NetworkManager is a dynamic network control and configuration daemon that attempts to keep network connections up and active. nmcli is a command-line tool used to interact with NetworkManager. This post will provide a comprehensive guide to using nmcli for managing network connections in Linux.

Installation

nmcli is usually installed by default on most Linux distributions that use NetworkManager. However, if it’s not installed, you can install it using your distribution’s package manager:

  • Debian/Ubuntu: sudo apt install network-manager
  • Fedora/CentOS/RHEL: sudo dnf install NetworkManager or sudo yum install NetworkManager
  • Arch Linux: sudo pacman -S networkmanager

Basic Usage

Displaying Network Connections

To list all available network connections:

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nmcli connection show

This will display a table with the connection name, UUID, type, and device.

Displaying Network Devices

To list all network devices:

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nmcli device show

This will show information about each network device, including its state, type, and hardware address.

Activating a Connection

To activate a connection (e.g., MyWiFi):

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nmcli connection up MyWiFi

Deactivating a Connection

To deactivate a connection (e.g., MyWiFi):

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nmcli connection down MyWiFi

Editing Connections

You can modify existing connections using nmcli. For example, to edit the Wi-Fi password for a connection named MyWiFi:

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nmcli connection modify MyWiFi wifi-sec.psk "your_new_password"

Then, you need to deactivate and activate the connection for the changes to take effect:

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nmcli connection down MyWiFi
nmcli connection up MyWiFi

Creating a New Wi-Fi Connection

To create a new Wi-Fi connection, you’ll need the SSID and password:

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nmcli device wifi connect "YourWiFiSSID" password "YourWiFiPassword" name "MyNewWiFi"

Replace "YourWiFiSSID", "YourWiFiPassword", and "MyNewWiFi" with your actual Wi-Fi network’s SSID, password, and the desired connection name, respectively.

Creating a New Ethernet Connection

For Ethernet connections, you typically don’t need to specify a password. You can create a new Ethernet connection with a specific connection name:

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nmcli connection add type ethernet con-name MyEthernet ifname eth0

Replace MyEthernet with your desired connection name and eth0 with the interface name if it’s different.

Setting a Static IP Address

To configure a static IP address for a connection (e.g., MyEthernet):

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nmcli connection modify MyEthernet ipv4.method manual
nmcli connection modify MyEthernet ipv4.address 192.168.1.100/24
nmcli connection modify MyEthernet ipv4.gateway 192.168.1.1
nmcli connection modify MyEthernet ipv4.dns 8.8.8.8

Replace the IP address, gateway, and DNS server with your desired values. Again, you’ll need to deactivate and activate the connection for the changes to take effect.

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nmcli connection down MyEthernet
nmcli connection up MyEthernet

Removing a Connection

To remove a connection (e.g., MyOldWiFi):

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nmcli connection delete MyOldWiFi

Useful Tips and Tricks

  • Tab Completion: nmcli supports tab completion, making it easier to enter commands and connection names.
  • Help: Use nmcli --help or nmcli <command> --help for detailed information about commands and options.
  • Profiles: NetworkManager saves connection profiles, so you can easily switch between different network configurations.
  • Troubleshooting: If you encounter issues, check the NetworkManager logs (usually in /var/log/syslog or /var/log/messages) for error messages.

Conclusion

nmcli is a powerful and versatile tool for managing network connections in Linux. By mastering the commands outlined in this guide, you can easily configure and troubleshoot your network settings from the command line. This is especially useful for headless servers or when you prefer a command-line interface.