文档总结9-linux中的openssh-server

1.修改用户名与ip

    linux中关于ssh的操作大多需要用desktop与server两个虚拟机进行操作，那么修改两台虚拟机中的用户名及ip就十分重要了。

下面以desktop为例：

1）修改用户名

[root@localhost Desktop]# hostname           ##查看用户名

localhost

[root@localhost Desktop]# vim /etc/sysconfig/network     ##修改文件添加HOSTNAME=desktop

[root@localhost Desktop]# vim /etc/hosts      ##修改文件中第一行第二个主机名为desktop

[root@localhost Desktop]#init 6                                    ##重启，更改生效

2）修改ip

[root@desktop Desktop]# nmcli connection show                                            ##显示所有网络连接

[root@desktop Desktop]# nmcli connection delete "System eth0"                   ##删除System eth0连接

[root@desktop Desktop]# nmcli connection add con-name eth0 ifname eth0 type ethernet ip4 172.25.254.10/24

                                                                                                                          ##添加名为eth0的新网络连接

server虚拟机与desktop虚拟机设置原理相同，在此不做演示，敬请谅解

2.openssh-server

 

功能：让远程主机可以通过网络访问sshd服务，开始一个安全shell

 

3.客户端连接方式

ssh 远程主机用户@远程主机ip

[root@desktop0 ~]# ssh root@172.25.254.11

The authenticity of host '172.25.254.11 (172.25.254.11)' can't be established.

ECDSA key fingerprint is eb:24:0e:07:96:26:b1:04:c2:37:0c:78:2d:bc:b0:08.

Are you sure you want to continue connecting (yes/no)? yes ##连接陌生主机时需要建立认证关系

Warning: Permanently added '172.25.24.11' (ECDSA) to the list of known hosts.

root@172.25.254.11's password: ##远程用户密码

Last login: Tue Oct  17 11:41:35 2017

[root@server ~]# ##登陆成功

 

ssh 远程主机用户@远程主机ip -X ##调用远程主机图形工具

ssh     远程主机用户@远程主机ip command ##直接在远程主机运行某条命令

 

 

 

 

4.sshkey加密

1 )生成公钥私钥

[kiosk@foundation90 ~]$ ssh-keygen ##生成公钥私钥工具

Generating public/private rsa key pair.

Enter file in which to save the key (/root/.ssh/id_rsa):[enter] ##加密字符保存文件（建议用默认）

Created directory '/root/.ssh'.

Enter passphrase (empty for no passphrase): [enter] ##密钥密码，必须>4个字符

Enter same passphrase again: [enter] ##确认密码

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:

ab:3c:73:2e:c8:0b:75:c8:39:3a:46:a2:22:34:84:81 [e-mail]

The key's randomart image is:

+--[ RSA 2048]----+

|o                |

|E.               |

|..               |

|.  . o           |

|.o. * . S        |

|oo.o o   .       |

|+ =. .  .        |

|o. oo.+..        |

|    ..o*.        |

+-----------------+

[root@server0 ~]# ls /root/.ssh/

id_rsa  id_rsa.pub

id_rsa ##私钥，就是钥匙

id_rsa.pub ##公钥，就是锁

 

2 )添加key认证方式

[kiosk@foundation90 Desktop]$ ssh-copy-id -i /root/.ssh/id_rsa.pub  root@172.25.0.11

ssh-copy-id ##添加key认证方式的工具

-i ##指定加密key文件

/root/.ssh/id_rsa.pub ##加密key

root ##加密用户为root

172.25.0.11 ##被加密主机ip

 

3）分发钥匙给client主机

[kiosk@foundation90 Desktop]$ scp /home/kiosk/.ssh/id_rsa root@172.25.254.10:/root/.ssh/

 

4）测试

 

[root@desktop0 ~]# ssh root@172.25.254.90  ##通过id_rsa直接连接不需要输入用户密码

Last login: Tue Oct 17 23:10:07 2017

[kiosk@foundation90 ~]$

 

5）添加公钥认证方式

通过发送公钥来免密码进入desktop和server

[kiosk@foundation90 .ssh]$ ssh-copy-id -i id_rsa.pub root@172.25.254.10

[kiosk@foundation90 .ssh]$ ssh-copy-id -i id_rsa.pub root@172.25.254.11

5.提升openssh的安全级别

1）openssh-server配置文件

/etc/ssh/sshd_config

78 PasswordAuthentication yes|no ##是否开启用户密码认证，yes为支持no为关闭

48 PermitRootLogin yes|no ##是否允许超级用户登陆

49 AllowUsers student westos ##用户白名单，只有在名单中出现的用户可以使用sshd建立shell

50 DenyUsers westos ##用户黑名单

 

2）控制ssh客户端访问

vim /etc/hosts.deny

sshd:ALL ##拒绝所有人链接sshd服务

 

vim /etc/hosts.allow

sshd:172.25.254.250 ##允许250主机链接sshd

 

sshd:172.25.254.250， 172.25.254.180 ##允许250和180链接

 

sshd:ALL EXCEPT 172.25.254.200 ##只不允许200链接sshd

 

 

3）ssh登陆提示修改

vim /etc/motd ##显示登陆后字符

 

不要连我！！！  ##在登陆后就会显示这个字符