Network Manager - Network Config

NetworkManager manages network devices and activates connection profiles on many Linux desktops and servers. It is not universal, so confirm that it owns the target interface before using nmcli to change configuration.

Devices and Connections

A device is a kernel interface such as enp1s0 or wlan0. A connection is a stored profile containing IPv4, IPv6, DNS, Wi-Fi, routing, and other settings. One device can have several profiles, but normally only an applicable profile is active at a time.

$ nmcli device status
$ nmcli connection show
$ nmcli connection show --active

CheckWhat is a NetworkManager connection profile?

Inspecting Effective State

Show the active profile and device details:

$ nmcli -f GENERAL,IP4,IP6 device show enp1s0
$ nmcli connection show 'Wired connection 1'

Profile settings, runtime DHCP results, and kernel state can differ. Compare with ip address, ip route, and the resolver. The deprecated nm-tool should not be the basis of a current workflow.

CheckWhich command lists active NetworkManager profiles?

Modifying and Activating a Profile

Modify a named profile explicitly, then activate it in a maintenance window:

$ sudo nmcli connection modify 'Wired connection 1' ipv4.method auto
$ sudo nmcli connection up 'Wired connection 1'

Modification changes persistent profile data; activation can replace live addresses, routes, and DNS. A remote change needs console access, saved original settings, and an independent timed rollback. Never rely on the connection being changed to carry its own recovery command.

CheckWhat is the difference between connection modify and connection up?

Verifying and Protecting Secrets

After activation, verify profile state, kernel addresses and routes, DNS, both address families, and the intended application. Wi-Fi, VPN, 802.1X, and mobile profiles can contain secrets. Limit profile permissions and avoid printing secret fields into shared logs or shell transcripts.

CheckWhat proves more than NetworkManager reporting “connected”?

Summary

You can now manage NetworkManager profiles without confusing them with interface objects.

Confirm NetworkManager owns the target device.
Distinguish stored profiles from active runtime state.
Inspect devices, all profiles, and active profiles separately.
Modify, activate, recover, and verify as distinct steps.

Practice

In the practice terminal, run: nmcli device status If NetworkManager is installed it lists devices and their state. Command not found means it does not manage this machine.

NetworkManager is not universal - confirm it owns the interface first.