Manage Network Connections From the Linux Command Line with nmcli

Network connectivity is a fundamental requirement for any Linux system, especially in servers and headless environments where graphical tools are not available. The nmcli (Network Manager Command-Line Interface) is a command-line utility used to manage network connections through the terminal. It allows users to view network status, create and modify connections, and control network devices efficiently without relying on a GUI.

• Manage network connections (create, modify, delete, activate, deactivate)
• Display detailed status of network devices and connections
• Works without a graphical interface (ideal for servers and headless systems)
• Supports automation and scripting for network management tasks
• Provides flexible and structured control over NetworkManager operations

Core Concept of nmcli

nmcli serves as a command-line interface for controlling NetworkManager, the service responsible for network configurations in Linux systems.

• Enables configuration and monitoring of network settings without relying on graphical tools
• Manages the full lifecycle of network connections, including creation, modification, activation, and deletion
• Optimized for terminal-only environments such as servers and remote systems
• Supports automation through scripting, making network management efficient for administrators and DevOps workflows

Example 1: List All Network Connections

Displays all saved network configurations on the system. Helps identify available connections along with details like name, UUID, type, and associated device.

Command:

nmcli connection show

• nmcli: Invokes the NetworkManager command-line tool
• connection: Targets saved network connections
• show: Displays details of all connections

Output:

Example 2: Check Device Status

Shows the current state of all network devices. Helps identify whether devices are connected or disconnected along with additional information like the device type and the connection type it is associated with.

Command:

nmcli dev status

• nmcli: Runs the NetworkManager CLI tool
• dev: Refers to network devices
• status: Shows current device state

Output:

Example 3: Display Device Details

Shows detailed information about a specific network device. Useful for checking IP address, MAC address, driver details, and other configuration data.

Command:

nmcli device show eno1

• nmcli: Runs the NetworkManager CLI tool
• device: Targets network devices
• show: Displays detailed information
• eno1: Specifies the device name (replace with your actual interface)

Output:

Example 4: Add a New Ethernet Connection

Creates a new network connection for a specified interface. Useful for setting up a new network or configuring additional interfaces on the system.

Syntax:

nmcli connection add type <connection_type> ifname <interface_name> con-name <connection_name>

• connection_type: Specifies the type of connection (e.g., ethernet, wifi)
• interface_name: Name of the network interface
• connection_name: User-defined name for the connection

Command:

nmcli connection add type ethernet ifname eth1 con-name my_eth_connection

• nmcli: Invokes the NetworkManager CLI tool
• connection: Targets connection management
• add: Creates a new connection
• type ethernet: Specifies connection type
• ifname eth1: Defines the network interface
• con-name my_eth_connection: Assigns a custom name

Output:

• This command creates a new Ethernet connection named "my_eth_connection" associated with the network interface "eth1". Adjust the interface name and connection name as needed.

Verification Command:

nmcli connection show

Output:

Example 5: Modify Connection Settings

Modifies the settings of an existing network connection. Commonly used to configure static IP addresses, gateway, and other network parameters.

Syntax:

nmcli connection modify <connection_name> <setting_name> <setting_value>

• connection_name: Name of the connection to modify
• setting_name: Network parameter to change (e.g., ipv4.addresses)
• setting_value: New value for the specified setting

Command:

nmcli connection modify my_eth_connection ipv4.addresses "192.168.1.2/24" ipv4.gateway "192.168.1.1"

• nmcli: Invokes the NetworkManager CLI tool
• connection: Targets connection management
• modify: Updates an existing connection
• my_eth_connection: Specifies the connection name
• ipv4.addresses "192.168.1.2/24": Sets static IP with subnet mask
• ipv4.gateway "192.168.1.1": Defines the gateway address

Note: Changes may require reactivating the connection to take effect

Command:

nmcli connection up my_eth_connection

Syntax

nmcli [OPTIONS] OBJECT { COMMAND | help }

• OPTIONS: Modify the behavior of the command or the format of its output
• OBJECT: Specifies the target for the operation.
• COMMAND: Defines the action to perform on the specified object, for example show, add, or modify

Common OBJECT Values

• nm: Shows NetworkManager status
• connection or con: Manages network connections
• device or dev: Manages network devices

Options Available in nmcli Command in Linux

1. -t, --terse

Displays output in a compact, machine-readable format by removing headers and formatting.

• Useful for scripting and automation where clean, parseable output is required
• Reduces unnecessary text and presents data in a simple delimiter-based format
• Commonly used in shell scripts for extracting values

Syntax:

nmcli -t <object> <command>

Example: Display Device Status in Pretty Format

Shows formatted output with headings and aligned columns.

Command:

nmcli -t device status

Output:

2. -p, --pretty

Displays output in a well-structured and human-readable format with headings and spacing.

• Improves readability when working directly in the terminal
• Adds formatting such as section headers and aligned columns
• Useful for manual inspection of network details

Syntax:

nmcli -p <object> <command>

Example: Display Device Status in Pretty Format

Shows formatted output with headings and aligned columns.

Command:

nmcli -p device status

Output:

3. -m, --mode {tabular | multiline}

Controls how output is displayed by switching between tabular (default) and multiline formats.

• tabular: shows data in rows and columns
• multiline: shows each field on a separate line for detailed viewing
• Useful when working with detailed device or connection information

Syntax:

nmcli -m {tabular | multiline} <object> <command>

Example: Example: Display Device Details in Multiline Format

Shows detailed information where each field is printed on a separate line.

Command:

nmcli -m multiline device show

Output:

4. -f, --fields

Displays only selected fields from the output instead of showing all available information.

• Helps in filtering specific data fields
• Reduces clutter when only limited information is required
• Can use all to display all fields or common for commonly used fields

Syntax:

nmcli -f <field_names> <object> <command>

Example: Display Only General Device Information

Shows only GENERAL fields for each device.

Command:

nmcli -f GENERAL device show

Output:

5. -v, --version

Displays the installed version of the nmcli tool.

• Useful for checking compatibility and debugging issues
• Helps verify installed NetworkManager version

Syntax:

nmcli -v

Output:

6. -h, --help

Displays help information about nmcli commands and usage.

• Provides a quick reference for syntax and available options
• Useful for beginners and troubleshooting command usage

Syntax:

nmcli -h

Output: