题记：不管性能测试过程还是系统运维，我们会经常排查环境的连通性问题，除了我们知道的ping命令外，最常用的就是telnet命令，很多系统默认未安装telnet，以下是逐步安装教程。

1、检测telnet-server的rpm包是否安装

[root@mysql57server2 ~]# rpm -qa telnet-server

2、输出空白，表示没有安装，执行如下命令，安装telnet-server

[root@mysql57server2 ~]# yum install telnet-server

Loaded plugins: fastestmirror

Loading mirror speeds from cached hostfile

Resolving Dependencies

--> Running transaction check

---> Package telnet-server.x86_64 1:0.17-64.el7 will be installed

--> Finished Dependency Resolution

Dependencies Resolved

=======================================================================================================================================================================================================================================

Package Arch Version Repository Size

=======================================================================================================================================================================================================================================

Installing:

telnet-server x86_64 1:0.17-64.el7 Base 41 k

Transaction Summary

=======================================================================================================================================================================================================================================

Install 1 Package

Total download size: 41 k

Installed size: 55 k

Is this ok [y/d/N]: y ---------确认输入y

Downloading packages:

telnet-server-0.17-64.el7.x86_64.rpm | 41 kB 00:00:00

Running transaction check

Running transaction test

Transaction test succeeded

Running transaction

Installing : 1:telnet-server-0.17-64.el7.x86_64 1/1

Verifying : 1:telnet-server-0.17-64.el7.x86_64 1/1

Installed:

telnet-server.x86_64 1:0.17-64.el7

Complete!

3、检测telnet的rpm包是否安装

[root@mysql57server2 ~]# rpm -qa telnet

4、输出为空白，说明没安装，执行下面命令安装

[root@mysql57server2 ~]#yum install telnet

Loaded plugins: fastestmirror

Loading mirror speeds from cached hostfile

Resolving Dependencies

--> Running transaction check

---> Package telnet.x86_64 1:0.17-64.el7 will be installed

--> Finished Dependency Resolution

Dependencies Resolved

=======================================================================================================================================================================================================================================

Package Arch Version Repository Size

=======================================================================================================================================================================================================================================

Installing:

telnet x86_64 1:0.17-64.el7 Base 64 k

Transaction Summary

=======================================================================================================================================================================================================================================

Install 1 Package

Total download size: 64 k

Installed size: 113 k

Is this ok [y/d/N]:y---------确认输入y

Downloading packages:

telnet-0.17-64.el7.x86_64.rpm | 64 kB 00:00:00

Running transaction check

Running transaction test

Transaction test succeeded

Running transaction

Installing : 1:telnet-0.17-64.el7.x86_64 1/1

Verifying : 1:telnet-0.17-64.el7.x86_64 1/1

Installed:

telnet.x86_64 1:0.17-64.el7

Complete!

5、重新启动xinetd守护进程

[root@mysql57server2 ~]# service xinetd restart

Redirecting to /bin/systemctl restart xinetd.service

6、测试

[root@mysql57server2 ~]# telnet

telnet>