How to Disable NetworkManager in CentOS/RHEL 8?

NetworkManager is a daemon that manages network connections on Red Hat Enterprise Linux (RHEL) and CentOS systems. It handles both wired and wireless connections, including Ethernet, WiFi, mobile broadband, VPNs, and other network interfaces. The daemon provides a graphical user interface for managing network settings on desktop environments such as GNOME or KDE.

NetworkManager is designed to automatically detect and configure connections based on the available network devices and their properties. It uses mechanisms like DHCP (Dynamic Host Configuration Protocol), PPP (Point-to-Point Protocol), and static IP addresses to connect to networks dynamically. Additionally, it supports advanced features like bonding multiple interfaces together for increased bandwidth or redundancy.

Understanding NetworkManager

How NetworkManager Works

NetworkManager works by using a combination of tools and protocols. It uses DHCP to assign IP addresses automatically, Wireless Extensions (WEXT) for wireless network support, and various plugins like the wired plugin for Ethernet interfaces and the Wi-Fi plugin for wireless ones. It also interacts with system components such as dnsmasq for DNS resolution, wpa_supplicant for WPA/WPA2 encryption support, and ModemManager for managing cellular data modems.

Advantages and Disadvantages

Disabling NetworkManager

There are scenarios where disabling NetworkManager is necessary, such as when specific network configurations are required or when it interferes with other network services. Here are the methods to disable NetworkManager in CentOS/RHEL 8.

Method 1: Using systemctl Commands

First, stop the NetworkManager service

sudo systemctl stop NetworkManager

Disable it from starting at boot time

sudo systemctl disable NetworkManager

Verify the service status

sudo systemctl status NetworkManager

Method 2: Using nmcli Command

You can temporarily disable all network interfaces managed by NetworkManager using the nmcli utility

sudo nmcli networking off

To re-enable networking later

sudo nmcli networking on

Method 3: Complete Removal (Optional)

If you want to completely remove NetworkManager from the system

sudo yum remove -y NetworkManager*

Warning: Removing packages can cause dependency issues. Proceed with caution and ensure no critical dependencies are removed.

Alternative Network Management

After disabling NetworkManager, you can use traditional network configuration methods

Using network-scripts

Install the legacy network service

sudo yum install -y network-scripts

Enable and start the network service

sudo systemctl enable network
sudo systemctl start network

Manual Configuration

Configure network interfaces manually by editing configuration files in /etc/sysconfig/network-scripts/. For example, edit /etc/sysconfig/network-scripts/ifcfg-eth0

TYPE=Ethernet
BOOTPROTO=static
IPADDR=192.168.1.100
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
DNS1=8.8.8.8
ONBOOT=yes

Benefits and Drawbacks

Conclusion

Disabling NetworkManager in CentOS/RHEL 8 provides greater control over network configurations and can improve system performance. However, it requires manual network management and removes the convenience of automatic network detection. The decision should be based on your specific requirements and technical expertise level.