start-dfs.sh失败：
nikita@master:/usr/local/hadoop/sbin$ ./start-dfs.sh
Starting namenodes on [master]
ERROR: namenode can only be executed by root.
Starting datanodes
ERROR: datanode can only be executed by root.
Starting secondary namenodes [master]
ERROR: secondarynamenode can only be executed by root.
nikita@master:/usr/local/hadoop/sbin$ sudo ./start-dfs.sh
Starting namenodes on [master]
master: Permission denied (publickey,password).
Starting datanodes
localhost: Permission denied (publickey,password).
Starting secondary namenodes [master]
master: Permission denied (publickey,password).
运行“ ssh master”-确定； 运行“ sudo ssh master”-权限被拒绝
如何解决？ 如何在没有'sudo'的情况下运行start-dfs.sh？