ssh-copy-id命令
它可以把本地主机的公钥复制到远程主机的authorized_keys文件上，ssh-copy-id命令也会给远程主机的用户主目录（home）和~/.ssh, 和~/.ssh/authorized_keys设置合适的权限。
~/.ssh
~/.ssh/authorized_keys
ssh-copy-id -i ~/.ssh/id_rsa.pub hadoop@namenode1
