First steps with NetworkManager

Goal: Connect to the Internet via Wi-Fi or Ethernet using NetworkManager from the command line.

About: For our current purposes, NetworkManager is a network management tool that provides easy automatic connection to the Internet. NetworkManager manages your network interfaces, detects available connections and automatically connects network devices when connections for the device become available. In practice, NM provides “set it and forget it” functionality—after connecting to a network on a given network interface, NM remembers the connection and will automatically connect you in the future (unless you disable automatic connection, of course).

References:

• For a comprehensive Linux networking guide, I recommend the Fedora documentation project’s Networking Guide. For NetworkManager in particular, see the section on Using the NetworkManager Command Line Tool, nmcli.
• Of course there is always man NetworkManager and man nmcli and the references therein.
• Also consider ArchWiki: NetworkManager, but the coverage of relevant topics is somewhat patchy at the time of writing.
• Arch Wiki: Network Configuration has useful general networking information for Arch Linux

Contents of this article

Installation

Install the networkmanager package:

sudo pacman -S networkmanager

The networkmanager package contains a few things: the NetworkManager daemon itself, the nmcli command line interface, and the nmtui and a text user interface.

Use systemd-resolved for DNS resolution

I recommend using the systemd-resolved service, which NetworkManager can then use for DNS resolution, i.e. converting human-readable domain names into computer-friendly IP addresses.

• You probably won’t need to install anything—systemd-resolved is part of the systemd package, which is installed by default on an Arch system (Source).

• Start and enable the systemd-resolved service (if necessary):

  # Check service status
  systemctl status systemd-resolved.service
  
  # If the service is not active and running, enable and start it
  systemctl enable --now systemd-resolved.service
  

Disable currently running network daemons (if needed)

Explanation: if you had previously used other services for network configuration, these services’ daemons would conflict with NetworkManager. See ArchWiki: NetworkManager/Installation for a discussion of this issue.

If you’re on a fresh install of Arch Linux you should have nothing to worry about, but if you’ve been using Arch for a while you should double check for other network services and stop them. Common network configuration services include dhcpcd and systemd-networkd; here is how you could check their status and disable them if necessary:

# Check the service is inactive (dead) or not found
systemctl status dhcpcd.service
systemctl disable dhcpcd.service  # disable if active

# And so on for other services...
systemctl status systemd-networkd.service
systemctl disable systemd-networkd.service

Start NetworkManager

Finally enable and start the NetworkManager service:

systemctl enable --now NetworkManager.service

Reboot to ensure all changes take effect.

Hello world network connection

Check network interfaces

You must have an available wireless interface to use Wi-Fi and an Ethernet interface to use wired Ethernet, so you should first check you have these network interfaces available.

You can list network interfaces with the ip link command:

# List network interfaces
ip link       
ip -c link    # you can use the `-c` flag for colored output

You should expect a loopback, Ethernet, and wireless interface; here is an example ip link output on my computer:

$ ip link
1: lo         # ...additional output ommitted...
2: enp0s31f6  # ...additional output ommitted...
3: wlp4s0     # ...additional output ommitted...

Wired network interfaces are conventionally prefixed with en and wireless interfaces with wl, in the above example lo is my loopback interface, enp0s31f6 is my Ethernet interface, and wlp4s0 is my wireless interface.

Troubleshooting

• If ip link does not show a wireless interface, your wireless network card probably requires a kernel driver that does not ship by default with Arch, and you will have to install this kernel driver and load the corresponding kernel module.

  This falls beyond the scope of this guide—you will need to know the manufacturer and model of your wireless network card (use lspci -v (or lsusb -v if the wireless device is connected via USB) and search the output for “Network controller”) and what kernel driver is currently handling the network card device (use lspci -k or lsusb -k). Then consult ArchWiki: Network configuration/Wireless and the references therein to see if your network card should be using a different kernel driver.

