Liunx 中使用ssh登录配置问题

一、使用SSH无密码登录问题设置；

1：在需要无密码登录的主机上运行如下命令      

     $ ssh-keygen -t rsa     

将会在用户文件夹下生成：.ssh/ 

2：将.ssh文件夹下的id_ras.pub ;传到需要登录的主机上

$scp ./.ssh/id_ras.pub root@10.0.0.2:/root/

3:将10.0.0.2主机上将id_ras.pub>>到authorized_keys 中

$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

4：完成；可以使用ssh无密钥登录了

二、出现无法的登录的解决办法

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
5c:9b:16:56:a6:cd:11:10:3a:cd:1b:a2:91:cd:e5:1c.
Please contact your system administrator.
Add correct host key in /home/user/.ssh/known_hosts to get rid of this message.
Offending key in /home/user/.ssh/known_hosts:1
RSA host key for ras.mydomain.com has changed and you have requested strict checking.
Host key verification failed.

解决方案一：需要在要远程登录的机器中删除.ssh/known_hosts 文件；

如果设置了无密钥登录，那么可能在登录时有warn，每次都要进行；比较输入yes；解决方案就是；删除本机的.ssh/known_hosts文件

Solution #2: Remove keys  //只删远程连接机器的key


Use the -R option to removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed hosts. If your remote hostname is server.example.com, enter:
$ ssh-keygen -R {server.name.com}
$ ssh-keygen -R {ssh.server.ip.address}
$ ssh-keygen -R server.example.com

Solution #3: Add correct host key in /home/user/.ssh/known_hosts


It is not necessary to delete the entire known_hosts file, just the offending line in that file. For example if you have 3 server as follows.
myserver1.com,64.2.5.111 ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEA11FV0EnGahT2EK8qElocjuHTsu1jaCfxkyIgBTlxlrOIRchb2pw8IzJLOs2bcuYYfa8nSXGEcWyaFD1ifUjfHelj94AAAAB3NzaC1yc2EAAAABIwAAAIEA11FV0E
nGahT2EK8qElocjuHTsu1jaCfxkyIgBTlxlrOIRchb2pw8IzJLOs2bcuYYfa8nSXGEcWyaFD1ifUjfHelj94H+uv304/ZDz6xZb9ZWsdm+264qReImZzruAKxnwTo4dcHkgKXKHeefnBKyEvvp/2ExMV9WT5DVe1viVwk=
myserver2.com,125.1.12.5 ssh-rsa
AAAAB3NzaC1yc2EAAAABIwAAAQEAtDiERucsZzJGx/1kUNIOYhJbczbZHN2Z1gCnTjvO/0mO2R6KiQUP4hOdLppIUc9GNvlp1kGc3w7B9tREH6kghXFiBjrIn6VzUO4uwrnsMbnAnscD5EktgI7fG4ZcNUP 5+J7sa3o+rtmOuiFxCA690DXUJ8nX8yDHaJfzMUTKTGxQz4M/H2P8L2R//qLj5s3ofzNmgSM9lSEhZL/IyI4NxHhhpltYZKW/Qz4M/H2P8L2R//qLj5s3ofzNmgSM9lSEhZL/M7L0vKeTObue1SgAsXADtK3162a/Z6MGnAazIviHBldxtGrFwvEnk82+GznkO3IBZt5vOK2heBnqQBfw=
myserver3.com,125.2.1.15 ssh-rsa 
5+J7sa3o+rtmOuiFxCA690DXUJ8nX8yDHaJfzMUTKTGx0lVkphVsvYD5hJzm0eKHv+oUXRT9v+QMIL+um/IyI4NxHhhpltYZKW
as3533dka//sd33433////44632Z6MGnAazIviHBldxtGrFwvEnk82/Qz4M/H2P8L2R//qLj5s3ofzNmgSM9lSEhZL/M7L0vKeTObue1SgAsXADtK3162a/Z6MGnAazIviHBldxtGrFwvEnk82+GznkO3IBZt5vOK2heBnqQBfw==


To delete 2nd server (myserver.com), open file:
# vi +2 .ssh/known_hosts


And hit dd command to delete line. Save and close the file. Or use following
$ vi ~/.ssh/known_hosts


Now go to line # 2, type the following command
:2


Now delete line with dd and exit:
dd
:wq


Solution 4: Just delete the known_hosts file If you have only used one ssh server


$ cd
$ rm .ssh/known_hosts
$ ssh ras.mydomain.com