Linux 之 SSH 理解

SSH 理解

一、服务端sshd_conf配置文件理解

Port 22                                                 #ssh 连接默认端口
PermitRootLogin yes                           #是否允许root用户登陆
PermitEmptyPasswords no                 #禁止空密码登陆
UserDNS no                                         #不使用DNS反解释
GSSAPIAuthentication no                    #禁用可加快初始连接的等待时间
ListenAddress  10.3.151.                      #只监控允许该网段的机器远程过来
#配置文件所在位置/etc/ssh/sshd_config

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二、快速创建无密码远程登陆其它主机

1、主机环境

10.3.151.193  可直接控制访问10.3.151.222

2、在10.3.151.193上创建密钥对

[root@localhost ~]# ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.
The key fingerprint is:
95:b4:14:45:60:9e:39:b2:89:02:d9:d4:55:3d:1f:80 [email protected]
The key's randomart image is:
+--[ DSA 1024]----+
|    .. ...BB+.   |
|   +  .  =E=o .  |
|  o .   . O  o . |
|   .   . = .  .  |
|    . . S        |
|     .           |
|                 |
|                 |
|                 |
+-----------------+

备注：以下命令可直接快速创建密钥对
ssh-keygen -t dsa -P ' ' -f ~/.ssh/id_dsa > /dev/null 2>&1

[root@localhost ~]# ls -al .ssh/
总用量 20
drwx------.  2 root root 4096 6月   6 15:08 .
dr-xr-x---. 26 root root 4096 5月  27 15:25 ..
-rw-------   1 root root  668 6月   6 15:08 id_dsa                 #私钥
-rw-r--r--   1 root root  616 6月   6 15:08 id_dsa.pub           #公钥
-rw-r--r--   1 root root  786 5月  31 18:51 known_hosts

3、把公钥发送到要远程控制的主机

[root@localhost ~]# ssh-copy-id -i .ssh/id_dsa.pub  [email protected]
The authenticity of host '10.3.151.222 (10.3.151.222)' can't be established.
RSA key fingerprint is 55:5c:2f:0d:67:6d:b0:64:3e:7a:81:dd:54:9d:07:40.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '10.3.151.222' (RSA) to the list of known hosts.
[email protected]'s password: 
Now try logging into the machine, with "ssh '[email protected]'", and check in:

    .ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

4、在被远程控制的机器上，查看.ssh下的文件

[root@localhost ~]# ls -al .ssh/
总用量 16
drwx------.  2 root root 4096 6月   6 15:11 .
dr-xr-x---. 24 root root 4096 5月  23 15:21 ..
-rw-------.  1 root root  616 6月   6 15:11 authorized_keys      #上传后生成的文件
-rw-r--r--.  1 root root  787 5月  23 13:05 known_hosts

5.测试10.3.151.193的机器是否可以直接访问10.3.151.222的机器（不需要密码）

[root@localhost ~]# ssh [email protected] /sbin/ifconfig eth2
eth2      Link encap:Ethernet  HWaddr 00:50:56:B9:DA:C7  
                    inet addr:10.3.151.222  Bcast:10.3.151.255  Mask:255.255.255.0
                    inet6 addr: fe80::250:56ff:feb9:dac7/64 Scope:Link
                    UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
                    RX packets:667797 errors:0 dropped:0 overruns:0 frame:0
                    TX packets:206514 errors:0 dropped:0 overruns:0 carrier:0
                    collisions:0 txqueuelen:1000 
                    RX bytes:341023267 (325.2 MiB)  TX bytes:120677605 (115.0 MiB)