Hadoop格式化namenode 出错 Error: A JNI error has occurred, please check your installation and try again Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/hadoop/security/authorize/Refr

一般是修改配置文件：etc/hadoop/hadoop-env.sh的时候出现的错误

1. export JAVA_HOME=/usr/jdk
2. export HADOOP_COMMON_HOME=~/hadoop-2.7.0（Hadoop的安装位置）

一定要仔细检查，小心前边的~