You now have Raspberry Pi networking set up the systemd way. Share and enjoy.

- THE END -

PS: If you also want your Pi to act as an access point (AP mode), continue with the next step.

a) Add udev rule to create virtual ap interface for each wlan interface, e.g.:

sudo nano /etc/udev/rules.d/70-ap-interface.rules

and enter the following in it:

SUBSYSTEM=="net", KERNEL=="wlan*", ACTION=="add", RUN+="/sbin/iw dev %k interface add ap%n type __ap"

b) Create config file for the ap0 interface:

sudo nano /etc/systemd/network/20-ap0.network

with the following contents:

[Match]
Name=ap0

[Network]
Address=192.168.11.254/28
DHCPServer=yes

c) Trigger manual ap0 creation and configuration:

sudo udevadm trigger --action=add /sys/class/net/wlan0
sudo systemctl restart systemd-networkd

d) Check the status:

networkctl status ap0

The ap0 interface should be in no-carrier state (for now) and have an IP address.

a) Install the package:

sudo apt install hostapd

b) Since hostapd is not "systemd-ready" yet (doesn't come with a .service file), we will create our own .service file for it:

sudo nano /etc/systemd/system/hostapd@.service

 with the following contents:

[Unit]
Description=Advanced IEEE 802.11 AP and IEEE 802.1X/WPA/WPA2/EAP Authenticator
Requires=sys-subsystem-net-devices-%i.device
After=sys-subsystem-net-devices-%i.device
Before=network.target
Wants=network.target

[Service]
Type=simple
ExecStart=/usr/sbin/hostapd /etc/hostapd/hostapd-%I.conf

[Install]
Alias=multi-user.target.wants/hostapd@%i.service

a) Create config file for the wireless network:

sudo nano /etc/hostapd/hostapd-ap0.conf

with the following contents:

interface=ap0
country_code=US
hw_mode=g

ssid=raspberrypi
channel=6
ignore_broadcast_ssid=0

auth_algs=1
wpa=2
wpa_passphrase=password
wpa_key_mgmt=WPA-PSK

wmm_enabled=0

Replace country_code with the same one you've chosen in step 4.

Replace ssid and wpa_passphrase with the name and password of your wireless network.

b) Enable and start hostapd on ap0:

sudo systemctl enable hostapd@ap0
sudo systemctl start hostapd@ap0

c) Check the status:

networkctl status ap0

The ap0 interface should now be in configured state.

d) At this point you should be able to see your wireless network, be able to connect to it and log into your Raspberry Pi through it:

ssh pi@192.168.11.254

As a final step, we need to make sure wpa_supplicant on wlan0 starts after hostapd on ap0.

To do this, we need to add an override file:

sudo mkdir /etc/systemd/system/wpa_supplicant@wlan0.service.d
sudo nano /etc/systemd/system/wpa_supplicant@wlan0.service.d/override.conf

 and enter the following in it:

[Unit]
Wants=hostapd@ap0.service
After=hostapd@ap0.service

[Service]
ExecStartPre=/bin/sleep 3

Now, reboot your Pi and cross your fingers... and legs... and ears.

If everything went right, you should see the wireless network you set up and be able to connect to it and log into your Raspberry Pi.