How to Monitor NetworkManager Changes Using 'nmcli monitor' (with examples)

The nmcli monitor command is a utility for observing real-time changes in NetworkManager connection status. NetworkManager is a daemon that manages network interfaces in a flexible manner, supporting both wireless and wired connections. This command-line tool enables users to monitor the status of their network connections, providing an immediate output when there is a change in the network status. It is particularly useful for system administrators and users who need to manage and troubleshoot network connectivity in real-time.

Use case: Start monitoring NetworkManager changes

Code:

nmcli monitor

Motivation:

Monitoring changes in network connection status is essential for anyone managing a networked environment. Whether you’re a network administrator responsible for a fleet of computers, a developer who needs a stable connection for deploying applications, or a regular user attempting to diagnose connectivity issues, knowing exactly when and how the network connection changes can provide invaluable insights. This use case is ideal when you need immediate feedback on network status changes to take proactive actions (like switching to backup connections or alerting users to network issues).

Explanation:

• nmcli: This is the command-line interface of NetworkManager. It provides commands for interacting with the daemon to manage network settings.
• monitor: This is a sub-command of nmcli that, when executed, puts nmcli into a mode where it continuously outputs information about any changes in network connection status. It doesn’t require any additional arguments, as it is designed to automatically track all network-related events such as interfaces connecting or disconnecting, changes in connection properties, and more.

Example output:

Running the nmcli monitor command will output something resembling:

NetworkManager state is now CONNECTED_GLOBAL
Device 'enp3s0' successfully activated with 'Home_Network'
Connection 'VPN_Connection' is now deactivated

This output exemplifies a real-time log of connection changes. Each line represents a network event, such as a device being activated or a VPN being disconnected, reflecting the dynamic network environment. The details in these messages are crucial for diagnosing or understanding network behavior, allowing rapid response to incidents.