hadoop配置免密码ssh登录

在master上更改权限在搭建hadoop集群时，需要机器相互可以免密码ssh，操作如下（四台机器都要操作）：

ssh-keygen -t rsa
讲产生的公钥复制到master机器上并重命名，以hadoop1为例子：

scp ~/.ssh/id_rsa.pub root@host:~/id_rsa.pub.1
讲所有的迷药追加到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