hadoop-0.20.2安装找不到JAVA_HOME解决办法

在安装hadoop-0.20.2时出现了找不到JAVA_HOME,配置方法跟官方的版本一致，具体请参考前边的文章或者网上的文档。最好每台机子上配置的JDK都一样，要不然会出现很奇怪的问题。配置好以后，运行start-all.sh时，确出现如下的报错：
======================================================================+
|      Error: JAVA_HOME is not set and Java could not be found         |
+----------------------------------------------------------------------+
| Please download the latest Sun JDK from the Sun Java web site        |
|       > http://java.sun.com/javase/downloads/ <                      |
|                                                                      |
| Hadoop requires Java 1.6 or later.                                   |
| NOTE: This script will find Sun Java whether you install using the   |
|       binary or the RPM based installer.                             |
+======================================================================+
明明在hadoop-env.sh设置好了，为了保险，又在/etc/profile设置了一遍。以hadoop用户登陆系统，在任意路径执行 echo $JAVA_HOME ,显示"/usr/local/jdk"，是我服务器jdk正确的路径啊！再查一下文档，云：需要jdk1.6以上的版本，我使用的是 jdk1.6.0_16，应该符合要求的。

那问题又会在哪里呢？grep一把，看那些文件包含字符串JAVA_HOME.先搜hadoop/conf，只有hadoop-env.sh包含这个字串。再换一个目录hadoop/bin,查看一下,其输出如下：
[root@hadoops2 hadoop]# grep JAVA_HOME bin/*bin/hadoop:export JAVA_HOME=/usr/local/jdkbin/hadoop:#   JAVA_HOME        The java implementation to use.  Overrides JAVA_HOME.
bin/hadoop:if [ "$JAVA_HOME" != "" ]; then
bin/hadoop:  #echo "run java in $JAVA_HOME"
bin/hadoop:  JAVA_HOME=$JAVA_HOME
bin/hadoop:if [ "$JAVA_HOME" = "" ]; then
bin/hadoop:  echo "Error: JAVA_HOME is not set."
bin/hadoop:JAVA=$JAVA_HOME/bin/java
bin/hadoop:CLASSPATH=${CLASSPATH}:$JAVA_HOME/lib/tools.jar
bin/hadoop-config.sh:if [ -z "$JAVA_HOME" ]; then
bin/hadoop-config.sh:      export JAVA_HOME=$candidate
bin/hadoop-config.sh:  if [ -z "$JAVA_HOME" ]; then
bin/hadoop-config.sh:|      Error: JAVA_HOME is not set and Java could not be found         |
bin/rcc:#   JAVA_HOME        The java implementation to use.  Overrides JAVA_HOME.
bin/rcc:if [ "$JAVA_HOME" != "" ]; then
bin/rcc:  #echo "run java in $JAVA_HOME"
bin/rcc:  JAVA_HOME=$JAVA_HOME
bin/rcc:if [ "$JAVA_HOME" = "" ]; then
bin/rcc:  echo "Error: JAVA_HOME is not set."
bin/rcc:JAVA=$JAVA_HOME/bin/java
bin/rcc:CLASSPATH=${CLASSPATH}:$JAVA_HOME/lib/tools.jar

嘿！好几个文件都与JAVA_HOME相关呢。接着挨个查看文件，感觉hadoop-config.sh这个文件嫌疑最大，其内容刚好有一段与运行hadoop报错内容相一致，我把程序片段贴在下面：
# attempt to find java
if [ -z "$JAVA_HOME" ]; then
  for candidate in \
    /usr/lib/jvm/java-6-sun \
    /usr/lib/j2sdk1.6-sun \
    /usr/local/jdk \
    /usr/java/jdk1.6* \
    /usr/java/jre1.6* \
    /Library/Java/Home ; do
    if [ -e $candidate/bin/java ]; then
      export JAVA_HOME=$candidate
      break
    fi
  done
  # if we didn't set it
  if [ -z "$JAVA_HOME" ]; then
    cat 1>&2 <<EOF
+======================================================================+
|      Error: JAVA_HOME is not set and Java could not be found         |
+----------------------------------------------------------------------+
| Please download the latest Sun JDK from the Sun Java web site        |
|       > http://java.sun.com/javase/downloads/ <                      |
|                                                                      |
| Hadoop requires Java 1.6 or later.                                   |
| NOTE: This script will find Sun Java whether you install using the   |
|       binary or the RPM based installer.                             |
+=====================================================================
我在这段中间加如行 " /usr/local/jdk \",然后在运行，一切就正常了！
希望对大家有所帮助！