-2.2.0.tar.gz，启动起来后，总是出现这种警告：

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

原因是apache官网提供的二进制包，里面的native库，是32位的，坑跌啊，现在服务器谁还有32位的啊。

$ file $HADOOP_PREFIX/lib/native/libhadoop.so.1.0.0
libhadoop.so.1.0.0: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked, BuildID[sha1]=0x9eb1d49b05f67d38454e42b216e053a27ae8bac9, not stripped

我们需要下载Hadoop 2.2.0源码，在 64 位Linux下重新编译，然后把32位的native库用64位的native库替换。

1. 下载Hadoop 2.2.0 源码包，并解压

$ wget http://mirrors.hust.edu.cn/apache/hadoop/common/hadoop-2.2.0/hadoop-2.2.0-src.tar.gz
$ tar zxf hadoop-2.2.0-src.tar.gz

2. 安装下面的软件

 $ sudo yum install cmake lzo-devel  zlib-devel  gcc autoconf automake libtool   ncurses-devel openssl-deve

3. 安装Maven

安装 Maven 3.1.4

$ wget http://mirror.esocc.com/apache/maven/maven-3/3.1.4/binaries/apache-maven-3.1.4-bin.tar.gz
$ sudo tar zxf apache-maven-3.1.4-bin.tar.gz -C /opt
$ sudo vim /etc/profile
export MAVEN_HOME=/opt/apache-maven-3.1.4export PATH=$PATH:$MAVEN_HOME/bin

注销并重新登录，让环境变量生效。

4. 安装Ant

$ wget http://apache.dataguru.cn//ant/binaries/apache-ant-1.9.4-bin.tar.gz
$ sudo tar zxf apache-ant-1.9.4-bin.tar.gz -C /opt
$ sudo vim /etc/profile
export ANT_HOME=/opt/apache-ant-1.9.4
export PATH=$PATH:$ANT_HOME/bin

5. 安装Findbugs

$ wget http://prdownloads.sourceforge.net/findbugs/findbugs-2.0.3.tar.gz?download
$ sudo tar zxf findbugs-2.0.3.tar.gz -C /opt
$ sudo vim /etc/profile
export FINDBUGS_HOME=/opt/findbugs-2.0.3
export PATH=$PATH:$FINDBUGS_HOME/bin

6. 安装protobuf

编译Hadoop 2.2.0，需要protobuf的编译器protoc。一定需要protobuf 2.5.0以上，yum里的是2.3，太老了。因此下载源码，编译安装。

$ wget https://protobuf.googlecode.com/files/protobuf-2.5.0.tar.gz
$ tar zxf protobuf-2.5.0.tar.gz
$ cd protobuf-2.5.0
$ ./configure
$ make
$ sudo make install

7. 给Hadoop源码打一个patch

最新的Hadoop 2.2.0 的Source Code 压缩包解压出来的code有个bug 需要patch后才能编译。否则编译hadoop-auth 会提示下面错误：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.5.1:testCompile (default-testCompile) on project hadoop-auth: Compilation failure: Compilation failure:
[ERROR] /home/chuan/trunk/hadoop-common-project/hadoop-auth/src/test/java/org/apache/hadoop/security/authentication/client/AuthenticatorTestCase.java:[84,13] cannot access org.mortbay.component.AbstractLifeCycle
[ERROR] class file for org.mortbay.component.AbstractLifeCycle not found

Patch: https://issues.apache.org/jira/browse/HADOOP-10110

wget https://issues.apache.org/jira/secure/attachment/12614482/HADOOP-10110.patch; patch -p0 < HADOOP-10110.patch 

8. 编译 Hadoop

cd hadoop-2.2.0-src
mvn package -DskipTests -Pdist,native -Dtar

9. 替换掉32位的native库

用 hadoop-2.2.0-src/hadoop-dist/target/hadoop-2.2.0/lib/native 替换掉 hadoop-2.2.0/lib/native。

rm -rf ~/local/opt/hadoop-2.2.0/lib/native
cp ./hadoop-dist/target/hadoop-2.2.0/lib/native ~/local/opt/hadoop-2.2.0/lib/

然后重启Hadoop集群，会看到控制台下不再有警告信息了。

10 解决Ubuntu下启动失败的问题

在Ubuntu上，那就不是一点WARN了，而是启动不起来，会出错，原因在于，在./sbin/start-dfs.sh第55行，

NAMENODES=$($HADOOP_PREFIX/bin/hdfs getconf -namenodes)

在shell里单独运行这样命令，

./bin/hdfs getconf -namenodes

OpenJDK 64-Bit Server VM warning: You have loaded library /home/soulmachine/local/opt/hadoop-2.2.0/lib/native/libhadoop.so which might have disabled stack guard. The VM will try to fix the stack guard now.
It‘s highly recommended that you fix the library with ‘execstack -c <libfile>‘, or link it with ‘-z noexecstack‘.
14/02/14 13:14:50 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
localhost

最后一行的localhost，才是有效的namenode，但是由于前面有一大堆warning，脚本把这一大堆字符串，按空格隔开，每个单词都看作是namenode，接下来就错的稀里哗啦。

根本原因，还是因为32位native库。

把自带的32位native目录删除，用编译好的64位native目录拷贝过去，再运行

./bin/hdfs getconf -namenodes
localhost

这下就对了！