Hadoop启动时SSH免密码登录

现在在学习大数据，买了一台云服务器，照着网上的教程安装的。现在在启动（start-all.sh）Hadoop的时候老是要求输入密码，后面在真实环境下不可能每一次通信都要求手动输入密码的，所以，免密码很重要：
现在直接上代码：

ssh-keygen -t rsa -P ""Generating public/private rsa key pair.Enter file in which to save the key (/root/.ssh/id_rsa): Your identification has been saved in /root/.ssh/id_rsa.Your public key has been saved in /root/.ssh/id_rsa.pub.The key fingerprint is:a0:0d:8a:b4:dd:e7:92:6f:44:25:36:9a:5b:75:10:a8 root@richardThe key's randomart image is:+--[ RSA 2048]----+|        .oo      ||       = o .     || .  . * = .      ||..o..E +         ||......=.S        ||     .+.         ||     o..         ||      o.         ||      ..         |+-----------------+

接下来将密钥写入ssh中

cat /root/.ssh/id_rsa.pub >> /root/.ssh/authorized_keys/etc/init.d/ssh reload

再次启动hadoop就没有密码输入的要求了。