Linux配置SSH免密码登录

我们如果在Linux上通过ssh命令去登录另一台Linux机器，正常情况下，需要输入另一台机器的密码，但是如果我们需要频繁的登录的时候，每次都输入密码不免得很繁琐，所以这里对配置ssh免密码登录做一下记录。

1. 准备环境

• 系统环境： rhel-server-7.4-x86_64
  这里演示的是一个Linux系统通过ssh命令登录到本机上（多台机器原理和步骤也是一样的），Linux系统已经在 /etc/hosts文件中配置了主机名 bigdata111
  

2. 配置步骤

• 刚开始，如果我们不做任何配置，那么我们通过ssh命令登录到Linux系统需要输入密码：

[[email protected] ~]# ssh bigdata111
[email protected]'s password: 
Last login: Mon Jul 15 21:32:06 2019 from 192.168.2.1
[[email protected] ~]# 

• 对需要免密码登录其他机器的Linux系统生成**对（谁需要免密码登录，就谁生成**对，假设服务器A需要登录服务器B的时候不需要输入密码，那么就是服务器A需要生成**对），这边通过ssh-****** -t rsa命令生成**对，一路回车即可

[[email protected] ~]# ssh-****** -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:
SHA256:Zywosk7DO6rD6AcV2weNS5AjF6mlxSudvOtQ07aGdYw [email protected]
The key's randomart image is:
+---[RSA 2048]----+
|  .o= o          |
| . X + .         |
|  X O o          |
| + B.ooo .       |
|  +ooEooS +      |
| o.+=.o  +       |
|o.*..o           |
|o+o=.            |
|=+=o             |
+----[SHA256]-----+
[[email protected] ~]#

上面命令执行成功后，生成的**对会在**/root/.ssh**目录下，

[[email protected] .ssh]# pwd
/root/.ssh
[[email protected] .ssh]# ll
total 12
-rw-------. 1 root root 1679 Jul 15 21:36 id_rsa
-rw-r--r--. 1 root root  397 Jul 15 21:36 id_rsa.pub
-rw-r--r--. 1 root root  526 Jul 14 06:34 known_hosts
[[email protected] .ssh]#

• 将生成的公钥发送给目标机器（需要免密码登录到哪台机器上），在这个过程，需要输入目标机器的密码

[[email protected] ~]# ssh-copy -i .ssh/id_rsa.pub [email protected]
bash: ssh-copy: command not found...
[[email protected] ~]# ssh-copy-id -i .ssh/id_rsa.pub [email protected]
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: ".ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
[email protected]'s password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh '[email protected]'"
and check to make sure that only the key(s) you wanted were added.

[[email protected] ~]# 

发送成功之后，公钥会被保存在.ssh/authorized_keys文件中

[[email protected] ~]# cd .ssh/
[[email protected] .ssh]# ll
total 16
-rw-------. 1 root root  397 Jul 15 21:42 authorized_keys
-rw-------. 1 root root 1679 Jul 15 21:36 id_rsa
-rw-r--r--. 1 root root  397 Jul 15 21:36 id_rsa.pub
-rw-r--r--. 1 root root  526 Jul 14 06:34 known_hosts
[[email protected] .ssh]# pwd 
/root/.ssh
[[email protected] .ssh]# cat authorized_keys 
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDHaiWaO/X4CQuSHX7brpRoiH9NZ9sTD3By+meSeCUjLeGYYLSNyB6mzbPxSlSYZLmktD7wwR33cEdyH75vca4qyhruqB6JeUerE7VFOUS+jT4mVNxctWeiCxnMNRYQyfgNlwoTbgSROKzeiaQduW0yHiWkWnjzqjq913OFh16jQKKvDyNpoI0ltW/i2qopGshBZwETaSzdVVdL+3FzX4DL4O9mb9NC3XHH5JrQG5xmsvnWdpWT/SPyOUBpJryTFGeQ46zeekQMJXfUyXDp/8tTD1dtsSorGV20wEJuoO/Z+IQYik36DdExH5mRS7nB6QEm4tUyDcJU5mXy/cfHehAN [email protected]
[[email protected] .ssh]# 

• 经过上述配置，免密码登录配置完成，现在我们再执行ssh bigdata111执行远程登录时，发现不用再输入密码了

[[email protected] .ssh]# ssh bigdata111
Last login: Mon Jul 15 21:33:47 2019 from 192.168.2.111
[[email protected] ~]#