hadoop配置免密碼ssh登錄

在master上更改權限在搭建hadoop集羣時，需要機器相互可以免密碼ssh，操作如下（四臺機器都要操作）：

ssh-keygen -t rsa
講產生的公鑰複製到master機器上並重命名，以hadoop1爲例子：

scp ~/.ssh/id_rsa.pub root@host:~/id_rsa.pub.1
講所有的迷藥追加到authorized_keys中：

cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
cat ~/id_rsa.pub.1 >> ~/.ssh/authorized_keys
cat ~/id_rsa.pub.2 >> ~/.ssh/authorized_keys
cat ~/id_rsa.pub.3 >> ~/.ssh/authorized_keys
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys