linux基本命令及操作7（ssh server）

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openssh-server

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

使用户root@172.25.254.213连接root@172.25.254.213

ssh root@172.25.254.213
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

在用户root@17225.254.213 /Desktop/目录下建立文件法file1 file2 ... file10 ls查看

   3.sshkey加密
1.生成公钥私钥
[root@server0 ~]# 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 root@server0.example.com
[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
[root@server0 ~]# ssh-copy-id -i /root/.ssh/id_rsa.pub root@172.25.254.113
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
172.25.254.113      ##被加密主机ip

3.分发钥匙给主机root@172.25.254.213

[root@server0 ~]# scp /root/.ssh/id_rsa root@172.25.254.213:/root/.ssh/

4.测试

[root@desktop0 ~]# ssh root@172.25.254.113 ##通过id_rsa直接连接不需要输入用户密码
Last login: Mon Oct 3 03:58:10 2016 from 172.25.0.250
[root@server0 ~]#

         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

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