HADOOP Exception in thread "main" org.apache.hadoop.security.AccessControlException: Permission deni
错误：Exception in thread "main" org.apache.hadoop.security.AccessControlException: Permission denied: user=PC-TIAN, access=WRITE, inode="/":root:supergroup:drwxr-xr-x
dfs.permissions
– 如果是true则检查权限，否则不检查（每一个人都可以存取文件）
– 于NameNode上设定
– 默认值：true
