NetworkManager Linux: Complete Guide to Network Management Service

NetworkManager is a powerful network management service that provides automatic network detection and configuration for Linux systems. It simplifies network administration by handling complex networking tasks behind the scenes while offering both graphical and command-line interfaces for manual configuration.

What is NetworkManager?

NetworkManager is a daemon that manages network interfaces and connections on Linux systems. It automatically detects available networks, manages connection profiles, and handles network switching seamlessly. Unlike traditional network configuration methods that require manual editing of configuration files, NetworkManager provides dynamic network management with support for various connection types including Ethernet, Wi-Fi, mobile broadband, and VPN.

Key Features of NetworkManager

• Automatic Network Detection: Automatically discovers and connects to available networks
• Connection Profiles: Stores network configurations for easy switching
• Multiple Interface Support: Manages various connection types simultaneously
• Policy-based Routing: Intelligent routing decisions based on network policies
• VPN Integration: Built-in support for various VPN protocols
• Power Management: Optimizes network usage for battery-powered devices

Installing NetworkManager

Most modern Linux distributions come with NetworkManager pre-installed. However, if you need to install it manually, here are the commands for different distributions:

Ubuntu/Debian

sudo apt update
sudo apt install network-manager network-manager-gnome

Red Hat/CentOS/Fedora

sudo dnf install NetworkManager NetworkManager-wifi
# For older versions using yum:
sudo yum install NetworkManager NetworkManager-wifi

Arch Linux

sudo pacman -S networkmanager networkmanager-openvpn

NetworkManager Service Management

NetworkManager runs as a systemd service. Here are the essential service management commands:

Starting and Enabling NetworkManager

sudo systemctl start NetworkManager
sudo systemctl enable NetworkManager

Checking Service Status

sudo systemctl status NetworkManager

Expected Output:

● NetworkManager.service - Network Manager
   Loaded: loaded (/lib/systemd/system/NetworkManager.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2025-08-26 02:08:15 IST; 2h 15min ago
     Docs: man:NetworkManager(8)
 Main PID: 1234 (NetworkManager)
    Tasks: 3 (limit: 4915)
   Memory: 15.2M
      CPU: 2.345s

Restarting NetworkManager

sudo systemctl restart NetworkManager

Command Line Interface: nmcli

The nmcli (NetworkManager Command Line Interface) is the primary tool for managing NetworkManager from the terminal. It provides comprehensive control over network connections and settings.

Basic nmcli Syntax

nmcli [OPTIONS] OBJECT { COMMAND | help }

Common nmcli Objects

• general – NetworkManager general status and operations
• networking – Overall networking control
• radio – NetworkManager radio switches
• connection – NetworkManager connections
• device – Devices managed by NetworkManager

Managing Network Connections

Viewing Available Connections

nmcli connection show

Sample Output:

NAME                UUID                                  TYPE      DEVICE 
Wired connection 1  f1c92c98-8c4f-4b38-9a5e-7f2d6c8b9e3a  ethernet  enp0s3 
MyWiFi             a8b7c6d5-4e3f-2g1h-9i8j-7k6l5m4n3o2p  wifi      wlp2s0 
VPN Connection     b9a8c7d6-5e4f-3g2h-1i9j-8k7l6m5n4o3p  vpn       --

Viewing Connection Details

nmcli connection show "MyWiFi"

Creating a New Ethernet Connection

nmcli connection add type ethernet con-name "Office-LAN" ifname enp0s3 \
    ip4 192.168.1.100/24 gw4 192.168.1.1

Creating a Wi-Fi Connection

nmcli connection add type wifi con-name "Home-WiFi" ifname wlp2s0 \
    ssid "MyHomeNetwork" wifi-sec.key-mgmt wpa-psk wifi-sec.psk "mypassword"

Device Management

Listing Network Devices

nmcli device status

Expected Output:

DEVICE  TYPE      STATE         CONNECTION         
enp0s3  ethernet  connected     Wired connection 1 
wlp2s0  wifi      connected     MyWiFi             
lo      loopback  unmanaged     --

Viewing Device Details

nmcli device show enp0s3

Connecting and Disconnecting Devices

# Connect to a specific network
nmcli device connect wlp2s0

# Disconnect a device
nmcli device disconnect wlp2s0

Wi-Fi Management

Scanning for Wi-Fi Networks

nmcli device wifi list

Sample Output:

BSSID              SSID           MODE   CHAN  RATE        SIGNAL  BARS  SECURITY  
aa:bb:cc:dd:ee:ff  MyHomeNetwork  Infra  6     130 Mbit/s  85      ▂▄▆█  WPA2      
11:22:33:44:55:66  OfficeWiFi     Infra  11    54 Mbit/s   65      ▂▄▆_  WPA2 WPS  
77:88:99:aa:bb:cc  PublicHotspot  Infra  1     54 Mbit/s   45      ▂▄__  --

