Linux下SSH免密码登录

[hadoop@hadoop1 ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/hadoop/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/hadoop/.ssh/id_rsa.
Your public key has been saved in /home/hadoop/.ssh/id_rsa.pub.
The key fingerprint is:
26:96:da:89:60:3d:90:75:43:bf:eb:56:d1:52:d9:68 hadoop@hadoop1
The key's randomart image is:
+--[ RSA 2048]----+
|    ..+      +   |
|   o . o    E .  |
|  o     .  +     |
|   o   . .o .    |
|  o o + S  o     |
| . . * + ..      |
|    o o ..       |
|       ..        |
|       ..        |
+-----------------+
[hadoop@hadoop1 ~]$ cd .ssh
[hadoop@hadoop1 .ssh]$ scp -r id_rsa.pub hadoop@hadoop3:/home/hadoop/.ssh/authorized_keys
The authenticity of host 'hadoop3 (192.168.127.120)' can't be established.
RSA key fingerprint is 03:be:af:08:19:27:6d:15:7e:dd:90:fa:09:b3:14:2f.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'hadoop3,192.168.127.120' (RSA) to the list of known hosts.
hadoop@hadoop3's password: 
id_rsa.pub                                                       100%  396     0.4KB/s   00:00    
[hadoop@hadoop1 .ssh]$ ssh hadoop3
Last login: Sat Aug  4 17:35:22 2012 from hadoop1

[hadoop@hadoop3 ~]$ chmod 700 .ssh/
[hadoop@hadoop3 ~]$ cd .ssh
[hadoop@hadoop3 .ssh]$ chmod 600 authorized_keys

[root@hadoop3 .ssh]# vi /etc/ssh/sshd_config 
AuthorizedKeysFile      .ssh/authorized_keys  把前面的#号去掉
[root@hadoop3 .ssh]# /etc/rc.d/init.d/sshd restart
Stopping sshd:                                             [  OK  ]
Starting sshd:                                             [  OK  ]