nixpkgs/nixos/doc/manual/configuration/wireless.section.md

Wireless Networks

For a desktop installation using NetworkManager (e.g., GNOME), you just have to make sure the user is in the networkmanager group and you can skip the rest of this section on wireless networks.

NixOS will start wpa_supplicant for you if you enable this setting:

{
  networking.wireless.enable = true;
}

NixOS lets you specify networks for wpa_supplicant declaratively:

{
  networking.wireless.networks = {
    echelon = {                # SSID with no spaces or special characters
      psk = "abcdefgh";
    };
    "echelon's AP" = {         # SSID with spaces and/or special characters
      psk = "ijklmnop";
    };
    echelon = {                # Hidden SSID
      hidden = true;
      psk = "qrstuvwx";
    };
    free.wifi = {};            # Public wireless network
  };
}

Be aware that keys will be written to the nix store in plaintext! When no networks are set, it will default to using a configuration file at /etc/wpa_supplicant.conf. You should edit this file yourself to define wireless networks, WPA keys and so on (see wpa_supplicant.conf(5)).

If you are using WPA2 you can generate pskRaw key using wpa_passphrase:

$ wpa_passphrase ESSID PSK
network={
        ssid="echelon"
        #psk="abcdefgh"
        psk=dca6d6ed41f4ab5a984c9f55f6f66d4efdc720ebf66959810f4329bb391c5435
}

{
  networking.wireless.networks = {
    echelon = {
      pskRaw = "dca6d6ed41f4ab5a984c9f55f6f66d4efdc720ebf66959810f4329bb391c5435";
    };
  };
}

or you can use it to directly generate the wpa_supplicant.conf:

# wpa_passphrase ESSID PSK > /etc/wpa_supplicant.conf

After you have edited the wpa_supplicant.conf, you need to restart the wpa_supplicant service.

# systemctl restart wpa_supplicant.service