配置hadoop-1.2.1出现localhost: Error: JAVA_HOME is not set.

配置hadoop-1.2.1出现localhost: Error: JAVA_HOME is not set.

具体为：

hadoop@dy-virtual-machine:~/hadoop-1.2.1$ start-all.sh
starting namenode, logging to /home/hadoop/hadoop-1.2.1/libexec/../logs/hadoop-hadoop-namenode-dy-virtual-machine.out
localhost: starting datanode, logging to /home/hadoop/hadoop-1.2.1/libexec/../logs/hadoop-hadoop-datanode-dy-virtual-machine.out
localhost: Error: JAVA_HOME is not set.
localhost: starting secondarynamenode, logging to /home/hadoop/hadoop-1.2.1/libexec/../logs/hadoop-hadoop-secondarynamenode-dy-virtual-machine.out
localhost: Error: JAVA_HOME is not set.
starting jobtracker, logging to /home/hadoop/hadoop-1.2.1/libexec/../logs/hadoop-hadoop-jobtracker-dy-virtual-machine.out
localhost: starting tasktracker, logging to /home/hadoop/hadoop-1.2.1/libexec/../logs/hadoop-hadoop-tasktracker-dy-virtual-machine.out
localhost: Error: JAVA_HOME is not set.

解决方法:

在/hadoop-1.2.1/conf/文件夹里有个hadoop-env.sh的文件，它的作用是配置与hadoop运行环境相关的变量

找到：

# The java implementation to use. Required.
# export JAVA_HOME=/usr/lib/jvm/java-6-sun

将#号去掉，变为：

改成你本机的jdk路径，执行完退出

：wq

若你不清楚自己的jdk路径，你可以先执行 echo $JAVA_HOME   进行查看