如何在CentOS7.0上安装telnet-server？ "CentOS7.0上安装telnet-server的详细步骤，让你轻松搭建远程登陆环境"

telnet server is a server software used for remote login in CentOS 7.0 system. This article will provide a detailed guide on how to install a telnet server on CentOS 7.0 and answer some commonly asked questions.

In order to install telnet server, we need to make sure that the telnetserver package is already installed on the system. You can use the following command to check if it is installed:

    
      rpm qa | grep telnetserver
    
  

If it is not installed, you can use the following command to install it:

    
      sudo yum install telnetserver
    
  

After the installation, we need to start the telnet service and enable it to start on boot. You can achieve this by using the following command:

    
      sudo systemctl start telnet.socket
      sudo systemctl enable telnet.socket
    
  

Next, we need to configure the telnet service. The configuration file is located in the /etc/xinetd.d/ directory and the file name is telnet. You can open the configuration file using the following command:

    
      sudo vi /etc/xinetd.d/telnet
    
  

The content of the configuration file is as follows:

    
      service telnet{
        flags       = REUSE
        socket_type = stream
        wait        = no
        user        = root
        server      = /usr/sbin/telnetd
        log_on_failure += USERID
        disable     = no
      }
    
  

The meaning of each parameter is as follows:

Parameter Definitions:

flags: Service flag, REUSE means the port can be reused.

socket_type: Socket type, stream means using TCP protocol.

wait: Whether to wait for client connection, no means no waiting.

user: The username running the telnet service, default is root.

server: The executable file path of the telnet service, default is /usr/sbin/telnetd.

log_on_failure: The information logged on login failure, +=USERID means recording user ID.

disable: Whether to disable the telnet service, no means enabled.

According to the actual requirements, you can modify the parameters in the configuration file. If you need to restrict only specific IP addresses of clients to connect, you can add the only_from parameter in the configuration file as shown below:

    
      service telnet{
        ...
        only_from       = 192.168.1.0/24
        ...
      }
    
  

After saving the configuration file, you need to restart the xinetd service to make the configuration take effect:

    
      sudo systemctl restart xinetd
    
  

Now, the telnet server is successfully installed and configured. You can test if the telnet service is working properly by using the following command:

    
      telnet localhost
    
  

If you can successfully connect and see the welcome message, it means that the telnet service is running properly.

FAQs

Q1: How to check the running status of the telnet service?

A1: You can use the following command to check the running status of the telnet service:

    
      sudo systemctl status telnet.socket
    
  

Q2: How to configure the telnet service to deny connections from certain IP addresses?

A2: You can add the no_access parameter in the telnet service configuration file to specify the IP address or subnet to deny connections. For example, to deny connections from the 192.168.2.0/24 subnet:

    
      service telnet{
        ...
        no_access       = 192.168.2.0/24
        ...
      }
    
  

After saving the configuration file, restart the xinetd service to make the configuration take effect:

    
      sudo systemctl restart xinetd
    
  

That's all for the installation and configuration of telnet server. If you have any further questions, feel free to ask and leave a comment. Thank you for reading!

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