How to modify IP address in centos

Modifying the CentOS IP address is divided into three steps: modify the IPADDR, NETMASK, and GATEWAY parameters in the /etc/sysconfig/network-scripts/ifcfg-eth0 file. Save the file and restart the network service (systemctl restart network). Optional: Write scripts to automate the IP address modification process.

CentOS modify IP address: Don't be scared by those complicated tutorials!

Many novices get overwhelmed when they see modifying CentOS IP addresses, and they are confused by various tutorials. Actually, it's not that complicated! In this article, I will tell you how to easily get it done in a way that you can definitely understand. After reading this article, you can not only modify the IP, but also understand the principles behind it, and even write a script yourself to automate the process.

First of all, you have to understand that the network configuration of CentOS mainly relies on files in /etc/sysconfig/network-scripts/ directory, especially ifcfg-eth0 (or ifcfg-ens33 , depending on your network card name, you can view it with the ip addr command). This file is like a network-configured "ID card", which records all the information of your network card, including the IP address, subnet mask, gateway, etc.

Basic knowledge review: Don't be afraid, this part is very simple

You only need to know, in the ifcfg-eth0 file, several key parameters:

• DEVICE : Your network card name, such as eth0 or ens33 .
• BOOTPROTO : Start the protocol, generally set to static to represent static IP, and dhcp means dynamically obtaining IP. We modify the IP here, of course we need to set it to static .
• IPADDR : Your IP address, such as 192.168.1.100 .
• NETMASK : Subnet mask, such as 255.255.255.0 .
• GATEWAY : Gateway address, such as 192.168.1.1 .

Core concept: Modify configuration files and restart network services

Modifying the IP address is actually to modify the three parameters of IPADDR , NETMASK , and GATEWAY in ifcfg-eth0 file. Don't be afraid, use a text editor (such as vi or nano ) to open this file and modify it.

For example, suppose we want to change the IP address to 192.168.1.101 , the subnet mask remains unchanged and the gateway remains unchanged, then the content of the modified ifcfg-eth0 file may look like this (note: adjust DEVICE according to your network card name):

 <code class="bash">DEVICE=eth0 BOOTPROTO=static IPADDR=192.168.1.101 NETMASK=255.255.255.0 GATEWAY=192.168.1.1 ONBOOT=yes</code>

After modification, save the file. Then, restart the network service and let the modification take effect:

 <code class="bash">systemctl restart network</code>

or

 <code class="bash">service network restart</code>

Advanced usage: Automating with scripts

For situations where IP addresses are often modified, writing a script will be much more convenient. The following is a simple shell script that can modify the IP address according to the parameters:

 <code class="bash">#!/bin/bash IP=$1 NETMASK=$2 GATEWAY=$3 sed -i "s/IPADDR=.*/IPADDR=$IP/g" /etc/sysconfig/network-scripts/ifcfg-eth0 sed -i "s/NETMASK=.*/NETMASK=$NETMASK/g" /etc/sysconfig/network-scripts/ifcfg-eth0 sed -i "s/GATEWAY=.*/GATEWAY=$GATEWAY/g" /etc/sysconfig/network-scripts/ifcfg-eth0 systemctl restart network echo "IP address changed successfully!"</code>

Using this script, you can run it like this:

 <code class="bash">./my_ip_script.sh 192.168.1.102 255.255.255.0 192.168.1.1</code>

Common Errors and Debugging: Don't panic, take your time

The most common mistake is to forget to restart the network service after modifying the file. Also, the network card name is written incorrectly, resulting in invalid modification. If you still cannot connect to the network after modification, check your firewall settings to make sure that the network connection is not blocked. Use the ip addr command to check the status of the network card to see if the IP address is modified successfully.

Performance Optimization and Best Practices: Keeping Code Clean

The sed command is used in the script to replace it, which is relatively efficient. Remember to keep your configuration files neat and annotate your scripts clearly for future maintenance. Developing good programming habits will help you avoid many detours in the days ahead.

Remember, practice brings true knowledge! If you do more hands-on, you can become a CentOS network configuration expert! Don’t be afraid of making mistakes, making mistakes is part of learning. I wish you success!

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