• If ip link shows a wireless interface, but its status shows status DOWN, your Wi-Fi might be blocked. You can unblock it with rfkill unblock wifi; see man rfkill for more information.

Check-in point: The ip link command lists both a wireless and Ethernet network interface (in addition to the loopback interface lo).

Ethernet

Ethernet should be plug and play (assuming NetworkManager.service is enabled)—just plug a working Ethernet cable into your computer (potentially via a USB adapter) and NetworkManager should take care of the rest. You can verify your connection with nmcli general status or nmcli device status, which should show a connected state.

Your mileage may vary, of course, but Ethernet network connections have always worked automatically for me when using NetworkManager.

Wi-Fi

First enable Wi-Fi and list available wireless networks:

# Ensure Wi-Fi is enabled---verify status with `nmcli radio wifi`
nmcli radio wifi on

# List available Wi-Fi networks
$ nmcli device wifi list

# Example output of `nmcli device wifi list`:
BSSID              SSID            MODE   CHAN  RATE        SIGNAL  BARS  SECURITY
AA:11:BB:22:CC:33  MyCoolNetwork   Infra  6     230 Mbit/s  95      ▂▄▆_  WPA2
DD:44:EE:55:FF:66  AnotherNetork   Infra  6     195 Mbit/s  90      ▂▄▆_  WPA1 WPA2
GG:77:HH:88:II:99  FooBarNetwork   Infra  6     175 Mbit/s  85      ▂▄▆_  --

Identify your desired network’s SSID, and connect as follows:

# Specify network SSID and password (for secured networks)
nmcli device wifi connect {SSID} password [password]

# Example: connecting to MyCoolNetwork
nmcli device wifi connect 'MyCoolNetwork' password 'my_secure_password'

# Unsecured networks don't need a password
nmcli device wifi connect 'FooBarNetwork'

Special characters: you may want to place [password] in literal (single) quotes, as in the above example, to ensure password with special characters are interpreted literally.
Example problem: something like password foo!bar or password foo$bar would cause problems with history or variable expansion, assuming the passwords contain the literal characters ! and $.
Solution: use password 'foo!bar' or password 'foo$bar' instead.

Checking basic network status

Here are a few basic commands to help you check your network status when using NetworkManager.

Connection status

Use nmcli general status to show general NetworkManager status. Here is an example output for an active wireless connection

# Example output of `nmcli general status`
$ nmcli general status
STATE      CONNECTIVITY  WIFI-HW  WIFI     WWAN-HW  WWAN
connected  full          enabled  enabled  enabled  enabled

See the GENERAL COMMANDS section of man nmcli for more information.

Use nmcli device status to see the connection status of each of your network interfaces. Here is example output for an active wireless connection on a wireless network with the SSID FooBarNetwork:

# Example output of `nmcli device status`
$ nmcli device status
DEVICE  TYPE      STATE         CONNECTION
wlan0   wifi      connected     FooBarNetwork
enp0s1  ethernet  unavailable   --
lo      loopback  unmanaged     --

Use nmcli device show for more detailed information than nmcli device status. See the DEVICE MANAGEMENT COMMANDS section of man nmcli for more information.

Configured connections

Use nmcli connection show to show the human-readable name, UUID, and interface of all previously configured network connections (e.g. to see Wi-Fi networks you have connected to in the past). Use nmcli connection show --active to show only current connections.

NetworkManager stores connection files in /etc/NetworkManager/system-connections/—note that Wi-Fi passwords are stored in plain text and are protected only with root access permissions. See ArchWiki: NetworkManager/Encrypted Wi-Fi passwords for ways to encrypt Wi-Fi passwords.

IP addresses

You can list the IP address associated with each of your network interfaces with the ip address command:

# List network interfaces and their corresponding IP addresses
ip address       # `ip addr` or even `ip a` should work, too
ip -c addresses  # use the `-c` flag for colored output

The output of ip address is a bit verbose—check the inet field of each interface for an IPv4 address and the inet6 field for an IPv6 address.