eclipse + tomcat 开发遇到的棘手问题

把下载下来的eclipse包解压后，双击执行eclipse，出现如下错误：
A Java Runtime Environment (JRE) or Java Development Kit (JDK)
must be available in order to run Eclipse. No Java virtual machine
was found after searching the following locations:
/home/dgc/java/eclipse/jre/bin/java
java in your current PATH

系统安装的jdk版本是jdk1.6.0_21，在／etc/profile文件中加入的代码是：
export JAVA_HOME=/opt/jdk1.6.0_21/
export PATH=$JAVA_HOME/bin:$PATH
export CLASSPATH=.:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar:$CLASSPATH

在/etc/environment文档中的PATH为：
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/opt/jdk1.6.0_21/bin/:/opt/jdk1.6.0_21/jre/bin/"

望大虾们能够解决，谢谢！