问题导读：
1.编译源码前需要安装哪些软件？
2.安装之后该如何设置环境变量？
3.为什么不要使用JDK1.8？
4.mvn package -Pdist -DskipTests -Dtar的作用是什么？
1. 前言
Hadoop-2.4.0的源码目录下有个BUILDING.txt文件，它介绍了如何在Linux和Windows下编译源代码，本文基本是遵照BUILDING.txt指示来操作的，这里再做一下简单的提炼。
第一次编译要求能够访问互联网，Hadoop的编译依赖非常多的东西，一定要保证机器可访问互联网，否则难逐一解决所有的编译问题，但第一次之后的编译则不用再下载了。
如不能上网可以参考：虚拟机三种网络模式该如何上网指导
2. 安装依赖
在编译Hadoop 2.4.0源码之前，需要将下列几个依赖的东西安装好：
1) JDK 1.6或更新版本（本文使用JDK1.7，请不要安装JDK1.8版本，JDK1.8和Hadoop 2.4.0不匹配，编译Hadoop 2.4.0源码时会报很多错误）
2) Maven 3.0或更新版本
3) ProtocolBuffer 2.5.0
4) CMake 2.6或更新版本
5) Findbugs 1.3.9，可选的（本文编译时未安装）
在安装好之后，还需要设置一下环境变量，可以修改/etc/profile，也可以是修改~/.profile，增加如下内容：
export JAVA_HOME=/root/jdk
export CLASSPATH=$JAVA_HOME/lib/tools.jar
export PATH=$JAVA_HOME/bin:$PATH
export CMAKE_HOME=/root/cmake
export PATH=$CMAKE_HOME/bin:$PATH
export PROTOC_HOME=/root/protobuf
export PATH=$PROTOC_HOME/bin:$PATH
export MAVEN_HOME=/root/maven
export PATH=$MAVEN_HOME/bin:$PATH
本文以root用户在/root目录下进行安装，但实际可以选择非root用户及非/root目录进行安装。
2.1. 安装ProtocolBuffer
标准的automake编译安装方式：
1) cd /root
2) tar xzf protobuf-2.5.0.tar.gz
3) cd protobuf-2.5.0
4) ./conigure --prefix=/root/protobuf
5) make
6) make install
2.2. 安装CMake
1) cd /root
2) tar xzf cmake-2.8.12.2.tar.gz
3) cd cmake-2.8.12.2
4) ./bootstrap --prefix=/root/cmake
5) make
6) make install
2.3. 安装JDK
1) cd /root
2) tar xzf jdk-7u55-linux-x64.gz
3) cd jdk1.7.0_55
4) ln -s jdk1.7.0_55 jdk
2.4. 安装Maven
1) cd /root
2) tar xzf apache-maven-3.0.5-bin.tar.gz
3) ln -s apache-maven-3.0.5 maven
3. 编译Hadoop源代码
完成上述准备工作后，即可通过执行命令：mvn package -Pdist -DskipTests -Dtar，启动对Hadoop源代码的编译。请注意一定不要使用JDK1.8。
编译成功后，jar文件会放在target子目录下，可以在Hadoop源码目录下借用find命令搜索各个target子目录。
编译成功后，会生成Hadoop二进制安装包hadoop-2.4.0.tar.gz，放在源代码的hadoop-dist/target子目录下：
main:
[exec] $ tar cf hadoop-2.4.0.tar hadoop-2.4.0
[exec] $ gzip -f hadoop-2.4.0.tar
[exec]
[exec] Hadoop dist tar available at: /root/hadoop-2.4.0-src/hadoop-dist/target/hadoop-2.4.0.tar.gz
[exec]
[INFO] Executed tasks
[INFO]
[INFO] --- maven-javadoc-plugin:2.8.1:jar (module-javadocs) @ hadoop-dist ---
[INFO] Building jar: /root/hadoop-2.4.0-src/hadoop-dist/target/hadoop-dist-2.4.0-javadoc.jar
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] Apache Hadoop Main ................................ SUCCESS [4.647s]
[INFO] Apache Hadoop Project POM ......................... SUCCESS [5.352s]
[INFO] Apache Hadoop Annotations ......................... SUCCESS [7.239s]
[INFO] Apache Hadoop Assemblies .......................... SUCCESS [0.424s]
[INFO] Apache Hadoop Project Dist POM .................... SUCCESS [2.918s]
[INFO] Apache Hadoop Maven Plugins ....................... SUCCESS [6.261s]
[INFO] Apache Hadoop MiniKDC ............................. SUCCESS [5.321s]
[INFO] Apache Hadoop Auth ................................ SUCCESS [5.953s]
[INFO] Apache Hadoop Auth Examples ....................... SUCCESS [3.783s]
[INFO] Apache Hadoop Common .............................. SUCCESS [1:54.010s]
[INFO] Apache Hadoop NFS ................................. SUCCESS [9.721s]
[INFO] Apache Hadoop Common Project ...................... SUCCESS [0.048s]
[INFO] Apache Hadoop HDFS ................................ SUCCESS [4:15.270s]
[INFO] Apache Hadoop HttpFS .............................. SUCCESS [6:18.553s]
[INFO] Apache Hadoop HDFS BookKeeper Journal ............. SUCCESS [16.237s]
[INFO] Apache Hadoop HDFS-NFS ............................ SUCCESS [6.543s]
[INFO] Apache Hadoop HDFS Project ........................ SUCCESS [0.036s]
[INFO] hadoop-yarn ....................................... SUCCESS [0.051s]
[INFO] hadoop-yarn-api ................................... SUCCESS [1:35.227s]
[INFO] hadoop-yarn-common ................................ SUCCESS [43.216s]
[INFO] hadoop-yarn-server ................................ SUCCESS [0.055s]
[INFO] hadoop-yarn-server-common ......................... SUCCESS [16.476s]
[INFO] hadoop-yarn-server-nodemanager .................... SUCCESS [19.942s]
[INFO] hadoop-yarn-server-web-proxy ...................... SUCCESS [4.926s]
[INFO] hadoop-yarn-server-applicationhistoryservice ...... SUCCESS [9.804s]
[INFO] hadoop-yarn-server-resourcemanager ................ SUCCESS [23.320s]
[INFO] hadoop-yarn-server-tests .......................... SUCCESS [1.208s]
[INFO] hadoop-yarn-client ................................ SUCCESS [9.177s]
[INFO] hadoop-yarn-applications .......................... SUCCESS [0.113s]
[INFO] hadoop-yarn-applications-distributedshell ......... SUCCESS [4.106s]
[INFO] hadoop-yarn-applications-unmanaged-am-launcher .... SUCCESS [3.265s]
[INFO] hadoop-yarn-site .................................. SUCCESS [0.056s]
[INFO] hadoop-yarn-project ............................... SUCCESS [5.552s]
[INFO] hadoop-mapreduce-client ........................... SUCCESS [0.096s]
[INFO] hadoop-mapreduce-client-core ...................... SUCCESS [37.231s]
[INFO] hadoop-mapreduce-client-common .................... SUCCESS [27.135s]
[INFO] hadoop-mapreduce-client-shuffle ................... SUCCESS [4.886s]
[INFO] hadoop-mapreduce-client-app ....................... SUCCESS [17.876s]
[INFO] hadoop-mapreduce-client-hs ........................ SUCCESS [14.140s]
[INFO] hadoop-mapreduce-client-jobclient ................. SUCCESS [11.305s]
[INFO] hadoop-mapreduce-client-hs-plugins ................ SUCCESS [3.083s]
[INFO] Apache Hadoop MapReduce Examples .................. SUCCESS [9.855s]
[INFO] hadoop-mapreduce .................................. SUCCESS [5.110s]
[INFO] Apache Hadoop MapReduce Streaming ................. SUCCESS [7.778s]
[INFO] Apache Hadoop Distributed Copy .................... SUCCESS [12.973s]
[INFO] Apache Hadoop Archives ............................ SUCCESS [3.265s]
[INFO] Apache Hadoop Rumen ............................... SUCCESS [11.060s]
[INFO] Apache Hadoop Gridmix ............................. SUCCESS [7.412s]
[INFO] Apache Hadoop Data Join ........................... SUCCESS [4.221s]
[INFO] Apache Hadoop Extras .............................. SUCCESS [4.771s]
[INFO] Apache Hadoop Pipes ............................... SUCCESS [0.032s]
[INFO] Apache Hadoop OpenStack support ................... SUCCESS [8.030s]
[INFO] Apache Hadoop Client .............................. SUCCESS [7.730s]
[INFO] Apache Hadoop Mini-Cluster ........................ SUCCESS [0.158s]
[INFO] Apache Hadoop Scheduler Load Simulator ............ SUCCESS [7.485s]
[INFO] Apache Hadoop Tools Dist .......................... SUCCESS [6.912s]
[INFO] Apache Hadoop Tools ............................... SUCCESS [0.029s]
[INFO] Apache Hadoop Distribution ........................ SUCCESS [40.425s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 21:57.892s
[INFO] Finished at: Mon Apr 21 14:33:22 CST 2014
[INFO] Final Memory: 88M/243M
[INFO] ------------------------------------------------------------------------
附1:编译环境
整个过程是在阿里云64位主机上进行的，2.30GHz单核1G内存：
[root@AY140408105805619186Z hadoop-2.4.0-src]# uname -a
Linux AY140408105805619186Z 2.6.18-308.el5 #1 SMP Tue Feb 21 20:06:06 EST 2012 x86_64 x86_64 x86_64 GNU/Linux
[root@AY140408105805619186Z ~]# cat /etc/redhat-release
CentOS release 5.8 (Final)
附2：版本信息
名称
版本
包名
说明
Maven
3.0.5
apache-maven-3.0.5-bin.tar.gz
使用3.2.1可能会有问题
CMake
2.8.12.2
cmake-2.8.12.2.tar.gz
JDK
1.7.0
jdk-7u55-linux-x64.gz
不能使用JDK1.8.0
Protocol Buffers
2.5.0
protobuf-2.5.0.tar.gz
Hadoop
2.4.0
hadoop-2.4.0-src.tar.gz
附3：常见错误
1) unexpected end tag: </ul>
[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-javadoc-plugin:2.8.1:jar
(module-javadocs) on project hadoop-annotations: MavenReportException:
Error while creating archive:
[ERROR] Exit code: 1 -
/root/hadoop-2.4.0-src/hadoop-common-project/hadoop-annotations/src/main/java/org/apache/hadoop/classification/InterfaceStability.java:27:
error: unexpected end tag: </ul>
[ERROR] * </ul>
[ERROR] ^
[ERROR]
[ERROR] Command line was: /root/jdk1.8.0/jre/../bin/javadoc @options @packages
原因是InterfaceStability.java中的注释问题：
解决办法，将JDK换成1.7版本，使用JDK1.8编译就会遇到上述问题，将</ul>行删除可以解决问题，但后续还会遇到类似的问题，所以不要使用JDK1.8编译Hadoop 2.4.0。