Ubuntu和CentOS配置SSH无密码登录

一、安装ssh

Ubuntu中使用命令：

1. $sudo apt-get install openssh-server openssh-client

$sudo apt-get install openssh-server openssh-client

CentOS中使用命令：

1. $sudo yum install openssh-server openssh-client

$sudo yum install openssh-server openssh-client

启动ssh使用命令：

1. $sudo service sshd start

$sudo service sshd start

二、配置无密码登录SSH

Ubuntu中配置如下：

1. $ ssh-keygen -t dsa -P ''
2. Generating public/private dsa key pair.
3. Enter file in which to save the key (/home/aaron/.ssh/id_dsa):
4. Created directory '/home/aaron/.ssh'.
5. Your identification has been saved in /home/aaron/.ssh/id_dsa.
6. Your public key has been saved in /home/aaron/.ssh/id_dsa.pub.
7. The key fingerprint is:
8. bd:2c:ed:ab:6d:a9:b2:45:88:32:08:5a:d2:d9:ad:cc aaron@ubuntu
9. The key's randomart image is:
10. +--[ DSA 1024]----+
11. | |
12. | . o . |
13. |o + . . |
14. |o+ o o . . |
15. |o o E . S . |
16. | o . o . |
17. | o +. |
18. | .. +o |
19. | .oo++. |
20. +-----------------+

$ ssh-keygen -t dsa -P ''
Generating public/private dsa key pair.
Enter file in which to save the key (/home/aaron/.ssh/id_dsa):
Created directory '/home/aaron/.ssh'.
Your identification has been saved in /home/aaron/.ssh/id_dsa.
Your public key has been saved in /home/aaron/.ssh/id_dsa.pub.
The key fingerprint is:
bd:2c:ed:ab:6d:a9:b2:45:88:32:08:5a:d2:d9:ad:cc aaron@ubuntu
The key's randomart image is:
+--[ DSA 1024]----+
|                 |
| . o .           |
|o + . .          |
|o+ o o . .       |
|o o E . S .      |
|   o   . o .     |
|        o +.     |
|      .. +o      |
|      .oo++.     |
+-----------------+

（注：回车后会在~/.ssh/下生成两个文件：id_rsa和id_rsa.pub。这两个文件是成对出现的。）

将id_dsa.pub里面的内容加到用于认证的公钥文件中，命令如下：

1. $ cat id_dsa.pub >> authorized_keys

$ cat id_dsa.pub >> authorized_keys

可以将这个生成的authorized_keys拷贝到别的机器上面

1. $ cat ~/.ssh/authorized_keys | \
2. ssh aarron@192.168.1.108 "cat - >> ~/.ssh/authorized_keys"

$ cat  ~/.ssh/authorized_keys | \
ssh aarron@192.168.1.108 "cat - >> ~/.ssh/authorized_keys"

登录localhost。在终端输入命令：ssh localhost(注：当ssh远程登录到其它机器后，你控制的是远程的机器，需要执行退出命令才能重新控制本地主机。)执行退出命令。输入命令：exit

如果配置过程中出现问题，一般的问题都是文件权限设置的不对，请把.ssh和authorized_keys的访问权限分别设置为755个600，命令如下：

1. $ chmod 755 ~/.ssh
2. $ chmod 600 ~/.ssh/authorized_keys

$ chmod 755 ~/.ssh
$ chmod 600 ~/.ssh/authorized_keys

上面是以Ubuntu平台为例子，下面来说说怎么在CentOS平台上面配置。

首先，需要设置一下/etc/ssh/sshd_config文件，请将/etc/ssh/sshd_config文件中下面三行的注释去掉：

1. $sudo vim /etc/ssh/sshd_config
2. RSAAuthentication yes
3. PubkeyAuthentication yes
4. AuthorizedKeysFile .ssh/authorized_keys

$sudo vim /etc/ssh/sshd_config
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile      .ssh/authorized_keys

其余的步骤和在Ubuntu下配置是一样的。