最近在搭建Hadoop集群，为了操作方便，需要Master用无密码验证的方式的SSH登陆Slave。 1.原理： Master作为客户端，要实现无密码公钥认证，连接到服务器Salve上时，需要在Master上生成一个密钥对，包括一个公钥和一个私钥，而后将公钥复制到所有的Salve上。当Master通过SSH链接到Salve上时，Salve会生成一个随机数并用Master的公钥对随机数进行加密，并发送给Master。Master收到加密数之后再用私钥解密，并将解密数回传给Salve，Salve确认解密数无误之后就允许Master进行连接了。这就是一个公钥认证过程，期间不需要手工输入密码，重要的过程是将Master上产生的公钥复制到Salve上。
2.在Master上登陆Hadoop用户，，执行以下命令，生成密钥对，并把公钥文件写入授权文件中，并赋值权限
[hadoop@master bin]$ ssh-keygen -t rsa -P ”Generating public/private rsa key pair.Enter file in which to save the key (/home/hadoop/.ssh/id_rsa):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:93:21:fb:20:01:c9:13:a3:28:01:6c:57:3b:a0:e0:e2 hadoop@masterThe key’s randomart image is:+–[ RSA 2048]—-+|*.++..||+==+. .||*o…o. .||+ ..o o|| E . o S||. o .||.|||||+—————–+[hadoop@master bin]$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys[hadoop@master bin]$ chmod 600 ~/.ssh/authorized_keys
3 切换root用户，配置sshd，取消被注释的公钥字段， RSAAuthentication yes # 启用 RSA 认证 PubkeyAuthentication yes # 启用公钥私钥配对认证方式 AuthorizedKeysFile .ssh/authorized_keys # 公钥文件路径（和上面生成的文件同） 并保存设置，然后重启sshd，即可测试本机的SSH
[hadoop@master bin]$ su root密码：bash-4.1# vim /etc/ssh/sshd_configbash-[ OK ]Starting sshd:[ OK ]
4.本机测试：这里我用了localhost，IP地址，hostname来进行测试，可以发现均不需要输入密码。
[hadoop@master bin]$ ssh localhostThe authenticity of host ‘localhost (::1)’ can’t be established.RSA key fingerprint is 3a:99:7f:41:68:bd:3b:80:43:bb:8a:5c:62:73:1f:45.Are you sure you want to continue connecting (yes/no)? yesWarning: Permanently added ‘localhost’ (RSA) known hosts.[hadoop@master ~]$ ssh The authenticity ()’ can’t be established.RSA key fingerprint is 3a:99:7f:41:68:bd:3b:80:43:bb:8a:5c:62:73:1f:45.Are you sure you want to continue connecting (yes/no)? yesWarning: Permanently added ” (RSA) known hosts.Last login: Wed Jun ::1[hadoop@master ~]$ ssh mastersysconfig/system-releaseThe authenticity )’ can’t be established.RSA key fingerprint is 3a:99:7f:41:68:bd:3b:80:43:bb:8a:5c:62:73:1f:45.Are you sure you want to continue connecting (yes/no)? yesWarning: Permanently added ‘master’ (RSA) known hosts.Last login: Wed Jun
下面介绍Master用无密码验证的方式的SSH登陆Slave
1.首先在Slave上创建用户hadoop，并设置密码
-bash-4.1# useradd hadoop-bash-4.1# ls -l /home总用量 8drwx—— 2 hadoop hadoop 4096 6月 10 12:58 hadoopdrwx—— 2 xcxc4096 7月 9 2013 xc-bash-4.1# passwd hadoop更改用户 hadoop 的密码 。新的 密码：重新输入新的 密码：passwd： 所有的身份验证令牌已经成功更新。
2.切换到Master，并将Master上的公钥scp到Slave节点的Hadoop用户上
[hadoopauthenticity of host ‘slave2 (172.16.1.20)’ can’t be established.RSA key fingerprint is 67:22:ba:43:ad:fe:a2:d4:ad:43:26:4b:71:d0:54:af.Are you sure you want to continue connecting (yes/no)? yesWarning: Permanently added ‘slave2,172.16.1.20’ (RSA) to the list of known hosts.hadoop@slave2’s password:id_rsa.pub[hadoop@master ~]$
3.拷贝完后到Slave节点上，公钥追加授权文件，并修改权限
[hadoop@master ~]$ ssh hadoop@slave2hadoop@slave2’s password:[hadoop@slave2 ~]$ lsid_rsa.pub[hadoop@slave2 ~]$ mkdir ~/.ssh[hadoop@slave2 ~]$ chmod 700 ~/.ssh/[hadoop@slave2 ~]$ cat ~/id_rsa.pub >> ~/.ssh/authorized_keys[hadoop@slave2 ~]$ chmod 600 ~/.ssh/authorized_keys[hadoop@slave2 ~]$人生最大的错误是不断担心会犯错
