How to set up a CentOS system to disable unnecessary network ports and services

How to set up the CentOS system to disable unnecessary network ports and services

1. Introduction
In the Linux system, network ports and services are key components for the computer to communicate with the outside world. However, not all network ports and services are necessary, and some may even present security risks. Therefore, it is very important for servers running CentOS systems to disable unnecessary network ports and services. This article will explain how to disable unnecessary network ports and services through simple settings.

2. Disable unnecessary ports

1. Check the currently open ports
   First, we need to check the currently open ports of the system. Run the following command in the terminal:

   netstat -tuln | grep LISTEN

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   This command will display all currently listening ports. Note that all ports can only be viewed with root privileges. Based on the output results, identify unnecessary ports.

2. Disable unnecessary ports
   To disable unnecessary ports, we need to edit the system’s firewall configuration file. Run the following command in the terminal to edit the firewall configuration file:

   vi /etc/sysconfig/iptables

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   In the file, there is one rule for each port that is allowed access. Find the rule corresponding to the port you want to disable, and add a # symbol before the line to make the line a comment. For example, to disable port 80, change the following rule:

   -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT

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   to:

   # -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT

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   Save and close the file.

3. Restart the firewall
   After editing the firewall configuration file, we need to restart the firewall for the changes to take effect. Run the following command in the terminal:

   service iptables restart

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   In this way, the disabled port will no longer be open to the outside world, thus improving the security of the server.

3. Disable unnecessary services
In addition to disabling unnecessary ports, we also need to disable unnecessary services. For CentOS systems, we can use the system's own service management tool to disable services.

1. View currently running services
   First, we need to view the currently running services. Run the following command in the terminal:

   service --status-all

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   This command will display all currently running services. Note that all services can only be viewed with root privileges. Based on the output results, identify unnecessary services.

2. Disable unnecessary services
   To disable unnecessary services, we need to use the chkconfig command. Run the following command in the terminal to disable the service:

   chkconfig  off

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   where is the name of the service to be disabled. For example, to disable the Apache service, run the following command:

   chkconfig httpd off

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   After running the above command, the service will no longer run automatically at system startup.

3. Stop the currently running service
   If a service is currently running, we also need to stop it. Run the following command in the terminal to stop the service:

   service  stop

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   where is the name of the service you want to stop. For example, to stop the Apache service, run the following command:

   service httpd stop

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   The service will stop running immediately.

4. Summary
By disabling unnecessary network ports and services, we can improve the security of the CentOS system and reduce potential security risks. When disabling a port, we need to edit the firewall configuration file and restart the firewall for the changes to take effect. When disabling a service, we need to use the chkconfig command to disable the service and stop the currently running service as needed. I hope the methods provided in this article can help you protect the security of your CentOS server.

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