Linux_入门 远程连接访问主机

1.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

2.客户端连接方式

ssh    远程主机用户@远程主机ip

[root@desktop0 ~]# ssh root@172.25.0.11

The authenticity of host '172.25.0.11 (172.25.0.11)' 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 '172.25.0.11' (ECDSA) to the list of known hosts.

root@172.25.0.11's password:                 ##远程用户密码

Last login: Mon Oct  3 03:13:47 2016

[root@server0 ~]#                    ##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

3.sshkey加密

1.生成公钥私钥

[root@localhost ~]# 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):                   ######加密字符保存文件（建议用默认）

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

Enter same passphrase again:                                                     ##确认密码

Passphrases do not match.  Try again.                                        ###两次输入不匹配

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /root/.ssh/id_rsa.
4000

Your public key has been saved in /root/.ssh/id_rsa.pub.

The key fingerprint is:

43:c5:1b:27:79:64:31:8b:4e:08:c1:19:fe:c3:0b:58 root@localhost

The key's randomart image is:

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

|     .++ ..o=.   |

|     .o. o=ooo   |

|      E o o*.    |

|     o + o.      |

|    . . S .      |

|       . +       |

|        .        |

|                 |

|                 |

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



id_rsa        ##私钥，就是钥匙

id_rsa.pub    ##公钥，就是锁

2.添加key认证方式

3.分发钥匙给client主机

4.测试

4.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登陆提示修改该

vim /etc/motd        ##显示登陆后字符

hello world        ##在登陆后就会显示这个字符