Connecting to Wi-Fi Networks

# Connect to an open network
nmcli device wifi connect "PublicHotspot"

# Connect to a secured network
nmcli device wifi connect "MyHomeNetwork" password "mypassword"

Connecting to Hidden Wi-Fi Networks

nmcli connection add type wifi con-name "HiddenNetwork" \
    wifi.ssid "HiddenSSID" wifi-sec.key-mgmt wpa-psk \
    wifi-sec.psk "password" wifi.hidden yes

Static IP Configuration

Configuring Static IP for Ethernet

nmcli connection modify "Wired connection 1" \
    ipv4.addresses 192.168.1.100/24 \
    ipv4.gateway 192.168.1.1 \
    ipv4.dns 8.8.8.8,8.8.4.4 \
    ipv4.method manual

Applying Configuration Changes

nmcli connection up "Wired connection 1"

Reverting to DHCP

nmcli connection modify "Wired connection 1" ipv4.method auto
nmcli connection up "Wired connection 1"

VPN Configuration

Creating an OpenVPN Connection

nmcli connection add type vpn con-name "MyVPN" \
    vpn-type openvpn \
    vpn.data "remote=vpn.example.com,connection-type=tls,cert=/path/to/cert.pem,key=/path/to/key.pem,ca=/path/to/ca.pem"

Connecting to VPN

nmcli connection up "MyVPN"

Viewing VPN Status

nmcli connection show --active

Network Troubleshooting

Checking NetworkManager Status

nmcli general status

Output Example:

STATE         CONNECTIVITY  WIFI-HW  WIFI     WWAN-HW  WWAN    
connected     full          enabled  enabled  enabled  enabled

Monitoring Network Activity

nmcli monitor

Reloading Network Configuration

sudo nmcli general reload

Checking DNS Configuration

nmcli device show | grep DNS

Configuration Files and Locations

Main Configuration File

NetworkManager’s main configuration is stored in:

/etc/NetworkManager/NetworkManager.conf

Connection Profiles

Individual connection profiles are stored in:

/etc/NetworkManager/system-connections/

Sample Configuration File Structure

[main]
plugins=keyfile,ifupdown

[ifupdown]
managed=false

[device]
wifi.scan-rand-mac-address=no

GUI Management Tools

GNOME Network Settings

For GNOME desktop environments, access network settings through:

gnome-control-center network

NetworkManager Applet

The system tray applet provides quick access to network connections:

nm-applet

Advanced NetworkManager Features

Connection Priorities

# Set connection priority (higher numbers = higher priority)
nmcli connection modify "MyWiFi" connection.autoconnect-priority 10

MAC Address Randomization

nmcli connection modify "MyWiFi" wifi.cloned-mac-address random

Connection Zones (Firewalld Integration)

nmcli connection modify "Office-LAN" connection.zone work

Performance Optimization

Disabling Unused Interfaces

# Disable Wi-Fi if not needed
nmcli radio wifi off

# Disable WWAN
nmcli radio wwan off

Connection Timeout Settings

nmcli connection modify "MyConnection" \
    ipv4.dhcp-timeout 30 \
    connection.autoconnect-retries 3

Security Best Practices

Setting Connection Permissions

# Restrict connection to specific users
nmcli connection modify "SecureWiFi" \
    connection.permissions user:admin:username

Certificate-based Authentication

nmcli connection add type wifi con-name "Enterprise-WiFi" \
    wifi.ssid "CorpNetwork" \
    wifi-sec.key-mgmt wpa-eap \
    802-1x.eap tls \
    802-1x.identity "username" \
    802-1x.client-cert "/path/to/client.crt" \
    802-1x.private-key "/path/to/private.key"

Common Issues and Solutions

NetworkManager Not Starting

# Check for conflicting services
sudo systemctl disable networking
sudo systemctl stop networking
sudo systemctl start NetworkManager

DNS Resolution Problems

# Reset DNS configuration
sudo systemctl restart systemd-resolved
nmcli general reload

Wi-Fi Connection Issues

# Reset Wi-Fi interface
sudo nmcli radio wifi off
sudo nmcli radio wifi on
nmcli device wifi rescan

Conclusion

NetworkManager provides a comprehensive solution for network management in Linux environments. Its combination of automatic configuration capabilities and extensive manual control options makes it suitable for both desktop users and system administrators. Whether you’re managing a single laptop or multiple servers, understanding NetworkManager’s features and commands will significantly improve your network administration efficiency.

The key to mastering NetworkManager lies in understanding its layered approach: the service manages devices and connections, while tools like nmcli provide the interface for configuration and monitoring. Regular practice with the command-line tools, combined with knowledge of the configuration files, will give you complete control over your Linux network infrastructure.