登陆ssh不需要使用密码

假设A，B两服务器，现在需要在A机上用root登陆B机，而不需要输入密码，那我们可按照下面的步骤来做：
1）在A机上生成钥匙对

A# ssh-keygen -t rsa  
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
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:
f6:61:a8:27:35:cf:4c:6d:13:22:70:cf:4c:c8:a0:23 mlsx@mlsx

2）把在A机生成的id_rsa.pub拷贝到B机上

scp -P 3721 /root/.ssh/id_rsa.pub  

xx.xx.xx.xx

:/tmp

3）用root帐号登陆B机，进入其主目录，创建authorized_keys文件，并设置好权限

B# cd ~/.ssh
#cat /tmp/id_rsa.pub >>authorized_keys
#chmod  400 authorized_keys

4）测试

ssh -p 3721 xx.xx.xx.xx