Auto-connect to Wifi with systemd-networkd

Preliminaries

Let’s suppose you have systemd-networkd configured to auto-connect to a wired interface, but sometimes you also need to connect to a (certain) wireless network.

Please replace <interface> with the name of your wireless interface, e.g. wlp2s0.¹
Find it out with ip link.

Action

Create a new .network file in /etc/systemd/network with something like the following:

[Match]
Name=<interface>

[Link]
RequiredForOnline=routable

[Network]
DHCP=ipv4

You might want to give this file a higher priority over other configurations. This is done through leading numbers, e.g. 20- for wired, 10- for wireless.

If you know the exact SSID you can procede with

wpa_passphrase mySSID >> /etc/wpa_supplicant/wpa_supplicant-<interface>.conf

On my machine, this included the passphrase both encrypted and in cleartext as a comment. Edit the config file to remove the latter.

If you need to scan your networks first you can use the instructions in the wpa_cli chapter.

Now start/restart and ultimately enable the service:

systemctl start wpa_supplicant@<interface>.service
systemctl restart systemd-networkd.service
systemctl enable wpa_supplicant@<interface>.service

With a bit of luck that’s all that was needed.

For good measure I stopped and disabled the general wpa_supplicant.service; but it did not seem to interfere with anything at any point.

wpa_cli

You can use the wpa_cli shell to find out about available networks/SSIDs.

However, this requires to add some extra values to the top of
/etc/wpa_supplicant/wpa_supplicant-<interface>.conf:

ctrl_interface=/run/wpa_supplicant
ctrl_interface_group=1000
update_config=1

Restart the service: systemctl restart wpa_supplicant@<interface>.service

Now, issuing wpa_cli (/sbin/wpa_cli on Debian) should give you a simple prompt >. If it doesn’t, make sure ctrl_interface_group corresponds to the group of the user you are trying to connect as. If that still isn’t enough, you might need to specify the interface and/or the control interface on the command line to correspond with the above configuration, e.g.:
wpa_cli -i <interface> -p /run/wpa_supplicant

Enter scan, then after a while (you should see WPS-AP-AVAILABLE) scan_results.

Because i was unable to figure out how to make wpa_cli store the password encrypted I recommend to quit at this point and create the configuration with wpa_passphrase; but wpa_cli can do it too:

• add_network (make note of the numerical )
• set_network <id> ssid “<SSID>”
• set_network <id> psk "password"
• enable_network <id> (you should see CTRL-EVENT-CONNECTED)
• save_config
• quit

Check /etc/wpa_supplicant/wpa_supplicant-<interface>.conf if the desired network has been saved.